Wavefront-Guided Programmable Spectacles – Related Metrics

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Wavefront-Guided
Programmable Spectacles
– Related Metrics
Lawrence Sverdrup, Sean Sigarlaki,
Jeffrey Chomyn, Jagdish Jethmalani,
Andreas Dreher
Ophthonix, Inc.
23rd February 2007
All content  2007 Ophthonix, Inc. All Rights Reserved
Outline
• Background on Ophthonix Technology and
Metrics for Wavefront Correction Accuracy
• Wavefront Candidacy, a Metric for iZon
Lens Preference
• Chromatic Aberration Reduction and the
“Effective Abbe Value” Metric
Ophthonix Inc. Technology
• Z-View Wavefront Aberrometer
• iZon Wavefront-Guided Spectacle Lens
Z-View Wavefront Aberrometer
• Diffractive Talbot
sensor
• Less expensive than
Shack-Hartmann
devices
• Higher spatial
resolution than SH
devices
• Binocular Viewing
• Specifies Prescription
iZon™ – Lens Configuration
Cover
Lens blank
(sphere cylinder,
axis in surface)
iZonik™ polymer
iZon Lens Technology
(Ophthalmic Technologies XVII, SPIE vol. 6426A, Jan 2007)
Target Fringes
Recorded Fringes
0.20µm Z4,-4 + 0.29µm Z4,0 @ 5mm
Example of iZon Lens Capability
Target
Fringes
4.4 mm
Diameter
Lens Blank
Error
6 mm
Diameter
Erase
Lens Blank
Error
6 mm
Diameter
Programmed
Fringes
4.4 mm
Diameter
Metrics for Wavefront
Correction Accuracy
Correction Factor =
ZP
P
Z P ⋅ ZG
P
= cos (θ ) =
Purity =
Z P ZG
ZG
RMS Accuracy = 1 −
( ZG − Z P ) ⋅ ( ZG − Z P )
ZG
2
ZG = Zernike vector programming goal
ZP = Zernike vector actually programmed
Zernike RMS Accuracy of 89.5%
Target Fringes @ 4.57mm
Fringes Measured in Lens
Wavefront Candidacy,
a Metric for
iZon Spectacle Lens Preference
Subjective Preference Study
• iZon lens prescribed by the Z-View vs. a
conventional lens prescribed by an
optometrist via manifest refraction.
• Both lenses based on 1.6 index plastic and
have identical AR coatings.
• 67 patients from 7 independent practices.
• Sites and tester double masked. Subjects
wore each pair for 7 days and the order of
wear was randomized.
• Subjects filled out a lifestyle questionnaire
after wearing each pair. Data from the
questionnaires was analyzed.
Neural Network Training
• Back-propagation network with one hidden
layer
• High-order aberration measurements were
used as input parameters
• Output:
Value of 1 = iZon lens preferred
Value of 0 = Conventional lens preferred
Results: Neural Network Profiling
Rel. Preference Weight
Dependence of Patient Preference on Amount
of Spherical Aberration
0.6
0.5
0.4
0.3
0.2
Average
Physiological
Level
0.1
0
0
0.1
0.2
0.3
Spherical Aberration [ D/mm^2 ]
0.4
of Trefoil
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Average
Trefoil
Magnitude
0
0.05
0.1
0.15
Trefoil [ D/mm ]
0.2
of Coma
0.6
0.5
0.4
0.3
0.2
Average
Coma
Magnitude
0.1
0
0
0.2
0.4
Coma [ D/mm ]
0.6
Patient Profiling in Z-View Software
• Z-View Aberrometer
software
incorporates the
neural network
algorithm which
automatically
identifies patients
who would benefit
from iZon lens
correction.
Reduction of Chromatic
Aberration in Spectacle Lenses
Threshold for Obvious TCA Blur
30
d mm ⋅ Pdiopter
10 ⋅ V
Threshold 1 : 0.1∆
Measurable Degradation
well before Threshold
Distance from Optical Center (mm)
TCA =
25
20
15
10
5
0
1
Threshold for Obvious TCA Blur
Abbe Value = 42
Mo Jalie
Ophthalmic Lenses & Dispensing
0
2
4
6
Power (diopters)
8
10
Study Involving Polycarbonate1
• VA of 40 eyes with an average acuity of
20/13
• VA reduced linearly to 20/31 through 16
diopters of prism
P∆ =
1 Hampton
d mm ⋅ Pdiopters
10
et al., JAOA, Volume 62, No. 19 (1991) pp. 760-765
Programmable Layer has
Chromatic Effects
Two requirements for
chromatic effects:
• Optical Power
• Different Abbe Values
Effective Abbe Number
by Design
P1 + P2 = P
P1 P2
+
=0
V1 V2
P1 P2
P
+
=
V1 V2 Veffective
Effective Photopic Abbe Value –
Laser Displacement Measurements
P∆
P∆
TCA ≡
=
V V photopic
Veffective photopic
P∆
1 ( 39r543 + 12r594 )
≡
= ... =
⋅
170
TCA
( r543 − r594 )
Chromatic Aberration Measurement
Set-Up
Beam
Forming
Aperture
Variable
Attenuator
Beam
Steering
Device
Laser
Spatial
Filter
Aperture
Camera
Test
Lens
Parameter
Value
Spatial Filter Aperture Diameter
10 µm
Beam Forming Aperture (BFA) Diameter
500 µm
Distance Between Apertures
50 cm
Distance from Lens to Camera
50 cm
Distance from BFA to Lens
2.5 cm
Pure Lens Materials
Effective Abbe Value Measurements
70
Effective Abbe Value
60
50
40
30
20
Polycarbonate Ave
CR39 Ave
1.6 Plastic Ave
10
0
0
5
10
15
Distance from the Optical Center (mm)
20
Composite iZon Lens
Effective Abbe Value for a Composite iZon Lens
4
Effective Abbe Value
Relative to Base Plastic
2
Radius 1
Radius 2
Radius 3
Radius 4
0
-2
-4
-6
0
5
10
15
Radial Distance from Optical Center (mm)
20
Conclusions
• Wavefront profiles have been successfully used to
predict patient preference for wavefront-guided
lenses using a neural net based metric
• A new metric, the effective photopic Abbe value, has
been used to characterize the chromatic quality of
ophthalmic lenses, including composite lenses.
• Measurements demonstrate that the iZon lens has
a significantly elevated effective Abbe value and
chromatic quality in the lens periphery (where TCA is
important) as compared to that of the base plastic.
www.izonlens.com
(858) 869-2100
(877) FOR-iZon

Wavefront-Guided Programmable Spectacles – Related Metrics

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