弱视的临床视觉电生理研究进展及其评述

近年来视觉电生理技术广泛地应用于弱视的临床研究,取得了丰富的成果。本文结合近年来弱视的临床视觉电生理研究进展,分别对于眼电图、视网膜电图、视觉诱发电位等视觉电生理指标的定义、产生机制及其在弱视的临床电生理研究中的意义等进行综述,并对相关研究结论的争议做一评述。     

Visual electrophysiology in children with tumours affecting the visual pathway Case reports

In 9 children (8–14 years of age) with orbital, suprasellar or postchiasmal tumours, visual loss was studied by visual electrophysiology in relation to ophthalmologic and neuroimaging findings. Pattern electroretinography (PERG) and pattern visual evoked potentials (PVEP) to full and half-field pattern-reversal stimulation were recorded and PERG and PVEP changes were related to the tumour location. PERG wave P50 attenuation was found associated with the central retinal dysfunction in the child with orbital rhabdomyosarcoma; PVEP wave P100 delay was associated with the optic nerve dysfunction in a child with retrobulbar chondrosarcoma and in a child with optic nerve glioma; PVEP wave P100 asymmetry was associated with the crossed fibers dysfunction in a child with hypothalamic germinoma, and PVEP wave P100 uncrossed asymmetry was associated with postchiasmal dysfunction in children with postchiasmal tumours (one with pilocytic astrocytoma and two with angioma). On the other hand, normal PERG suggested that there was no central retinal dysfunction in a child with pleomorphic adenoma of the lacrimal gland, and normal PVEP to full and half-field stimulation excluded visual pathway dysfunction at the chiasm in a child with suprasellar arachnoidal cyst. Follow-up was useful in indicating whether visual dysfunction was progressive or not. We conclude that PERG and PVEP findings contributed to understanding whether the dysfunction originated was at the retina, in the optic nerve, chiasm or postchiasmal pathway.     

头低位模拟失重状态对于正常青年人视觉电生理的影响

目的:观察头低位模拟失重状态下正常人视觉电生理的变化。方法:男性健康志愿者6例,-6°头低位卧床模拟失重状态,在受试前、受试第2,5d测量双眼的视觉诱发电位和视网膜电图。按照国际视觉电生理协会的临床电生理标准(2008年修订),记录高、中、低3种空间频率下的图形视觉诱发电位(P-VEP),以及国际标准下的视杆细胞反应、最大混合反应、振荡电位、视锥细胞反应和30Hz闪烁光反应。结果:P-VEP中P100波潜伏期在各种空间频率下均无显著改变,波幅在高空间频率下在受试前及受试第2,5d之间有显著改变,差异具有统计学意义(P<0.05),在中、低空间频率下无显著差异。在视网膜电图中,视锥细胞反应及闪烁光反应在受试前后无显著变化(P>0.05);视杆细胞反应及最大混合反应波的潜伏期在受试前及受试第2d之间有显著改变(P<0.05),而波幅无明显改变(P>0.05);振荡电位总和波波幅在受试前后无显著改变(P>0.05)。结论:头低位卧床模拟失重状态下可导致人视觉诱发电位及视网膜电图的改变,从而影响正常人视觉功能。     

综合视觉电生理检测对白内障术后视功能恢复的评估

目的 评价术前综合视觉电生理检测在判断白内障手术视功能预后中的作用。方法 白内障患者３１５例（４０８眼）术前常规检测图形翻转视觉诱发电位（ＰＶＥＰ）、红蓝光视网膜电图（ＦＥＲＧ）和视网膜电图的振荡电位（ＯＰｓ）。正常对照组１６２例（２６６眼）。术后检查眼底,术后３ｍｏ查矫正视力。结果 术后矫正视力≥０．５（Ⅰ组）和〈０．５（Ⅱ组）者与对照组相比,术前ＰＶＥＰ的Ｐ１００波振幅均下降、潜伏期均延长,后     

Visual Electrophysiologic Findings in Patients From an Extensive Brazilian Family with Leber's Hereditary Optic Neuropathy Visual electrophysiology in LHON

