Assessment of central visual function after successful retinal detachment surgery by pattern visual evoked cortical potentials.

The pattern of visual recovery after successful surgery by pattern visual evoked cortical potentials (VECP), visual acuity, colour vision, and critical fusion frequency was investigated in 14 eyes with retinal detachment involving the macula. The temporal tuning characteristics in the evoked potentials were measured as based on the P100 amplitude and the frequency necessary for evoking 0 mu V amplitude, which was defined as an objective critical fusion frequency by extrapolating the curve. Significant improvement in visual acuity and colour vision was observed within 2 months postoperatively. A significantly increased P100 peak latency became shorter as the postoperative days increased. In general, a good correlation was noted between the P100 peak latency and subjectively measured visual acuity, colour vision, and critical fusion frequency. The objective critical fusion frequency measured by VECP recovered gradually during the 6 months after surgery. Functional recovery was not related to the length of time the macula was detached before surgery.     

Assessment of macular function by multifocal electroretinogram before and after macular hole surgery

AIM: To evaluate macular function before and after successful surgical closure of idiopathic macular holes using multifocal electroretinogram (ERG). METHODS: 40 patients (40 eyes) with idiopathic macular holes were examined using multifocal ERG both before and after vitreous surgery. The postoperative period was from 1 to 12 months. RESULTS: Preoperatively, the electrical retinal response densities in the foveal and the perifoveal area were apparently decreased. After a mean postoperative period of 3-6 months, the foveal and perifoveal area electrical retinal response densities improved to two to four times the preoperative level and the improvement continued to 1 year after surgery. CONCLUSION: In macular holes, the decrease in retinal electrophysiological response was not limited to the fovea but involved an area of the perifovea of 1.6 disc diameters. The electrical retinal response density of these areas gradually improved after macular hole closure.     

Assessment of macular function by focal electroretinogram and pattern electroretinogram before and after epimacular membrane surgery

PURPOSE: To evaluate macular function before and after surgical peeling of idiopathic epimacular membrane (EMM). METHODS: Logarithm of the minimal angle of resolution visual acuity and results of focal (central 9 x 9 degrees) electroretinogram (fERG), pattern electroretinogram (pERG), and optical coherence tomography (OCT) assessment of macular volume were evaluated for 22 eyes of 22 patients (mean age +/- SD, 63.20 +/- 10.0 years) with EMM preoperatively (baseline) and 6 months after surgical peeling. Preoperative visual acuity and fERG and pERG amplitudes observed in EMM eyes were compared with those in 15 age-matched control eyes. RESULTS: In the preoperative evaluation, EMM eyes had a significant (P < 0.01; one-way analysis of variance) reduction in visual acuity and fERG and pERG amplitudes and an increase in OCT macular volume when compared with controls. In EMM eyes, the decrease in visual acuity was significantly correlated (P < 0.01, Pearson test) to the reduction in fERG and pERG amplitudes. At the postoperative evaluation, EMM eyes had a correlated significant (P < 0.01) increase in visual acuity, fERG amplitude, and pERG amplitude with respect to the preoperative values. All EMM eyes had a significant (P <0.01) reduction in macular volume, and retinal microanatomy was restored to normal conditions. CONCLUSION: In EMM eyes, the decrease in visual acuity is related to dysfunction of both preganglionic (abnormal fERG) and ganglionic (abnormal pERG) macular elements. Surgical removal of EMM may induce improvement of the function of both outer and innermost macular retinal layers, leading to a related increase in visual acuity.     

Color-coded pattern suppresses visual evoked cortical potentials and electroretinograms

We developed a new visual stimulating system for recording visual evoked cortical potentials and electroretinograms. The stimulus was a color checkerboard, in which each check kept its chromaticity but changed its luminance with its corresponding check. Color-coded pattern stimuli using red and green checks did not produce visual evoked cortical potentials, while yellow checks produced clear responses in a normal subject. Moreover, five color stairs from red and green to yellow showed only that the more colors are different, the smaller the visual evoked cortical potentials become. In addition electroretinogram recordings indicated that color-coded patterns behave in the same way as in visual evoked cortical potentials. The mechanism that causes the small color visual evoked cortical potentials may already be present in the retina. Color perception may be able to induce a suppression of responses for luminance contrast that appears to be formed already in the retina. Retinal responses were affected whether the stimulus field was color coded or not. Pattern electroretinograms appear to be more than the sum of local on and off responses.     

