屈光不正对P-VEP影响及法医学意义
摘要
在临床法医学鉴定中经常涉及到视功能评定的问题，由于被鉴定人常常夸大视功能障碍程度或伪装成视功能障碍，因此，在法医学如何准确客观评定视功能障碍程度是法医学所面临的一个重要课题。视觉诱发电位(visual evoked potential简称VEP)是一种客观评定视功能的方法，在法医学上应用VEP评定视功能具有特殊意义。按刺激光的不同可以将视觉诱发电位分为闪光视觉诱发电位(flash visual evoked potential，F-VEP)和图形视觉诱发电位(pattern visual evoked potential，P-VEP)。P-VEP波群中常用于诊断的是P_(100)(亦称P_1)，其振幅和潜伏期受诸多因素影响。其中屈光状态的影响往往易被忽略，而造成假阳性，从而不能正确判断被检者真实的视功能状态。目前对于屈光不正对VEP的影响的研究主要从其潜伏期、波幅的绝对值变化方面研究，且常限于同一空间频率刺激，对于屈光不正对不同空间频率刺激的VEP的波幅变化率的影响无明确报导。本次试验对40人(80只眼)给予不同的屈光负荷后进行不同空间频率刺激下的VEP检查，通过对其波幅变化率及潜伏期进行比较，进一步探讨屈光不正对VEP的影响及在法医学鉴定中的应用价值。
试验对象与方法
试验对象：来自于中国医科大学在校本科生40人(80眼)，均为男性，年龄为20～25岁，眼科常规检查正常，除近视外无其他眼病，所有眼矫正视力均在1.0以上。
方法：让被检眼注视屏幕中央，遮盖另眼，采用三种不同空间频率(8×8、16×16、32×32)的棋盘格分别刺激，记录最佳矫正视力(1.0，相对屈光负荷为OD)下和分别在此基础上给予+2.00D、+4.00D、+6.00D和+8.00D屈光负荷下的P-VEP波形，相对
屈光负荷为OD组设为对照组，其余屈光负荷组为实验组，与对照
组相比计算出各实验组的P；。波幅的变化率及潜伏期变化值。
统计学分析：采用 SPSS for indows．0统计分析软件，应用
L检验及方差分析方法进行统计分析。
结 果
1．三种不同空间频率堆 X 8、16 X 16J2 X 32）刺激诱发出的
P；。波幅的下降率均随凸透镜屈光度的增加而逐渐增加，H者之间
的相关系数分别为0．999J．992和0．957，P；。振幅的下降率均与
所加凸透镜屈光度之间存在正相关关系。同时结果表明在相同屈
光负荷下，P；。波幅的下降率随刺激空间频率的增加而增加。
2．不同屈光负荷在不同空间频率方格刺激下的P－VEP中
Pl。波幅的下降率离散系数明显小于绝对值的变化值离散系数，经
配对t检验：t＝＝－15．026，P＜0．001。
3．在 40人 80只受试眼中，除 8 x 8格空间频率刺激下＋2
．00 D屈光负荷组中100潜伏期与对照组相比无显著性差异外K
＞O．05入其余实验组中在同一空间频率格刺激中，随着屈光负荷
的增加，P；。潜伏期延长值也明显增加；在相同屈光负荷下，随着刺
激格空间频率的增高，P；。潜伏期延长值也明显增加。
讨 论
1．屈光不正对P－VEP中P；。波幅的影响
本次实验通过对40人80只眼在不同屈光负荷下的VEP检
测，经统计学分析得出：在同一空间频率刺激下，P；co波幅随着凸透
镜屈光度数的增加而降低，其下降率随凸透镜屈光度数的增加而
增高，即Pl。振幅的下降率与凸透镜屈光度之间存在正相关关系。
这是由于正屈光负荷使图象在视网膜上的成像变得模糊，导致视
敏度下降，且这种视敏度下降程度随屈光负荷的增加而增加。
·2·
对于同一屈光负荷下，P；。波幅的下降率随刺激空间频率的提
高而增高，这说明在不同空间频率中，屈光负荷对小方格刺激所诱
发出VEP的影响要大于对大方格刺激的影响。
诱发电位反应波的幅值叩波幅）在健康个体内和个体间的
变异较大，因此不能简单说一个人P；。波幅低，就是神经元本身的
病变。本实验通过对不同屈光负荷在不同空间频率刺激下诱发出
Pl。波幅的下降值的离散率及其下降率的离散率进行统计学分析
卜检验入P＜0．001，波幅下降率的离散率明显小于波幅下降值的
离散率，即其个体差异性较小，可以用于不同个体间的比较。
2．屈光不正对P－VEP中P；。潜伏期的影响
潜伏期主要反映被测试的感觉或运动系统的粗径有髓纤维的
传导功能。潜伏期长，说明传导速度减慢。本实验结果证明，随着
屈光负荷的增加，P；。潜伏期延长值也相继提高，这是由于屈光负
荷的增加使图象在视网膜上成像的图形边缘变得更加模糊，导致
潜伏期的延长。本组实验显示在同一屈光负荷下随着空间频率的
提高，P；。潜伏期延长值也相继增加，说明在屈光负荷对P；。潜伏
期的影响中，高空间频率刺激较低空间频率刺激更为敏感。
3．正确认识屈光不正对P－VEP的影响在客观评价视功能中
的法医学意义
在眼损伤的法医学鉴定中可以充分利用屈光不正对P－VEP
Introduction
The identification of clinical forensic medicine often includes the determination of visual function. It is important to find an objective way in determining visual function because people undergoing identification sometimes tend to exaggerate the visual disturbance or pretend to be incomplete in visual function ( blandness ). Visual evoked potential. (VEP) is an objective method to determine visual function. According to the difference of stimulation lights, the VEP is classified as flash visual evoked potential ( F - VEP) and pattern visual evoked potential ( P - VEP). In P - VEP wave group, the P100, also known as P, ,is usually used in the identification in forensic medicine. However , the amplitude of vibration and latent period of the P100 are affected by many factors. Among these factors, the refraction state is usually easy to be neglected, which results in false positive reaction. Therefore , the real visual function of people undergoing identification cannot be determined correctly.
