ARVO 2012 Annual Meeting Abstracts

Transcription

270 Imaging of Function, Perfusion, and Oxymetry
Monday, May 7, 2012, 1:45 PM - 3:30 PM
Hall B/C Poster Session
Program #/Board # Range: 2154-2205/D1218-D1269
Organizing Section: Multidisciplinary Ophthalmic Imaging Group
Contributing Section(s): Visual Psychophysics/Physiological Optics
Program Number: 2154 Poster Board Number: D1218
Presentation Time: 1:45 PM - 3:30 PM
Retinal Blood Flow In Proliferative Diabetic Retinopathy By Fourier-domain
Optical Coherence Tomography: Measurements Before And After Panretinal
Photocoagulation
Jennifer C. lee1, Brandon Wong1, Elnaz Rakhshan1, Ou Tan2A, Srinivas R. Sadda1,
David Huang2B, Amani A. Fawzi3. 1Ophthalmology, Doheny Eye Institute - USC,
Los Angeles, CA; AOphthalmology, BCasey Eye Institute, 2Oregon Health &
Science Univ, Portland, OR; 3Ophthalmology-Univ of Southern Cal, Doheny Eye
Institute, Los Angeles, CA.
Purpose: The purpose of this study is to determine retinal venous blood flow in
proliferative diabetic retinopathy(PDR) as compared to normal eyes using Doppler
Fourier-domain optical coherence tomography(FD-OCT), and to determine the
effect of panretinal photocoagulation(PRP) on retinal blood flow.
Methods: This is a prospective interventional pilot study. Inclusion criteria were a
clinical diagnosis of PDR without prior PRP or vitreous hemorrhage. Double
circular Doppler scans of peripapillary blood vessels were performed using the
RTVue FD-OCT system (Optovue Inc., Fremont, CA, USA). Retinal blood flow
was measured according to a previously described method where candidate vessels
are chosen by computer algorithms and in post-processing the reader manually
refines the results. Total retinal blood flow was measured by summing the flow
from all detectable veins. Pre-PRP Doppler FD-OCT scans were analyzed for all
PDR subjects (6), and post-PRP Doppler FD-OCT scans were analyzed on four of
them at the time of submission.
Results: Blood flow at baseline was not significantly different between PDR and
control eyes (p=0.86), however, post-PRP there was a trend for decreasing blood
flow in PDR (p=0.06). Compared to controls, PDR eyes had statistically significant
decrease in venous velocity at baseline (p=0.01) and post- PRP laser (p=0.01),
along with statistically non-significant increased venous caliber (p=0.15) (Table 1).
Conclusions: Retinal venous velocity is slower in PDR eyes compared to normal
eyes. There is a trend towards decreased total retinal blood flow in the early 7-8
weeks post-PRP period. Additional patients and sequential post-PRP follow-up are
ongoing to further characterize the retinal vascular effects of PDR and PRP
treatment.
Commercial Relationships: Jennifer C. lee, None; Brandon Wong,
None; Elnaz Rakhshan, None; Ou Tan, Optovue (P); Srinivas R. Sadda, Carl
Zeiss Meditec, Optovue, Inc. (F), Heidelberg Engineering (C), Topcon Medical
System (P); David Huang, Carl Zeiss Meditec, Inc. (P), Optovue, Inc. (F, I, C, P,
R); Amani A. Fawzi, None
Support: NIH Grant R01-EY013516 (Huang PI)
Variability and Repeatability of Quantitative, SD-OCT Doppler Blood Flow in
Young and Elderly Healthy Subjects
Faryan Tayyari1, Firdaus Yusof1,2, Michal Vymyslicky1, John G. Flanagan1,3,
Christopher Hudson1,3. 1School of Optometry and Vision Sciences, University of
Waterloo, Waterloo, ON, Canada; 2Department of Optometry and Visual Science,
International Islamic University of Malaysia, Bandar Indera Mahkota, Kuantan,
Malaysia; 3Department of Ophthalmology and Vision Sciences, University of
Toronto, Toronto, ON, Canada.
Purpose: The purpose was to determine the within-session variability and
between-session repeatability of SD-OCT Doppler measurement of retinal blood
flow in young and elderly healthy subjects.
Methods: SD-OCT Doppler blood flow was non-invasively measured using the
RTVue system (Optovue Inc., USA). One eye of each of 6 healthy young (mean
age 25.7; SD 3.5 years) and 6 healthy elderly (mean age 63.1; SD 1.8 years)
subjects was randomly selected for the study and the pupil was dilated using
Mydriacyl 1%. A double circular scanning pattern was employed. A minimum of
six separate SD-OCT Doppler measurements (i.e. each separate measurement
comprising an upper nasal pupil scan and a lower nasal pupil scan) were acquired at
each session. Measurements were repeated on a second day. Retinal blood flow
was calculated, using data from valid scans only, by summing flow from all
detectable venules. The coefficient of variation and the coefficient of repeatability
were calculated for each individual.
Results: The individual COVs for retinal blood flow for young subjects ranged
from 2 to 51.9% (median 28.8%) and for the elderly subjects ranged from 0.6 to
81.2% (median 9.9%). The group mean CORs for retinal blood flow for young
subjects were 30.5 µl/min (median 29.5 µl/min, relative to a mean effect 39.8
µl/min) and for elderly subjects were 16.9 µl/min (median 7.2 µl/min, relative to a
mean effect 34.7 µl/min).
Conclusions: The Doppler SD-OCT in general gave consistent measurements of
retinal blood flow in normal subjects, while the data was far more repeatable for the
elderly group. The relatively small sample size needs to be considered when
interpreting these results.
Commercial Relationships: Faryan Tayyari, None; Firdaus Yusof,
None; Michal Vymyslicky, None; John G. Flanagan, Carl Zeiss Meditec (F),
Heidelberg Engineering (F, C); Christopher Hudson, Optovue Inc. (F)
Support: Ontario Research Fund
Retinal Blood Flow in Patients with Sickle Cell Retinopathy assessed by
Retinal Function Imager
Apurva K. Patel1,2, Gennady Landa1,2, Chavakij Bhoomibunchoo1, Nicole
Scripsema1, James Saunders1,3, Richard B. Rosen1,2. 1The Einhorn Clinical
Research Center and Bendheim Family Retina Center, Department of
Ophthalmology, New York Eye and Ear Infirmary, New York, NY;
2
Ophthalmology, New York Medical College, Valhalla, NY; 3Rush Medical
College, Chicago, IL.
Purpose: To evaluate retinal blood flow velocities in patients with sickle cell
retinopathy(SCR) by using Retinal Function Imager (RFI).
Methods: Fifteen patients with SCR underwent testing with the RFI. A comparison
to the values of normal subjects was performed.
Results: In the eyes of patients with sickle cell retinopathy, mean arterial and
venous blood flow velocities were measured as 3.07+0.71 mm/sec and 2.12+0.54
mm/sec, respectively. While both arterial and venous velocities were found to be
reduced in patients with SCR in comparison to normal subjects, only for retinal
venous blood flow velocity there was a statistically significant difference (p=0.115
for arterial and p=0.003 for venous blood flow velocity).
Conclusions: Reduced retinal blood flow may play an important role in the
development of sickle cell retinopathy.
Commercial Relationships: Apurva K. Patel, None; Gennady Landa,
None; Chavakij Bhoomibunchoo, None; Nicole Scripsema, None; James
Saunders, None; Richard B. Rosen, OD-OS Clarity (C), OPKO-OTI/Optos (C),
Topcon Medical Systems, Inc (C)
Support: None
Combined Functional And Morphologic Parameters In Geographic Atrophy:
A Longitudinal Study
Elisabetta Pilotto1A, Francesca Guidolin1A, Enrica Convento1A, Luigi Spedicato1A,
Stela Vujosevic2, Fabiano Cavarzeran1A, Edoardo Midena1B,3. ADepartment of
Ophthalmology, BOphthalmology, 1University of Padova, Padova, Italy;
2
Fondazione GB Bietti-IRCCS, Padova, Italy; 3Fondazione G.B. Bietti per
l’Oftalmologia, IRCCS, Roma, Italy.
Purpose: To analyze on a long term basis microperimetry, standard shortwavelenght (SW-FAF) and near infrared-wavelenght fundus autofluorescent (NIRFAF) changes in eyes with geographic atrophy (GA) secondary to age-related
macular degeneration.
Methods: Fourteen consecutive patients (20 eyes) affected by GA were studied by
means of microperimetry to assess fixation and retinal sensitivity changes every six
months during follow-up. All patients performed SW-FAF and NIR-FAF at any
Copyright 2012 by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. For permission to reproduce any abstract, contact the ARVO Office at [email protected].
follow-up visit.
Results: Mean follow-up was 12.26 ± 4.45 months. Total hypoFAF area was
always significantly wider in NIR-FAF than in SW-FAF (5.05 ± 2.40 mm2 vs 4.45
±± 2.41 mm2, p=0.012 at baseline; 5.78 ±2.87 mm2 vs 5.21 ± 2.77 mm2, p<0.0001
at last follow-up visit). The mean GA enlargement was +0.76 ± 1.24 mm2/year in
SW-FAF and +0.92 ±1.10 mm2/year in NIR-FAF. Mean retinal sensitivity
significantly decreased from 7.79 ± 4.02 dB to 6.76 ± 4.50 dB (p=0.006). 47.3% of
the relative dense scotoma (≤ 5 dB) tested points at baseline evolved to absolute
scotoma. Relative scotomata characterized by hypoSW-FAF or hyperNIR-FAF had
a higher risk of evolving to absolute scotoma respectively than normo- and hyperFAF in SW-FAF (O.R.=2.70 and O.R.=2.68, respectively), and normo- and hypoFAF in NIR-FAF (O.R.=3.20 and O.R.=2.17 respectively).
Conclusions: SW-FAF, compared to NIR-FAF, may underestimate the baseline
extension and progression of GA. Different FAF patterns, assessed by SW-FAF
and NIR-FAF, have different relative risk of GA progression. SW-FAF should be
integrated with NIR-FAF in the follow-up of GA from both a morphological and
functional perspective.
Commercial Relationships: Elisabetta Pilotto, None; Francesca Guidolin,
None; Enrica Convento, None; Luigi Spedicato, None; Stela Vujosevic,
None; Fabiano Cavarzeran, None; Edoardo Midena, None
Support: None
Decrease in Retinal Vascular Caliber is associated with a Lower Renal
Function in Normotensive and Treatment-Naïve Hypertensive Subjects
Vincent Daien1, Ryo Kawasaki2, Max VILLAIN3A, Jean RIBSTEIN3B, Guilhem DU
CAILAR3B, Albert MIMRAN3B, Pierre FESLER3B. 1Ophthalmology, CHU
Montpelliler, Saint Gely Du Fesc, France; 2Ctr for Eye Research Australia,
University of Melbourne, Oakleigh East, Australia; AOphthalmology, BINTERNAL
MEDICINE, 3CHU Montpelliler, MONTPELLIER, France.
Purpose: Microvascular change has been postulated to represent one of the key
mechanisms of aging process of the kidney. Retinal vascular narrowing, which is
non-invasively assessed in vivo, has been used as a marker of the altered
microcirculation. The primary objective of this study was to assess the relation
between retinal vascular caliber and renal function in normotensive (NT;
systolic/diastolic blood pressure <140/90 mmHg) subjects and treatment-naïve
hypertensive (HT) subjects.
Methods: Fifty-seven NT subjects and 48 HT subjects were recruited for this
study. Their serum creatinine (SCreat) was < 1.5 mg/dL and they were all without
diabetes. Retinal vascular caliber was measured from fundus photographs using
semi-automated computer-assisted program and summarized as central retinal
artery equivalents (CRAE) and central retinal venular equivalent (CRVE). Renal
function was estimated with the glomerular filtration rate (eGFR) using the MAYO
clinic quadratic equation.
Results: Mean age of overall study subjects was 48+/-13 years old (mean +/- SD),
and 50% were women. Mean SCreat was 0.79+/-0.17 mg/dl and eGFR was 113.7
+/-12 ml/min/1.73m²; with no significant differences between NT and HT subjects.
The adjusted mean CRAE was significantly smaller in the HT group than in the NT
group (136.4 +/-2.1 µm vs. 148.4 +/- 1.7 µm; P<0.0001). Adjusted mean CRVE
was not significantly different between HT and NT (204.9 +/-3.2 µm vs. 210.4 +/2.6 µm; P=0.19). In all participants, CRAE and CRVE were positively and
significantly correlated to eGFR (univariate r²=0.16, P= 0.001 and r²=0.14, P=
0.001, respectively). This relation with eGFR remained significant for CRAE and
CRVE after adjusting for age, gender, mean arterial blood pressure, smoking,
glycemia, body mass index, total cholesterol, triglycerides (model r²=0.49;
P=0.0001 and model r² =0.29; P=0.002, respectively). When replacing eGFR by
1/Screat as possible predictive variables, the association between CRAE or CRVE
and renal function remained significant (model r²=0.51, p=0.0001 and model r²
=0.29; P=0.002, respectively).
Conclusions: In normotensive and treatment-naïve hypertensive subjects without
renal failure, a decrease in retinal vascular caliber (CRAE and CRVE) is associated
with a lower kidney function, independent of other potential confounding risk
factors. This may suggest common process in the microcirculation in the retina and
kidney, and warrants further studies to be documented.
Commercial Relationships: Vincent Daien, None; Ryo Kawasaki, None; Max
Villain, None; Jean Ribstein, None; Guilhem Du cailar, None; Albert Mimran,
None; Pierre Fesler, None
Support: None
Influence of Macular Choroidal Thickness on Visual Function in Highly
Myopic Eyes
Paola Giorno1, Mariacristina Parravano1, Francesco Oddone1, Andrea
Cacciamani1, Giulia Caminiti2, Enrico Peiretti2, Monica Varano1.
1
Ophthalmology, Fondazione GB Bietti-IRCCS, Rome, Italy; 2Odontostomatol &
Surgical Sci, University Eye Clinic of Cagliari, Cagliari, Italy.
Purpose: To explore the relationship between macular choroidal thickness (CT)
and scleral thickness (ST) with visual function in highly myopic eyes.
Methods: CT and ST were measured in highly myopic eyes (>6 diopters [D]) by
enhanced depth imaging optical coherence tomography (EDI-OCT) obtained by
Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany).
CT and ST were measured at 1000 µm interval on the horizontal section from 3
mm temporal to the fovea to 3 mm nasal to the fovea. In addition a complete
ophthalmological examination, visual acuity measurement and MP1
microperimetry (Nidek Technologies, Padova, Italy) were obtained. The
relationships between CT and ST and visual function were explored.
Results: twenty-four eyes from 15 highly myopic patients were included in the
analysis. The mean age was 50.5±9.63 years (range 40-60 years), the mean
refractive error was -13.2 (±5.5 D) and the mean axial lenght was 29.02±2.4 mm
and mean retinal sensitivity was 16.6±2.6 dB. The mean subfoveal CT and ST were
110.5±81µm and 235.21±81.3 µm respectively. No relationship was found between
CT and ST (R2<0.001, p=0.98), while a significant relationship was found between
CT and axial length (R2=0.35, p=0.0023) and MP1 mean retinal sensitivity (R2
=0.36, p=0.0017).
A strong relationship was found between mean retinal sensitivity and both axial
length (R2 =0.71, p<0.001) and refractive error (R2=0,60, p <0,001).
Conclusions: Retinal sensitivity, as measured by microperimetry, is related to
choroidal thickness which is related to axial length in highly myopic eyes.
Commercial Relationships: Paola Giorno, None; Mariacristina Parravano,
None; Francesco Oddone, None; Andrea Cacciamani, None; Giulia Caminiti,
None; Enrico Peiretti, None; Monica Varano, None
Support: None
Assess the Function and Health of Retina in vivo with Triple Wavelengths
Imaging Multispectral Reflectometry
Xiquan Cui, Scott Fraser. Biology, California Institute of Technology, Pasadena,
CA.
Purpose: Photoreceptor (PR) and retinal pigment epithelium (RPE) cells are
essential components of retina. Their dysfunction or loss causes various retinal
diseases or even blindness. Despite of their importance, until now there is no tool
that can provide adequate assessment to their function in an intact eye. We report a
functional retina imaging method - triple wavelengths imaging multispectral
reflectometry (TW-IMR) - to directly, quickly, quantitatively, and non-invasively
assay the health of retina.
