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Annual Changes in Refractive Error Over 3 Years Among Eyes with Early AMD

Ophthalmology, University of Pennsylvania, Philadelphia, PA

Commercial Relationships: J.A. Sbarbaro, None; M.G. Maguire, None.

Grant Identification: none

Abstract

Purpose: To describe the changes in refractive error in eyes with 10 or more large (>125µm) drusen and visual acuity 20/40 or better.

Methods: Refractive error was measured at baseline and annually for 3 years for the 1052 patients enrolled in the Complications of AMD Prevention Trial (CAPT). Certified examiners followed a standardized protocol. Spherical equivalent (SE; sphere + cylinder) was used as the measure of refractive error. The untreated eye of each patient was used for analysis. The mean change from baseline and proportion of eyes with a clinically significant change in refractive error were calculated. A 0.5 D change in SE was defined as clinically significant based on the effect of dioptric blur on visual acuity and the inter–examiner variation in the measurement of refractive error. Changes in eyes that developed late AMD were compared to changes in eyes that did not develop CNV. Differences from baseline were assessed by the paired t–test and by Cochran–Mantel–Haenszel test for general correlation.

Results: The mean spherical equivalent changed +0.03 D (SD=0.49) at 1 year, +0.02 D (SD=0.68) at 2 years, and 0.05 D (SD=0.84) at 3 years. The proportion of eyes that changed by greater than 0.5 D increased with time from 16% at 1 year, to 22% at 2 years, to 32% at 3 years (general correlation, p<0.0001). Over the three years of visits, 13% of these changes were hyperopic while 10% were myopic. Eyes that developed CNV had a mean hyperopic change of +0.27 D (p=0.004) at the visit in which their CNV was documented.

Conclusions:Although there was little change in the mean spherical equivalent, the variability of the change from baseline increased with each successive measurement. By 3 years, nearly a third of eyes had changes in refractive error likely to cause significant change in visual acuity. Eyes with newly diagnosed CNV underwent significant hyperopic shifts. These results in patients with early AMD should prove useful in the planning of future clinical studies.

Keywords: age–related macular degeneration • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • refractive error development

© 2004, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. For permission to reproduce any part of this abstract, contact the ARVO Office at arvo{at}arvo.org.