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease, associated with mitochondrial DNA (mtDNA) point mutations and characterized by bilateral, usually sequential, rapid loss of central vision. The purpose of this study was to investigate electrophysiologically a small cohort of members from an extensive Brazilian family affected by LHON. Pattern-reversal visual evoked potentials (PVEP), and full-field electroretinograms (ERG) were performed on the four index members, all carrying the 11778 homoplasmic mtDNA mutation. They were a 14-year-old recently affected male, his unaffected mother, and her two affected brothers. The three affected members all had bilateral profound visual loss with visual acuities that ranged from 20/250 to CF, cecocentral defects, and severe dyschromatopsia (by FM-100). The unaffected (carrier) female had normal visual acuities, visual fields and color discrimination. Severely prolonged P100 latencies and decreased N75-P100 peak amplitudes were found in pattern-reversal VEPs for three affected members. Normal PVEP responses were found in the carrier female. Rod and cone ERG responses were normal in two affected members, but both the carrier mother and her affected son showed reduced peak-to-peak amplitude for single-flash cone response and 30 Hz flicker, with normal b-wave implicit times. Thus, optic nerve function, evaluated by PVEP, was severely reduced in LHON affected members and normal in the carrier female. However, reduced ERG cone responses suggest that LHON can also affect retinal elements, even in the absence of fundus and other clinical changes that constitute the full and classical expression of LHON.     

老年性白内障电生理分析

目的:分析老年性白内障患者视觉电生理的改变。方法:对100例老年性白内障患者进行F-VEP、F-ERF检查。结果:F-VEP大多数正常,F-ERG表现为b波潜时延长,振幅降低。结论:视觉电生理检查对老年性白内障患者的视功能及预后判断有一定指导意义。     

妊娠高血压综合征视觉电生理改变观察

目的 探讨妊娠高血压综合征的视觉电生理改变。方法 对２８例妊娠高血压综合征患者５６只眼ＶＥＰ、ＥＲＧ的改变进行观察。结果 妊娠高血压综合征患者视觉电生理有异常改变,在妊娠高血压综合征无眼底改变患者,已出现ＶＥＰ Ｎ７５波替伏期显著改变（Ｐ〈０．０５）,ＥＲＧｂ波替伏期亦有显著改变（Ｐ〈０．０５）。结论 提示视觉电生理检查作为客观的视觉功能检查法,对妊娠高血压综合征视网膜病变具有早期诊断的价值。     

The application of Laplacian analysis in the recording of half-field pattern-onset evoked potentials

The Laplacian operator in electroencephalographic measurements consists of a mathematical combination of the responses from a number of electrodes (e.g., five in a crosswise montage). It enhances activity from sources lying underneath the area covered, relative to activity from outside this area. Thus, by appropriate positioning, the contributions of extrastriate and striate sources can be recorded selectively. To quantify the contribution of each hemisphere to half-field onset evoked potentials, the responses in two Laplacian operators, one over each hemisphere, were analyzed and compared to monopolar derivations and a bipolar derivation between the two hemispheres. Both the Laplacian and bipolar analyses were helpful in interpretation of the responses.     

视网膜分枝静脉阻塞的视网膜电图和图形视诱发电位的观察

目的：探讨视网膜电图（ｅｌｅｃｔｒｏｒｅｔｉｎｏｇｒａｍ,ＥＲＧ）和视觉诱发电位（ｖｉｓｕａｌ ｅｖｏｋｅｄ ｐｏｔｅｎｔｉａｌ,ＶＥＰ）对视网膜静脉分枝阻塞（ｂｒａｎｃｈ ｒｅｔｉｎａｌ ｖｅｉｎ ｏｃｃｌｕｓｉｏｎ,ＢＲＶＯ）检测的意义。方法：根据眼底荧光血管造影（ｆｕｎｄｕｓ ｆｌｕｏｒｅｓｃｅｉｎ ａｎｇｉｏｇｒａｐｈｙ,ＦＦＡ）将ＢＲＶＯ分为缺血型（ｈｅｍｏｒｒｈａｇｉｃ ｒｅｔｉｎｏｐ     

Age-related alterations in retinal function

Age-related visual deficits that occur in the absence of recognized visual disease are frequently observed. Many of the optical factors contributing to these deficits have been delineated, but the contributing neurophysiological alterations have not been clearly defined. This investigation examined age-related variations in the retinal and cortical processing of visual information. Pattern-specific retinal potentials (pattern electroretinogram or PERG in this series) and cortical potentials (VECPs) were recorded from nine young visual normals (20–30 years) and nine healthy elderly individuals (70–80 years). All subjects had best corrected visual acuity of 20/30 or better. Checkerboard patterns (7.5–60 min. checks) were modulated in a counterphase mode (2.0 and 7.5 rps). PERGs and VECPs were simultaneously recorded. Significant age-related alterations in waveform amplitude and latency were observed for both biopotentials. The VECP alterations were largely the result of the reduction in retinal illumination associated with senile miosis, but this factor could not account for most of the observed PERG alterations. These results suggest that neurophysiological changes in the retina may underlie some of the visual deficits observed in healthy elderly adults.     