Present studies in effects of ametropia on VEP mainly focus on the changes of absolute values of amplitude of wave and latent period, and limit the stimulation with single spatial frequency. There is no definite report on effects of ametropia on VEP with stimulations of different space frequencies.
Our experiment examined the VEP with stimulations of different space frequencies after different refraction loads in 80 eyes of 40 people. We discussed the effects of ametropia on VEP and its application
in the identification of forensic medicine through the comparison of variation rate of the amplitude of wave and the comparison of the latent period.
Materials and methods
Forty undergraduates aging from 20 to 25 at China Medical University were included in our experiment. The results of ocular examination of these students were normal. All of these students had no ocular diseases except myopia, the corrected visual acuity of all 80 eyes was 1.0.
The examined eye stared at the center of screen, and we covered the other eye. Three kinds of tessellated stimulation of different spatial frequencies (8x8, 16x16, and 32 x32) were used. We recorded the optimum corrected visual acuity of 1.0 with relative refraction load of OD. At the same time, the shapes of P - VEP wave with different refraction loads of + 2.00D, + 4.00D, + 6.00D, and + 8.00D were also recorded. The relative refraction load of OD was as control, and the other refraction loads were as experiment groups. The changes of amplitude of P100 and latent period were calculated and compared between control and experiment groups.
Results
1. The decrease rates of amplitude of P100 induced by the stimulations of 3 space frequencies (8x8, 16 x 16, and 32 x 32) all increased with the increase of diopter of convex lens. The correlation coefficients were 0.999, 0.992, and 0.957, respectively. That means the decrease rate of amplitude of P100 has a positive correlation with the diopter of convex lens. With the same refraction rate, the decrease
rate of the amplitude of P100 increased with the increase of the spatial frequency of stimulation.
2. The dispersion coefficients of the decrease rate of amplitude of P100 with different refraction loads and space frequencies were significandy lower than the dispersion coefficients of the absolute values (Pairedt test, t = -15.026, P<0.001).