Methods: Rhodopsin is a critical protein in PR cells. It absorbs light
(photobleaching) and converts photons into visual signals. Thus, decreasing density
of functional rhodopsin directly leads to the degradation of vision or even
blindness. In addition, in order for the photobleached rhodopsin to absorb new
photons and capture subsequent light images, it has to be regenerated by the 11-cisretinal molecules exclusively supplied by the RPE cells in vivo. Therefore, the
regeneration speed of rhodopsin allows assessing the health of RPE cells. By
probing retina with light of three wavelengths and solving three independent
equations, TW-IMR is able to achieve the clean measurement of rhodopsin without
the interference of transient metarhodopsin III and eye movement.
Results: We mapped the optical density and regeneration speed of rod rhodopsin in
wild-type (Sprague Dawley) and diseased (Royal College of Surgeons) rats with a
field-of-view of 30º and resolution of 0.1º. We found that the regeneration of
rhodopsin in the diseased rats is >100 fold slower than that of the wild-type rats
even when they are both as young as1 month old, which is consistent with the
congenital dysfunction of RPE cells in the diseased rats. We were also able to
follow the decreasing density of functional rhodopsin in the diseased rats till it
becomes undetectable. Our results coincide with the degeneration of PR cells in
these rats.
Conclusions: TW-IMR overcomes many challenges of in vivo functional retina
imaging and offers a simple, direct, fast, and robust means to assess the health of
retina. We anticipate that it will play an important role in the classification,
research, diagnosis, treatment, and patient management of retinal diseases (e.g.
AMD).
Commercial Relationships: Xiquan Cui, None; Scott Fraser, None
Support: CIRM DR1-01444, BIMR 68909445
Imaging Of Rod And Cone Photoreceptor Activities Using Functional Optical
Coherence Tomography (fOCT) In The Macaque Retina
Wataru Suzuki1,2, Gen Hazazono1,3, Tsuguo Nanjo4, Koichi Ito4, Junpei Nishiyama4,
Manabu Tanifuji1, Kazushige Tsunoda3,1. 1Lab. for Integrative Neural Systems,
RIKEN, Wako-shi, Japan; 2Dep. of Ultrastructual Res., National Institute of
Neuroscience, Tokyo, Japan; 3Lab. of Visual Physiology, National Institute of
Sensory Organs, Tokyo, Japan; 4Nidek Co., LTD, Aichi, Japan.
Purpose: OCT signals in the photoreceptor layers significantly change after
application of light stimulation to the posterior retina. Since these signal changes
are dependent on the stimulus intensity and observed only in the stimulated region,
OCT can be used to evaluate the stimulus-evoked retinal activities (fOCT). In this
study, we have measured fOCT signals by the stimuli with different wavelengths of
light from the macaque retina in order to map the photoreceptors responses
originating from cones and rods.
Methods: We have developed a fOCT system based on spectral domain OCT
(SLD, 840 nm; band width 50 nm; Galvano Scanning mirror, 30 Hz). Following
dark-adaptation, the fundus of the anesthetized macaque retina was continuously
illuminated with light from a halogen lamp filtered through a green (λmax = 500 ±
15 nm) filter for rods or a yellow (λmax = 590 ± 15 nm) filter for M/L cones. The
evoked signals were calculated by dividing the consecutive images for 16 seconds
by those obtained during the initial 0.5 second, pixel by pixel, after spatial
alignment of the images.
Results: Continuous light stimulation through either green or yellow filter
gradually decreased the OCT signals in the inner and outer segment (IS/OS)
junction of the photoreceptor layer (up to 50% during 16 seconds’ stimulation).
When the light through green filter was applied, the fOCT signals at the perimacular region (10 degrees temporal from the fovea) were twice more intense than
those at the fovea. On the other hand, when the light through yellow filter was
applied, the fOCT signals at the fovea were three times more intense than those at
the peri-macular region.
Conclusions: Light through green or yellow filter evoked fOCT signals in the
IS/OS junction of the photoreceptor layer, and the response distributions correlated
well with the distribution of rod or cone photoreceptors, respectively.
Commercial Relationships: Wataru Suzuki, None; Gen Hazazono, None;
Tsuguo Nanjo, Nidek Co., LTD (E); Koichi Ito, Nidek Co., LTD (E); Junpei
Nishiyama, Nidek Co., LTD (E); Manabu Tanifuji, None; Kazushige Tsunoda,
None
Support: SENTAN, JST
Variability of Vascular Oxygen Content in a Rabbit Retinal Vein Occlusion
Model: A Study Using Hyperspectral Computer Tomographic Imaging
Spectroscopy
Gilberto Raul Lopez Jaime1, Amir H. Kashani2, Saloomeh Saati1, Gerald J.
Chader3, Mark S. Humayun4. 1Ophthalmology, Doheny Eye Institute/University of
Southern California, Los Angeles, CA; 2Ophthalmology, Associated Retinal
Consultants, Royal Oak, MI; 3Keck Sch of Med USC, Doheny Retina Institute, Los
Angeles, CA; 4Ophthalmology, Doheny Eye Institute - USC, Los Angeles, CA.
Purpose: To study the variation in intravascular oxygen saturation during an acute
retinal vein occlusion (RVO) in rabbits using snapshot hyperspectral computed
tomographic spectroscopy.
Methods: Eleven rabbits (3-4kg) were dilated using 2.5% phenylephrine and 1%
tropicamide ophthalmic drops and subsequently anesthetized with ketamine (5080mg/kg) and xylazine (5-10mg/kg). Baseline retinal vascular oxygen
measurements (oximetry) were made using a custom-made hyperspectral computed
tomographic imaging spectrometer coupled to a fundus camera as previously
described (Kashani AH et al. (2011)PLoS ONE 6(9): e24482). RVO were induced
using multiple applications of argon green laser (Iridex Corp) to the vein following
an intravenous injection of Rose Bengal (40 mg/kg); as described in (Ameri H et
al.Graefes Arch. Clin. Exp. Ophthalmol. 2008; 246(10):1429-1439). RVO
induction was confirmed after one hour by fluorescein angiography. Retinal
oximetry measurements were repeated in selected arterial and venous branches one
hour after RVO induction to evaluate changes in retinal vascular oxygen content.
Comparison of oximetry before and after RVO was done with the Student T-test.
Results: One hour after RVO induction, we observed statistically significant
reductions in the intravascular oxygen saturation in temporal retinal arteries
(85.1±6.5% vs. 80.5±6.9%, p<0.0001) and veins (72.4±4.5% vs. 64.2±4.3%,
p<0.0001), respectively. There were no statistically significant differences in
oxygen saturation measurements in the nasal control arteries and veins before and
after temporal vein RVO induction, respectively (Arteries: 85.4±1.0% vs.
84.3±0.5%, p=0.37; Veins: 71.6±0.5% vs. 71.7±6.3%, p=0.87).
Conclusions: Using an animal model of acute RVO, we demonstrate acute changes
in the intravascular oxygen content of arteries and veins within 1 hour of RVO
induction. This study demonstrates that our snapshot hyperspectral computer
tomographic spectroscopy system can detect significant variations in intravascular
retinal oxygen saturation after an acute vein occlusion. Further investigation of
retinal vascular disease models and human vein occlusions may provide useful and
novel information in the evaluation and management of ischemic retinal diseases.
Commercial Relationships: Gilberto Raul Lopez Jaime, Reichert Technologies
Inc. (F); Amir H. Kashani, Reichert Technologies Inc. (F, P); Saloomeh Saati,
Reichert Technologies Inc. (F); Gerald J. Chader, Reichert Technologies Inc. (F);
Mark S. Humayun, Reichert Technologies Inc. (F, P)
Support: None
Dual-Wavelength Photothermal OCT for Depth-Resolved Measurement of
Microvascular Hemoglobin Oxygen Saturation (SaO2)
Roman V. Kuranov1, Jeffrey Kiel1, Shams Kazmi2, Austin McElroy2, Andrew K.
Dunn2, Thomas E. Milner2, Timothy Q. Duong3. 1Ophthalmology, UTHSCSA, San
Antonio, TX; 2BME, UT Austin, Austin, TX; 3Research Imaging Inst/Ophthal, UT
Health Science Ctr San Antonio, San Antonio, TX.
Purpose: Objective of this study was to estimate depth resolution of DualWavelength Photothermal Optical Coherence Tomography (DWP-OCT) for
measuring hemoglobin oxygenation saturation (SaO2) in a murine brain model.
Methods: DWP-OCT was used to measure photothermal-induced optical
pathlength (op) variations versus depth in murine brain in vivo. The DWP-OCT
probe was directed at a 30 µm diameter arteriole under guidance of a surgical
microscope. Blood in the arteriole in vivo was excited with intensity-modulated
light at 770 nm and 800 nm. Ratio of op changes at the back of the arteriole wall
normalized by fluence of photothermal excitation light can be used to compute invivo SaO2 levels. We investigated depth resolution provided by DWP-OCT for
measuring in vivo SaO2 levels.
Results: DWP-OCT depth resolution can be estimated from depth-resolved op
measurements in tissue containing a single arteriole. Amplitude of op variation per
mW of photothermal excitation light (800 nm) with depth (orange) and its
approximation (blue) are shown in Fig. 1. We approximate depth dependence of op
by assuming spatial variation of temperature increase is Guassian so that op varies
as an error function: op ∝ Erf(a[z-z0]), where z0 = 568 µm is the center of
absorption (arteriole) and a = 0.031 µm-1 is inversely proportional to the effective
longitudinal size of the temperature increase. The longitudinal full width at half
maximum (FWHM) of the temperature increase z*= 2(ln2)^0.5/a = 45 µm gives
DWP-OCT depth resolution to measure SaO2 levels.
Conclusions: This study provides a numerical estimate of depth resolution of
DWP-OCT to measure SaO2 levels. DWP-OCT may be useful in layer-specific
quantification of abnormal tissue oxygenation in several retinal disorders such as
diabetic retinopathy.
Commercial Relationships: Roman V. Kuranov, Carl Zeiss Meditec (F),
provisional № 61/418,300 (P); Jeffrey Kiel, None; Shams Kazmi, None; Austin
McElroy, None; Andrew K. Dunn, None; Thomas E. Milner, provisional №
61/418,300 (P); Timothy Q. Duong, provisional № 61/418,300 (P)
Support: NIH Grant UL1 RR025767 (KL2 and Pilot)
Determinants Of Retinal Oxygen Saturation In Healthy Subjects
Alok K. Sahgal, Jean-Claude Mwanza, Sarah Moyer, Bruce Baldwin, Kathleen
Gordon, Seema Garg. Ophthalmology, University of North Carolina, Chapel Hill,
NC.
Purpose: Retinal oximetry is a novel imaging modality that non-invasively
measures retinal oxygen saturation. As an emerging technology, little is known
about normal oxygen measurements in healthy adults. In this study, we have
evaluated a cohort of healthy individuals to obtain normative values and determine
which factors influence retinal oxygen saturation (SO2).
Methods: Both eyes of 60 healthy subjects from European, African, Hispanic and
Asian descent underwent retinal oximetry (Oxymap, Reykjavik, Iceland) and color
fundus photography (Carl Zeiss, Dublin, CA). The SO2 values in retinal arterioles
(SaO2) and venules (SvO2) were measured in four retinal quadrants:
superotemporal, inferotemporal, superonasal, and inferonasal (the optic nerve was
used as the center of the retina). The global SO2 was defined as the average of the
four quadrant measurements in either arterioles or venules. The correlation between
SO2 and age was assessed using simple linear regression. Multivariate regression
analysis was performed to determine the association between global SO2 and
ethnicity, iris color, age, gender, eye laterality, refraction, history of smoking and
arterial hypertension. Only one eye randomly selected per patient was included in
the analysis.
Results: There were 15 subjects from each ethnic group. The average age was
41.8±14.1 years. The average global SaO2 was 93.4±3.0% and global SvO2 was
64.3±4.6%. Global SO2 did not differ between ethnic groups in either arterioles (p
= 0.72) or venules (p = 0.38). Statistically significant differences in SaO2 and SvO2
were observed between quadrants (both p < 0.001). Linear regression analysis
indicated that SO2 decreases with increasing age, but this effect was significant
only in subjects older than 50 years for SaO2 (R2 = 0.37, p = 0.004) and SvO2 (R2 =
0.58 , p < 0.001). In multivariate regression analysis, history of systemic
hypertension was the only significant determinant of both global SaO2 (β = -1.19, p
= 0.027) and global SvO2 (β = -2.37, p = 0.004) and quadrant SaO2 (β = -1.30 to 1.97, all p <0.01) and quadrant SvO2 (β = -2.27 to -3.34, all p < 0.01).
Conclusions: As a first step in evaluating this emerging technology, we have
established a preliminary, multi-ethnic normative database in retinal oximetry. We
observed significant variation in SO2 among retinal quadrants. Although older
people had lower SO2, history of systemic hypertension was the only significant
independent predictor of SO2. These factors should be taken into account when
translating retinal oximetry measurements into a clinically meaningful
interpretation. Future studies will build on these normal values from which to
compare retinal oximetry measurements in disease states.
Commercial Relationships: Alok K. Sahgal, None; Jean-Claude Mwanza,
None; Sarah Moyer, None; Bruce Baldwin, None; Kathleen Gordon,
None; Seema Garg, None
Support: Research To Prevent Blindness
Oxygen Saturation within Retinal Vessels Pre- and Post-Intravitreal Injection
with Bevacizumab using the Oxymap Retinal Oximeter
Lauren R. Schneider1, Nicole Scripsema2, Chavakij Bhoomibunchoo1, Richard
Rosen1. 1Ophthalmology, New York Eye and Ear Infirmary, New York, NY;
2
Ophthalmology, New York Medical College, New York, NY.
Purpose: To determine the effect of intravitreal bevacizumab on oxygen saturation
within primary and secondary retinal vessels.
Methods: Retrospective review. The Oxymap T1, an investigational device, was
used to quantitatively measure oxygenation in retinal vessels pre-injection and one
to two weeks post-injection of intravitreal bevacizumab. Blood changes its color
and optical density due to its level of oxygenated hemoglobin. The Oxymap
Analyzer captures two simultaneous images at 570nm (oxygen insensitive) and
600nm (oxygen sensitive). The ratio of these two opitcal densities at points along a
vessel is linearly related to its oxygen saturation. The software superimposes a
colored oxygenation map on all 50° images. Vessel segments can be selected for
detailed numerical analyses. All primary and secondary vessels were selected to
generate the mean arterial and venous oxygen saturation, respectively.
Results: This study included 13 eyes of 13 patients receiving intravitreal
bevacizumab for macular edema. Pre-injection vessel oxygenation was compared
directly to post-injection oxygenation. The mean age was 59.92 ± 12.41 years, 61.5
% were male, 53.8% were diabetic, 76.9% were hypertensive, and 7.7% had
glaucoma. Mean pre-injection arterial and venous blood oxygenation in primary
and secondary vessels was 102.19% ± 4.84% and 65.56% ± 7.22%, respectively,
and mean post-injection arterial and venous blood oxygenation was 100.99% ±
4.84% and 64.78% ± 10.47%, respectively. Paired t-tests did not reveal a
statistically significant difference between pre- and post-injection oxygenation (p =
0.697 for arterial oxygenation; p = 0.307 for venous oxygenation).
Conclusions: Based on the Oxymap data, intravitreal bevacizumab does not appear
to adversely affect retinal arterial or venous oxygenation in primary and secondary
vessels in patients receiving this treatment for macular edema.
Commercial Relationships: Lauren R. Schneider, None; Nicole Scripsema,
None; Chavakij Bhoomibunchoo, None; Richard Rosen, OPKO-OTI/Optos,
OD-OS Clarity, Topcon Medical Systems Inc. (C)
Support: None
Retinal Oxygen Saturation during Hyperoxia in Healthy Individuals
Olof B. Olafsdottir1, Thorunn S. Eliasdottir1, Jona V. Kristjansdottir2,3, Sveinn H.
Hardarson1,3, Einar Stefánsson2,3. 1Ophthalmology, University of Iceland,
Reykjavik, Iceland; 2Ophthalmology, Landspitali University Hospital, Reykjavik,
Iceland; 3Oxymap ehf., Reykjavik, Iceland.
