斜视性弱视儿童大脑视皮层损害的脑磁图研究

目的探讨内斜视性弱视患者,在不同视野黑白棋盘格翻转刺激条件下,大脑皮层活动脑磁图的变化。方法单眼内斜视性弱视患者4名,分别进行双眼、单眼全视野刺激,单眼颞侧以及鼻侧视野刺激,记录视觉诱发磁场成份之一的M100的振幅、潜伏期以及源定位的变化情况,与4名正常对照组进行比较。结果双眼全视野刺激,内斜视性弱视组大脑皮层反应M100的振幅降低、潜伏期延长（P〈0.05）;弱视眼鼻侧视网膜M100的振幅比颞侧视网膜M100的振幅降低、潜伏期延长（P〈0.05）;非弱视眼M100的振幅比正常对照组M100的振幅降低,潜伏期延长（P〈0.05）;内斜视性弱视组弱视眼全视野刺激源定位的X轴与正常组比较更偏向原点（P〈0.05）。结论内斜视性弱视眼的鼻侧网膜存在一定程度和一定范围的抑制,源定位上弱视眼存在眼优势柱的偏移,斜视性弱视的非弱视眼与正常组也存在功能的差异。     

弱视儿童由棋盘格和条栅刺激产生的视觉诱发电位的比较

目的 用视觉诱发电位探讨弱视儿童对刺激信号的不同处理方式，更好地指导临床。方法 以斜视性弱视儿童作受试对象。用棋盘格和水平、垂直条栅作为刺激图形，在不同的空间频率下分别记录视觉诱发电位。对N75和P100峰的潜伏期做分析比较。结果 斜视性弱视眼由棋盘格诱发的反应在中高空间频率下显著长于由条栅诱发的反应。结论 视觉系统对棋盘格和条栅刺激采取了不完全相同的处理机制。而斜视性弱视对于棋盘格刺激的处理影响更大。在临床上，用中、高空间频率的棋盘格刺激产生的视觉诱发电位反应来检查弱视更敏感、更可靠。     

先天性色觉异常患者的彩色视觉诱发电位改变

目的：初步探讨彩色视觉诱发电位（visual evoked potential,VEP)检查在临床应用的可行性,为临床诊断色觉异常提供新的方法。方法：应用计算机软件技术,制作4种翻转棋盘格作为视觉刺激模式,包括黑－白翻转棋盘格（对比度为95％）和等亮度红－白、绿－白和红－绿翻转棋盘格（饱和度为100％）。棋盘格大小为25’视角,翻转频率为0．8Hz。用多导程视觉电生理记录仪记录正常组30例色觉正常者和异常组13例先天性色觉异常者4种视觉刺激模式的瞬态VEP图形。结果：正常组4种视觉刺激模式VEPP1波潜伏期由短至长依次为红－白、黑－白、红－绿和绿－白,差异有非常显著意义（P＜0．01）;VEPP1波振幅由高至低依次为黑－白、红－白、红－绿、绿－白,差异有显著意义（P＜0．05）,其中红－白、红－绿、绿－白3种视觉刺激模式间VEPP1滤振幅比较,差异无显著意义（P＞0．05）。异常组VEPP1波潜伏期和振幅4种视觉刺激模式比较,差异均无显著意义（P＞0．05）,其中以黑－白翻转棋盘格刺激模式的潜伏期最短;红绿色盲和绿色盲患者对绿－白翻转棋盘格刺激无反应。正常组与异常组VEPP1波比较,4种视觉刺激模式的潜伏期差异均无显著意义（P＞0．05）;黑－白翻转棋盘格刺激模式的振幅差异无显著意义（P＞0．05）,红－白、绿－白和红－绿翻转棋盘格刺激模式的振幅差异有显著意义（P＜0．05）。结论：彩色VEP检查可为临床诊断色觉异常,尤其对于红绿色盲和绿色盲提供依据;目前彩色VEP检查尚缺乏定性和定量结果。     

弱视眼半视野图形视觉诱发电位的诊断价值

视觉诱发电位(Visual evoked potential VEP)是由光感图形刺激从视网膜节细胞到枕叶皮层产生的生理电位活动。视觉电生理不但是研究弱视的一种手段,而且是临床上早期发现弱视的一种客观先进的方法。 1960年cobb和Dawson首次发表了有关诱发电位研究的论文。1974年Arden设计了黑白方格翻转图形刺激方法来研究弱视。近年来国内将视觉诱发电位应用于弱视研究,而对于研究半视野诱发电位对弱视的诊断价值,尚未见报道。     

