LASIK, Epi–LASIK and PRK Past present and future

LASIK, Epi–LASIK
and PRK
Past present and future
Ioannis G. Pallikaris MD, PhD
Institute of Vision and Optics
University of Crete Medical School
Heraklion Crete Greece
Photorefractive Keratectomy
Kerr-Muir MG, Trokel SL, Marshall J, Rothery S.
Am J Ophthalmol. 1987 Mar 15;103(3 Pt 2):448-53
PRK used since 1980’s
Minimally invasive
procedure predictable,
safe up to -6.00D
Postoperative pain
Corneal haze
Regression of effect
Delayed visual
rehabilitation.
1990 Lasik Invention
Pallikaris IG, Papatzanaki ME, Stathi EZ,Frenschock O,
Georgiadis A.
Lasers Surg Med. 1990;10(5):463-8.
Lasik Advantages
Effective procedure
High predictability
Fast, Painless Recovery
Lack of Sub-Epithelial Haze
Pallikaris IG et al..Lasers Surg Med 1990
Are mainly due to the creation of a corneal hinged flap
Ideal flap thickness I
Until recently ideal flap has
been 130µm or greater in
order to guarantee
easier intraoperative
manipulations
better flap-to-bed fitting
fewer striae
fewer intraoperative
complications
(buttonhole, free cuts,
steps)
The deep lamellar cut will always
carry the risk of future iatrogenic
ectasia
Long term stability
Ideal flap thickness II
Shift towards thinner
flaps because of
Post-Lasik corneal ectasia
Pallikaris IG et al.JCRS 2001
Need for higher attempted
corrections
Kymionis GD et al.Am J Ophthalmol
2004
Trend for bigger ablation
zones, supplementary
topography, wavefront
guided treatments, flapinduced aberrations
Pallikaris IG et al. JCRS 2002
Sub Bowman Lasik
Sub-Bowman LASIK
Might be able to preserve the overall biomechanical
integrity of the cornea
Has better functional results than conventional flaps
(because a thinner flap can be better adjusted to the
ablated residual corneal bed as a result of less stromal
tissue in it’s composition)
can induce fewer aberrations than a conventional thicker
flap.
It can actually combine the advantages of
lamellar (LASIK) and surface (Epi-LASIK)
approaches.
Prospective study I
26 patients (47 eyes) mean age
28.78 ±6.98 (range, 20 to 54
years) underwent Sub
Bowman Lasik with the
Schwind microkeratome 90µm single use head
All patiens underwent Sub
Bowman Lasik Using the
Allegretto Wave Excimer Laser
(WaveLight Technologies,
Erlagen Germany)
Flap thickness
number of eyes
79.88 ±6.94µm for all eyes (range, 70 to 93µm)
18
16
14
12
10
8
6
4
2
0
70-79
80-89
flap thickness (µm)
90-100
Results I
Mean sph. equivalent. on the 1st postoperative day was -0.48 ±0.88 D
(range, -2.75 to 0.75 D)
Mean sph. equivalent on the 3rd postoperative day was -0.28±0.49 D
(range : -2 to 0.75 D)
0
sph.equivalent (D)
-1
1
2
-0,481382979
3
-0,281914894
-2
-3
-4
-5
-5,111702128
-6
preop
1st postop day
3rd postop day
Results II
Mean UCVA on the 1st
postoperative day was
0.80 ±0.21
(range, 0.20 to 1.20)
1
0,9
0,8
0,7
UCV A
0,6
0,5
0,4
Mean UCVA on the 3rd
postoperative day was
0.94 ±0.21
(range, 0.30 to 1.20)
0,3
0,2
0,1
0
1
preop
2
1st postop day
3
3rd postop day
Confocal images after ultra thin flap
(fast subepithelial nerve plexus recovery)
PREoperative
POSToperative
(1month)
Absence of subepithelial nerves
POSToperative
(3months)
Nerve regeneration
Complications
No intraoperative complications occurred
Few interface particles were observed on slit lamp
examination
On the 1st postoperative day 2 eyes presented
microstriae, 4 eyes presented DLK stage 1 and all were
successfully treated.