Purpose:
To detect whether hyperoxia affects oxygen saturation in retinal arterioles and
venules in healthy individuals. To test the sensitivity of a retinal oximeter.
Methods: Retinal vessel oxygen saturation was measured in 31 healthy individuals
with a spectrophotometric retinal oximeter (Oxymap ehf., Reykjavik, Iceland).
Oximetry was performed during breathing of room air, during breathing of 100%
O2 (10 minutes, 6L/min) and then again during breathing of room air (10 minutes
recovery). Statistical analysis was performed with Student’s t-test for paired
measurements.
Results: The table shows that the mean retinal vessel O2 saturation in both
arterioles and venules was significantly higher during hyperoxia compared to
normoxia. During hyperoxia the mean vessel diameter was significantly smaller. Pvalues are for comparison of baseline normoxia and hyperoxia.
The figure shows retinal O2 saturation during normoxia and hyperoxia in arterioles
and venules.
Conclusions: The retinal oximeter measures stable baselines and is sensitive to
changes in O2 saturation and vessel diameter. Breathing 100% O2 increases oxygen
saturation in retinal arterioles and venules and constricts them compared to
normoxic levels.
Commercial Relationships: Olof B. Olafsdottir, None; Thorunn S. Eliasdottir,
None; Jona V. Kristjansdottir, Oxymap ehf. (E); Sveinn H. Hardarson, Oxymap
ehf. (I, E, P); Einar Stefánsson, Oxymap ehf. (I, P, S)
Support: Icelandic Research Council, Landspitali - University Hospital Research
Fund
Variation in Retinal Vascular Oxygen Content Among Human Patients: A
Study Using Computed Tomographic Imaging Spectroscopy
Amir H. Kashani1, Gilberto Raul Lopez Jaime2, Saloomeh Saati2, Gerald J.
Chader3, Rohit Varma4, Mark S. Humayun5. 1Ophthalmology, Associated Retinal
Consultants, Royal Oak, MI; 2Ophthalmology, Doheny Eye Institute, University of
Southern California, CA; 3Keck Sch of Med USC, Doheny Retina Institute, Los
Angeles, CA; 4Ophthalmology, USC, Doheny Eye Institute, Los Angeles, CA;
5
Ophthalmology, Doheny Eye Institute - USC, Los Angeles, CA.
Purpose: To study the variation in human intravascular retinal oxygen saturation in
normal and disease states using snapshot hyperspectral computed tomographic
spectroscopy (HCTIS).
Methods: Sixty-five human subjects were dilated using 2.5% phenylephrine and
1% tropicamide ophthalmic drops for standard fundus photography. Fundus
photographs and retinal vascular oxygen measurements (oximetry) were made
using a custom made HCTIS coupled to a standard fundus camera as previously
described (Kashani AH et al., PLoS One, 2011). Oximetry measurements were
made along arteries and veins adjacent to the optic disc to evaluate retinal vascular
oxygen content. All comparisons were made using the Student T-test. All
procedures were performed under an IRB approved protocol and with informed
consent.
Results: The study population consisted of 45 controls, 10 glaucomatous, and 10
diabetic subjects (Age range 35-85; 30% male). Controls were limited to subjects
with refractive error less than +/-4D and/or mild-moderate cataracts. In control
subjects, mean arterial and venous oxygen saturation was 93±7% and 65±6% (p
less than 0.001) respectively. In diabetic subjects mean arterial and venous
saturation was 91±6% and 68±5% (p less than 0.001) respectively. In glaucomatous
subjects, mean arterial and venous saturation was 93±6% and 66±3% (p less than
0.001) respectively. Within the diabetic group, there was a significant decrease in
the arteriovenous difference from 27±6% in diabetics with nonproliferative disease
to 14±4% in diabetics with proliferative diabetic retinopathy (p=0.003). There was
no statistically significant difference in arterial or venous oxygen saturation
between control males and females (p greater than 0.1) or between controls age less
than 60 years and those greater than or equal to 60 (p greater than 0.1).
Conclusions: This study utilizes a novel technique (HCTIS) to demonstrate
variations in intravascular oxygen content among normal and diseased subjects.
Although the study size is small, these data confirm previous findings of decreased
arteriovenous difference in diabetic patients and provide useful normative data for
future studies. Further investigation with HCTIS may provide novel diagnostic
information in the evaluation and management of ischemic retinal diseases.
Commercial Relationships: Amir H. Kashani, Reichert Technologies Inc (F),
Reichert Technologies Inc. (P); Gilberto Raul Lopez Jaime, Reichert
Technologies Inc. (F); Saloomeh Saati, Reichert Technologies Inc (F); Gerald J.
Chader, Reichert Technologies Inc (F); Rohit Varma, Reichert Technologies Inc.
(F); Mark S. Humayun, Reichert Technologies Inc (F, P)
Support: None
Retinal Oxygen Extraction Fraction: the Ratio of Oxygen Consumption to
Delivery
Pang-yu Teng, Justin Wanek, Norman P. Blair, Mahnaz Shahidi. Ophthalmology &
Visual Sciences, University of Illinois at Chicago, Chicago, IL.
Purpose: Oxygen extraction fraction (OEF) is the fraction of oxygen removed by
the tissue from blood. By Fick’s principle, OEF equals the ratio of oxygen
consumption to delivery. In the brain, increased OEF has been associated with
cerebral ischemia and is considered a predictor of stroke. To our knowledge, OEF
has not been previously measured in the retinal tissue. The purpose of this study is
to report a method for quantitative measurement of retinal OEF in rat, and compare
retinal OEF under systemic normoxic and hypoxic conditions.
Methods: Retinal vascular oxygen tension (PO2) was measured using our
established optical section phosphorescence lifetime imaging system in 10 rats
ventilated with 21% (normoxia) and 10% (hypoxia) oxygen. Systemic arterial
blood gas tensions (PaO2, PaCO2), pH, hemoglobin concentration, mean blood
pressure (BP) and heart rate (HR) were obtained prior to imaging. Retinal vascular
PO2 measurements were converted to O2 contents. OEF was quantified in a retinal
sector, a zone bounded by 2 major arteries with a major vein between them, in
areas temporal and nasal to the optic disc. In each sector, retinal OEF was
calculated as (m[O2]A - [O2]V)/m[O2]A, where m[O2]A was the mean arterial O2
content of 2 major arteries and [O2]v was the venous O2 content. Paired Student’s ttest was used for comparative statistical analysis. Statistical significance was
accepted at p < 0.05.
Results: During normoxia, PaO2, PaCO2, pH, BP and HR were 93 ± 8 mmHg, 40 ±
5 mmHg, 7.38 ± 0.05, 113 ± 17 mmHg and 214 ± 36 beats/min, respectively (mean
± SD; N = 10). During hypoxia, PaO2, PaCO2, pH, BP and HR were 34 ± 4 mmHg,
41 ± 5 mmHg, 7.31 ± 0.05, 78 ± 22 mmHg and 162 ± 45 beats/min, respectively.
PaO2, pH, BP and HR under normoxia and hypoxia were significantly different (p ≤
0.002; N = 10). Under both normoxia and hypoxia, retinal OEF measurements
obtained in nasal and temporal areas were similar (p ≥ 0.18; N = 10). Retinal OEF
under hypoxia (0.71 ± 0.17) was significantly higher than under normoxia (0.46 ±
0.13) (p < 0.001; N =10).
Conclusions: Quantitative measurement of retinal OEF was reported for the first
time, demonstrating an increase in the fraction of oxygen extracted by retinal tissue
during hypoxia. Retinal OEF can indicate compromised oxygen delivery and may
become valuable for assessing retinal viability and ischemic injury.
Commercial Relationships: Pang-yu Teng, None; Justin Wanek,
None; Norman P. Blair, None; Mahnaz Shahidi, None
Support: NIH grants R01 EY17918, P30 EY01792, and Research to Prevent
Blindness
Retinal Oxygen Saturation In Eyes Treated With Plaque Radiotherapy
Emil Anthony T. Say, Alok K. Sahgal, Travis A. Meredith. Dept of Ophthalmology,
University of North Carolina, Chapel Hill, NC.
Purpose: To measure and compare retinal oxygen saturation (O2Sat) in eyes
treated using plaque radiotherapy with that of the fellow eye.
Methods: Eight patients with choroidal melanoma in one eye treated with plaque
radiotherapy were included in the study. O2Sat was determined using the Oxymap
(Reykjavik, Iceland) in both the treated eye and the fellow untreated eye. Arteriole
and venule O2Sat from the superotemporal, superonasal, inferotemporal, and
inferonasal quadrants of the treated eyes were compared to the corresponding
quadrants of the fellow eyes. In addition, O2Sat of the irradiated retinal
hemispheres were also compared to the opposite hemispheres of the same eye.
Comparative analysis was performed using paired t-test.
Results: Mean age at the time of O2Sat measurement was 61 years (Range 40-82)
and there were five females. Three patients were hypertensive, none were diabetic,
and one had glaucoma. Mean interval from plaque application to measurement of
O2Sat was 40 months (Range 2-88). All but one patient had radiation-related
complications following plaque radiotherapy, and four had received intravitreal
Bevacizumab prior to O2Sat measurement. The mean arteriole O2Sat in treated and
fellow eyes was 91.3±9.2% and 90.3±11.6%, while mean venule O2Sat was
67.1±11.2% and 65.9±5.4% respectively. The differences in arteriole (p = 0.19) and
venule (p = 0.61) O2Sat between treated and fellow eyes were not significant. Mean
arteriole O2Sat in the irradiated and opposite hemisphere was 97.0±6.5% and
95.6±5.9%, while mean venule O2Sat was 68.2±6.8% and 66.2±8.3% respectively.
There was also no significant difference in arteriole (p = 0.45) and venule (p =
0.28) O2Sat between the irradiated and opposite hemisphere of the treated eyes.
Conclusions: Although there appears to be a trend towards an increase of retinal
oxygenation in arterioles and venules of eyes receiving plaque radiotherapy
compared to their fellow eyes, as well as within the irradiated compared to the
opposite hemisphere of the treated eye, this difference did not reach statistical
significance.
Commercial Relationships: Emil Anthony T. Say, None; Alok K. Sahgal,
None; Travis A. Meredith, None
Support: None
Relative Retinal Vessel Oxygen Saturation In Diabetic Patients
Anu S. Patel, Nicole Scripsema, Chavakij Bhoomibunchoo, Richard B. Rosen.
Ophthalmology, New York Eye & Ear Infirmary, New York, NY.
Purpose: The purpose of this study was to evaluate differences in relative retinal
vessel oxygen saturation between patients with proliferative diabetes and controls.
Methods: Oxygen saturations were obtained using the Oxymap Retinal Oximeter
(Oxymap eph, Iceland) and Oxymap Analyzer Software. The system employs two
different wavelengths of light at each point along the primary branches of the
central retinal artery and central retinal vein to calculate the relative difference in
oxygen saturation. Diabetic and control patients were selected randomly following
complete ophthalmic evaluation. All diabetic patients demonstrated proliferative
diabetic retinopathy (PDR). Both eyes were analyzed whenever possible; however,
only one eye was randomly included in the analysis.
Results: 28 PDR patients and 18 control patients were selected. 17/28 patients
were female compared to 8/18 control patients (p=0.28). 4/28 diabetic patients were
Caucasian, 12/28 were Hispanic, and 7/28 were African American. Of the control
patients, 4/18 were Caucasian, 3/18 were Hispanic, and 3/18 were African
American. Baseline arterial oxygen saturation was lower in control patients
compared to diabetics (94.56% vs 105.11% (p<.001). Baseline venous oxygen
saturation was also lower in control eyes compared to diabetic eyes (62.0% vs
70.86%, p<.001). Total oxygen saturation was similar in control and diabetic
patients (32.56% vs 34.25%, p=.51). PDR patients were then sub-classified based
on history of panretinal photocoagulation(PRP). 20/28 patients had previous PRP.
Baseline arterial oxygen saturation was higher in eyes with PRP than those without
PRP (108.20% vs 98.00%, p=.037). When compared with controls, there was a
more significant difference between PRP and control eyes than non-PRP eyes and
control eyes (p<.001 vs p=.149). Baseline venous oxygen saturation, however, was
similar in both PRP eyes and non-PRP eyes (71.10% vs 69.29%, p=.602). When
compared with controls, there was a more significant difference between PRP and
control eyes than non-PRP eyes and control eyes (p<.001 versus p=.044).j Oxygen
extraction was higher in PRP eyes than non-PRP eyes (37.10% vs 28.71%, p=.015).
Conclusions: There is an increase in baseline arterial and subsequent venous
oxygen saturation in primary branches of the central retinal artery and vein in
patients with PDR compared to controls, most likely due to decreased perfusion of
capillary beds in diabetic patients. Further studies are warranted to evaluate the
possible diagnostic and therapeutic role of Oxymap analysis.
Commercial Relationships: Anu S. Patel, None; Nicole Scripsema,
None; Chavakij Bhoomibunchoo, None; Richard B. Rosen, OD-OS Clarity (C),
OPKO-OTI/Optos (C), Topcon Medical Systems, Inc (C)
Support: Bendheim-Lowenstein Retina Fund of the New York Eye and Ear
Infirmary
Measurements of Oxygen Saturation in Cat Retina Using a Near Infrared
Snapshot HYperspectral Imaging Fundus Camera
Makoto Saika1,2A, Yoko Hirohara1,2A, Toshifumi Mihashi1,2A, Hiroyuki Kanda2A,
Tomomitsu Miyoshi2B, Takashi Fujikado2A. 1Optics Lab, Topcon Corp, Itabashi,
Japan; ADept of Applied Vis Science, BIntegrative Physiology, 2Osaka Univ
Medical School, Suita, Japan.
Purpose: To measure oxygen saturation changes in retinal vessel noninvasively for
early diagnosis of retinal vascular diseases using near infrared snapshot
hyperspectral imaging fundus camera.
Methods: Six cats under general anesthesia were used as an acute ischemiareperfusion model. Retinal arterial oxygen saturation (SpO2) was varied by
changing the ratio of oxygen and nitrogen gasses while a pulse oximeter placed on
the tongue monitored SpO2. Retinal images over the range 700-900 nm were
obtained by a fundus camera attached with the snapshot system (Saika M, 2011
ARVO). Ninty-two×92 spatial images with 10 nm spectral-sampling were
reconstructed by the MART algorithm. To estimate oxygen saturation, a
multivariate regression model based on a modified Lambert-Beer law (Cohen AJ,
1976 IEEE) was used. The signal intensities from the hyperspectral images within
the central area of artery and retinal area without vessels were used to calculate the
oxygen saturation.
Results: The correlation between the SpO2 and the hyperspectral measurements
was shown in Fig.1 (R2=0.37, p<0.01). The retinal image of a cat and the maps of
snapshot hyperspectral oxygen saturation changes in retina at various SpO2
conditions were shown in Fig.2. The oxygen saturations in arteries were higher
than those in the veins. In this model, the oxygen saturation maps were not
correctly evaluated in area in that vessel diameter varied but the vessel diameter
was assumed to be a constant.
Conclusions: Retinal oxygen saturation measured by a near infrared snapshot
hyperspectral imaging fundus camera correlated significantly with that by pulse
oximeter. The results suggest that the oxygen saturation maps in retinal vessels are
able to be obtained by this method if the diameters of vessels are properly
calibrated.
Commercial Relationships: Makoto Saika, Topcon (E); Yoko Hirohara,
Topcon (E); Toshifumi Mihashi, Topcon (E); Hiroyuki Kanda,
None; Tomomitsu Miyoshi, None; Takashi Fujikado, None
Support: None
Retinal Vessel Oxygen Saturation In Healthy Individuals
Thorunn S. Eliasdottir1, Asbjorg Geirsdottir1, Olafur Palsson1, Sveinn H.
Hardarson1,2, Olof B. Olafsdottir1, Jona V. Kristjansdottir1,2, Einar Stefánsson1.
1
Ophthalmology, University of Iceland / Landspitali University Hospital,
Reykjavik, Iceland; 2Oxymap ehf., Reykjavik, Iceland.
Purpose: To determine the effects of age and gender on oxygen saturation in
retinal vessels of healthy eyes.