外斜视儿童多导视觉诱发电位的研究

目的探讨不伴有弱视的恒定性外斜视儿童的多导视觉诱发电位（ｖｉｓｕａｌｅｖｏｋｅｄｐｏｔｅｎ－ｔｉａｌｓ,ＶＥＰｓ）的临床意义及外斜视的发病机理。方法采用１４个盘状作用电极行全视野及半视野棋盘格翻转刺激,记录正常对照组与不伴有弱视的恒定性外斜组儿童的视觉诱发电位。结果斜视组全视野刺激所记录的双眼与单眼ＶＥＰｓ潜伏期（ＬＰ１）、振幅（ＡＮ１Ｐ１）比较,差异无显著性（Ｐ＞０．０５）,此结果与正常对照组不同;斜视组主眼和非主眼ＬＰ１较正常对照组延长（Ｐ＜０．０１）,斜视组非主眼ＡＮ１Ｐ１较正常对照组下降（Ｐ＜０．０１）;斜视组鼻、颞侧视网膜ＬＰ１、ＡＮ１Ｐ１比较,差异无显著性（Ｐ＞０．０５）。结论ＶＥＰｓ检测可为恒定性外斜视者的双眼视功能异常提供客观依据;恒定性外斜视者视力虽正常但ＶＥＰｓ并非正常,提示有初级视皮层功能障碍存在;不伴有弱视的恒定性外斜视者在单眼半视野刺激条件下,无颞侧视网膜抑制现象。     

弱视眼颜色视觉诱发电位的研究

目的通过对正常儿童与弱视儿童的颜色视觉诱发电位的对比分析,探讨颜色视觉诱发电位对弱视的临床应用价值。方法弱视儿童35名,正常儿童40名,分别进行左右眼的等亮度的黑-白、红-白、绿-白、蓝-白色棋盘格的图形翻转视觉诱发电位,并使用俞自萍设计的5色盲检查图分别检查受检者的色觉,记录结果并分析。结果(1)正常眼的颜色VEP的P1波的振幅以红-白刺激的振幅为最高,其次为蓝-白,再次为黑-白,绿-白刺激的振幅最低;P1波的潜伏期以红-白刺激的潜伏期为最短,其次为蓝-白,再次为黑-白,绿-白的潜伏期最长。(2)弱视组的VEP四种刺激的P1波的振幅均值均较正常组为低,P1波的潜伏期均值均较正常组延长。(3)弱视组的P1波的振幅降低:黑-白刺激与蓝-白刺激有显著性差异,红-白刺激与绿-白刺激无显著性差异;弱视组P1波的潜伏期延长:黑-白刺激无显著性差异,红-白、绿-白、蓝-白刺激均有显著性差异。(4)弱视组无色觉异常病例。结论(1)颜色VEP检查可作为弱视诊断的客观检查。(2)用蓝-白刺激的颜色VEP检查比常用的黑-白刺激的VEP检查更具合理性。(3)中心注视的弱视眼无色觉异常。     

非动脉炎性前部缺血性视神经病变图形视觉诱发电位与视力相关性研究

目的探讨非动脉炎性前部缺血性视神经病变（NAION）图形视觉诱发电位（P—VEP）的特点及其与视力、视野的相关性。方法临床病例自身对照研究。收集2011年3月至2015年4月就诊于天津市眼科医院,53例62只眼NAION患者,进行P—VEP等检查,对侧健眼44只眼作为对照组,分析其P—VEP特点以及其与视力、视野相关性。结果62只眼NAION患者P—VEP15’棋盘格P100波潜时、振幅与对照组相比,差异有统计学意义（P〈0．05）,P—VEP15’棋盘格P100波振幅与视力差异有统计学意义（P〈O．05）,15’棋盘格P100波潜时与视野平均敏感度（mean sensitivitv,MS）差异有统计学意义（P〈0．05）。结论NAION患者P—VEP15’棋盘格p100波振幅越低视力越差,但与视野损伤不一致。P—VEP与视野联合应用更能评价NAION视功能损伤情况。     

