Download Reduction of ocular chromatic aberration by a blue light filtering

Reduction of
ocular chromatic aberration
by a blue light filtering
intraocular lens
Jim Schwiegerling, PhD
Ophthalmology and Vision Science,
The University of Arizona
This study was funded by Alcon, which also assisted with preparation of this poster. 1
Introduction
BECAUSE
• Longitudinal chromatic aberration makes eyes myopic
focusing blue light, emmetropic focusing green light, and
hyperopic focusing red light,1 and
• Placing colored filters2 or achromatizing optics3 in front of
the eye can improve contrast sensitivity
THEREFORE
Blue light filters in intraocular lenses (IOLs) might provide
a visual benefit in reducing chromatic aberration
PURPOSE
To compare in vitro refractive error as a function of visible
wavelength for a blue light filtering IOL versus a clear IOL
2
1. Thibos LN, Bradley A, Zhang XX. Effect of ocular chromatic aberration on monocular visual performance. Optom Vis Sci. 1991;68:599-607.
2. Rieger G. Improvement of contrast sensitivity with yellow filter glasses. Can J Ophthalmol. 1992;27:137-138.
3. Manzanera S, Piers P, Weeber H, Artal P. Visual benefit of the combined correction of spherical and chromatic aberrations. Invest Ophthalmol
Vis Sci. 2007;48:1513.
Methods: Transmission Spectra
Ultraviolet and visible transmission spectra were measured
by placing AcrySof IOLs (Alcon Laboratories, Inc.) in a wet
cell spectrophotometer system.
Experimental design included:
– a Perkin-Elmer Lambda 35 UV/Visible spectrophotometer,
equipped with a Lab Sphere RSA-PE-20 integrating sphere
– a quartz cell (CVI Laser, LLC Wavefront Sciences Quartz Cuvette)
• shaped as a rectangular cylinder (5 × 19.8 × 34.3 mm)
• contained a custom insert to hold the IOL
• filled with Balanced Salt Solution
– 3 transmission spectra per IOL, from 20 IOLs with 30.0 D power
• 10 IOLs that filtered ultraviolet light only (model SA60AT)
• 10 IOLs that filtered ultraviolet and blue light (model SN60AT)
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Methods: Ocular Modeling
The 50% transmission points of the averaged transmission
spectra for each IOL were fitted to a well-established model of
the “chromatic eye,” which shows the variation of refractive
error of the human eye across the visible spectrum:
The “Chromatic Eye” Model
Refractive error, D
0.5
0
-0.5
-1
-1.5
-2
-2.5
375
425
475
525
575
625
Wavelength, nm
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“Chromatic eye” figure replotted from data in:
Thibos LN, Ye M, Zhang X, Bradley A. The chromatic eye: a new reduced-eye model of ocular chromatic
aberration in humans. Appl Opt. 1992;31:3594-3600.
Results: Transmission Spectra
100
90
% Transmission
80
70
60
50
40
30
20
SN60AT
SA60AT
10
0
375
425
50% transmission
at 409 nm
5
475
50% transmission
at 458 nm
525
575
Wavelength, nm
625
Results: Chromatic Refractive Error
(at 50% Transmission Wavelengths of IOLs)
-0.5
-1
y=
-0.90 D
0
y = -1.65 D
Refractive error, D
0.5
0.75 D = difference between the 2 IOL models
in effective ocular chromatic aberration
-1.5
-2
-2.5
375
425
475
525
575
625
Wavelength, nm
x = 409 nm
(λ from
SA60AT IOL)
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x = 458 nm
(λ from
SN60AT IOL)
“Chromatic eye” figure replotted from data in:
Thibos LN, Ye M, Zhang X, Bradley A. The chromatic eye: a new reduced-eye model of ocular chromatic
aberration in humans. Appl Opt. 1992;31:3594-3600.
Discussion:
The Blue Filter in Context
• The blue light filtering chromophore was designed to
protect the retina against phototoxicity mediated by blue
light1
• Among wavelengths in the visible spectrum, blue light is
most phototoxic2 and the most strongly aberrated
longitudinally (versus chromatic mean)3
• The correction of chromatic aberration reported in this
study was due to the chromophore that was intended to
protect the retina
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1. Sparrow JR, Miller AS, Zhou J. Blue light-absorbing intraocular lens and retinal pigment epithelium protection in
vitro. J Cataract Refract Surg. 2004;30:873-878.
2. Sparrow JR, Nakanishi K, Parish CA. The lipofuscin fluorophore A2E mediates blue light-induced damage to
retinal pigmented epithelial cells. Invest Ophthalmol Vis Sci. 2000;41:1981-1989.
3. Thibos LN, Ye M, Zhang X, Bradley A. The chromatic eye: a new reduced-eye model of ocular chromatic
aberration in humans. Appl Opt. 1992;31:3594-3600.
Conclusions
The blue light filtering SN60AT IOLs
reduced chromatic aberration in vitro
(relative to the UV filtering SA60AT IOLs)
by 0.75 D at the blue end of the visible spectrum
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Acknowledgements
The author thanks Xin Hong, PhD
(of Alcon Research, Ltd., Fort Worth, TX)
for providing source data.
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