Change in Visual Acuity in Exudative AMD Is Influenced by the Fellow Eye Status

Abstract

Abstract: : Purpose: To examine the rate of visual decline in eyes with exudative AMD as a function of the baseline visual status of the fellow eye relative to its pair. Methods: A longitudinal database of patients attending a specialist macular retinal clinic with an angiographic diagnosis of exudative AMD in one or both eyes with a minimum follow of one year was established. LogMAR distance (DVA) had been measured in both eyes of each patient to a standardised protocol at each visit. In patients with bilateral AMD, the eye with better DVA was nominated the better eye and the fellow the worse eye. 261 patients were seen at baseline and at 12 months. We regressed the change in DVA (dependent variable) over 12 months in the better eye against the change in DVA in the worse eye (independent variable). We also repeated the regression with the variables reversed. Results: By obtaining the bisector of the regression equations (better eye DVA_t1 – better eyeDVA_t0) = 0.413 – (0.927 x worse eye DVA_t1– worse eye DVA_t0) we computed the influence of the fellow eye status on change in visual acuity in better eyes and worse eyes. In other words in the absence of any change in the worse eye over a period of 12 months, the better eye would decrease by an average of about 4 lines of DVA. If however, the worse eye decreased by one line of vision then the better eye would only decrease by 3 lines. Conclusions: Our study shows that the level of visual acuity in one member of a pair of eyes influences the rate of visual change in the fellow eye and thus could act as a confounder. These findings emphasize the importance of the fellow eye status when examining visual outcomes in longitudinal studies and even more importantly when testing the effects of interventions in randomised controlled trials.

Keywords: age-related macular degeneration • visual acuity