屈光参差性弱视儿童脑磁图的初步研究

目的应用脑磁图技术研究屈光参差性弱视儿童视皮层功能损害,探讨屈光参差性弱视发病的可能中枢机制。方法记录4例健康儿童及5例屈光参差性弱视儿童在不同视野黑白棋盘格翻转刺激下的磁场反应,分析其M100振幅、峰值潜伏期及源定位。结果（1）单眼全视野刺激时,非弱视眼比正常组优势眼峰值潜伏期延长、振幅增高;弱视眼比正常组非优势眼峰值潜伏期延长、振幅下降。（2）半侧视野刺激时,弱视眼及非弱视眼各自半侧网膜刺激峰值潜伏期、振幅均无统计学差异。（3）弱视组双眼总和VEFs比正常组降低。（4）双眼全视野刺激时,弱视组偶极源定位在左、右侧大脑半球的X轴位置、Z轴位置比正常组偏向于顶叶。结论（1）弱视眼存在＂单眼抑制＂,而非弱视眼存在功能亢进;（2）弱视眼无半侧网膜抑制现象;（3）弱视组双眼全视野VEFs的M100源定位脱离传统视觉皮质17区、18区,趋向于顶叶。     

痉挛型脑瘫患儿模式翻转视觉诱发电位研究

目的：探讨模式翻转视觉诱发电位对痉挛型脑瘫患儿视觉功能及损伤部位的判断。方法：采用随机对照研究方法：观察组痉挛型脑瘫患儿30例其中痉挛型四肢瘫及双瘫各15例,对照组正常儿童30例,使用模式翻转视觉诱发电位观察半视野及全视野潜伏期及波幅的变化。结果：全视野模式翻转视觉诱发电位研究观察组P100潜伏期为113.55±8.14ms ,P100波幅为23.08±15.41μV,对照组P100潜伏期为105.05±5.58ms,P100波幅为31.65±7.37μV,两组 P100潜伏期及P100波幅经比较,差异具有统计学意义(P<0.05);全视野模式翻转视觉诱发电位痉挛型双瘫P100潜伏期为112.73±7.22ms,P100波幅为21.03±12.17μV,痉挛型四肢瘫P100潜伏期为114.37±9.02ms,P100波幅为25.14±18.06μV。两组P100潜伏期及P100波幅经比较,差异没有统计学意义( P>0.05);观察组与对照组半视野模式翻转视觉诱发电位各眼各视野的比较,均存在统计学差异(P<0.05),表现为观察组各眼各视野潜伏期均明显高于对照组;全视野结合半视野模式翻转视觉诱发电位潜伏期的变化总结发生在视觉通路的病变：包括视神经病变,视神经部分病变,视交叉后病变和视交叉病变。其中以视交叉后病变较多见。结论：模式翻转视觉诱发电位能有效了解痉挛型脑瘫患儿视觉障碍及损伤情况,以利于早期发现异常,早期干预。     

用电生理方法对屈光参差性弱视视网膜及视中枢损害的研究

目的　应用临床电生理手段对屈光参差性弱视的中枢及外周损害作一些探讨。方法　使用丹麦Evomatic 4 0 0 0型电生理仪 ,全视野翻转棋盘格作刺激 ,选择 90′、 4 6 6′、 2 0 7′三种空间频率 ,P VEP与P ERG同步记录的方法 ,对 2 1例单眼屈光参差性弱视儿童进行电生理检测 ,弱视眼P ERG记录使用双眼注视、注视标调整寻找b波最大振幅的方法 ,并与正常对照组儿童进行比较。结果　弱视眼P VEPN75潜伏期、P10 0 潜伏期较正常儿童延长 ,P10 0 振幅较正常儿童组降低。弱视眼P ERG与正常儿童组比较并无明显异常。结论　屈光参差性弱视的损害、神经传导的时间延迟主要发生在视觉通路视网膜以上的部位 ,视网膜并无明显受损。     

