Objective signs of photoreceptor displacement by binocular correspondence perimetry: a study of epiretinal membranes

Abstract

Purpose: To describe a method for quantitative mapping of metamorphopsia and abnormalities of oculocentric direction in subjects with epiretinal membranes.

Methods: Binocular correspondence perimetry was performed using red and green dichoptic stimuli applied in a rectangular grid pattern. The study included 9 healthy subjects and 10 subjects with a unilateral premacular epiretinal membrane and a healthy fellow eye. Interocular visuospatial correspondence was expressed in a visuospatial deviation score and the binocular correspondence perimetry plots were displayed in proportion to fundus photographs. A reference interval was defined as the 95% CI for the average visuospatial deviation score in healthy subjects.

Results: In 6 out of 10 subjects with epiretinal membranes, visuospatial alignment deviated beyond the reference interval found in healthy subjects, whereas 4 subjects were within the normal range. The deviation score increased with decreasing visual acuity, although indications of heterogeneity of the subject population were identified, suggesting that visual acuity reduction and metamorphopsia may be dissociated in some types of epiretinal membranes.

Conclusions: Binocular correspondence perimetry enables quantitative mapping of metamorphopsia and stratification of subjects with epiretinal membranes with respect to normative references. Data from healthy subjects appear to describe a physiological level of tolerance for changes in oculocentric direction, which may apply also to the changes induced by retinal traction.