Methods: The non-invasive retinal oximeter is based on a fundus camera (Oxymap
ehf., Reykjavik Iceland). It simultaneously captures images of the retina at 600 and
570nm and estimates retinal vessel oxygen saturation. Mean oxygen saturation of
hemoglobin was measured in retinal arterioles and venules of 111 healthy
individuals, aged 19 - 75 years. Of the 111 participants, 42 (38%) were males
(49±15 years, mean±SD) and 69 (62%) females (43±15 years).
Results: The figure illustrates the relationship between retinal vessel oxygen
saturation for males and females. The combined mean arteriolar oxygen saturation
for both groups is 93.1±3.4% and 55.6±5.7 in venules.
Conclusions: Venular oxygen saturation decreases by approximately 1.5% for
every ten years of age in males and 0.8% in females. There is no change in
arteriolar oxygen saturation with age. The study provides normative data for retinal
oximetry.
Commercial Relationships: Thorunn S. Eliasdottir, None; Asbjorg
Geirsdottir, None; Olafur Palsson, None; Sveinn H. Hardarson, Oxymap ehf. (I,
P); Olof B. Olafsdottir, None; Jona V. Kristjansdottir, Oxymap ehf. (E); Einar
Stefánsson, Oxymap ehf. (I, P, S)
Support: Icelandic Center for Research (Rannís), University of Iceland Research
Fund and Landspitali-University Hospital Research Fund.
Patterns Of Oxygen Saturation In Retinal Vein Occlusions As Measured With
Oxymap
Richard B. Rosen, Nicole Scripsema, Chavaki Bhoomibunchoo. Ophthalmology,
New York Eye & Ear Infirmary, New York, NY.
Purpose: To determine how oxygen saturation is altered in the setting of retinal
vein occlusions.
Methods: This was a retrospective review of patients being treated for RVO who
were imaged with Oxymap (Oxymap EPH, Reykjavik, Iceland). Exclusion criteria
included previous ocular surgeries and concurrent ocular conditions. Images were
excluded when the presence of heme obscured the identification of the primary and
secondary retinal vessels. Oxymap uses uses two wavelength differential analysis
(600 and 570nm) of images captured simultaneously to determine relative retinal
vessel oxygenation. For each patient imaged, fluorescein angiographies were
referenced to determine the precise area of occlusion and mean arterial and venous
oxygenation of this region was measured. The same values were computed in the
corresponding region of the normal eye. In BRVO and HRVO patients, the area of
occlusion identified as within the superior or inferior arcade. Mean oxygen
saturation in the unaffected arcade was also analyzed. We used paired t-tests to
compare mean oxygen saturation in affected and unaffected vessels in normal and
diseased eyes.
Results: 7 patients were included in the analysis. All of the patients were male.
There were 2 CRVOs, 3 BRVOs, and 2 HRVOs. Mean age was 56.86±10.32 years.
43% were Hispanic, 29% Asian, 14% African American and 14% Caucasian.
Imaging was complete an average of 4.71±3.80 months after the occlusion, with a
range from 2 weeks to 10 months.
Mean arterial oxygen saturation were significantly higher in the affected region of
the diseased eye (107.43±7.89%) compared to the corresponding region in the
normal eye (98.29±2.21%, p=0.016). Mean venous oxygen saturation was
significantly lower in the affected region (55.00±13.64%) versus the normal eye
(68.29±3.55%,p= 0.047). In the BRVO and HRVO patients, the arterial O2 sat in
the unaffected vessels of the occluded eye was similar to that of the normal eye
(100.20±2.86% and 99.20±1.79%, p=0.486). Mean venous O2 Sat in the unaffected
vessels of the occluded eye (75.40±6.02%) was significantly higher than both
normal eyes (68.40±3.78, p=0.008) and the area of occlusion (61.60±6.58%,
p=0.014).
Conclusions: We found a significant increase in arterial oxygen saturation and a
decrease in venous oxygen saturation in the region of retinal vein occlusions,
consistent with prior reports. In the case of branched and hemi-spheric retinal vein
occlusions, the venous saturation was higher in the unaffected region of the
occluded eye. It is possible that this is a result of compensatory mechanisms
attempting to maintain perfusion of the occluded region. We also noted that
independent of the time imaged after the occlusion, all patients demonstrated a
similar pattern of oxygen saturation.
Commercial Relationships: Richard B. Rosen, Clarity (C), OD-OS (C), OpkoOTI-Optos (C); Nicole Scripsema, None; Chavaki Bhoomibunchoo, None
Support: Bendheim-Lowenstein Retina Research Fund of the New York Eye and
Ear Infirmary Retina Center
Rebekka Heitmar, Robert J. Summers. Optometry and Vision Sciences, Aston
University, Birmingham, United Kingdom.
Purpose: To evaluate the influence of the duration of flicker-light provocation on
retinal vessel dilation.
Methods: Twelve healthy individuals (mean age 32 +/-7 yrs) underwent
continuous retinal vessel diameter measurement of both arterioles and venules
using the DVA (Dynamic Retinal Vessel Analyser; Imedos Systems, Germany).
Each subject underwent four measurement protocols, in a random order,
comprising 50s baseline measurement followed by 3 cycles each of 5, 7, 10 or 20s
flicker-light stimulation and 80s recovery (total duration: 305-350s).
Results: A stepwise forward regression analysis revealed no influence of age,
vessel diameter, blood or intra ocular pressure on retinal arteriolar or venular
dilation due to flicker provocation. Retinal vessel diameter changes (maximum
dilation, maximum constriction and dilation amplitude) due to flicker-light
provocation were independent of flicker duration for arteries (F(3,43)=0.7,
p=0.571) and veins (F(3,43)=2.5, p=0.075).
Conclusions: Shorter stimulation protocols may be sufficient to evaluate vessel
function. In addition, shorter protocols are also more suitable for those with
fixation problems.
Commercial Relationships: Rebekka Heitmar, None; Robert J. Summers,
None
Support: None
Blood Vessel Density and Distribution in Fundus Images
Attila Budai1,2A, Joachim Hornegger1,2A, Georg Michelson2B,2A. 1Pattern
Recognition Lab, University of Erlangen-Nuremberg, Erlangen, Germany;
A
Erlangen Graduate School in Advanced Optical Technologies (SAOT),
B
Department of Ophthalmology, 2University of Erlangen Nuremberg, Erlangen,
Germany.
Purpose: Our goal is to analyze and visualize the distribution of blood vessels in
fundus images to support the medical diagnosis by providing quantitative
measurements.
Methods: 15 color fundus images of healthy subjects and 15 images of diabetic
retinopathy (DR) patients are acquired by a CANON CF-60UVi camera
(3504x2336 pixels). Two set of segmentation results are used for evaluation:
manual segmentation by experts and results of an automatic segmentation method
developed by the authors. Both the input and the manual segmentation are available
online for research purposes (http://www5.informatik.unierlangen.de/research/data/fundus-images/). Using the binary vessel images vessel
density and distance maps are generated. Afterwards the vessel thicknesses are
calculated. The vessel density image is generated by counting the number of vessel
pixels in a large neighborhood (radius is 100 pixels). The distance map image
encodes distance to the closest vessel. These images support the localization of
regions with decreased blood supply. Histograms are generated to show the
distribution of the densities, distances and diameters. The statistical moments of
these histograms are used in an AdaBoost classifier to discriminate between healthy
and DR subjects. 10-fold cross-validation is used to evaluate the classification.
Results: The accuracy of the classification using the manual segmentations is
93.3%. The area under the ROC curve (AUC) is 0.953. The accuracy for our
segmentation method is 80.0% and AUC is 0.931. The figure shows an input image
with manually segmented vessels, corresponding density and distance maps and a
graph showing the average distribution of vessel densities in both groups.
Conclusions: We provide methods to analyze and visualize the distribution of
vascular tree of the human eye, and a novel classification method to distinguish
To Evaluate The Influence Of The Duration Of Flicker Light Provocation On
Retinal Vessel Dilation
between DR and healthy subjects using vessel tree based features only.
detection.
Commercial Relationships: Attila Budai, None; Joachim Hornegger,
None; Georg Michelson, None
Support: Erlangen Graduate School in Advanced Optical Technologies (SAOT)
Commercial Relationships: Jason M. Tokayer, None; Ou Tan, Optovue Inc.
(F); David Huang, Carl Zeiss Meditec Inc. (P), Optovue Inc. (F, I, C, R)
Support: NIH R01 EY013516
Flow Quantification in Small Macular Vessels via Frame Averaging with
Doppler Optical Coherence Tomography
Jason M. Tokayer1, Ou Tan2, David Huang2. 1Ming Hsieh Department of Electrical
Engineering, University of Southern California, Los Angeles, CA; 2Casey Eye
Institute, Oregon Health and Science University, Portand, OR.
Purpose: To measure flow in small macular vessels using Doppler Fourier-domain
optical coherence tomography (FD-OCT).
Methods: Normal eyes were scanned using the RTVue FD-OCT system (Optovue,
Inc. Fremont, CA). A double circle scanning protocol (DCSP) centered at the fovea
was used with diameters 1.9 mm and 2.2 mm, respectively. Blood vessel imprints
in the ganglion cell layer are enhanced after high-pass filtering each complex OCT
frame and axial summation of the intensity in this layer enables identification of the
transverse positions of the vessels. Vessels in each frame are matched to nearby
vessels in the other frames with the same circle diameter. The vessels are then
aligned using a non-linear least squares registration algorithm that exploits the
circular nature of the scans. Frame registration enables averaging of the Doppler
frequency shifts which are computed using the phase-resolved (PR) algorithm. The
PR algorithm is used here because high-pass filtering has been shown to distort
velocity estimates. Doppler angles are calculated by matching vessels on the
averaged images of each ring. Vessel diameters and flow are then computed.
Results: The PR method generally fails to illustrate a clear image for small macular
vessels due both to small Doppler phase shifts as well as near-perpendicular
incidence. Frame averaging helps to alleviate this problem by significantly
reducing phase noise (see attached image). Using the frame averaged Doppler
images we compute flow in the three small vessels in the image. The vessel
diameters are 47.7, 48.1 and 34.7 microns, respectively, and the respective flow
rates are -0.83, 0.31 and -0.65 microliters per minute.
Conclusions: Frame averaging can be used to quantify small retinal vessels in the
macula by reducing the phase noise floor. This may provide a method for
calculating total macular blood flow if it can be extended with automatic vessel
OCT Based Retinal Vessel Analysis For The Evaluation Of Hypertonic
Vasculopathy
Alexander K. Schuster1, Joachim E. Fischer1, Urs Vossmerbaeumer1,2. 1Mannheim
Institute for Public Health, University of Heidelberg, Universitätsmedizin
Mannheim, Germany; 2Department of Ophthalmology, Mainz University Hospital,
Germany.
Purpose: Evaluation of retinal vessels in cardiovascular disease traditionally relies
upon funduscopy, more recently digital photo analysis has expanded the spectrum.
As spectral domain optical coherence tomography allows an in-vivo assessment of
retinal tissue and its vessels on a histological scale our study aimed at using this
tool for the analysis of the retinal vasculature.
Methods: Circumferential peripapillar OCT scans (3D OCT 2000, Topcon Inc.)
and simultaneous digital non-mydriatic 45° fundus photos with centration on the
optic nerve head and were taken from 20 eyes (10 participants) with normal blood
pressure and 20 eyes (10 participants) with arterial hypertension above 120mmHg
(mean blood pressure). The diameter of all vessels intersecting the scan line was
measured in the OCT and used to calculate central vessel equivalents. Designation
to arteries vs. veins was ascertained through the fundus photo. A Matlab-based
(Mathworks, USA) software tool was used for measuring the arterial and venous
width on fundus photos and to calculate central vessel equivalents. A/V ratios were
calculated for all four groups and correlation coefficients were determined for the
two methods as well as with the individual mean arterial blood pressures.
Results: 40 eyes of 20 persons were included in the study. Mean arterial blood
pressure was 96mmHg (SD 4) in the control group and 132mmHg (SD 7) in the
hypertonic group. Mean AV-ratio as determined from OCT scans was 0.83 (SD
0.16) (normotonic) vs. 0.63 (SD 0.11)(hypertonic). Mean AV-ratio on fundus
images was 0.88 (SD 0.6) for the control group and 0.75 (SD 0.07) for the
hypertonic group. The correlation coefficient for the comparison of the two vessel
measurement methods was 0.51. A correlation coefficient of 0.81 (OCT)
respectively 0.82 (funduscopic) was determined for the two groups. Dependency on
blood pressure was on fundus photos -0.69, while on OCT scans -0.60.
Conclusions: Our results highlight the feasibility of retinal vessel measurements in
spectral domain OCT. The comparison displays a non-inferiority as compared to
fundus photo assessment. To our knowledge this is the first study to test a similar
approach for hypertensive retinopathy. Further research will elucidate influencing
factors and provide a broader basis for therapeutic approaches.
Commercial Relationships: Alexander K. Schuster, None; Joachim E. Fischer,
None; Urs Vossmerbaeumer, None
Support: None
Comparative Analysis of ARIA and IVAN Vessel Caliber Measuring Software
Applications
Vittorio Silvestri1, Peter Bankhead2, Larry D. Hubbard3A, Barbara E. Klein3B,
Stacy M. Meuer3B, Anne Mosher3B, Graham McGeown4, Ronald Klein5, Tim M.
Curtis4, Giuliana Silvestri4. 1Ophthalmology, Royal Hospital Trust, Belfast, United
Kingdom; 2Nikon Imaging Center, Heidelberg, Germany; ADept of Ophth and Vis
Sci, BOphthalmology & Visual Sciences, 3University of Wisconsin-Madison,
Madison, WI; 4Centre for Vision & Vascular Science, Queen's University Belfast,
Belfast, United Kingdom; 5Ophthalmology and Visual Sciences, Univ of Wisconsin
Sch of Med & Pub Hlth, Madison, WI.
Purpose: The relationship between changes in retinal vascular morphology and
systemic disease is well recognized. There are several software applications
available which map and measure the caliber of the retinal vessels. The aim of this
study is to compare the values generated by Automated Retinal Image Analyser
(ARIA), custom-written vessel segmentation and analysis software (Peter
Bankhead, Queen’s University Belfast) with the IVAN software which has been
used in many epidemiological studies (Nicola J. Ferrier, University of Wisconsin,
Madison).
Methods: The images selected for comparison were taken from the Irish Nuns Eye
Study (INES) cohort, captured on the Nidek AFC210 through dilated pupils. A
calibration figure was calculated from 26 eyes selected at random. The distance in
pixels from centre macula to centre optic disc (CM-CD) was measured in Adobe
Photoshop and recorded in a spreadsheet. Using the accepted distance of 4500µm
and the refraction values for each eye, the CM-CD value was adjusted using the
Spherical Equivalent Refraction (SER) for each eye. The resulting mean value for
calibration was 1px=6µm. A further 20 eyes (one eye from each individual) were
selected for the comparative caliber measurements. These were processed through
both applications. One major artery and vein in each quadrant were measured. To
avoid confusion all smaller retinal vessels were deleted. The values (label, no of
diameters and mean diameter) for the 8 chosen vessels from each image from both
platforms were exported to a spreadsheet. Averages for each quadrant were
calculated for arteries and veins and the percentage difference calculated.
Results: Results show that the ARIA software returned larger measurements for all
the vessels assessed. However the artery to vein (A/V) ratio was virtually identical
in both applications. The average values for the vessels and A/V ratios are shown in
µm in the table below.
Conclusions: Both applications are straightforward to use and produce similar A/V
ratios. However, in this small sample the ARIA software produces larger values for
each vessel. This is not unexpected as both pieces of software use different metrics
for defining the vessel edge. From a practical view point there are also some
important differences between the two platforms.
Commercial Relationships: Vittorio Silvestri, None; Peter Bankhead,
None; Larry D. Hubbard, None; Barbara E. Klein, None; Stacy M. Meuer,
None; Anne Mosher, None; Graham McGeown, None; Ronald Klein,
None; Tim M. Curtis, None; Giuliana Silvestri, None
Support: HPSS NI R&D
Quantitative Estimation of Vessel Tortuosity in Wide-field ROP Images
Alfredo Ruggeri, Enea Poletti. Dept of Information Engineering, University of
Padua, Padua, Italy.
