Progressive visual loss in subfoveal exudation in age-related macular degeneration: a meta-analysis using Lineweaver-Burke plots

Abstract

Purpose: To analyze the randomized clinical trials in exudative age-related macular degeneration (AMD) to reveal apparent differences in the behavior of untreated control eyes among these trials. Herein we test the hypothesis that the behavior of untreated control eyes is actually the same in all studies, with apparent differences arising from differences in the time of entry of eyes into clinical trials.

Design: Retrospective meta-analysis of prior clinical trials.

Methods: Control eye data from six AMD studies (Macular Photocoagulation Study, Subfoveal Surgery Trial, Photodynamic Therapy [TAP] With Visudyne, pegaptanib trial for neovascular AMD, anecortave acetate trial, and 360 degree Macular Translocation Study) were plotted on a double reciprocal plot of 1/(Letters Lost) vs 1/(Months After Enrollment). To account for differences in time of entry into clinical trials, we introduced a horizontal translation factor to shift each data subset horizontally to maximize r(2) for the cumulative trend line.

Results: Cumulative data for untreated control eyes fits a straight line on a double reciprocal plot (r(2) = .9521); an untreated eye would eventually deteriorate to a final vision of 20/640. The slope of the line predicts that patients would experience half of the maximum final vision within 10.88 months after exudation onset.

Conclusions: The pattern of vision loss experienced in AMD eyes with subfoveal neovascularization is uniform across a wide range of clinical trials, with apparent differences arising from differences in the time of entry of patients into clinical trials.