Resistance to Glare Disability Provided byBlue Light–Filtering IOLs:Contralateral-Controlled Study W. Andrew Maxwell, MD, PhD California Eye Institute; Fresno, CA and Billy R. Hammond, Jr, PhD Vision Sciences Laboratory, University of Georgia; Athens, GA Disclosures: This study was funded by Alcon Research, Ltd, which also assisted with the preparation of these slides. Dr. Maxwell is a consultant to Alcon.
Introduction • Background: Glare light, such as the light from oncoming headlights, can reduce visual performance. • Purpose: This study was designed to compare glare disability… …in eyes with intraocular lenses (IOLs) that filtered short-wave blue light… …versus… …contralateral eyes with IOLs that did not filter visible blue light. Schematic colors and shapes are not anatomically or scientifically accurate; they are for purposes of explanation only.
Methods: Subjects and Apparatus • Eligible subjects were at least 12 months post-implantation of • a control IOL (model SA60AT; Alcon) and • a contralateral IOL that filtered blue light (spherical SN60AT or aspheric SN60WF; Alcon) • Test apparatus was a 2-channel Maxwellian-view optical system to produce a glare light and a target light on the retina of the subject: neutral density filter holder wedge (circular attenuating filter, to change glare intensity) beam splitter beam splitter eye Channel 1: Glare light Produced by a xenon lamp, to mimic xenon headlights or to approximate daytime sunlight spectrum aperture Channel 2: Visual Target mirror pupil viewer (Produced by a halogen lamp) aperture neutral density filter holder
Methods: A Subject’s View of the Test • 1. Subject saw • A. a 3.1°-diameter halogen-light disk as the target • B. an annulus from the xenon channel with • a shape that was 20° inner and 22° outer diameter • an intensity that was too low to obscure the target A B Technician increased glare intensity • 2. Subject saw • A. the same central 3.1°-diameter disk, but • B. the brightness (ie, the glare) of the annulus was beginning to move toward obscuring the central target A B Technician increased glare intensity • 3. Subject saw • A. no central 3.1°-diameter disk, because • B. the glare from the annulus had obscured the central target. The intensity of the annulus of light at that point was defined as the glare disability value. A B Schematics are not exact representations; they are for purposes of explanation only.
Methods: Replicates and Analyses • Measurements • Masking: The technician who took the measurements was masked to the IOL type in each eye. • Replicates: 5 measures were taken per eye, unless a subject’s values had >5% variability, in which case up to4 additional trials were conducted. If extra trials were conducted, all trials were averaged into the mean result. • Analyses • Comparisons between IOL groups were performed using paired t-tests. • The mean values are presented as log energy values (µW/cm2).
Results: Demographics • At 5 clinical sites, a total of 52 subjects were enrolled. • 28 were women (54% of cohort) and 24 were men (46% of cohort). • Mean age = 76 ± 9 years • All subjects had a control SA60AT lens in 1 eye, and • 50% of subjects (26 of 52) had a contralateral model SN60AT lens(spherical IOL with the blue-filtering chromophore), and • 50% of subjects (26 of 52) had a contralateral model SN60WF lens(aspheric IOL with the blue-filtering chromophore). • The average duration of pseudophakia before entering the study was statistically similar between IOL groups, at • 5.2 ± 1.3 years for the eyes with blue-filtering IOLs, and • 5.6 ± 1.3 years for the eyes with control SA60AT IOLs, with • average duration between contralateral IOL implantations of 0.4 ± 1.1 years.
Results: Monocular Distance Visual Acuity (similar between groups)
Results: Glare Disability • For the overall population of 52 subjects at 5 clinical sites, significantly more glare light (P = 0.04) could be withstood by eyes with blue-filtering IOLs (1.97 ± 0.44 log µW/cm2) than by eyes with non-filtering control IOLs (1.88 ± 0.43 log µW/cm2)before losing sight of the target. • For the subpopulation of13 subjects at the Fresno site,†significantly more glare light(P < 0.05) could be withstood byeyes with blue-filtering IOLs thaneyes with non-filtering control IOLs before losing sight of the target †Site of Fogg, Maxwell, Lanier & Remington Eye Care
Discussion & Conclusions • Key finding: Compared with eyes with control IOLs, the eyes with blue-filtering IOLs had a higher mean threshold (higher mean resistance) to glare disability. • Proposed mechanism: The light entering the eye from the glare source was scattered toward the retina by the intraocular media, causing a veiling luminance over the visual target. Blue-filtering IOLs prevented some of the glare scatter. • Real-world applications: Analogous situations could occur under bright midday sunlight or when a driver is looking into oncoming headlights. By filtering such glare sources with a blue-filtering IOL, the visibility of a target within an individual’s sight line would be improved, and better edge detection could be provided, as was demonstrated by the model in this study. Read more at: • Hammond BR, Renzi LM, Sachak S, Brint SF. Contralateral comparison of blue-filtering and non-blue-filtering intraocular lenses: glare disability, heterochromatic contrast, and photostress recovery. ClinOphthalmol. 2010;4:1465-1473 • Gray R, Perkins SA, Suryakumar R, Neuman B, Maxwell WA. Reduced effect of glare disability on driving performance in patients with blue light–filtering intraocular lenses J Cataract Refract Surg 2011;37:38-44