Purpose: To develop a computer algorithm to estimate vessel tortuosity in retinal
images acquired with wide-field fundus cameras in Retinopathy of Prematurity
(ROP) infants. It will allow clinicians to recover an objective quantitative
estimation of tortuosity.
Methods: 130° retinal images were acquired with RetCam (Clarity Medical
Systems, Pleasanton, CA) in 20 normal and ROP (pre-plus and plus) infants. Given
the difficulty for humans to provide a quantitative assessment of tortuosity, 3
clinical graders and 3 ROP image experts independently ordered the images by
increasing tortuosity. In order to focus on tortuosity estimation alone and avoid
problems from possible errors in computerized vessel tracing, a manual tracing of
visible vessels was carried out by one of the authors and used for computer
tortuosity estimation.
Various indices of tortuosity, based on different geometrical features, were
assessed, both single and combined. The selection of the best weights to combine
indices was done using a “leave-one-out” technique. One image out of 20 was
chosen, the remaining 19 were used to find the optimal weights of the combination
under exam and the resulting combination was assessed on the left-out image. The
whole procedure was repeated 20 times, each time leaving-out a different image,
eventually yielding the combined index value for all the 20 images.
The criterion to select the best (single or combined) index was the correlation of its
ordering with ground truth (clinical graders’ average ordering).
Results: The table reports the Spearman Correlation Coefficient for each pair of
ordering. A remarkable improvement is shown when using combined over single
index, with combined index performing at clinical graders’ level.
Conclusions: The proposed algorithm was shown to behave in this dataset at a
level comparable to the best experts' (clinical graders). When paired with an
automatic vessel tracing technique (currently in late stage of development), it will
provide a completely automated tool for the reliable quantitative estimation of
vascular tortuosity in ROP images.
Commercial Relationships: Alfredo Ruggeri, None; Enea Poletti, None
Support: None
A Study of the Retinal Vascular Parent Branch-Daughter Branch Relationship
Based on an Automatic Vessel Width Measurement Method
Xiayu Xu1A, Joseph Reinhardt1A, John Goree1B, Michael D. Abramoff2. ABiomedical
Engineering, BPhysics and Astronomy, 1University of Iowa, Iowa City, IA;
2
Ophthalmology & Visual Sciences, Univ of Iowa Hospitals & Clinics, Iowa City,
IA.
Purpose: To study the retinal vascular parent branch-daughter branch relationship
on fundus images using an automatic retinal vascular branching vessel width
measurement method.
Methods: The automatic method designed for vessel width measurement at
branching points is a graph-based method. An electric field theory based graph
construction method is introduced. This method is motivated by the nonintersection property of the electric lines of force. After the vessel boundaries are
determined, the vessel width is determined as the Euclidean distance between the
two nodes on the vessel boundary that are extended from the same vessel centerline
pixel. The parent branch-daughter branch relationship was studied on a set of 150
fundus images from a population study. A set of 331 arteriolar branchings and 573
venular branchings were measured.
Results: Typical result images are given in Figure 1 (b). Our result showed that the
parent branch-daughter branch relationship in retinal arterial branchings fitted the
Murray’s proposal very well. The parent
branch-daughter branch relationship followed closely to a third power relationship,
as shown in Figure 2(a). However, the relationship in venular branchings was
different. The best fitting was found with a power of 2.4 as shown in Figure 2(b).
Conclusions: We propose a fully automatic method designed for retinal vascular
branching width measurement. This method was used to study the parent branchdaughter branch
relationship. Our result showed that the retinal arteriolar branchings follow the
Murray’s Law very well, while the venular branchings deviated from the Murray’s
Law.
Commercial Relationships: Xiayu Xu, None; Joseph Reinhardt, None; John
Goree, None; Michael D. Abramoff, None
Support: This work was supported by VA Merit grant, NIH EY018853, Research
to Prevent Blindness.
Retinal Blood Vessels Diameter in a Healthy Cohort as Measured by the
Spectral Domain OCT (SD OCT)
Dafna Goldenberg, Jonathan Shahar, Anat Loewenstein, Michaella Goldstein.
Ophthalmology, Tel Aviv Medical Center, Tel Aviv, Israel.
Purpose: To describe a method of measuring large retinal blood vessels diameter
using spectral-domain optical coherence tomography (SD-OCT).
Methods: A prospective study. 29 healthy subjects (58 eyes) with a mean age of
41.45 ±15.53 years, without any prior ocular history underwent SD-OCT exam.
Two cube scans composed of seven horizontal scans each, were placed at the
superior and inferior borders of the disc (one cube scan superiorly and one cube
scan inferiorly) to include the large retinal vessels originating from the disc The
diameter of the temporal retinal arteries and veins was measured and an artery to
vein ratio (a-v ratio) was calculated at 10 measurement points (480-1440 µm from
the optic disc border superiorly and inferiorly).
Results: Average retinal artery and vein diameter (µm) was 135.73 µm +/-15.64
and 151.32 µm +/-15.22 at the nearest measurement point at 480 µm with gradual
decrease to 123.01 +/- 13.43 and 137.69 +/-13.84 at 1440 µm, respectively. No
statistical difference was found in mean arterial diameter between the superior and
inferior arteries and between the right and left eyes at all measurement points. No
statistical difference was found in mean venous diameter between the superior and
inferior veins. Statistical significance between veins diameter in the right and left
eyes was found only at 960 and 1200 µm measurements points. The artery-vein
ratio (a-v ratio) was ~ 0.9 at all measurement points.
Conclusions: This is a novel non invasive method for retinal blood vessels
diameter measurement using the SD OCT imaging modality. This method coupled
with the infrared image may be useful for accurate evaluation of retinal vascular
caliber in retinal as well as systemic vascular diseases. It may serve in the future for
diagnosis and follow up of various primary and secondary ocular vascular
abnormalities.
Commercial Relationships: Dafna Goldenberg, None; Jonathan Shahar,
None; Anat Loewenstein, None; Michaella Goldstein, None
Support: None
Retinal Vessel Caliber And Risk Of Hypertension: A Systematic Review And
Individual-participant Meta-analysis
Jie Ding1, M K. Ikram1, Sophia Xie2, Ronald Klein3, Jiejing Wang4, Mary Frances
Cotch5, Ryo Kawasaki6, A Richey Sharrett7, Tienyin Wong1. 1Singapore National
Eye Centre, Singapore Eye Research Institute, Singapore, Singapore; 2Department
of Ophthalmology, Health Services and Ocular Epidemiology Research Unit,
Centre for Eye Research Australia, Melbourne, Australia; 3Ophthalmology and
Visual Sciences, Univ of Wisconsin Sch of Med & Pub Hlth, Madison, WI;
4
Department of Ophthalmology, Centre for Vision Research, University of
Melbourne, Melbourne, Australia; 5Division of Epidemiology and Clinical
Applications, Singapore Eye Research Institute, Bethesda, MD; 6Department of
Ophthalmology, Health Services and Ocular Epidemiology Research Unit, Centre
for Eye Research Australia, University of Melbourne, Melbourne, Australia;
7
Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health,
Baltimore, MD.
Purpose: Retinal vessel caliber may be a novel biomarker of hypertension risk.
The aim of this systematic review was to determine if retinal vessel caliber predicts
hypertension and provides information on the risk of hypertension independently of
traditional risk factors.
Methods: Relevant studies were identified through a search of MEDLINE (1950 to
July 2011) and EMBASE (1950 to July 2011), a review of reference lists, and
correspondence with experts. Studies were included if participants were derived
from a general population, retinal vessel caliber was measured from photographs at
baseline, and individuals were followed up to ascertain incident hypertension.
Prespecified data on individuals in each selected study were extracted into a
combined data set, and individual participant meta-analysis was conducted on
individuals who had no previous history of hypertension.
Results: Five population-based prospective cohort studies fulfilling the inclusion
criteria were included. Among 10476 participants who were followed for 3 to 10
years, 1928 (18.4%) developed hypertension. Narrower retinal arterioles (pooled
multivariate-adjusted hazard ratio, 1.13 [95%CI, 1.07, 1.19] per 20-µm decrease in
arteriolar caliber) and wider retinal venules (1.10 [95%CI, 1.03, 1.17] per 20-µm
increase in venular caliber) predicted hypertension. Inclusion of retinal vascular
caliber in hypertension risk stratification using traditional risk factors (age, sex,
systolic blood pressure, plasma total cholesterol level, fasting glucose, body mass
index and current smoking) showed a net reclassification improvement of 3.3%.
Conclusions: Retinal vessel caliber is independently associated with an increased
risk for hypertension.
Commercial Relationships: Jie Ding, None; M. K. Ikram, None; Sophia Xie,
None; Ronald Klein, None; Jiejing Wang, None; Mary Frances Cotch,
None; Ryo Kawasaki, None; A Richey Sharrett, None; Tienyin Wong, None
Support: None
Effects of Enhancement of Blood Vessel Contrast in OCT Fundus Images on
Registration Performance
Ying Li, Giovanni Gregori, Byron L. Lam, Philip J. Rosenfeld. Ophthalmology,
Bascom Palmer Eye Institute, Miami, FL.
Purpose: To investigate the effects of blood vessels’ contrast enhancing, using a
technique based on RPE segmentation, on the performance of a registration
algorithm for OCT fundus images (OFIs).
Methods: An automated algorithm, based on blood vessel features, was developed
to register OFIs to each other or to other en face imaging modalities, like color
fundus photography (CFP). Raster scans (200x200) acquired with a Cirrus HDOCT were used to generate the OFIs to be registered. It is well known that
enhanced OFIs, showing the blood vessels with higher contrast, can be obtained by
limiting the summation of OCT intensities along the axial direction to specific
retinal regions, in particular around the RPE layer.We use a very simple and fast
automated algorithm to obtain a rough RPE segmentation. A window of 20 pixels
above and 100 pixels below the RPE boundary is used to build the enhanced OFI.
Comparisons between the performance of the registration algorithm on OFIs and
enhanced OFIs were carried out in two particular settings. One is the registration
between OFIs and CFPs, and the other is the montage of several partially
overlapping OFIs in order to produce a larger field of view.
Results: Registration performance was measured by the mean registration error of
manually labeled matching points. The effects of enhancement of blood vessel
contrast in OFIs on registration performance are summarized in Table 1.
Conclusions: Enhancement of blood vessel contrast in OFIs, using a very simple
and fast algorithm, greatly improves the performance of our registration algorithm
for OFIs.
Commercial Relationships: Ying Li, None; Giovanni Gregori, Carl Zeiss
Meditec (F, P); Byron L. Lam, None; Philip J. Rosenfeld, Carl Zeiss Meditec (F,
R)
Support: NIH Center Core Grant P30EY014801, Research to Prevent Blindness
Unrestricted Grant, Department of Defense (DOD-Grant#W81XWH-09-1-0675),
Carl Zeiss Meditec.
Characteristics Of Intravascular Blood On Spectral-domain Optical
Coherence Tomography
Anne Willerslev, Xiao Q. Li, Michael Larsen. Department of Ophthalmology,
Glostrup Hospital, Denmark, Glostrup, Copenhagen, Denmark.
Purpose: The characteristics of intravascular blood on spectral-domain optical
coherence tomography (SD-OCT) scans of retinal and choroidal blood vessels were
examined in human subjects.
Methods: Examination of five healthy subjects and two patients with retinal or
systemic disease using SD-OCT at 800 nm.
Results: Healthy retinal vessels scanned at right angles to the line of observation
demonstrated longitudinal tri-layer patterns and cross-sectional figure-of-eight
patterns of high reflectivity. In central retinal artery occlusion with stagnant
intravascular blood no reflection from the blood was seen. In hypoperfused retinal
vessels in a patient with carotid artery occlusion the optical density of blood was
lower than normal and homogeneous. The highly perfused choroidal vessels
generally showed no reflectivity and figure-of-eight and longitudinal tri-layer
patterns were only observed rarely, the visibility being enhanced by a translucent or
atrophic pigment epithelium. The reflectivity of the streaming blood decreased with
an increasing shift in the angle of observation away from the rectangular, and was
absent when flow was directly toward or away from the point of observation.
Conclusions: The SD-OCT profile of the blood column in retinal and choroidal
vessels varies in a biphasic manner with flow velocity, being lowest at high and
low flow rates and highest at intermediate flow rates such as those typical of larger
vessels of a healthy retina. Our observations agree with in vitro studies using SD-
OCT and other optical modalities, ultrasonography and electrical conductivity
measurements. Past results have been successfully modeled assuming that
erythrocytes aggregate at low flow rates, a condition associated with low optical
scatter, whereas erythrocytes disaggregate at higher flow rates and become spatially
organized in a radial manner. At high flow rates and for flow along the line of
observation, the signal is lost because of the Doppler frequency-shift
retinal circulation and retinal vascular disease.
Commercial Relationships: Anne Willerslev, None; Xiao Q. Li, None; Michael
Larsen, None
Support: None
Dynamic Hyperspectral Retinal Oximetry in a Human with the Image
Mapping Spectrometer (IMS)
Theodore Smith1, Yuehong Tong1, Jennifer Acton1, Amani A. Fawzi2, Liang Gao3,
Tomasz S. Tkaczyk4. 1Ophthalmology, Columbia University, New York, NY;
2
Ophthalmology-Univ of Southern Cal, Doheny Eye Institute, Los Angeles, CA;
3
Bioengineering, Washington University, St. Louis, MO; 4Bioengineering, Rice
University, Houston, TX.
Purpose: We present a hyperspectral retinal camera capable of real-time imaging
of oxygen saturation dynamics, as demonstrated in a human experiment.
Methods: The Image Mapping Spectrometer (IMS) is a hyperspectral camera that
simultaneously acquires full 48 channel hyperspectral cubes in the range 470 nm 650 nm (spectral resolution ~ 3.6 nm) with a frame rate at 5.2 fps and spatial
resolution 350×350 pixels (Gao et al, Opt Express, 2010). We coupled it to a
standard fundus camera (Topcon TRC50X, Topcon Inc, Tokyo, Japan) and
acquired a hyperspectral movie of the optic disc region in a healthy 22 y/o female
with the illumination light of the camera (no flash). The absorption spectral
signature of oxy-hemoglobin was extracted from the reflectance data and used to
construct a relative oxygen saturation (ROS) map at each time point with known
techniques (Khoobehi et al, IOVS, 2004).
Results: The ROS maps fell in the normal ranges 0.05 - 0.2 found by Khoobehi et
al in primates. Measurement on the largest arteriole showed marked pulsatile
behavior (Fig 1, selected frames) consistent with the subject’s pulse, although the
frame rate was not fast enough to catch every pulse.
Conclusions: We report the first sub-second resolution dynamic hyperspectral
retinal oximetry in a human. An even faster frame rate would be better for
capturing arterial transients. This is a promising technique to investigate the normal
Commercial Relationships: Theodore Smith, None; Yuehong Tong,
None; Jennifer Acton, None; Amani A. Fawzi, None; Liang Gao, None; Tomasz
S. Tkaczyk, None
Support: NIH Grants R01-EY021470, R21EB009186, R21EB011598 and the New
York Community Trust
High-resolution Surface Coil Magnetic Resonance Imaging After Peribulbar
And Retrobulbar Injections
David R. Almeida1A, Michel J. Belliveau1A, Thomas Enright1B, Omar Islam1B, Sherif
R. El-Defrawy1A, Jeffrey Gale1A. AOphthalmology, BRadiology, 1Queen's
University, Kingston, ON, Canada.
Purpose: Retrobulbar and peribulbar blocks are commonly used forms of
anesthesia for ophthalmic surgical procedures; however, the precise anatomic
localization of injected solution is unknown for each technique. We set out to
examine the anatomic distribution of gadolinium contrast by high-resolution
surface coil magnetic resonance imaging (MRI) after peribulbar and retrobulbar
injection.
Methods: Comparative case series. Four eyes were randomized to either peribulbar
(n=2) or retrobulbar (n=2) injection of gadolinium and lidocaine 2% without
epinephrine. Serial MRI imaging with surface coil was performed to determine
anatomic distribution.
Results: Retrobulbar injection technique localizes to the intraconal space with
central nervous system (CNS) access via the optic canal, superior orbital fissure,
and cavernous sinus. Contrastingly, peribulbar administration produces a mostly
extraconal distribution; however, a small amount of intraconal solution may
communicate with the CNS via the inferior orbital fissure and pterygopalatine
fossa.