Discussion
Sub Bowman Lasik results in the creation of an ultra thin
flap which allows the correction of many diopters of
myopia without the fear of post-Lasik ectasia
It can lead to rapid and painless visual rehabilitation that
is apparent from the first postoperative day (in
dissociation with surface ablations)
The use of the Schwind 90µm single use head
microkeratome provides a safe and accurate procedure
without any intraoperative complications
EVOLUTION OF PHOTOREFRACTIVE TREATMENTS FOR
THE CORRECTION OF AMETROPIAS
PRK
Epithelial injury
•Postoperative pain
•Late visual recovery
•Risk of Haze
FDA approval:1995
Risk of corneal ectasia
Unpredictable
flap induced aberrations
Intrastromal incision
In a deep plane
in the stroma
Advanced Surface Ablations
LASIK
FDA approval:1999
Reasons for selecting a surface
treatment
Flap induced aberrations
Flap related complications
Preoperative dry Eye
Thin corneas for attempted correction
Epithelial basement membrane
dystrophies
Wavefront Aberration Map
Pre Flap
Post Flap
Pallikaris et al.Induced optical aberrations following formation of a laser in situ keratomileusis flap.
JCRS 2002; 28(10): 1737-41.
Epi-LASIK I
Surface ablation (epi-polis superficial)
Epithelium is separated as a sheet and replaced on the
ablated stroma
Special device (Epikeratome) -Automated procedure
No use of alcohol
Dealing with drawbacks of PRK (postoperative discomfort,
late visual recovery, haze) and avoiding risks of LASIK
Suitable in thin corneas
Epikeratome
Bowman’s layer
Corneal stroma
Intraocular Pressure
Epi-LASIK II
Centurion SES Epikeratome for epithelial separations
(Norwood Abbey, Australia)
Epi-LASIK III
Histological Studies I
Epithelium is separated underneath the basement membrane
Pallikaris IG, et al. Epi-LASIK: Comparative histological evaluation of mechanical and
alcohol - assisted epithelial separation. JCRS 2003
EPI-LASIK: Postoperative course
1 hour post surgery
1 day postop
Epithelial flap borders
Epithelial flap borders
DAY 3
Reepithelization
day
Confocal Images - Ablation Zone
Pre op
1 Month P op
6 Months P op
3 Months Pop
1 Year P op
Refractive results
163
treated eyes (average follow-up:12 months)
Attempted correction up to –8 D
Separated epithelial sheets of 9.5 to 10 mm
All eyes treated with the Wavelight Allegretto
Spherical Equivalent
1
-0,3
0
preop
1m
-0,19
-0,21
-0,17
3m
6m
1y
Mean SEq
-1
-2
Average Sph Eq
-3
-3,58
-4
-5
-6
Time
Scattergram of Attempted vs. Achieved Sph.Eq.
9
8
7
Attempted(D)
6
1 month (N=142)
5
3 months (N=111)
6 months (N=79)
4
3
2
1
0
0
1
2
3
4
5
Achieved(D)
6
7
8
9
Uncorrected Visual Acuity post Epi-LASIK
120%
100%
95%99%97%97%
81%
70%
80%
% eyes
91%93%
86%
Reep
1 month
60%
3 months
6 months
1 year
40%
20%
20%
0%
20/40 or better
20/25 or better
UCVA
BCVA Line gain/loss
70%
58%
60%
48%
50%
48%
46%
42%
40%
40%
1 month (N=142)
% eyes
37%
3 months (N=111)
6 months (N=79)
30%
1 year (N=26)
20%
20%
17%
12%
10%10%
10%
5%
4%
0% 0% 0%
2%
1%
0%
0%
-2
-1
0
Snellen lines
1
2
Incidence of corneal haze after myopic Epi-LASIK
100%
89%
90%
82%
80%
% of treated eyes
70%
67%
1 month
60%
50%
3 months
49%
6 months
39%
40%
1 year
27%
30%
16%
11%
20%
10%
12%
5%
1%0%
0%1%1%0%
0%0%0%0%
mild
moderate
marked
0%
clear
trace
Haze grade
Mean pain score on the first
postoperative day (N=163)
4
pain score
Oral medication
3Pain w/o medication
2Burning feeling
Discomfort
mean pain
1,46
1
1,07
0,82
0,65
0,38
0,18
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26
postoperative hours
The mean pain scores remained below the threshold of
burning sensation
PRK Revised
No need for suction (RD, Glaucoma concern)
No risk of corneal stromal cut
No keratome needed
Prophylactic PRK MMC
Catia Gambato, MD, Ophthalmology Volume 112, Number 2, February 2005
Gaston O. Lacayo III Curr Opin Ophthalmol 16:256—259. ª 2005
0.02% for 2 min standard. 12sec may be as
effective. >75um ablations.
