用P-VEP客观评价近视眼与正视眼的模糊辨别敏感性

Evaluation of blur detection sensitivity between myopia and emmetropia with pattern-VEP

目的应用Pattern-VEP法客观评价近视眼与正视眼的模糊辨别敏感性的不同。方法受试者34例,年龄18～28岁。分为正视组14例,平均屈光度(-0.17±0.28)D;近视组20例,平均屈光度(-3.73±0.85)D。散瞳验光后应用5mm人工瞳孔,分别造成0、+0.25、+0.5、+0.75、+1.00、+1.50D的离焦,逐一记录P-VEP振幅和潜伏期。结果用线性回归拟和实验结果,建立P100振幅与离焦值的回归方程,正视组为Y=13.34-6.995X,R2=0.987,近视组为Y=12.16-5.665X,R2=0.996,两组斜率比较差异有统计学意义(F=9.254,P=0.016)。斜率绝对值大表示模糊辨别敏感性好。结论近视眼的模糊辨别敏感性明显低于正视眼;采用P-VEP法客观评价视觉系统对视网膜离焦的敏感性是可行的。

Objective Previous studies have demonstrated that myopes has less sensitivity to the presence of retinal defocus and reduced accommodation response to blur stimuli, thereby producing an increased lag of accommodation and hyperopic retinal defocus during near work. The blur detection sensitivity was typically evaluated subjectively, and only in rare cases objectively. The purpose of this study was to objectively evaluate the blur detection sensitivity and compare its difference between emmetropia and myopia with transient visually pattern evoked potentials （P-VEP）. Methods Thirty-four subjects were classified into two groups in this study： 14 emmetropias with mean RE （ -0. 17 ±0.28） D and 20 myopes individuals with mean RE（ -3.73 ± 0.85 ） D. The age range of the subjects was 18 -28 years. Testing was conducted in monocular （oculus dominans） under the best correction condition. P-VEPs were recorded under the stimulation of six defocus conditions ： 0, ＋ 0.25 D, ＋ 0. 50 D, ＋0. 75 D, ＋ 1.00 D and ＋ 1.50 D. The P-VEP were recorded in contrast-reversing checkerboard stimulation patterns with the 10＇ visual angle,97% contrast and 1 Hz frequency. Amplitude and latency of the P-VEP were analyzed for each viewing condition. Results The diopter and the best correct visual acuities were insignificantly changed between before and after dilation of pupil （P 〉 0.05）. A regression line was used to fit the amplitude data plotted versus the defocus values for each subject. A significant difference was seen in the regression equation between the emmetropes and myopes （ Y = 13.34 - 6. 995X, R2 = 0. 987 in emmetropes and Y = 12, 16 -5,665X,R^2 = 0.996 in myopes, F = 9.254, P = 0.016 ） , showing the blur detection sensitivity in emmetrope subjects was higher than the myopia subjects. The slopes for emmetropes and myopes were - 6.995 （μV/D） and -5. 665 （μV/D）. Conclusion Individuals with myopia are less sensitivity to blur detection than individuals with emmetropia. It is feasible to evaluate the sensitivity to retinal defoeus by the transient P-VEP.