Conclusions: We show the full extent of spread of anesthetic blocks and
demonstrate the novel finding of pterygopalatine fossa extension, which provides a
readily accessible route for CNS toxicity after peribulbar injection. Additionally,
we highlight cavernous sinus involvement with the retrobulbar technique. MRI
with gadolinium contrast administration provides an important methodological
advantage over previous reports and is a safe, reproducible, and superior method of
orbital imaging.
Commercial Relationships: David R. Almeida, None; Michel J. Belliveau,
None; Thomas Enright, None; Omar Islam, None; Sherif R. El-Defrawy,
None; Jeffrey Gale, None
Support: Queen's University
Effect of Quality Parameters on Validity of Doppler FD-OCT Scans
SOWMYA SRINIVAS1, Ou Tan2, ROHIT VARMA1, MUNEESWAR GUPTA
NITTALA1, DAVID HUANG2, SRINIVAS R. SADDA1. 1OPTHALMOLOGY,
DOHENY EYE INSTITUTE, LOS ANGELES, CA; 2Ophthalmology, Oregon
Health & Science Univ, Portland, OR.
Purpose: Doppler optical coherence tomography (OCT) has been advanced as a
new technology for measuring retinal blood flow, but image quality must be
optimized in order to achieve valid or reliable blood flow results. The purpose of
this study was to correlate image quality parameters at the time of scan acquisition
with the likelihood of obtaining a valid Doppler OCT retinal blood flow result.
Methods: Doppler OCT scans (Optovue RTvue FD-OCT) of 285 eyes from 274
subjects were obtained as part of the Chinese American Eye Study. Ten automated
image quality parameters were generated by the machine including Acceptable scan
number, Average signal strength index (Avg SSI), Average root mean square of
inner limiting membrane (Avg ILM RMS), Average acceptable frames, Average
continuous acceptable frames, Average maximum eye movement (Avg max EM),
Average maximum frame depth shift (Avg max frame depth shift), Pooled coefficient of variance for inner limiting membrane angle (Pooled CV of ILM),
Average inner limiting membrane angle (Avg ILM angle) and Root mean square
standard deviation of inner limiting membrane angle (RMS sd ILM angle). Retinal
blood flow was then calculated using Doppler OCT of Retinal Circulation
(DOCTORC) grading software as described in prior publications. The DOCTORC
software also automatically determines whether the blood flow result is valid and
reliable.The influence of the 10 image quality parameters on the validity of the
blood flow measurement was analyzed using univarate and then multivariate
logistic regression.
Results: Of the ten quality parameters, only 6 were found to significantly correlate
with the validity of the Doppler blood flow measurements. Acceptable scan number
(OR, 1.54; 95%CI, 1.23-1.93) was the most predictive factor followed by Average
acceptable frames (OR, 1.49; 95%CI, 1.03-2.17), Average continuous acceptable
frames (OR, 1.26; 95%CI, 1.002-1.59), Average ILM RMS (OR, 0.96; 95% CI,
0.93-0.99), RMS sd ILM angle (OR, 0.84; 95%CI, 0.71-0.99), and Pooled CV of
ILM angle (OR, 0.19; 95%CI, 0.01-0.54). The quality parameters which did not
appear to influence validity were Average ILM angle, Average max EM, Average
max frame depth shift, and Average SSI.
Conclusions: Several image quality parameters appear to correlate with Doppler
OCT scans yielding valid retinal blood flow results. These observations may be
useful in developing optimized quality metrics which can assist operators in
successfully obtaining adequate Doppler OCT scans.
Commercial Relationships: SOWMYA Srinivas, None; Ou Tan, Optovue, Inc
(F, P); ROHIT Varma, None; MUNEESWAR GUPTA Nittala, None; DAVID
Huang, Carl Zeiss Meditec, Inc (P), Optovue, Inc (F, I, C, P, R); SRINIVAS R.
Sadda, Carl Zeiss Meditec (F), Heidelberg Engineering (C), Optovue, Inc (F),
Topcon Medical System (P)
Support: NIH grant R01 EY013516
Dual Beam Doppler Optical Coherence Tomography at 1060nm
Cedric Blatter1, Laurin Ginner1, Amardeep S. Singh1, Tilman Schmoll1, Leopold
Schmetterer2, Rainer A. Leitgeb1. 1Center for Medical Physics & Biomedical
Engineering, Medical University Vienna, Vienna, Austria; 2Clinical Pharmacology,
Medical University of Vienna, Vienna, Austria.
Purpose: To image the blood flow dynamics quantitatively independent of the
axial Doppler angle and to contrast the vasculature network of the retina with high
penetration using a Dual Beam Doppler Swept Source OCT System at 1060nm.
Methods: Traditional Doppler OCT is highly sensitive to motion artifacts due to
the dependence on the Doppler angle. This limits its reproducibility in clinical
practice. To overcome this limitation, we use a bidirectional technique. Here, the
volume is probed from two distinct illumination directions, allowing reconstruction
of the true flow velocity. The principle was implemented with Swept Source OCT
at 100,000 A-Scans/s. Furthermore, measurement at 1060nm shows better
penetration below the RPE, so that choroidal flow can be effectively quantified.
Simple flow contrast can be achieved by calculating the phase variance between
successive B-scans. The dual beam approach permits intrinsic bulk motion
correction and offers the advantage to contrast the full range of flow present at the
retina from small capillaries up to large vessels at the ONH.
Results: Circumpapillary Doppler OCT scan series over time have been recorded
for three healthy volunteers. The angle independent quantitative flow dynamics
have been extracted from specific vessel cross-sections of arteries and veins. The
quantitative analysis profits from the intrinsic stability with respect to motion over
time. The flow values fit well with previous findings. Furthermore we assessed
choroidal flow quantitatively in selected vessel cross-section close to the optic
nerve head. This marks an important step since the choroidal perfusion is believed
to play an important role for retinal health and disease. Highly sensitive flow
contrasting based on phase variance has been performed on the parafoveal capillary
network of the inner retina in a patch of 1.5x1.5mm. Capillaries smaller than 10µm
could be well visualized. The sensitivity benefits greatly from the bulk motion
independence of the dual beam approach.
Conclusions: We introduce a large penetration bidirectional Doppler OCT system
capable to perform quantitative imaging of retinal flow dynamics in the human
retina. We demonstrated the advantage of 1060nm center wavelength to assess
quantitatively the choroidal perfusion that plays a major role for various retinal
diseases. The flow quantification and visualization may therefore lead ultimately to
a better understanding and an enhanced early diagnosis of major retinal diseases.
Commercial Relationships: Cedric Blatter, None; Laurin Ginner,
None; Amardeep S. Singh, None; Tilman Schmoll, None; Leopold Schmetterer,
None; Rainer A. Leitgeb, None
Support: European FP 7 HEALTH program. Grant 201880, FUN OCT
Morpho-functional Analysis In A Family With Oculocutaneous Albinism
Paolo Trabucco1, Pier Luigi Grenga2, Vittoria De Rosa1, Serena Fragiotta3,
Francesca Verboschi3, Enzo M. Vingolo4. 1Ophthalmology, Univ of Rome La
Sapienza, Latina, Italy; 2Ophthalmology - S.M. Goretti Latina, University of Rome,
Rome, Italy; 3Sapienza, Latina, Italy; 4UOC Ophthal Hosp, University La Sapienza
of Rome, Roma, Italy.
Purpose: to evaluate the anatomic and functional changes in patients with
oculocutaneous albinism.
Methods: we analyzed two siblings: a child of 6 years and a girl of 16 years with
oculocutaneous albinism (OCA); both were submitted to a complete ophthalmic
examination, SD-OCT and Microperimetry. SD-OCT (Heidelberg Engineering,
Germany) was performed in both patients to analyse the average foveal thickness.
Microperimetry with analysis of retinal sensitivities and fixation patterns were
performed using a MP-1 (NIDEK Technologies) with a red cross of 2° as the
fixation target, white background illumination of 4 asb, Goldman III stimuli with a
projection time of 200 ms, and a customized grid of 68 stimuli around 10° centered
on the fovea. Because of poor cooperation, the child was submitted just to fixation
study. Fixation patterns were classified according to Fuji et al.
Results: In the girl BCVA was 6/20 in the right eye and 8/20 in the left eye.
Microperimetry revealed an unstable and poor central fixation in both eyes due to
nystagmus and an average retinal sensitivities of 19.5 dB in both eyes. In the child,
BCVA was 8/20 in the right eye and 6/20 in the left eye. Microperimetry revealed a
stable and central fixation in the right eye and a relatively unstable and central
fixation in the left eye. In both patients SD-OCT revealed absence of foveal pit, and
preservation of the inner retinal layers and thickened fovea with a central thickness
of 336 µm (Right Eye) and 338 µm (Left Eye) in the girl and 319 µm in both eyes
in the child.
Conclusions: this study confirms all the typicals alterations of OCA and the
importance of imaging techniques, such as SD-OCT and microperimetry, in the
morpho-functional evaluation of this disease. In both patients, SD-OCT revealed
absence of the foveal pit with preservation of the inner retinal layers. Nystagmus,
another typical sign of OCA, although in different degrees, was present in both
patients and altered the stability of fixation. In our opinion, Microperimetry is a
very useful tool to evaluate visual function in patients with OCA and could be also
very valuable to perform a rehabilitation program in the future.
Commercial Relationships: Paolo Trabucco, None; Pier Luigi Grenga,
None; Vittoria De Rosa, None; Serena Fragiotta, None; Francesca Verboschi,
None; Enzo M. Vingolo, None
Support: None
Structural and Functional Correlation Between Multifocal
Electroretinography and Microperimetry in Hydroxychloroquine Toxicity
Kristin S. Suhr1, David Warrow2, Jeanne L. Rosenthal2A, Carol M. Lee3, Chavakij
Bhoomibunchoo4, Richard B. Rosen4, William H. Seiple5. 1Ophthalmology, Illinois
Eye and Ear Infirmary, Chicago, IL; AOphthalmology, 2New York Eye and Ear
Infirmary, New York, NY; 3Ophthalmology, New York Univ Sch of Med, New
York, NY; 4Ophthalmology, New York Eye & Ear Infirmary, New York, NY;
5
Research, Lighthouse International, New York, NY.
Purpose: To evaluate the efficacy of the OPKO SLO/SD-OCT microperimetry in
detecting hydroxychloroquine toxicity by comparing changes in sensitivity with
retinal changes found on SD-OCT and multifocal electroretinography.
Methods: Seven patients on long term hydroxychloroquine therapy and three
normal patients were clinically evaluated by (i) complete ophthalmologic
examination, (ii) fundus photography, (iii) spectral density ocular coherence
tomography with SLO microperimetry (OPKO/OTI), and (iv) mfERG (Veris).
Results: In patients with fundus, SD-OCT, and mfERG changes (n=3) loss of
sensitivity in the macular region was detected by microperimetry. Microperimetry
abnormalities topographically correlated with structural changes of the
photoreceptor inner segment/outer segment (IS/OS) junction and thinning of the
outer nuclear layer found on SD-OCT. The average retinal sensitivities collected by
the SLO microperimetry were also compared to the mfERG results demonstrating
corresponding areas of reduced responses.
Conclusions: Microperimetry provided complementary results to the mfERG and
appeared to be able to detect abnormalities in retinal function in patients with
hydroxychloroquine toxicity. Microperimetry may be another useful and less
invasive objective method for detecting and monitoring subclinical changes in
patients on hydroxychloroquine therapy.
Commercial Relationships: Kristin S. Suhr, None; David Warrow,
None; Jeanne L. Rosenthal, None; Carol M. Lee, None; Chavakij
Bhoomibunchoo, None; Richard B. Rosen, Opko/OTI/Optos, Clarity, OD-OS
(C); William H. Seiple, None
Support: None
Cortical Reorganization After Optic Neuritis: A Functional Neuroimaging
Approach
Tony GARCIA, Anne-Claire VIRET, Céline PEREZ, Céline CAVEZIAN, Paméla
LALIETTE, Françoise HERAN, Olivier GOUT, Sylvie CHOKRON. Fondation
Ophtalmologique A. Rothschild, 75019 PARIS, France.
Purpose: Previous studies have suggested an early cortical reorganization after
optic neuritis involving extra-striate areas, particularly the lateral occipital complex
located in the parvocellular pathway. Parvo and magnocellular pathways are known
to convey respectively high and low spatial frequencies present in a visual scene.
The objective of the present study is to characterize cortical reorganization at the
acute phase of a first episode of optic neuritis using a visual categorization task of
natural scenes that controls the spatial frequency content of the stimulus. Using this
experimental design, we aim to assess the pattern of cortical reorganization when
targeting the parvo- or magnocellular pathways in optic neuritis patients.
Methods: A categorization task of natural scenes filtered in low spatial
frequencies, high spatial frequencies or unfiltered was used. This experiment was
coupled to a recording of brain activation by functional MRI in order to study the
pattern of cortical activation during the visual categorization task. Three groups
were individually analyzed: right optic neuritis patients, left optic neuritis ones and
healthy volunteers as controls.
Results: Fifteen patients were prospectively recruited: seven experiencing their
first episode of right acute unilateral optic neuritis and eight a left. Twenty five
healthy volunteers were also included.
In the control group the right eye as the left eye activated temporo-parieto-occipital
areas bilaterally with a greater volume in the hemisphere contralateral to the visual
stimulation.
In the left optic neuritis group, both for the affected eye and the fellow eye, low
spatial frequencies activated more areas than high spatial frequencies. This effect
was bilateral but more sustained activity was observed in the contralateral side of
the stimulated eye.
In the right optic neuritis group, for the affected as well as for the fellow eye, high
spatial frequencies recruited more areas than low spatial frequencies, bilaterally but
mainly contralateral.
Conclusions: The present findings show for the first time a different pattern of
cortical activation depending on the laterality of the optic neuritis and on the spatial
frequency of the visual scene. Given the fact that there is a hemispheric
specialization for spatial frequency processing with a left hemisphere specialization
for high spatial frequencies and a right hemisphere specialization for low spatial
frequencies, the present results raise the question of an interaction between the
lesion side in optic neuritis patients and the hemispheric specialization for visual
processing in cortical reorganization.
Commercial Relationships: Tony Garcia, None; Anne-Claire Viret,
None; Céline Perez, None; Céline Cavezian, None; Paméla Laliette,
None; Françoise Heran, None; Olivier Gout, None; Sylvie Chokron, None
Support: None
provided 3 µm axial and ~ 5 µm resolutions in the chicken retina and pupil, at a 22
µs line scan rate and ~7 ms time resolution for volumetric integration of the retinal
IOSs. The fOCT system was interfaced with a full field ERG system (Diagnosys
LLC), and was used for generation of the visual stimuli and collection of ERG
traces simultaneously with the IOS recordings. IOS, ERG and pupil dynamics
recordings were acquired from healthy White Leghorn (Gallus gallus domesticus)
chicken.
Results: fOCT recordings from the inner retinal layers showed positive IOSs
(increase in tissue reflectivity) peaking at ~33 ms and negative IOSs (decrease in
the reflectivity), peaking at 67 ms to 73 ms post stimulus on-set. IOSs measured
from the OS and RPE showed a strong negative peak at 34 ms and a positive one at
67 ms post stimulus on-set. Pupil constriction was observed as early as ~50 ms post
stimulus on-set, peaking at ~150 ms with a subsequent slow dilation that continued
for more than 1s post stimulus on-set.
Conclusions: Reproducible visually evoked IOSs were measured from all retinal
layers in an in vivo chicken model with a combined fOCT+ERG system. Direct
correlation was established between the time courses of the measured IOS, ERG
and pupil dynamics. These results show the ability of fOCT technology for probing
non-invasively light-induced physiological processes in the animal retina.
Commercial Relationships: Alireza Akhlagh Moayed, None; Sepideh Hariri,
None; Vivian Choh, None; Kostadinka K. Bizheva, None
Support: The Natural Sciences and Engineering Research Council of Canada
(NSERC).