特发性黄斑裂孔手术前后的视功能改变

玻璃体手术自1991年以来已成为治疗黄斑裂孔的主要手段,而手术后的视功能改善情况成为评价手术成功与否的关键,其指标主要表现在手术后远、近视力有所提高,视物变形有所减轻,中心暗点有所减轻,色觉敏感度有所提高,多焦ERG、立体视觉以及对比敏感度有所改善。     

特发性黄斑裂孔手术治疗前后的视功能

目的 探讨特发性黄斑裂孔手术治疗前后患者的视功能。方法 19例(19只眼)特发性黄斑裂孔患者,其中2期3只眼,3期10只眼,4期6只眼。采用玻璃体视网膜手术治疗黄斑裂孔。术前和术后均进行国际标准视力、激光视网膜视力、明视强度反应ERG和Humphrey　30-2程序视野测定。 结果 (1)国际标准视力：术前视力0.01至0.1,术后视力0.04至0.4,术前术后视力改变差异无显著性的意义(p＞0.05)。(2)激光视网膜视力：术前激光视网膜视力0.12至0.4,术后激光视网膜视力 从0.2至0.63。术前和术后激光视网膜视力改变差异有显著性的意义(P＜0.05)。(3)ERG明视强度反应曲线：术前和术后b波最大振幅Rmax(μV)和代表曲线斜率的n值的改变差异均无显著性的意义(P＞0.05)。术后半饱合光刺激强度K(cd·sec/m2)的对数单位Log值,较术前降低,差异有显著性的意义(P＜0.05)。(4)Humphrey视野：术后 0～10° 较术前光阈值提高,差异 有显著性的意义(P＜0.05)。术前和术后15～30°光阈值差异无显著性的意义(P＞0.05)。 结论 手术治疗IMH能提高视网膜黄斑部视锥细胞功能。（中华眼底病杂志,2000,16：213-284）     

Senescence of visual function as studied by visually evoked cortical potentials

Visual functions in senescence were assessed quantitatively by the pattern reversal visually evoked cortical potentials (VECP) in human subjects and animals. The results obtained in the elderly showed an elevation of contrast threshold, ie, lowered sensitivity, for higher spatial frequency, and a rise in the luminance thresholds. There was also an overall suppression in the temporal frequency curves, a sensitivity decrease for the upper half of the visual field, a blue-yellow defect and a decrease in the amplitude of accommodation. Studies of the pseudophakic eye with an intraocular lens verified that the lower transparency and yellowish changes of the crystalline lens and senile miosis do not entirely account for the depressed visual function in the elderly. The delay of P100 peak latency of the VECP in patients with juvenile Parkinson's disease after cessation of L-dopa indicated the deficiency of dopamine in these patients, which in turn was considered as a clinical model of senescence. Optic nerve fiber counts in mice showed a significant decrease in the aged group. It was considered that there is neuronal senescence other than in the eye itself. The results can be illustrated by the following daily life experience. In the evening, an elderly person would have difficulty in identifying a cat as a calico cat if the cat were atop a wall and running quickly through the visual field. It was surprising, however, that the senescence found in the visual function was not as great as that found in the other sensory organs. As further studies, investigation of the feedback mechanism from the brain to the retina and the compensatory mechanism should be made.     

Assessment of macular function by multifocal electroretinogram before and after epimacular membrane surgery.

PURPOSE: To evaluate macular function before and after successful surgical peeling of idiopathic epimacular membranes by means of multifocal electroretinogram (ERG) and measuring the first order Kernel. METHODS: Multifocal ERG of 10 patients (10 eyes) with idiopathic epimacular membrane were recorded before and after successful macular peeling. The retinal response densities of areas 1 and 2 were compared pre- and postoperatively and the functional state of the retina beneath the epimacular membrane was evaluated. The postoperative period was 3-6 months. RESULTS: Preoperatively, the electrical retinal response densities in the foveal and the perifoveal area were apparently decreased. After a mean postoperative period of 3 months the electrical response densities of the above areas improved. This improvement continued 6 months after the operation. CONCLUSION: In idiopathic epimacular membranes, the decrease in retinal electrophysiologic response was not limited to the fovea but also involved the perifoveal area. The electrical retinal response density of these areas gradually improved after peeling of the epimacular membrane.     