Influence of simultaneous pattern-reversal electroretinogram recording on visual evoked potentials

Little is known about the influence of the presence of a gold-foil electrode on pattern-reversal visual evoked potential recording, although simultaneous pattern-reversal electroretinography has been applied in several clinical investigations. We compared the results of pattern-reversal visual evoked potentials simultaneously recorded with pattern-reversal electroretinograms with those obtained during separate pattern-reversal visual evoked potential recording in 10 normal subjects. Transient response (reversal rate, 1 Hz; check size, 30) and steady-state response (reversal rate, 5 Hz; check size, 120, 60, 30, 15 and 7.5) were analyzed under the stimulus contrast condition of 90%. Neither P100 latency in transient responses nor amplitudes in steady-state responses exhibited significant change at any check size when they were recorded separately or simultaneously with pattern-reversal electroretinograms. The results suggest that the gold-foil electrode exerts no significant influence on pattern-reversal visual evoked potentials. Simultaneous pattern-reversal electroretinogram and visual evoked potential recording is therefore confirmed to be a clinically useful method. This procedure makes the synchronous recording of both responses possible under the identical stimulus conditions.     

Chromatic VEP in children with congenital colour vision deficiency

Visual evoked potentials to chromatic stimulus (cVEP) are believed to selectively test the parvocellular visual pathway which is responsible for processing information about colour. The aim was to evaluate cVEP in children with red‐green congenital colour vision deficiency. VEP responses of 15 colour deficient children were compared to 31 children with normal colour vision. An isoluminant red‐green stimulus composed of horizontal gratings was presented in an onset‐offset manner. The shape of the waveform was studied, as well as the latency and amplitude of positive (P) and negative (N) waves. cVEP response did not change much with increased age in colour deficient children, whereas normative data showed changes from a predominantly positive to a negative response with increased age. A P wave was present in 87% of colour deficient children (and in 100% of children with normal colour vision), whereas the N wave was absent in a great majority of colour deficient children and was present in 80% of children with normal colour vision. Therefore, the amplitude of the whole response (N‐P) decreased linearly with age in colour deficient children, whereas in children with normal colour vision it increased linearly. P wave latency shortened with increased age in both groups. cVEP responses differ in children with congenital colour vision deficiency compared to children with normal colour vision.     

Guidelines for clinical electroretinography in the dog

These procedures described for the dog ERG were approved at the 1st European Conference on Veterinary Visual Electrophysiology in Vienna, Austria, May 30, 2000. Dr. Narfström was Chair of the Committee for a Harmonized ERG Protocol, appointed by the European College of Veterinary Ophthalmology (ECVO), and Dr. Ofri was secretary. The other coauthors are committee members. Guidelines for ERG procedures in other animal species for clinical and laboratory studies are planned for in the future and the present guidelines are planned to be revised on a biannual basis. A brief report of the recommended procedures is available in the Conference Proceedings book.     

Assessment of visual acuity by evoked potential recording: Ambiguity caused by temporal dependence of spatial frequency selectivity

The spatial-frequency selectivity of pattern evoked potentials depends on the stimulus repetition rate: responses to low spatial frequencies are emphasized by stimulating at 16–20 Hz, while responses to high spatial frequencies are emphasized at 5–8 Hz. These findings are consistent with the suggestion that pattern EP's are a mixture of pattern responses and responses to local flicker. To a first approximation the “local flicker” responses resemble EP's produced by flickering a light similar to the patterned stimulis in all respects except for absence of pattern. Any developmental changes in the temporal tuning of pattern responses and/or local flicker responses might distort the results of studies in which pattern EP's have been used as an index of either (a) the development of visual acuity or (b) acuity changes due to visual deprivation. Methods of minimizing this problem are suggested.     

Flash visual evoked potentials in patients with periventricular leucomalacia in children less than 1 year of age

Background and Aim:

Children with periventricular leucomalacia (PVL) are known to have visual impairment of various forms starting from reduced vision, field defects, congnitive problems, and problems with hand eye coordination. There is very scant data/literature on the visual evoked potentials (VEPs) at an early age in children with PVL. We did a study to evaluate the flash visual evoked potentials (fVEPs) in children with PVL less than 1 year of age.

Materials and Methods:

A total of nine children diagnosed as having PVL on magnetic resonance imaging were included in the study. The mean age was 9.7± 3.5 months. All children underwent handheld fVEPs under sedation at two different flash frequencies 1.4 and 8 Hz.

