Reduction ofocular chromatic aberrationby 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.
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 providea 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 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)
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 “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 50% transmissionat 409 nm 50% transmissionat 458 nm
Results: Chromatic Refractive Error(at 50% Transmission Wavelengths of IOLs) y =-0.90 D y = -1.65 D 0.75 D = difference between the 2 IOL modelsin effective ocular chromatic aberration x = 458 nm (λ fromSN60AT IOL) x = 409 nm(λ fromSA60AT 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 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 IOLsreduced chromatic aberration in vitro(relative to the UV filtering SA60AT IOLs)by 0.75 D at the blue end of the visible spectrum
Acknowledgements The author thanks Xin Hong, PhD(of Alcon Research, Ltd., Fort Worth, TX)for providing source data.