扫描图像视觉诱发电位视力与国际视力表视力的比较

Comparison of Objective Assessment Using the Sweep Pattern Visual Evoked Response Acuity(SPVERA) and Illiterate E Visual Acuity

目的研究扫描图像视觉诱发电位视力与国际视力表视力之间的相关性。方法通过对一组正常视力者插片模拟视力下降,并记录扫描图像VEP,研究二者的相关性。在SPVEP视力测定时,应用八个不同空间频率的垂直光栅作为刺激,刺激时间频率为25Hz,每一空间频率SPVEP振幅的均值经傅立叶转换分析显示,绘制振幅-空间频率曲线,并通过外推法估计视力。结论在视力中等度损害时,SPVEP视力与国际视力表视力相关性好。当国际视力表视力低于0.42时,SPVEP视力高于国际视力表视力;当国际视力表视力高于0.42时,SPVEP视力低于国际视力表视力。

Objective To compare the vision objectively assessed by SPVERA with the illiterate E Acuity in normal subjects. Methods The effect of artificially induced image defocusing on visual acuities （Vas） measured by SPVEP and illiterate E chart measurement was studied in 14 normal subjects. SPVEP was recorded using vertical gratings of 8 different spatial frequencies ranging from 0.235 9 to 30.203 2 c/deg. The responses were averaged and displayed through the discrete Fourier transform on the monitor display. SPVERA was determined by extrapolating the PVER amplitude-spatial frequency function to baseline. SPVERA was compared with illiterate E visual acuity measured under the same conditions of optical defocus. Results With moderate defocusing（〈＋1.0diopter（D）,VA〉0.42）, the SPVERA were equal to or poorer than the illiterate E visual acuity. With more defocus （〉＋2.0diopter （D）,VA〈0.3）,the SPVERA became better than the illiterate E chart Visual Acuity. The correlation between the two acuities was r2=0.919. Conclusion SPVERA and the illiterate E visual acuity correlated to a certain degree. We conclude that the SPVERA is effective in estimating vision objectively.