3. In the 80 eyes of these 40 students, no difference was found between the latent period of the control and that of stimulation of 8 x 8 spatial frequency with + 2.00D refraction load ( P > 0. 05 ). In other experiment groups with stimulation of same spatial frequency, the e-longation of latent period of P100 increased significandy with the increase of the refraction load. And with the same refraction load, the e-longation of latent period of P100 also increased significandy with the increase of the spatial frequency of the stimulation.
Discussion
1. Effects of ametropia on amplitude of P100
Our experiment determined the VEP of different refraction loads in 40 st
试验对象与方法
试验对象：来自于中国医科大学在校本科生40人(80眼)，均为男性，年龄为20～25岁，眼科常规检查正常，除近视外无其他眼病，所有眼矫正视力均在1.0以上。
方法：让被检眼注视屏幕中央，遮盖另眼，采用三种不同空间频率(8×8、16×16、32×32)的棋盘格分别刺激，记录最佳矫正视力(1.0，相对屈光负荷为OD)下和分别在此基础上给予+2.00D、+4.00D、+6.00D和+8.00D屈光负荷下的P-VEP波形，相对
屈光负荷为OD组设为对照组，其余屈光负荷组为实验组，与对照
组相比计算出各实验组的P；。波幅的变化率及潜伏期变化值。
统计学分析：采用 SPSS for indows．0统计分析软件，应用
L检验及方差分析方法进行统计分析。
结 果
1．三种不同空间频率堆 X 8、16 X 16J2 X 32）刺激诱发出的
P；。波幅的下降率均随凸透镜屈光度的增加而逐渐增加，H者之间
的相关系数分别为0．999J．992和0．957，P；。振幅的下降率均与
所加凸透镜屈光度之间存在正相关关系。同时结果表明在相同屈
光负荷下，P；。波幅的下降率随刺激空间频率的增加而增加。
2．不同屈光负荷在不同空间频率方格刺激下的P－VEP中
Pl。波幅的下降率离散系数明显小于绝对值的变化值离散系数，经
配对t检验：t＝＝－15．026，P＜0．001。
3．在 40人 80只受试眼中，除 8 x 8格空间频率刺激下＋2
．00 D屈光负荷组中100潜伏期与对照组相比无显著性差异外K
＞O．05入其余实验组中在同一空间频率格刺激中，随着屈光负荷
的增加，P；。潜伏期延长值也明显增加；在相同屈光负荷下，随着刺
激格空间频率的增高，P；。潜伏期延长值也明显增加。
讨 论
1．屈光不正对P－VEP中P；。波幅的影响
本次实验通过对40人80只眼在不同屈光负荷下的VEP检
测，经统计学分析得出：在同一空间频率刺激下，P；co波幅随着凸透
镜屈光度数的增加而降低，其下降率随凸透镜屈光度数的增加而
增高，即Pl。振幅的下降率与凸透镜屈光度之间存在正相关关系。
这是由于正屈光负荷使图象在视网膜上的成像变得模糊，导致视
敏度下降，且这种视敏度下降程度随屈光负荷的增加而增加。
·2·
对于同一屈光负荷下，P；。波幅的下降率随刺激空间频率的提
高而增高，这说明在不同空间频率中，屈光负荷对小方格刺激所诱
发出VEP的影响要大于对大方格刺激的影响。
诱发电位反应波的幅值叩波幅）在健康个体内和个体间的
变异较大，因此不能简单说一个人P；。波幅低，就是神经元本身的
病变。本实验通过对不同屈光负荷在不同空间频率刺激下诱发出
Pl。波幅的下降值的离散率及其下降率的离散率进行统计学分析
卜检验入P＜0．001，波幅下降率的离散率明显小于波幅下降值的
离散率，即其个体差异性较小，可以用于不同个体间的比较。
2．屈光不正对P－VEP中P；。潜伏期的影响
潜伏期主要反映被测试的感觉或运动系统的粗径有髓纤维的
传导功能。潜伏期长，说明传导速度减慢。本实验结果证明，随着
屈光负荷的增加，P；。潜伏期延长值也相继提高，这是由于屈光负
荷的增加使图象在视网膜上成像的图形边缘变得更加模糊，导致
潜伏期的延长。本组实验显示在同一屈光负荷下随着空间频率的
提高，P；。潜伏期延长值也相继增加，说明在屈光负荷对P；。潜伏
期的影响中，高空间频率刺激较低空间频率刺激更为敏感。
3．正确认识屈光不正对P－VEP的影响在客观评价视功能中
的法医学意义
在眼损伤的法医学鉴定中可以充分利用屈光不正对P－VEP
Introduction
The identification of clinical forensic medicine often includes the determination of visual function. It is important to find an objective way in determining visual function because people undergoing identification sometimes tend to exaggerate the visual disturbance or pretend to be incomplete in visual function ( blandness ). Visual evoked potential. (VEP) is an objective method to determine visual function. According to the difference of stimulation lights, the VEP is classified as flash visual evoked potential ( F - VEP) and pattern visual evoked potential ( P - VEP). In P - VEP wave group, the P100, also known as P, ,is usually used in the identification in forensic medicine. However , the amplitude of vibration and latent period of the P100 are affected by many factors. Among these factors, the refraction state is usually easy to be neglected, which results in false positive reaction. Therefore , the real visual function of people undergoing identification cannot be determined correctly.