Reduction of myofibroblast activity / haze
(compared to Corticosteroids)
Faster visual recovery (CSF) and confocal
microscopic normalization
Safety up to 9 yrs max experience
MMC application
MMC Therapeutic application
Laura T. Muller, MD, J Cataract Refract Surg 2005; 31:291–296
Alexandre S. Marcon, M.D.Cornea 21(8): 828–830, 2002.
Post complicated Lasik flap
(Minimum 3 weeks waiting time.)
PTK for corneal dystrophies
Haze / regression treatment post PRK
Combination with PTK
Reduce attempted correction (15-80% based on
PTK need)
Cellular effects of mitomycin-C on human corneas
after photorefractive keratectomy
Human corneas: 0, 1min, 2min MMC
Delay in epithelial healing @ 2min
Delay in anterior KC repopulation @2 >1 min
No difference in endothelial, mid and posterior
kc populations.
Conclusion: optimal MMC application 1 min
J CATARACT REFRACT SURG - VOL 32, OCTOBER 2006
Madhavan S. Rajan, MRCOphth, FRCS, David P.S. O’Brart, MD, FRCS, FRCOphth,Anne Patmore,
John Marshall, PhD
Intaoperative corneal cooling in PRK
Yoshihiro Kitazawa, MD, J Cataract Refract Surg 1999; 25:1349–1355
Pre, intra post operative corneal cooling (8deg
BSS)
Prospective randomized treatment >8D myopia.
F/U 2 yrs
Effects in pain, haze, regression
Practically: We apply frozen CL immediately
post PRK for 1 min
Postop pain score
Postop haze
Predictability
LASEK
Hassan Hashemi, MD J Refract Surg 2004;20:217-222
Jin Kook Kim, MDJ Cataract Refract Surg 2004; 30:1405–1411
Less stimulation of kc than PRK in rabbits (high
ablations)
Advantage vs PRK for small – medium
corrections ?
Not as good as LASIK for high corrections
(12.3% haze, regression)
Latest Research
Cytochrome-c peroxidase effect
Sergio Zaccharia Scalinci, MD,
J CATARACT REFRACT SURG - VOL 31, OCTOBER 2005
3 times application after
PRK vs placebo
Significantly faster
reepithelialization in
treated eyes
Cultured epithelial cells on PRK surface
Yasutaka Hayashida,
Hayashida, Osaka, Japan
Investigative Ophthalmology & Visual Science, February 2006, Vol.
Vol. 47, No. 2
Limbal stem cells harvested – cultured preop
Cultured cells applied on PRK surface
immediately postop
These epithelial cells SURVIVE
Ideal corneal stromal profile with no haze @ 2
months in rabbits
Cultured epithelial cells on PRK surface
Yasutaka Hayashida,
Hayashida, Osaka, Japan
Investigative Ophthalmology & Visual Science, February 2006, Vol.
Vol. 47, No. 2
Immature epithelium
Activated keratocytes
Normal epithelium and stroma
Thank you for your attention!
Institute of Vision and Optics
University of Crete Medical School
Heraklion Crete Greece