Pattern visual evoked cortical potentials predict postoperative visual acuity after cataract surgery in patients with glaucoma

Visual acuity after cataract surgery in patients with glaucoma cannot be predicted accurately. We studied preoperative recordings of pattern visual evoked cortical potentials (PVECPs) to evaluate postoperative vision in patients with glaucoma and cataract. Fifty patients with glaucoma and no cataract and 31 patients with glaucoma and cataract who underwent phacoemulsification were included in this study. Age and P100 component significantly correlated with postoperative visual acuity with multiple linear regression analysis. A significantly greater number of patients with glaucoma, cataract, and a P100 component preoperatively showed a visual acuity of 0.7 or better postoperatively, as compared to those without a P100 component. PVECP before cataract surgery was able to predict postoperative good visual acuity in patients with glaucoma and cataract.     

Objective assessment of senile changes in visual function by visually evoked cortical potentials

The P100 peak latency of pattern visually evoked cortical potentials (P-VECP) was found to increase and amplitude decrease in the elderly depending on stimulus conditions. Using either of these as a criterion, changes of visual function with aging were quantitatively assessed both in humans and animals. Contrast threshold was found to increase at higher spatial frequency ranges and the luminance threshold increased more than 0.8 log unit. Also, the contrast threshold increased due to a smaller pupillary area and there was progressive decrease of the temporal frequency curves with age for lower frequency ranges of less than 10 rev/sec. In addition, a sensitivity decrease for the upper visual field was detected plus blue-yellow defects and a decrease in the amplitude of accommodation. In order to exclude the effect of senile changes of the crystalline lens, the luminance threshold, the accommodation power and color sense were investigated in pseudo-phakic eyes with a posterior chamber lens. No significant differences were found between phakic and pseudo-phakic eyes. Accordingly, it was suggested that reduced transparency and yellowish changes of the crystalline lens do not essentially contribute to the loss of function in the elderly found in the present study, but the neuronal pathway was responsible. As a clinical model of senescence, cases of juvenile parkinsonism were investigated, during L-dopa treatment and after ceasing it. The deficiency of the neural-transmitter of the higher visual pathway was indicated in the elderly, also. Animal experiments on neuronal dysfunction in rats and mice suggested no aging effects in ERGs, whereas VECP peak latency for higher temporal frequencies increased with age. The assumption that the elderly changes occur at the neuronal level was supported by a loss of optic nerve fibers in mice with age. The numbers of optic nerve fibers measured were 48,115, 50,875 in the 3-month-old and 6-month-old groups, respectively, and decreased to 43,175 in the 30-month-old group. Though our results indicated the senescence of visual function at the neuronal level, it was not as much as shown by other sensory organs. It was therefore presumed that there might be a certain feed-back system from the brain to the retina.     

Accommodation power determined with transient pattern visual evoked cortical potentials in diabetes

Changes of accommodation power by aging were measured with pattern reversal visual evoked cortical potentials (VECPs) in 45 normal subjects and 32 patients suffering from diabetes mellitus. Transient VECPs were recorded by increasing minus power lenses in front of the eye at one-diopter steps, up to the point where no VECP was recordable. It was found that the amplitude of the P₁₀₀ component became attenuated linearly with increased accommodation stimulus. The regression line was calculated from the VECP amplitude vs. accommodation stimulus plots (in diopters) and the objective accommodation was determined by extrapolating the line to 0V amplitude.The measured accommodation power with pattern VECPs was attenuated significantly in the normal group over 40 years old and in diabetics, and also was found to be larger by approximately 2.5 diopters than that obtained subjectively by the near-point rule.Abbreviations PVECP pattern visual evoked cortical potential     

Assessment of patients with suspected non-organic visual loss using pattern appearance visual evoked potentials

Background The aim of the study was to validate the use of the short duration pattern onset visual evoked potential (PappVEP) in the objective assessment of visual acuity (VA) in patients referred with presumed non-organic visual loss. Methods The combination of minimum check size and minimum contrast required to elicit a consistently discernible PappVEP (amplitude ≥5 μV) were measured in ten normal subjects under conditions of induced optical blur (0 to +3 dioptres) and the relationship to Snellen VA established. The data from 100 consecutive patients (167 eyes) referred for possible non-organic visual loss (NOVL) and 20 patients with confirmed visual pathway dysfunction were reviewed in relation to the results in normal subjects. Results Snellen VA, under conditions of blur, could be predicted in normal subjects from the check size and contrast required to elicit a criterion PappVEP. These data were tabulated and a quantitative guideline established for the estimation of VA in the patients referred with suspected NOVL. Most (88%) patients referred with suspected NOVL had normal electrophysiology and PappVEPs consistent with normal Snellen VA. In others, they suggested a degree of non-organic overlay. In 20 cases of organic visual loss, PappVEPs were in close agreement with subjective VA. Conclusions The short duration pattern onset visual-evoked potential is confirmed as a clinically useful tool in the objective assessment of patients with suspected non-organic visual loss.     