Present studies in effects of ametropia on VEP mainly focus on the changes of absolute values of amplitude of wave and latent period, and limit the stimulation with single spatial frequency. There is no definite report on effects of ametropia on VEP with stimulations of different space frequencies.
Our experiment examined the VEP with stimulations of different space frequencies after different refraction loads in 80 eyes of 40 people. We discussed the effects of ametropia on VEP and its application
in the identification of forensic medicine through the comparison of variation rate of the amplitude of wave and the comparison of the latent period.
Materials and methods
Forty undergraduates aging from 20 to 25 at China Medical University were included in our experiment. The results of ocular examination of these students were normal. All of these students had no ocular diseases except myopia, the corrected visual acuity of all 80 eyes was 1.0.
The examined eye stared at the center of screen, and we covered the other eye. Three kinds of tessellated stimulation of different spatial frequencies (8x8, 16x16, and 32 x32) were used. We recorded the optimum corrected visual acuity of 1.0 with relative refraction load of OD. At the same time, the shapes of P - VEP wave with different refraction loads of + 2.00D, + 4.00D, + 6.00D, and + 8.00D were also recorded. The relative refraction load of OD was as control, and the other refraction loads were as experiment groups. The changes of amplitude of P100 and latent period were calculated and compared between control and experiment groups.
Results
1. The decrease rates of amplitude of P100 induced by the stimulations of 3 space frequencies (8x8, 16 x 16, and 32 x 32) all increased with the increase of diopter of convex lens. The correlation coefficients were 0.999, 0.992, and 0.957, respectively. That means the decrease rate of amplitude of P100 has a positive correlation with the diopter of convex lens. With the same refraction rate, the decrease
rate of the amplitude of P100 increased with the increase of the spatial frequency of stimulation.
2. The dispersion coefficients of the decrease rate of amplitude of P100 with different refraction loads and space frequencies were significandy lower than the dispersion coefficients of the absolute values (Pairedt test, t = -15.026, P<0.001).
3. In the 80 eyes of these 40 students, no difference was found between the latent period of the control and that of stimulation of 8 x 8 spatial frequency with + 2.00D refraction load ( P > 0. 05 ). In other experiment groups with stimulation of same spatial frequency, the e-longation of latent period of P100 increased significandy with the increase of the refraction load. And with the same refraction load, the e-longation of latent period of P100 also increased significandy with the increase of the spatial frequency of the stimulation.
