光学诱导散光对视觉信号传导及皮层反应的影响

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

目的研究光学诱导不同程度散光产生的视觉信号对皮层反应时间及强度的影响；研究散光是否可导致视觉信号传导时程异常，观察视觉信号传导时间及视皮层反应强度与散光程度的量化关系。方法完全随机设计研究。对视力或矫正视力正常的被检者眼前依次放置0～5D度数正柱镜片诱导不同程度散光。每一实验镜片条件下行单眼图形视觉诱发电位（PVEP）检查。记录P100振幅和潜伏期。数据采用单因素方差分析、配对t检验和Pearson相关性检验。结果当采用较低空间频率的刺激时（60＇棋盘格刺激），P100潜伏期随散光程度的增加变化不显著，无相关性，单因素方差分析示差异无统计学意义（F=0．290，P〉0．05），P100振幅随散光程度的增加而逐渐降低（F=3．947，P〈0．01；r=-0．470，P〈0．01）；当采用较高空间频率刺激时（15’棋盘格刺激），P100潜伏期随散光程度的增加而延长（F=10．850，P〈0．01；r=0．647，P〈0．01），P100振幅亦随散光程度增加而逐渐降低（F=14．280．P〈0．01；r=-0．699，P〈0．01）。结论成像于视网膜上的物像引起视觉中枢反应的时间和强度与视网膜物像的清晰度和空间频率密切相关，高空间频率的清晰物像引起视觉环路上的神经元发生反应较早较强：低空间频率的物像在清晰度下降时虽有皮层神经元反应强度的下降，但反应时间无明显延长。

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.