Evaluating the visual experience: visual acuity and the visual analogue scale

PURPOSE: To attempt a comparison of the visual experience [assessed using a visual analogue scale (VAS)] with visual acuity in a group of normally-sighted adult optometric patients. METHODS: A single-item 100 mm paper VAS was administered to a sequence of 142 normally-sighted pre-presbyopic patients. Each individual was invited to indicate their recent subjective distance visual experience between the extremes of 'dreadful' (0 mm) and 'perfect' (100 mm). Each patient's binocular visual acuity was then determined at 6 m using a high-contrast logMAR chart under usual consulting room conditions. RESULTS: A weak association was revealed between the subjective indication of recent visual experience and the actual level of binocular acuity recorded in this normally-sighted group of subjects. On the basis of group responses a statistically significant discontinuity in the scores recorded with the VAS was demonstrated between patients who attained a clinical acuity better or worse than 0.10 logMAR units (6/7.5). Patient gender, age, and whether spectacles were habitually worn for distance viewing, were each revealed to be not statistically significant features. CONCLUSIONS: For normally-sighted optometric patients the subjective criterion of visual satisfaction would appear to be only loosely associated with the contemporaneous record of clinical acuity.     

The role of early visual cortex in visual short-term memory and visual attention

We measured cortical activity with functional magnetic resonance imaging to probe the involvement of early visual cortex in visual short-term memory and visual attention. In four experimental tasks, human subjects viewed two visual stimuli separated by a variable delay period. The tasks placed differential demands on short-term memory and attention, but the stimuli were visually identical until after the delay period. Early visual cortex exhibited sustained responses throughout the delay when subjects performed attention-demanding tasks, but delay-period activity was not distinguishable from zero when subjects performed a task that required short-term memory. This dissociation reveals different computational mechanisms underlying the two processes.     

Pattern visual evoked potentials visual acuity--the evaluation of visual acuity of less than 0.1

PURPOSE: We previously developed a new method for estimating objective visual acuity by means of pattern visual evoked potentials (PVEP). In this study, this method was applied to the evaluation of visual acuity of 0.05 and 0.01. METHODS: Ten subjects with visual acuity of 0.05 and ten normal subjects with visual acuity of 0.01 were examined. The visual acuity of the subjects was decreased step by step by means of plus spherical lenses of increasing power. In the PVEP study, the stimulus consisted of black and white checkerboards with a visual angle of 8 degrees (central stimulus) and a global field with a 5 degrees central circular scotoma (peripheral stimulus), contrast level of 15%, and a frequency of 0.7 Hz. One hundred PVEP responses were averaged per session. We reported that there was a linear relation between log subjective visual acuity of 0.1-1.0 and log check size of the patterns with PVEP. In reference to that, the check sizes of the patterns were estimated at 66' with visual acuity of 0.05, and 107' with visual acuity of 0.01. Each visual acuity was then used with other check sizes of three patterns. RESULTS: With central stimulus the P100 components of O1, O2, and Oz were recorded with 66' and 82' patterns at visual acuity of 0.05(central stimulus). The P100 components of O1, O2, and Oz were 107', 137' and 161' at visual acuity of 0.01(central stimulus). There was no P100 component at visual acuity of 0.05 and 0.01(peripheral stimulus). CONCLUSION: This method of PVEP is a useful tool as an objective estimation of visual acuity less than 0.1 and is presumed to stimulate preferentially the X retinal ganglion cell to parvocellular pathway.     

Asymmetries in visual acuity around the visual field

Human vision is heterogeneous around the visual field. At a fixed eccentricity, performance is better along the horizontal than the vertical meridian and along the lower than the upper vertical meridian. These asymmetric patterns, termed performance fields, have been found in numerous visual tasks, including those mediated by contrast sensitivity and spatial resolution. However, it is unknown whether spatial resolution asymmetries are confined to the cardinal meridians or whether and how far they extend into the upper and lower hemifields. Here, we measured visual acuity at isoeccentric peripheral locations (10 deg eccentricity), every 15° of polar angle. On each trial, observers judged the orientation (± 45°) of one of four equidistant, suprathreshold grating stimuli varying in spatial frequency (SF). On each block, we measured performance as a function of stimulus SF at 4 of 24 isoeccentric locations. We estimated the 75%-correct SF threshold, SF cutoff point (i.e., chance-level), and slope of the psychometric function for each location. We found higher SF estimates (i.e., better acuity) for the horizontal than the vertical meridian and for the lower than the upper vertical meridian. These asymmetries were most pronounced at the cardinal meridians and decreased gradually as the angular distance from the vertical meridian increased. This gradual change in acuity with polar angle reflected a shift of the psychometric function without changes in slope. The same pattern was found under binocular and monocular viewing conditions. These findings advance our understanding of visual processing around the visual field and help constrain models of visual perception.