Discussion
1. Effects of ametropia on amplitude of P100
Our experiment determined the VEP of different refraction loads in 40 st
引文
1. Rover J, Bach M. Pattern electroretinogram plus visual evoked potentials :a decisive test in patients suspected of malingering. Doc ophthalmol, 1987,66:245～251
2．黎晓新，孙肖琪，胡雨桐等．屈光负荷对正常皮层视觉诱发电位的影响．北京医科大学学报，1990，22：229～230
3．李建东，李海生，王永龄等．图形视觉诱发电位与屈光不正之关系．实用眼科杂志，1988，6：338～340
4．梅军，易莲芳，喻长泰．视力客观检测方法的研究．临床眼科杂志，1999，7：83～84
5．潘映辐主编．临床诱发电位学．北京：人民卫生出版社，1999，422～423
6．吴乐正，吴德正．临床视觉电生理学．北京：科学出版社，1999，321～328
7. Harter MR, White CT. Effects of contour sharpness and check-size on visually evoked cortical potentials. Vision Res, 1968,8:701～703
8. Harter MR, White CT. Evoked cortical responses to checkboard pattern: effect of check-size as a function of visual acuity. Electroencephalogr Clin Neurophysiol, 1970, 28:48～50
9. Millodot M, Riggs LA. Refraction determined electrophysiologically. Arch Ophthal, 1970, 84:272～274
10. Erwin CW. Pattern reversal evoked potentials. Am J EEG Technol, 1981,20:161～162
11. Millodot M, Newton I. VEP measurement of the amplitude of accommodation. Br J Ophthalmol, 1981, 65:294～298
12．刘技辉，宋嗣荣，于平阳等．运用VEP评价视功能的法医学探
讨．中国法医学杂志，1991，6：98～101
13. Shahrokhi F. Pattern shift visual evoked responese: two hundred patients with optic neuritis and/or multiple sclerosis. Arch Neurol, 1978, 35: 36～38
14．徐玉华，杜立，何庆华等．图象反转视觉诱发电位对屈光不正性弱视联合治疗后视功能评价的分析．实用眼科杂志，1988，6：541～544
15．刘技辉，宋嗣荣．应用图象视觉诱发电位评价视敏度的法医学研究．中国医科大学学报，1996，25：473～475
16．李少敏，蔡浩然，郭静秋．屈光参差性弱视的多导视觉诱发电位的研究．北京医科大学学报，1994，26：100～101
2．黎晓新，孙肖琪，胡雨桐等．屈光负荷对正常皮层视觉诱发电位的影响．北京医科大学学报，1990，22：229～230
3．李建东，李海生，王永龄等．图形视觉诱发电位与屈光不正之关系．实用眼科杂志，1988，6：338～340
4．梅军，易莲芳，喻长泰．视力客观检测方法的研究．临床眼科杂志，1999，7：83～84
5．潘映辐主编．临床诱发电位学．北京：人民卫生出版社，1999，422～423
6．吴乐正，吴德正．临床视觉电生理学．北京：科学出版社，1999，321～328
7. Harter MR, White CT. Effects of contour sharpness and check-size on visually evoked cortical potentials. Vision Res, 1968,8:701～703
8. Harter MR, White CT. Evoked cortical responses to checkboard pattern: effect of check-size as a function of visual acuity. Electroencephalogr Clin Neurophysiol, 1970, 28:48～50
9. Millodot M, Riggs LA. Refraction determined electrophysiologically. Arch Ophthal, 1970, 84:272～274
10. Erwin CW. Pattern reversal evoked potentials. Am J EEG Technol, 1981,20:161～162
11. Millodot M, Newton I. VEP measurement of the amplitude of accommodation. Br J Ophthalmol, 1981, 65:294～298
12．刘技辉，宋嗣荣，于平阳等．运用VEP评价视功能的法医学探
讨．中国法医学杂志，1991，6：98～101
13. Shahrokhi F. Pattern shift visual evoked responese: two hundred patients with optic neuritis and/or multiple sclerosis. Arch Neurol, 1978, 35: 36～38
14．徐玉华，杜立，何庆华等．图象反转视觉诱发电位对屈光不正性弱视联合治疗后视功能评价的分析．实用眼科杂志，1988，6：541～544
15．刘技辉，宋嗣荣．应用图象视觉诱发电位评价视敏度的法医学研究．中国医科大学学报，1996，25：473～475
16．李少敏，蔡浩然，郭静秋．屈光参差性弱视的多导视觉诱发电位的研究．北京医科大学学报，1994，26：100～101