Lateral inhibition in the human visual system in healthy subjects and in patients with glaucoma

Abstract

Purpose In glaucoma, the density of retinal ganglion cells (RGCs) is reduced. It is largely unknown whether and how this influences the spatial interactions between the remaining RGCs. A decrease in lateral inhibition might arise and could result in a larger than expected response to some stimuli, which could mask RGC loss on functional glaucoma testing. The aim of this study was to compare lateral inhibition in the visual system between glaucoma patients and healthy subjects. Methods A case‐control study was performed with 14 glaucoma patients and 50 healthy subjects. Cases were selected to have advanced visual field loss in combination with a normal visual acuity. Controls had to have a negative ophthalmic and family history, normal eye pressure, and a normal acuity. Experiments were performed monocularly. Lateral inhibition was measured psychophysically on a computer screen, with (1) a modified illusory movement experiment and (2) a contrast sensitivity (CS) test. The illusory movement was quantified by nulling it with a real movement; measure of lateral inhibition was the amount of illusory movement. Log CS was measured at 1 and 4 cpd; measure of lateral inhibition was the difference between log CS at 1 and 4 cpd. Both measures of lateral inhibition were compared between cases and controls; analyses were adjusted for age with multiple linear regression Results There was no difference in lateral inhibition between cases and controls (P=0.76 for illusory movement; P=0.84 for CS testing). Log CS was lower in the cases than in the controls at both 1 (‐0.21; P=0.006) and 4 (‐0.22; P=0.016) cpd. Conclusion Lateral inhibition is not decreased in glaucoma patients, at least not in patients with a normal visual acuity.