Results:

The mean latency of N1 and P1 on stimulation with 1.4 Hz was 47.9± 15.2 and 77.7± 26.0 ms, respectively. However, on stimulation with 8 Hz the mean latency of N1 and P1 was 189.8± 25.6 and 238.4± 33.6 ms, respectively. The mean amplitude with 1.4 Hz and 8 stimulation frequency was 5.6± 4.5 and 5.59± 3 mV, respectively.

Conclusion:

We have found for the first time that there is a change in the latency and the delay occurs at 8 Hz frequency but not at 1.4 Hz. We also conclude that amplitudes by fVEPs may be normal even in presence of periventricular changes. The amplitudes of fVEPs are not reliable in children with PVL.     

The role of visual evoked potential and electroretinography in the preoperative assessment of osteo‐keratoprosthesis or osteo‐odonto‐keratoprosthesis surgery

Purpose: To determine the value of electroretinography (ERG) and visual evoked potential (VEP) in predicting visual outcome in patients undergoing osteo‐keratoprosthesis (OKP) or osteo‐odonto‐keratoprosthesis (OOKP) surgery. Methods: We performed a retrospective cohort study of 143 eyes in 101 patients who underwent OKP or OOKP surgery. The subjects underwent ERG, VEP testing or both up to 6 months prior to surgery. The ERG and VEP results were classified into four categories based on wave amplitude, latency and configuration. The main outcome was the maximum best‐corrected visual acuity (maxBCVA) reached at any time postoperatively. Results: One hundred thirty‐four cases had undergone preoperative ERG, 82 VEP and 73 both examinations. The sensitivities of ERG and VEP to detect maxBCVA ≥ 0.05 were 68.5% and 87%, respectively, while the specificity was 63.2% for ERG and 47.4% for VEP. The maxBCVA was significantly better in patients with normal ERG (p = 0.033) and those with normal VEP (p = 0.048), once having defined appropriate normal and abnormal cut‐off levels. When comparing fellow eyes in patients who underwent surgery in both eyes, maxBCVA was better in the eyes that had better VEP results (p = 0.013). Conclusion: Eyes demonstrating normal ERG or VEP achieved better visual outcome than those with abnormal results. In addition, VEP proved instrumental in determining the eye with the best prognosis when comparing both eyes of a given patient.     

视觉电生理联合检测对开角型青光眼早期诊断的临床意义

目的探讨图形视网膜电图(P-ERG)、振荡电位(Ops)和图形视觉诱发电位(P-VEP)联合检测对开角型青光眼早期诊断的价值。方法对60例(105只眼)可疑青光眼、30例(60只眼)正常人进行上述3项检测。结果在可疑青光眼组,上述3项检测阳性率依次为57.1%、33.3%和47.6%,两项以上异常为36.1%,联合检测的阳性率为70.6%。结论视觉电生理联合检测较单一检测阳性率高,对开角型青光眼的早期诊断有意义。     

视觉诱发电位检查在多发性硬化诊治中的价值

多发性硬化(MS)是自身免疫性中枢神经系统疾病.在视觉系统,病变可累及视网膜、视神经、视交叉、视丘、视放射等全部视觉通路.目前研究显示,视觉诱发电位(VEP)检查能早于临床症状对MS进行诊断,在反映MS的视觉传导通路病变上优于磁共振成像(MRI).VEP、视网膜电图(ERG)结合相干光断层扫描(OCT)、扫描激光偏振仪(SLP)等技术可以对MS患者视网膜的病变进行评价和诊断.对VEP检查技术的改进能够为MS的诊治提供更多资料.     

Spatial frequency mechanisms in human vision investigated by evoked potential recording

Two visually evoked brain responses were elicited simultaneously by stimulating the eye with two superimposed sinewave grating patterns that were temporally modulated at slightly different rates. The VEP to one grating was comparatively little affected by the presence of the other grating when the two spatial frequencies were very different, but mutual attenuation grew stronger and stronger as the spatial frequencies of the two gratings were progressively brought together. The attenuation rose to a sharp maximum when the two spatial frequencies were equal. This held at each of the five spatial frequencies tested. This finding can be explained if the spatially-selective mechanisms responsible for grating VEPs contain multiple subunits of narrower spatial frequency bandwidth. The two-grating technique was also used to search for evidence of multiple subunits that are most sensitive at the same spatial frequency, but are tuned to different temporal frequencies. Findings were quite different for temporal and for spatial tuning. Attenuation of one grating VEP was greatest when the temporal frequency of the other grating fell within a broad frequency range of about 3-30 reversals sec-1: maximum attenuation could occur when the gratings had quite different temporal frequencies. This finding denies that for every given temporal frequency there is a subunit maximally sensitive to that frequency.