早期糖尿病性视网膜病变mf-ERG一阶kernel反应改变

目的观察早期糖尿病性视网膜病变(简称糖网病)眼视网膜功能。方法将临床确诊为糖尿病并且最佳矫正视力在1.0以上、OCT检查视网膜厚度正常、眼底镜检正常或为轻度非增生性糖尿病性视网膜病变患者共27例54眼作为糖尿病组(按眼底检查情况分为轻度糖网病组与糖尿病无糖网病组);另将正常同龄27例35眼作为正常对照组,分别行多焦视网膜电图一阶kernel反应(first order kernel,FOK)检查;将检查结果分别作比较。结果与正常对照组相比,糖尿病组FOK P1波1环的振幅密度值降低,差异有高度显著性(P=0.0002);N1波5环、P1波4~5环的峰时均有延迟,差异有显著性(P=0.0378、0.0172、0.0026);其后极部30°范围内P1波峰时也延迟,差异有显著性(P=0.0121)。与糖尿病无糖网病组相比,轻度糖网病组FOK N1波4环的振幅密度值增高,差异有显著性(P=0.0469);N1波3、5环,P1波3~5环的峰时均延迟,差异有显著性(P=0.0084、0.0428、0.0102、0.0128、0.0070);其后极部30°范围P1波峰时明显延迟,差异有高度显著性(P=0.0027)。结论糖尿病患者视力尚正常时,其黄斑中心凹感光细胞功能已有所下降;早期糖网病FOK局部反应增高可能与糖尿病早期视网膜局部血流异常增加有关;糖尿病眼FOK的峰时延迟较振幅下降更为敏感,峰时可作为糖网病检测的独立指标;早期糖网病眼视网膜功能异常并非仅局限于内层视网膜;FOK是检测早期糖尿病性视网膜病变的有效手段。     

应用Flash MX制作阻尼振动动画

分析了阻尼振动的运动方程,介绍利用Flash MX制作阻尼振动演示动画的思路和过程。动画演示使学生更形象、直观地接受阻尼振动的概念。     

无视网膜病变的糖尿病患者多焦视网膜电图的变化

目的通过采用多焦视网膜电图（mfERG）对正常对照组、尚未出现视网膜病变的糖尿病患者进行检测，了解mfERG发现糖尿病早期视功能变化的能力。方法采用mfERG进行视功能检测，所有受检者分为33例（33只眼）正常对照组以及63例（63只眼）糖尿病组，其中糖尿病组患者均无视网膜病变。对2组mfERG中N1波与P1波的反应密度与潜伏期进行比较。结果mfERG在糖尿病视网膜病变发生前已有异常，主要表现为环1、环2的P1波反应密度以及环1-环3与环5的N1波反应密度降低。结论mfERG能够在糖尿病视网膜病变出现之前，客观定量地发现早期视功能的变化程度与范围。     

特发性视网膜前膜患者的多焦视网膜电图改变

目的:应用多焦视网膜电图(multifocalelectroretinogram,mfERG)对正常对照眼和特发性视网膜前膜眼进行检测并比较两者之间的差异。方法:用VERISScience4.0视诱发反应图像系统对17例(20只眼)正常对照者和15例(19只眼)特发性视网膜前膜患者进行检测。结果:特发性视网膜前膜患者皆出现程度不同多焦视网膜电图异常,与正常对照组的比较显示视网膜前膜组1～6环的P1波反应密度值和1～6环的N1波潜伏期与正常对照组有显著性差异,视力与第一环振幅无相关但与第一环的潜伏期存在相关。结论:多焦视网膜电图可用于对特发性视网膜前膜患者进行视功能评估。     

Color electroretinography

Electroretinograms to white and color stimuli were recorded in four normal subjects and nine subjects with different cone dysfunctions, including protanopia, cone dystrophy, cone dystrophy with supernormal b-waves at dark adaptation, cone dystrophy with missing b-waves during light adaptation and rod-cone dystrophy with blue cone hypersensitivity. Color stimuli were obtained with Kodak Wratten filters in blue, blue-green, green, yellow and red. Electroretinograms to all stimuli were recorded during dark and light adaptation with different stimulus intensities and to 30-Hz flicker stimulation. In protanopia, responses to red during light adaptation and flicker stimulation were reduced. All cone dystrophies showed reduced amplitudes and prolonged implicit times to red when dark adapted. The light-adapted responses were equally reduced to all color stimuli in cone dystrophy and cone dystrophy with supernormal b-waves. Contrary to other cone dystrophies, in cone dystrophy with missing b-waves, responses to red were severely reduced and responses to green were preserved, indicating a predominantly red cone dysfunction. Blue cone hypersensitivity was clearly distinct from other dystrophies in having large responses to blue and blue-green and much smaller responses to all other colors in all stimulus conditions. The electroretinogram with color stimuli allowed separation of different cone dysfunctions and identification of new retinal dysfunction syndromes.     