Repeatability Of Retinal Oximetry Using Ultra-high Resolution Optical
YUFENG YE1,2, Hong Jiang1, Meixiao Shen3, Byron L. Lam1, Delia DeBuc1, Lili
Ge1,3, Mitra Sehi1, Jianhua Wang1. 1Ophthalmology, Bascom palmer eye institute,
MIAMI, FL; 2Hangzhou First People Hospital, Hangzhou, China; 3School of
Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, China.
Purpose: Retinal oxygen saturation provides important information about the
metabolic state of the retina. Many ocular diseases, such as diabetic retinopathy,
glaucom, and retinal vein occlusion, have changes of retinal blood flow and oxygen
saturation. The purpose of this study was to investigate the feasibility and
repeatability of retinal oximetry using slit-lamp adapted ultra-high resolution
optical coherence tomography (SL-UHR-OCT).
Methods: SL-UHR-OCT was developed with an advanced optical delivery system
adapted into a slit-lamp for retinal imaging. The system has a ~3µm depth
resolution. Fringe patterns for spectral analysis were obtained from the central
retinal artery and vein. A-scans at central wavelengths of 805 and 855 nm were
analyzed for calculating optical density ratios (ODRs), representing oxygen
saturation in the retinal vessels. Both eyes of twenty healthy subjects (15 women
and 5 men, age 37.7 ± 9.4 years) were imaged 2 different sessions on the same day.
Coefficients of repeatability (CRs) were calculated. Bland-Altman plot of the
difference between the two measurements was used to evaluate consistency.
Results: Mean retinal arterial ODR were 0.75 (SD 0.61) and 0.72 (SD 0.69) in
sessions 1 and 2, respectively. ODR’s mean (SD) values of the vein were 0.13
(0.63) and 0.14 (0.74) between two sessions, which were significantly lower than
arterial ODR (P < 0.05). The CRs between the two sessions were 1.55 and 1.70 for
the artery and vein respectively. The range of inter-sessions correlation coefficient
(ICC) was 0.23-0.35 (Figure 1).
Conclusions: We demonstrated the feasibility and documented the repeatability of
using OCT oximetry for evaluating retinal oxygen saturation. The extended
function of measuring oxygen saturation may expand OCT usage for ophthalmic
research. Further studies of large sample of healthy and diseased eyes are needed to
In Vivo Measurement And Correlation Of Visually Evoked Retinal And Pupil
Responses Of Chicken With Functional Optical Coherence Tomography
Alireza Akhlagh Moayed1A, Sepideh Hariri1A, Vivian Choh1B, Kostadinka K.
Bizheva1A. APhysics and Astronomy, BSchool of Optometry, 1University of
Waterloo, Waterloo, ON, Canada.
Purpose: To measures in vivo visually evoked intrinsic optical signals (IOSs) from
individual layers of the chicken retina using functional optical coherence
tomography (fOCT) and correlate their time course with the pupil response to
visual stimuli of different colour, intensity and duration.
Methods: A high speed fOCT system was used to measure in vivo visually-evoked
IOSs from individual layers of the chicken retina and pupil dynamics in response to
optical stimuli of different color, duration and intensity. The 1060 nm fOCT system
assess and optimize measured variations.
Commercial Relationships: YUFENG Ye, None; Hong Jiang, None; Meixiao
Shen, None; Byron L. Lam, None; Delia DeBuc, None; Lili Ge, None; Mitra
Sehi, None; Jianhua Wang, None
Support: This study was supported by research grants from NIH Center Grant P30
EY014801 and Research to Prevent Blindness (RPB).
Retinal Oximetry In Glaucoma Patients Using Ultra-high Resolution Optical
Mitra Sehi1, Hong Jiang2, Yufeng Ye2, Richard K. Lee2, Jianhua Wang2.
1
Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Palm Beach
Gardens, FL; 2Ophthalmology, Bascom Palmer Eye Institute, University of Miami,
Miami, FL.
Purpose: To assess retinal oxygen saturation in glaucomatous eyes and to compare
it with normal eyes, using slit-lamp adapted ultra-high resolution optical coherence
tomography (SL-UHR-OCT).
Methods: SL-UHR-OCT was developed with a ~3µm depth resolution and light
delivery scanning system mounted on a slit-lamp. Fringe patterns for spectral
analysis of OCT images were obtained from the central retinal artery and vein. Ascans at the central wavelengths of 805 and 855 nm were analyzed for calculating
optical density ratios (ODRs), which represent oxygen saturation in the retinal
vessels.
Results: Seven eyes of 4 patients with perimetric glaucoma (treated IOP 14.6±3.3,
visual field mean deviation 12.1±9.4 and pattern standard deviation 7.4±4.5) were
imaged and compared with 20 eyes of 10 healthy subjects. ODR of the retinal
artery was 0.21 ±0.17 in glaucomatous eyes, and was significantly lower than that
of healthy controls (0.87 ± 0.57, p=0.003). ODR of the retinal vein was 0.06 ± 0.30
in glaucomatous eyes, which was not significantly different from healthy controls
(0.20 ± 0.38, p=0.26). The usage of oxygen (ODR difference between artery and
vein) was 0.15 ± 0.31 in glaucomatous eyes, which was significantly lower than
that of normal controls (0.67 ± 0.63, p=0.03).
Conclusions: We demonstrated that oxygen saturation levels of the retinal artery
and oxygen usage were lower in glaucoma patients compared with normal controls.
Larger studies are required to examine the correlation between vascular
dysfunction, oxygen saturation and structural changes in glaucoma.
Commercial Relationships: Mitra Sehi, None; Hong Jiang, None; Yufeng Ye,
None; Richard K. Lee, None; Jianhua Wang, None
Support: NIH Core Grant P30 EY014801 and an unrestricted grant from Research
to Prevent Blindness (RPB)
Optophysiological Characterisation of Retinal Ganglion Cell Responses to
Bleach Stimuli by UltraHigh Resolution Optical Coherence Tomography
James E. Morgan1, Irina A. Erchova2A, James Fergusson2B, Alexandre R.
Tumlinson3, Frank Sengpiel2C, Wolfgang Drexler4. 1Ophthalmology, University
Hospital of Wales, Cardiff, United Kingdom; ASchool of Optometry and Visual
Sciences, BSchool of Optometry and Visual sciences, CSchool of Biosciences,
2
Cardiff University, Cardiff, United Kingdom; 3Zeiss Meditec, Dublin, CA; 4Center
for Medical Physics & Biom Eng, Medical University Vienna, Vienna, Austria.
Purpose: Functional characterization of retinal neurons in response to light flashes
is essential for clinical testing and diagnostics. The purpose of this project was to
test whether light driven activity in the inner retina could be detected and quantified
in vivo by UltraHigh Resolution Optical Coherence Tomography (UHR-OCT).
Methods: We developed an efficient 1050 nm Fourier domain UHR-OCT device
for retinal imaging. The device was linked to animal electrophysiological recording
from the lateral geniculate nucleus (LGN) in treeshews and superior colliculus (SC)
in rats. Animals (treeshew n=2 and rat n=2) were anaesthetized with 1.2%
isoflurane and the ocular movements were minimized by application of
neuromuscular blocking agent gallamine to allow imaging of the same retinal areas
over time. The EEG, heart and respiratory rate were monitored during these
experiments and used to gate the acquisition and image processing. A small area of
retina 60 um2 was sampled optically every 20 ms for 5s. Light flashes of different
intensity (max 95% cone bleach) were presented for 2s; a recovery period up to 30
min was allowed between different stimuli.
Results: Stimulation with bright flash (bleach) resulted in changes in inner retinal
optical responses that coincided temporally with the flash and the magnitude of
evoked responses correlated with flash brightness. For the brightest flash the
average change in contrast was 27% for ON response and 22% for OFF response,
with individual values ranging from 2.2% to 62%. A variety of temporal patterns of
response were observed on the time scales from 60 ms to 1200 ms (on average 415
ms). Some of the patterns were consistent with average firing rate responses of
retinal ganglion cells (short latency phasic responses with ON or OFF preferences);
the other patterns (longer latency tonic responses) were more likely to originate
from blood vessels/glia.
Conclusions: We have successfully developed a 1050nm Fourier domain UHROCT customized for animal use which can generate optical cross sections of the
retina in vivo. Using this set up we were able to demonstrated light-evoked optical
changes in the inner retina consistent with both metabolic and functional RGC
responses.
Commercial Relationships: James E. Morgan, None; Irina A. Erchova,
None; James Fergusson, None; Alexandre R. Tumlinson, x (E); Frank Sengpiel,
None; Wolfgang Drexler, None
Support: MRC (G0800547)
Ultrahigh-speed wide-field Microangiography in a Single Patch
Rainer A. Leitgeb1, Cedric Blatter1, Thomas Klein2, Wolfgang Wieser2, Christoph
M. Eigenwillig2, Robert Huber2, Tilman Schmoll3. 1Ctr of Med Phys & Biomed
Eng, Medical University of Vienna, Vienna, Austria; 2Lehrstuhl für BioMolekulare
Optik, Ludwig-Maximilians-Universität, Munich, Germany; 3Center of Med Phys
& Biomed Eng, Medical University Vienna, Vienna, Austria.
Purpose: To visualize comprehensively the retinal and choroidal microvascular
network over a large field of view using MHz optical coherence tomography at
1060nm as a non-invasive complement to fluorescein angiography.
Methods: The method is based on functional Swept source OCT using speckle
variance as vessel contrasting technique. This highly sensitive technique detects
small changes in the speckle pattern between successive intensity tomograms
caused by tissue blood flow and is insensitive to trigger timing artifacts of phase
sensitive techniques. The use of Megahertz A-Scan rate FDML laser at 1050nm
allows for wide-field angiography of the inner retina as well as of the choroidal
vasculature acquired in a single recording within only a few seconds. Typically 5
tomograms are recorded at each vertical location to calculate the corresponding
variance image. High lateral sampling is maintained and permits resolving the
vessel network down to the capillary level. The axial resolution is 18µm at 1.4MHz
A-scan rate.
Results: We present wide field angiographic maps of healthy volunteers over a
field of 30x30degree that has been obtained in a single volume recording without
patching. The recording of a single volume takes only 5sec covering 30x30deg.
Since the method uses changes between successive tomograms recorded at 500Hz
the speckle variance technique is on the one hand sensitive to flow velocities of
only 70µm per second typical for the smallest capillaries in the parafoveal bed. On
the other hand larger velocities will immediately give rise to speckle decorrelation
and large variance signatures. Thus the velocity range is covering the full vascular
system. The center wavelength of the FDML laser of 1060nm allows for better
penetration to visualize also the outer choroidal vasculature.
Conclusions: The ultra-high imaging speed offers a completely new perspective
for imaging the retinal vascular network from a large field of view in a single
recording down to the smallest capillaries in the parafoveal region. The fact that a
large field of view can be obtained without patching several recordings marks a
major step towards non-invasive retinal vascular imaging as a complement to
fluorescein angiography. Further improvement in speed could be obtained by
employing multi-beam approaches to scan the retina.
Commercial Relationships: Rainer A. Leitgeb, None; Cedric Blatter,
None; Thomas Klein, None; Wolfgang Wieser, None; Christoph M. Eigenwillig,
None; Robert Huber, None; Tilman Schmoll, None
Support: EU-FP7 HEALTH FUNOCT grant 201880
Non-invasive Intensity-based Motion Contrast Swept Source Optical
Coherence Tomography For In Vivo Visualization Of The Human Retinal
Microvasculature
Reza Motaghiannezam1, Florian M. Heussen2, Srinivas R. Sadda2, Scott E. Fraser1.
1
Biology, California Institute of Technology, Pasadena, CA; 2Doheny Eye Institute
- USC, Los Angeles, CA.
Purpose: To validate a novel intensity-based motion sensitive method, called
differential logarithmic intensity variance (DLOGIV), for 3D microvasculature
imaging and foveal avascular zone (FAZ) visualization in the in vivo human retina
using swept source optical coherence tomography (SS-OCT) at 1060 nm.
Methods: A motion sensitive SS-OCT system was developed operating at 50,000
A-lines/s with 5.9 µm axial resolution, and used to collect 3D images over scanning
angles of ~6 degrees* 6 degrees. Multiple B-scans were acquired at each individual
slice through the retina and the variance of differences of logarithmic intensities as
well as the differential phase variances (DPV) were calculated to identify regions of
motion (microvasculature). En face images were generated for qualitative and
quantitative assessment of the FAZ in four eyes of two normal subjects, and
fluorescein angiography (FA) was performed for subsequent comparison.
Results: En face DLOGIV images were capable of capturing the microvasculature
through depth with an equal performance compared to the DPV. The sensitivity and
resolution of parafoveal capillary meshwork images from both DLOGIV and DPV
were significantly greater than FA images of the same regions (Figure 1). While
DLOGIV, DPV and FA captured and quantified FAZs in two eyes of one healthy
subject (Figures 1(c,e,g)), no FAZ was discernible in either eye of the other healthy
subject (Figures 1(d,f,h)).
Conclusions: We could prove the feasibility of a novel imaging method
(DLOGIV) for non-invasive, dye-free visualization and quantification of the retinal
microvasculature using a SS-OCT at 1060nm. Compared to DPV, DLOGIV does
not rely on phase information. Therefore, it is less sensitive to the phase instability
of the system and environment, and there is no need for phase compensation
algorithms and additional optical modules. As such, DLOGIV may be
advantageous to both DPV and invasive FA for imaging the retinal
microvasculature and be a helpful diagnostic tool in the future.
Sciences, Copenhagen University, Copenhagen, Denmark; 3Dept of
Ophthalmology, Rigshospitalet, Copenhagen, Denmark; 4Oxymap ehf., Reykjavik,
Iceland; 5Ophthalmology, University of Iceland, Reykjavik, Iceland.
Purpose: To validate snapshot spectrophotometric retinal oxygen saturation
measurements, by comparison to femoral arterial saturation over a wide range of
oxygen saturation.
Methods: Female domestic pigs were used for all experiments. Oxygen
concentrations in inspired air were changed using a mixture of room air, pure
oxygen and pure nitrogen, ranging from 5 % to 100 % oxygen concentration. At
each level of inspiratory oxygen concentration, femoral arterial blood gas analysis
and retinal oximetry was performed.
Retinal oximetry was made using a commercial instrument (Oxymap Retinal
Oximeter T1, Oxymap ehf, Reykjavik, Iceland). The instrument consists of a
fundus camera (Topcon TRC-50DX, Topcon, USA) coupled with a beam splitter
and two digital cameras. Images are acquired simultaneously at two wavelengths
(570 nm and 600 nm) and specialized software automatically detects retinal blood
vessels.
Results: Regression analysis (fig. 1) reveals a highly significant linear relationship
between femoral arterial saturation and retinal artery ODR values (R2 = 0.965, p
<0.001).
Analysis of the data using human calibration values resulted in abnormally high
saturation values. The retinal oxygen saturation measurements were recalibrated by
comparing femoral arterial saturation and retinal arterial saturation at 5-21%
inspiratory vO2 percentage.
Results for femoral blood gas analysis and retinal vessel oximetry are presented in
table 1.
Conclusions: Spectrophotometric snapshot oximetry is sensitive to systemic
oxygen saturation changes over a wide range. Care should be taken when
comparing measurements between humans and animal models.
Commercial Relationships: Sindri Traustason, None; Jens F. Kiilgaard, None;
Robert A. Karlsson, Oxymap ehf. (I, E, P); Sveinn H. Hardarson, Oxymap ehf.
(I, P); Einar Stefansson, Oxymap ehf. (I, P); Morten D. de La Cour, None
Support: The Danish Eye Health Society
Commercial Relationships: Reza Motaghiannezam, None; Florian M.
Heussen, None; Srinivas R. Sadda, Carl Zeiss Meditec (F), Heidelberg
Engineering (C), Optovue Inc. (F), Topcon Medical Systems (P); Scott E. Fraser,
None
Support: CIRM, DFG Grant He 6094/1-1; Research to Prevent Blindness
Physician Scientist Award; Beckman Institute for Macular Research
Validation of Snap-shot Retinal Oximetry by Porcine Experiments
Sindri Traustason1,2, Jens F. Kiilgaard3, Robert A. Karlsson4, Sveinn H.
