Electrophysiological research on the effects of optic-induced astigmatism on transmission time and response intensity of visual signals in the visual cortex

Abstract

Objective To evaluate the contribution of different degrees of astigmatism on the latency and amplitude of pattern visual evoked potentials (PVEPs).The effect of astigmatism on the transmission and response intensity of visual signals in the visual cortex was evaluated.Methods It was a random designed study.PVEPs were measured in subjects with normal or normal corrected visual acuity using a checkerboard pattern stimulus under varying conditions using different astigmatic trial lens powers in succession (0-5 D).Paired samples t test,analysis of variance and Pearson correlation was performed.Results When a lower spatial frequency (60' checkerboards stimulus) was used,there was little change in the latency of P100 (F=0.290,P＞0.05).However,when a higher spatial frequency (15' checkerboards stimulus) was used,VEP latency increased with a greater degree of astigmatism (F=10.850,P＜0.01; r=0.647,P＜0.01).There was a gradual reduction of amplitudes of P100 as convex cylindrical lens power increased (when 60' checkerboards were used, F=3.947,P＜0.01; r=-0.470,P＜0.01; when 15' checkerboards were used,F=14.280,P＜0.01; r=-0.699,P＜0.01).Conclusion The transmission of visual signals depends on the quality of the visual image formed on the retina.Visual signal transmission time and response intensity in the visual cortex are affected not only by the defocus of the retinal image but also by the spatial frequency of the pattern stimulus.With a high spatial frequency,the transmission of visual signals is faster and the response intensity of the visual cortex is greater if the visual image formed on the retina is clear. Key words: Astigmatism; Evoked potentials,visual,pattern; Optic inducing; Phototransduction