Submicrovolt full-field cone electroretinograms: artifacts and reproducibility

The clinical utility of submicrovolt full-field 30-Hz (cone) electroretinograms was assessed by quantifying their contamination by electrical and photoelectric artifacts from xenon-flash stimulators and their test-retest variation in patients with retinitis pigmentosa. Artifacts obtained in saline with four commonly used electrodes varied with electrode type and consisted of an early, brief electrical component and a superimposed, extended photoelectric component. Techniques for minimizing these artifacts are described. Electroretinogram recordings from patients with advanced retinitis pigmentosa or congenital rod monochromatism indicate that these artifacts can be virtually eliminated with bipolar lenses. To assess test-retest variation, narrow-band-filtered responses were obtained twice during 6 weeks from patients with amplitudes less than 1 μV; threshold criteria for signficant (p<0.05) change in amplitude with this technique were approximately 0.25 log unit for each of two different systems.     

Photoreceptor synapses degenerate early in experimental choroidal neovascularization

Severe visual loss in patients with age-related macular degeneration is associated with the development of choroidal neovascularization (CNV). The pathogenic mechanisms for CNV formation have been extensively investigated, but remarkably little research has addressed the mechanisms for dysfunction of the retina in CNV. Using laser-induced CNV in mice, we evaluated the mechanisms of retinal dysfunction. At 3 days, 1 week, 2 weeks, and 4 weeks after laser application, retinas under experimental CNV were characterized physiologically (ERG recordings, synaptic uptake of the exocytotic marker FM1-43, and light-induced translocation of transducin), histologically, and immunohistochemically. ERG amplitudes were reduced by 20% at 1 week after CNV. Depolarization-induced FM1-43 uptake in photoreceptor synapses was selectively reduced by 45% at 1 week after CNV. Although photoreceptor outer segments were shortened by 36%, light adaptation as measured by transducin translocation was mostly preserved. Early in CNV (3 days to 1 week), Muller cells demonstrated induction of c-fos and pERK expression. Also, the density of macrophage-like, F4/80 immunoreactive cells increased approximately 3-fold. Minimal photoreceptor death occurred during the first week, and was variable thereafter. At later times in CNV formation (> or =2 weeks), expression of photoreceptor synaptic markers was reduced in the outer plexiform layer, indicating loss of photoreceptor synaptic terminals. ERG amplitudes, synaptic uptake of FM1-43, and the induction of c-fos and pERK in Muller cells were altered within 1 week of experimental CNV, suggesting that during CNV formation, deficits in retinal function, in particular photoreceptor synaptic function, precede degeneration of photoreceptor terminals and photoreceptor cell death.     

Optimal discrimination of an Abyssinian cat recessive retinal degeneration: a short electroretinogram protocol is more efficient than a long one

AIM: To determine the diagnostic efficiency of scores in a long protocol ectroretinogram (ERG) for Abyssinian cat slow recessive rod/cone dystrophy. METHODS: Kittens (n = 22) were bred from homozygous,affected and heterozygous normals. Ophthalmoscopy was regularly performed and disease signs noted. Cats (age > or = 8 months, 40 sessions, 1-3 repeats) were dark-adapted overnight, anaesthetized and simultaneous binocular ERG recorded using a long protocol. Conventional a- and b-amplitudes and peak implicit times were measured and b/a ratios calculated, initially only for ERG to the maximum photopic and scotopic stimulus. Principal components factor analysis was applied to various subsets of these scores plus age at testing. RESULTS: Six cats with ophthalmoscopic change were classed as affected. Three cats, one tested three times, were suspect. The rest were considered normal. The first analysis, of 80 eyes and 37 parameters, showed that the first factor was the only effective one. Using it, the groups overlapped 5%, scotopic amplitudes and b/a ratios loaded higher than peak times, the eyes were very similar, and age and photopic b/a ratios loaded poorly. The groups were discriminable with all the data. A second analysis, with eyes averaged and the 20 measures loading over 0.5 on the first factor, showed better group separation on factor I alone. An iterative search with varying data sets found that factor I was optimal, with eight ERG measures to the three brightest scotopic and one brightest photopic response. It produced a large absolute separation and classified the suspects consistently. With b/a ratios on these four ERG also included, 12 parameters gave better separation. CONCLUSION: Twelve scores on four ERG separate affected from normal cats with a wide gap and consistently classify suspects. It may work for earlier ages. Additional data probably adds noise. This combination of optimal scores needs confirmation in new data.     