Motion-Evoked pattern visual evoked potentials in glaucoma

PURPOSE: To evaluate motion-evoked brain potentials for glaucoma diagnosis. PATIENTS AND METHODS: Stripe patterns were presented in Maxwellian view under different stimulus conditions not combined in a factorial design. Spatial frequencies of 0.33 and 0.88 cycles/degree, with speeds of 10 and 5.9 degrees/second and contrasts of 0.04 and 0.93 were used. A 32 degrees whole field and a peripheral 32 degrees-27 degrees annular stimulus were used. Duration of motion was 200 milliseconds, and the interstimulus interval was 1,800 milliseconds. Recordings were obtained from Oz and P3. Thirty-four healthy patients, 12 glaucoma suspects, and 26 patients with open-angle glaucoma were tested. RESULTS: Normal response amplitudes decrease with age only under low contrast conditions, whereas response peak times increase under most conditions. Normal responses are much larger at P3 than at Oz, whereas in open-angle glaucoma, much less difference is seen. In these patients, the response amplitude at P3 is significantly reduced under all conditions, whereas a delay in peak time is less pronounced. A small but significant negative correlation (r = -0.44, P < 0.05) between response amplitude and mean perimetric defect was observed only with the annular stimulation. At a specificity of 90%, a sensitivity of approximately 76.7% for the low contrast and low spatial frequency condition was observed. CONCLUSIONS: Motion-evoked responses recorded at P3 are altered in open-angle glaucoma and thus can be useful as an additional test in glaucoma diagnosis.     

Assessment of macular function by multifocal electroretinogram in diabetic macular edema before and after vitrectomy

The purpose of this study was to assess the effects of vitrectomy on retinal function in macular and paramacualr areas in patients with diabetic macular edema (DME). Ten eyes of 9 patients with successful vitrectomy for DME were evaluated by multifocal electroretinogram (mfERG), optical coherence tomography (OCT), and visual acuity preoperatively and 1, 2, 3, 4, 5 and 6 months postoperatively. Compared with pretreatment values, the response of the positive wave (P1) in macular and paramacular areas tended to decrease in latency from the second postoperative month, and increase in amplitude at the third postoperative month. There was no significant change in response of the negative wave (N1). The tendency in the change of macular function is coincident with that of macular morphology. Therefore, The multifocal ERG may provide objective criteria for the functional evaluation of DME before and after vitrectomy.     

Use of the scanning laser ophthalmoscope for recording pattern electroretinography and visual evoked cortical potentials

With a scanning laser ophthalmoscope (SLO) variable patterned stimuli can be projected onto the retina. During alternation of these patterns visual evoked cortical potentials and pattern ERGs can be recorded. The configurations of the SLO-elicited potentials and peak latencies correspond to those evoked during conventional stimulation. During pattern stimulation the fundus and alternating pattern stimuli are observed simultaneously on a video monitor. Thus the examiner always knows the exact location of the stimulus on the retina. Scanning laser ophthalmoscopy could be a clinically interesting method of recording evoked potentials, because it enables the patient's retina to be viewed continuously at low light levels and makes electrophysiological examination of a defined region of the retina possible.     