Hardarson5, Einar Stefansson5, Morten D. de La Cour1,2. 1Department of
Ophthalmology, Glostrup Hospital, Glostrup, Denmark; 2Faculty of Health
Scanning Laser Oximetry: A New Approach To Metabolic Imaging Of The
Retina
Gisli H. Halldorsson1, Robert A. Karlsson1, Einar Stefánsson1,2. 1Oxymap,
Reykjavik, Iceland; 2Ophthalmology, University of Iceland / Landspitali University
Hospital, Reykjavik, Iceland.
Purpose: To develop and test a system for retinal oximetry based on scanning laser
ophthalmoscopy (SLO).
Methods: Images from an SLO (Optos Ltd, UK) were analyzed using two
wavelength oximetry algorithm (Oxymap ehf, Reykjavik, Iceland). The green
channel (532 nm) was used as an oxygen insensitive image and the red channel
(633 nm) was used as an oxygen sensitive image. The software identifies retinal
blood vessels, choose measurements points automatically, calculates optical density
ratios and estimates oxygen saturation in arterioles and venules. The results are
presented with a pseudocolor oxygen map as shown in the figure. The figure shows
pseudocolor oxygen map of the fundus where the red color of the arterioles
represents 90-100% oxygen saturation and the green color of the venules indicate
50-70% oxygen saturation.
Results: The system successfully produced pseudocolor images showing oxygen
saturation in retinal arterioles and venules (figure). In one eye mean retinal
arteriolar oxygen saturation was 95% and the mean venular oxygen saturation was
66%. In another individual mean arteriolar oxygen saturation was measured 107%
and the venular mean was 55%.
Conclusions: It is technically possible to derive information on retinal vessel
oxygen saturation from a scanning laser ophthalmoscope with two wavelength
oximetry algorithm. Preliminary results are promising and suggest that scanning
laser ophthalmoscopy may be used for retinal oximetry.
Commercial Relationships: Gisli H. Halldorsson, Oxymap ehf (I, E, P); Robert
A. Karlsson, Oxymap ehf (I, E, P); Einar Stefánsson, Oxymap ehf (I, P)
Support: None
Multi-wavelength Photoacoustic Ophthalmoscopy for Retinal Oximetry
Hao F. Zhang1, Shuliang Jiao2, Qing Wei1, wei song1. 1Biomedical Engineering,
Northwestern University, Evanston, IL; 2Ophthalmology, University of Southern
California, Los Angeles, CA.
Purpose: To demonstrate the capability of photoacoustic ophthalmoscopy (PAOM)
in measuring retinal hemoglobin oxygen saturation (sO2) based on multiwavelength optical illumination and ultrasonic detection.
Methods: In PAOM, nanosecond laser pulses illuminate the retina at a 20-kHz
pulse repetition rate and a high-sensitivity small-footprint ultrasonic transducer
(center frequency: 35 MHz; bandwidth: 50%) detects the ultrasonic waves
generated from retina as a result of optical absorption. By combing time-resolved
recording of the laser-induced ultrasound with raster scanning of the illuminating
light across the region of interest, a three-dimensional image was acquired within
three seconds. To measure retinal sO2, a circular trajectory was scanned around the
optic disk and three optical wavelengths (570 nm, 578 nm, and 588 nm) were used
sequentially. Based on the molecular extinction coefficients differences between
oxy-hemoglobin and deoxy-hemoglobin at the three optical wavelengths, sO2 in
each retinal vessel scanned by the circular trajectory was calculated. The PAOM
was also integrated with an optical coherence tomography (OCT), which provided
optical alignment prior to PAOM imaging and complementary imaging contrast to
PAOM. Doppler OCT was performed together with multi-wavelength PAOM to
validate sO2 measurements.
Results: Through circular scan around the optic disk, multi-wavelength PAOM
acquired the sO2 levels in all the major retinal vessels and, therefore, retinal veins
and arteries were separated according to the measured sO2 values, which agreed
with other literature data. Doppler OCT scanned the same circular trajectory as
multi-wavelength PAOM and the blood flow direction in every retinal vessel
imaged by PAOM was obtained. As a result, retinal arteries and veins were also
separated based on the fact that venous bloods flow inward and arterial bloods flow
outward. The two independently achieved arterial-venous separations matched in
every single vessel, which validated the PAOM measurements. We imaged several
Sprague Dawley rats (body weight: ~ 500 g) and the results were consistent.
Conclusions: Being the only optical-absorption-based retinal imaging technology,
PAOM hold promise in both fundamental study and clinical diagnosis of diseases,
such as diabetic retinopathy, which manifest early pathological alterations in retinal
oxygenation. In the future, by combining sO2 measurement with precise blood flow
measurement by Doppler OCT, we can potentially acquire global or regional
metabolic rate of oxygen in retina.
Commercial Relationships: Hao F. Zhang, 20100245770, 20100245769,
20100245766 (P); Shuliang Jiao, 20100245770, 20100245769, 20100245766
(P); Qing Wei, None; wei song, None
Support: NIH 1RC4EY021357, NIH 1R01EY019951, NSF CBET-1055379
The Impact Of Stimulus Duration In Mesopic Microperimetry
Margherita Casciano1,2, Enrica Convento1,2, Evelyn Longhin1,3, Stela Vujosevic2,3,
Edoardo Midena1,2. 1Department of Ophthalmology University of Padova, Padova,
Italy; 2The International Microperimetry Reading Centre, Padova, Italy;
3
Fondazione G. B. Bietti, IRCCS, Roma, Italy.
Purpose: To evaluate if different light stimuli duration may modify final sensibility
thresholds during microperimetry (MP) examination.
Methods: Twenty healthy subjects (20 eyes) were enrolled in this study. Two
consecutive microperimetry examinations (MAIA; CenterVue, Padova, Italy) were
performed 30 minutes apart from each other, with following parameters: 37-stimuli
grid covering central 24° of the macula, 4-2 threshold strategy, fixation target: red
circle of 1° diameter, stimulus size Goldmann III, background luminance set at 4
asb, stimulus dynamic range 36 dB. Duration of light stimulus was set at 200 msec
or 40 msec. The sequence of exams with the 2 different stimuli duration was
randomly performed. Fixation stability was determined for each examination.
Stable fixation was indicated when more than 75% of the fixation points were
located within a predetermined circle area of 2° (P1), regardless of the position of
the foveal center. Relatively unstable fixation was indicated if less than 75% of the
fixation points were located within a 2° circle, but if more than 75% of the fixation
points were located within a 4° circle area (P2). Unstable fixation was indicated if
less than 75% were located within a 4° circle.
Results: Mean age of included subjects was 27.5±3.9 years. Mean light thresholds
were significantly reduced with 40 msec-MP (24.7±1.1 dB) versus 200 msec-MP
(28.1±1.0 dB) examination, (p=0.0001). Mean duration of 40 msec exams was
4.7±0.3 min, versus 4.7±0.5 min of 200 msec, (p>0.1). Fixation was stable in all
subjects with 40 and 200 msec stimuli duration. The number of fixation points in
P1 and P2 areas did not show any difference between 40 msec-MP and 200 msecMP examination, (p>0.1).
Conclusions: Short stimuli duration decreases mean retinal thresholds during
microperimetry examination in normals. Fixation stability seems not to be
dependent on stimuli duration in normals. This finding should be taken into account
in planning clinical trials.
Commercial Relationships: Margherita Casciano, None; Enrica Convento,
None; Evelyn Longhin, None; Stela Vujosevic, None; Edoardo Midena, None
Support: None
Retinal Hemodynamic Response to Hyperoxia
Margaret M. O' Halloran1, Chris Dainty1, Eamonn O' Donoghue2. 1Applied Optics
Group, School of Physics, National University of Ireland, Galway, Galway,
Ireland; 2Department of Ophthalmology, University College Hospital Galway,
Galway, Ireland.
Purpose: To improve the accuracy in the determination of the vascular reactivity of
normal, healthy eyes during hyperoxic provocation using a high resolution imaging
modality - a confocal scanning laser ophthalmoscope.
Methods: Imaging is performed with a manufacturer modified HRT classic. It has
been modified to enable imaging of the retina at a 10, 2, or 1 degree field of view
(FOV). It acquires a sequence of 32 frames at a single focal plane to obtain a video
of the vasculature in approximately 1.5 s. A number of sequences were obtained, at
the 2 degree FOV, of a selected vessel segment before and during the
administration of 100% oxygen via a non-rebreather mask. Each sequence was then
registered and averaged. The vessel diameter before and during hyperoxic
provocation was determined using vessel tracking and edge detection techniques
applied to the average image, and the magnitude of vasoconstriction was
subsequently calculated.
Results: 8 eyes of 7 normal subjects were imaged. Arterioles approximately 1 disc
diameter from the optic nerve head were imaged before and during hyperoxia. A
constriction of the vessels was observed in all cases, with a mean % constriction of
8.1 ± 2.0 %. To investigate the repeatability, the same vessel segment in one
subject was measured during 3 different imaging sessions. A mean % constriction
of 8.32 ± 0.2 % was obtained.
Conclusions: To the best of our knowledge, this is the first application of a high
resolution imaging modality to the assessment of retinal vascular reactivity. This
promises to improve the accuracy and reproducibility of the assessment of
reactivity.
Commercial Relationships: Margaret M. O' Halloran, None; Chris Dainty,
None; Eamonn O' Donoghue, None
Support: PTRLI-4 and SFI grant 07/IN1/1906
Retinal Pulse Wave Velocity Increases With Age In Medically Validated
Healthy Volunteers
Konstantin E. Kotliar1,2A, Marcus Baumann2A,2B, Alexander Djimandjaja2A, Ines
Lanzl2B, Uwe Heemann2A, Martin Halle2C,3, Arno Schmidt-Trucksaess3. 1Mech Eng
& Control Processes, St Petersburg Technical Univ, St Petersburg, Russian
Federation; ANephrology, BOphthalmology, CPreventive and Sports Medicine,
2
Technische Universität München, Munich, Germany; 3Division of Sports
Medicine, University of Basel, Basel, Switzerland.
Purpose: We demonstrated previously in a pilot study that both aging with not
excluded cardiovascular risk factors and mild arterial hypertension are associated
with elevated retinal pulse wave velocity (rPWV) as a measure of retinal arterial
stiffness. Whether rPWV increases with age in a cohort of medically validated
healthy subjects is investigated.
Methods: 71 healthy 41.0±12.1 (range: 20 - 66) years old volunteers were
examined. The following cardiovascular risk factors were excluded: overweight,
increased blood pressure, cholesterol level and blood glucose. Time dependent
alterations of vessel diameter were assessed by the Dynamic Vessel Analyzer
(IMEDOS Systems, Jena, Germany) in a segment of a retinal artery. The data was
filtered and evaluated by methods of mathematical signal analysis and rPWVs were
calculated.
Results: rPWV amounted to 370±100 (range: 180 - 620) RU(relative units)/s in the
whole group. 1RU corresponds to 1µm in the Gullstrand’s eye model. rPWV
increased significantly with age: r=0.41 (Pearson’s correlation, p<0.005). There
was a weak negative correlation with vessel diameter: r=-0.27, p<0.05 as well as a
weak positive correlation with mean arterial pressure: r=0.22, p<0.05.
Conclusions: Our results show that healthy aging with excluded cardiovascular
risk factors is associated with increased rPWV and hence with age-related elevation
of retinal arterial stiffness. However rPWV increases in medically validated healthy
volunteers to a much less extent than in hypertensive subjects or in subjects with
not excluded cardiovascular risk.
Commercial Relationships: Konstantin E. Kotliar, None; Marcus Baumann,
None; Alexander Djimandjaja, None; Ines Lanzl, None; Uwe Heemann,
None; Martin Halle, None; Arno Schmidt-Trucksaess, None
Support: Else-Kröner-Fresenius-Stiftung P27/10//A33/10
Comparison Of Retinal Sensitivity In Normal Subjects Using Two Types Of
Microperimetry Devices
Hong T. Liu, Millena Bittencourt G. Bittencourt, Mohanmed Ibrahim, Kristen
Bowles, Yasir Sepah, Owhofasa Agbedia, Jithin Yohannan, Afsheen Khwaja, Diana
V. Do, Quan D. Nguyen. Wilmer eye institute, Johns Hopkins, Baltimore, MD.
Purpose: To evaluate the comparability and potential correlation of retinal light
sensitivity obtained by Nidek MP-1™ (Nidek Technologies, Italy) and OPKO
Spectral-OCT/SLO™ (OPKO Health Inc., USA).
Methods: Subjects with no known ocular diseases were enrolled in the study. The
inclusion criteria were best-corrected visual acuity of 20/20 or better with a
refractive error within ±6 diopters (D) and astigmatism within ±1.0 D. Both eyes of
each subject were tested using MP-1 and the Spectral-OCT/SLO™. The test
settings are summarized in Table 1.
Results: 14 normal subjects (25 eyes) with a mean age of 31 years (range: 20-45
years) were enrolled. 3 eyes were excluded due to poor foveal fixation or high
refractive error. The mean spherical equivalent refractive error was -2.47DS (range
+0.50 to -6.00 DS). The results of the retinal light sensitivity comparisons are
summarized in Table 2. The sensitivity of the 4 central points in the pattern was
also evaluated and the results are summarized in Table 3.
Conclusions: The lack of correlation between MP1 and SD OCT/SLO™ may be
explained by the intrinsic difference in background luminance between devices and
stimulus attenuation scale, creating different stimulus-contrast and retinal light
adaption. Our pilot study has shown that it is unlikely for the MP1 and SD
OCT/SLO to be used interchangeably. SD OCT/SLO™ offers a wider range of
sensitivity detection, which may allow finer differentiation of retinal sensitivity.
However, additional studies, with a greater number of subjects among other factors,
are indicated to confirm our findings.
Commercial Relationships: Hong T. Liu, None; Millena Bittencourt G.
Bittencourt, None; Mohanmed Ibrahim, None; Kristen Bowles, None; Yasir
Sepah, None; Owhofasa Agbedia, None; Jithin Yohannan, None; Afsheen
Khwaja, None; Diana V. Do, None; Quan D. Nguyen, Research funding has been
provided by OPKO Health. (F)
Support: None
Double-Scanning to Visualize the Retinal Micro-Vasculature with PhaseResolved Optical Frequency Domain Imaging
Boy Braaf1, Koenraad A. Vermeer1, Kari V. Vienola1, Victor Arni D. P. Sicam1,
Johannes F. de Boer1,2. 1Imaging Group, Rotterdam Ophthalmic Institute,
Rotterdam, The Netherlands; 2LaserLaB, Department of Physics and Astronomy,
VU University Amsterdam, Amsterdam, The Netherlands.
Purpose: To visualize the retinal micro-vasculature with phase-resolved optical
frequency domain imaging (OFDI).
Methods: A scan-pattern was developed for a two-fold scanning of retinal
structures with high location stability. This method enabled phase-resolved OFDI
imaging with a long time-delay which enhances the visualization of blood flows
with a low flow velocity component parallel to the OCT-bundle. This technique
was implemented in a 1-µm OFDI system from an earlier study (Braaf et al., Optics
Express 2011) with custom phase-stabilization software for imaging of blood flow.
The macula of a healthy volunteer was scanned over an area of 3 mm x 3 mm with
a time-delay of 2.48 ms between two B-scans at the same location to visualize
blood flows with velocities down to 0.4 mm/s for an 89° angle of incidence.
Results: The retinal micro-vasculature was successfully visualized around the
foveal avascular zone (Fig. 1) by integration of the absolute phase difference at
every location. Several small arteries and veins as well as arterioles and venules can
be resolved for vessel diameters down to 40 µm. A cross-sectional intensity image
(Fig. 2) is shown with the retinal blood flow marked in red. This image clearly
shows the cross-sectional visualization of the numerous vessels that are observed in
figure 1. This type of vascular imaging is clinically relevant for the screening of
ocular pathologies with early micro-vasculature changes.
Conclusions: The retinal micro-vasculature can be imaged with OFDI using the
double-scanning method.
Commercial Relationships: Boy Braaf, None; Koenraad A. Vermeer,
None; Kari V. Vienola, None; Victor Arni D. P. Sicam, None; Johannes F. de
Boer, OCT Technology (P)
Support: Stichting Wetenschappelijk Onderzoek Oogziekenhuis (SWOO) Prof.
Dr. H.J. Flieringa and the Dutch MS Research Foundation

ARVO 2012 Annual Meeting Abstracts

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