Paradoxical improvement of visual acuity in macular disease

Abstract

Purpose: Improvement in visual acuity is often considered the best indicator of the effectiveness of a treatment in age-related maculopathy. However, during the course of the disease, the location of the patients' preferred retinal locus of fixation may change. This can lead to an unexpected functional improvement, unrelated to treatment.

Methods: From a running database of 1,369 retina patients, we identified 116 patients over 60 years of age when age-related maculopathy was diagnosed based on the following inclusion criteria: one study eye with an initial acuity of the logarithm of the minimum angle of resolution (logMAR) 0.7 or worse, a fellow eye with central fixation and a follow-up period of 3 years or more with precise documentation of the preferred retinal locus of fixation and scotoma distribution for both eyes using scanning laser ophthalmoscopy-based microperimetry.

Results: We expected an improvement in the visual acuity in one eye (study eye) without the possibility of improvement due to previous or concurrent treatment in that eye. Twelve patients met the selection criteria. Over time, these patients had significant improvements in the visual acuity in the weaker study eye, characteristically accompanied by a concurrent decrease in visual acuity in the other eye, which initially had better visual acuity. Moreover, in all the study eyes, an unstable pseudo-central von Noorden fixation pattern evolved into a more stable eccentric preferred retinal locus.

Conclusions: Visual acuity remains the gold standard for assessing visual functioning in age-related maculopathy when interpreted with caution. Improvements in visual acuity can occur solely due to the course of the disease in the other eye and as a result of its impact on binocular fixation characteristics. This finding has significant implications for low-vision rehabilitation and evaluation of various therapies in large long-term clinical studies.