Electrophysiologic Research On Effects Of Optic Induced Ametropia Upon Visual Signals Transmitting And Response Intensity Of Visual Cortex

Objective:Researchs have revealed that the effect of optical defocus on the steady state pattern reversal visual-evoked response(P-VEP) and the effect of spacial frequancy on P-VEP,saperately.This study was to evaluate the contribution of different degree of retinal defocusing to the latency and amplitude of P-VEP.From which we evaluate the contrbution of refractive errors to the visual signals transmitting and response intensity of visual cortex.Methods:We used a set of convex cylindrical and concave spherical trial lenses with different diopters(cylindrical trial lenses:1D step,0D to 5D,with axis in the vertical meridian;spherical trial lenses:-1D step,0D to -6D,0D means no trial lens) on the basis of optimal refraction to imitate different levels of astigmatism and hyperopia.Pattern reversal visual evoked potentials(PVEP) of were measured in 13 volunteers(six of them participated in the cylindrical trial lenses group that mimical astigmatism,7 after cycloplegia participated in the spherical trial lenses group that inimical hyperopia) with normal or normal corrected visual acuity,whose visual acuity was reduced by adding astigmatic or negative trial lenses with different diopters in succession,to assess the influence of trial lenses on the latency and amplitude of P100.The PVEP were measured in 15' and 60' spatial frequencies saperately.The correlation of refractive error and latency and amplitud of P-VEP was assessed using Peason correlation analysis and paired t test.Present study followed the Statement of Helsinki,and the written consent information was obtained from all the subjects and this clinical trail was approved by the Ethic Committee of Tianjin Eye Hospital before the examination.Results:When larger check size(60' arc) was used,there were usually little change in the latencies of P100(r=0.083,P＞0.05) after wearing convex cylindrical lens; When concave spherical lens were used,they were mildly prolonged when the negative trial lenses were -5D and -6D(r=0.468,P＜0.01).However,there was a gradual reduction of amplitudes as a function of convex cylindrical and concave spherical lens power(r=-0.470,P＜0.001 and r=-0.468,P＜0.001).When smaller check size(15' arc) was used,The latency changed as a function of convex cylindrical and concave spherical lens power(r=0.647,P＜0.001,and r=0.669,P＜0.001),and amplitude were also changed as a function of convex cylindrical and concave spherical lens power(r=-0.699,P＜0.001 and r=-0.595,P＜0.001).Variations greater than 2Ds of the trial lenses could significantly induce several tens of milliseconds prolongation of the latencies of P100 when the spatial frequencies were at 15' arc(P＜0.01).Conclusions:Retinal defocusing could prolongage lantency of P100 wave.The latency of P100wave is affected by both defocusing of retinal image and spatial frequency of the pattern stimulus.The transmitting of visual signals dependeds on the quality of the visual image formed on the retina.Anisometropia more than 2Ds could induce tens of millisecends time delaying of of the transmitting of visual signals.