图形翻转视觉诱发电位检查对白内障术后视力评估的价值

目的:探讨图形翻转视觉诱发电位(pattern reversal visual evoked potential,PRVEP)检查对白内障术后视力评估的价值。方法:回顾性分析2012-10/2013-05在同济医院眼科住院,并在白内障超声乳化术及人工晶状体植入手术前后接受PRVEP检查的的成年白内障患者72例114眼的病例资料,其中76眼为老年性白内障,38眼为并发性白内障。根据晶状体混浊程度及晶状体核硬度将数据分为两组:核硬度Ⅰ,Ⅱ,Ⅲ级为A组,核硬度Ⅳ,Ⅴ级为B组,应用统计学方法进行数据间的相关性分析。结果:A组:(1)术前:视力平均值为0.344,PRVEP检查P100波的潜伏期平均值为107ms,N75-P100波的振幅平均值为4.633μV;术后:视力平均值为0.672,PRVEP检查P100波的潜伏期平均值为104.37ms,N75-P100波的振幅平均值为4.400μV。(2)手术前后视力与P100波的潜伏期呈显著负相关(P<0.01);手术前后视力与N75-P100波的振幅呈显著正相关(术前P<0.01,术后P<0.05)。(3)手术前后视力改善行数与P100波的潜伏期变化值无相关性。B组:(1)术前:视力平均值为0.116,P100波的潜伏期平均值为118.905ms,N75-P100波的振幅值为1.650μV;术后:视力平均值为0.576,P100波的潜伏期平均值为108.429ms,N75-P100波的振幅值5.132μV。(2)术前视力与P100波的潜伏期呈现显著负相关(P<0.05),而术后视力与P100波的潜伏期没有相关性;手术前后视力与N75-P100波的振幅没有相关性。(3)手术前后视力改善行数与P100波的潜伏期变化值没有相关性。结论:由白内障手术前后两组视力与PRVEP的P100波的潜伏期及N75-P100波的振幅的相关性可知,PRVEP受患者术前视力(即屈光间质混浊程度)影响较大,PRVEP检查不能作为白内障术后视力预后的判断指标,白内障手术前的PRVEP检查没有临床意义。     

Surface distribution of steady-state cortical potentials evoked by visual half-field stimulation

The surface distribution of steady-state cortical potentials (VECP) evoked by visual half-field stimulation was analyzed by using the fast Fourier transform (FFT). For all ten normal subjects, checkerboard stimulation of the lower visual half-field evoked the largest response at electrode location Oz, with stimulation for the upper visual half-field at Pz. Recording at Pz, a phase difference of approximately 180° was observed for cortical potentials evoked by lower and upper half-field stimulation, the response being bigger for upper field than for full-field stimulation. Comparing the VECP elicited by stimulation of the right and the left half-field, six of ten subjects displayed the highest amplitude at the contralateral cortex (anatomical type), three subjects at the midline (central type), and one subject at the ipsilateral cortex (paradoxical lateralization type). At Oz there was little phase difference in the VECP with stimulation of the right and left visual half-field, and the amplitude was about half that for full-field stimulation. However, with the electrode placed at the temporal region of the skull there was a big phase difference of VECP signals; consequently, the sum of the amplitudes did not amount to the amplitude for full-field stimulaion.The dipole theory of scalp distribution of VECP signals was found to be also applicable to conditions of steady-state stimulation, including polarity reversal for upper and lower visual half-field stimulation.

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Zusammenfassung Bei visueller Halbfeldreizung wurde die Verteilung der durch Umkehr-Schachbrettmusterreize ausgelösten kortikalen Potentiale über der Sehrinde durch Schnelle Fourier-Transformation analysiert.Für das untere Gesichtshalbfeld waren die kortikalen Antworten bei allen Betrachtern bei Ableitung von Oz, für das obere Gesichtshalbfeld bei Ableitung von Pz am größten. Bei Ableitung von Pz wurde für die Antworten des unteren und oberen Halbfeldes eine Phasenverschiebung von ca. 180° beobachtet, wobei die Antworten des unteren Gesichtshalbfeldes größer waren als bei gleichzeitiger Reizung beider Halbfelder.Bei einem Vergleich der Antworten des rechten und linken Gesichtshalbfeldes zeigten 6 von 10 Betrachtern die größten Antworten über der gegenüberliegenden Sehrinde (anatomischer Typ), drei Betrachter über der Mitte (zentraler Typ) und ein Betrachter über der gleichseitigen Sehrinde (Typ paradoxer Lateralisierung). Die von Oz abgeleiteten Antworten zeigten bei Reizung des rechten und linken Halbfeldes nur geringe Phasenverschiebung, ihre Größe betrug etwa die Hälfte jener bei gleichzeitiger Reizung beider Halbfelder. Bei Ableitung über den temporalen Anteilen der Sehrinde war eine beträchtliche Phasenverschiebung der Antworten erkennbar, wobei sich die Summe der Antworten von jener bei gleichzeitiger Reizung beider Halbfelder unterschied.Die Dipol-Theorie der Oberflächenverteilung visuell evozierter kortikaler Potentiale — einschließlich der Potentialumkehr bei Reizung des oberen und unteren Gesichts-Halbfeldes — war auch für Umkehr-Schachbrettmuster anwendbar.

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Prof. Dr. med. E. Dodt, Parkstr. 1, D-6350 Bad Nauheim, F.R.G.