Alterations in electroretinograms and retinal morphology in rabbits treated with vigabatrin

PURPOSE: To determine whether long-term treatment with the anti-epileptic drug vigabatrin causes damage to rabbit retina. METHODS: Five rabbits were treated continuously with a daily dose of vigabatrin solution per orally during a period of 1-8 months. Two rabbits receiving water were used as controls. Repeated full-field electroretinograms (every two weeks) were assessed during this period. Vigabatrin serum concentration was repeatedly measured for securing successful drug administration. After termination of treatment the rabbits were sacrificed and the morphology of the sectioned retina was studied. RESULTS: In all rabbits treated with vigabatrin the serum analyses repeatedly demonstrated elevated drug concentration. Full-field electroretinograms demonstrated normal rod function in all treated rabbits, but reduced cone function in two of the five treated rabbits verified by 30Hz flicker stimulation. Morphologic studies of the sectioned retina demonstrated GFAP immunoactivity of the glial cells localized in the retinal periphery in all five treated rabbits, one of which had staining also in the centrally localized glial cells. The treated rabbits also demonstrated a weaker GAD staining in the IPL and less positive amacrine cells, compared to the controls. Only two treated rabbits had normal GABA staining while three had an enhanced GABA immunoreactivity and undistinguishable fibers in the IPL. In three out of five treated rabbits the Müller cells were short, stubby and fragmented, with swollen endfeet. CONCLUSION: This study demonstrates changes in histopathology caused by vigabatrin in an animal model, which has not been reported previously. We have found that vigabatrin orally administrated to rabbits does not affect rod function but may reduce cone function in the full-field electroretinogram, which is similar to the previously reported vigabatrin effect on the human ERG. The results indicate that vigabatrin may damage or influence, at least one cell type in the rabbit retina.     

Changes in the s-Wave of Multifocal Electroretinograms in Eyes with Primary Open-Angle Glaucoma

Purpose To determine whether the s-wave is present in the multifocal electroretinogram (mfERG) and whether it is altered in eyes with primary open-angle glaucoma (POAG).Methods A Visual Evoked Response Imaging System was used to record mfERGs from 15 eyes of 15 normal adults, as control eyes, and from 15 eyes of 15 patients with POAG. The stimulus consisted of 37 hexagonal stimulating elements with luminances of 200cd/m² (white), 66.6cd/m² (gray), and 4cd/m² (black). The white or black element was presented at five different base periods (bpds) from 13.3 to 213.3ms according to a binary m-sequence. In the intervals between the white and black (or white) elements, gray elements were inserted at 75Hz. The changes in the amplitude and implicit time of the s-wave of the all-trace waveform of the first-order kernel of the mfERG were compared with the mean deviation (MD) of retinal sensitivity in the whole visual field measured with a Humphrey Field Analyzer.Results The s-wave was present as a positive wavelet on the descending limb of the first-order kernel response of the mfERGs of all eyes with POAG. The s-wave amplitude increased with prolongation of the bpd, as occurs in normal eyes. The mean amplitudes of the s-waves at bpds of 53.3 and 106.7ms were significantly smaller in the eyes with POAG than in the control eyes. The correlation between the s-wave amplitude and the severity of disturbance in the entire visual field indicated by the MD was not significant in eyes with POAG.Conclusions The characteristics of the s-wave in glaucomatous eyes were the same as those in the control eyes, but the amplitude of the s-waves in POAG eyes was significantly lower than that in the control eyes. This suggests that ganglion cells may be involved in the development of the s-wave. When comparing the s-wave with static perimetry, more local responses of the s-wave and more local retinal sensitivity in the static perimetry will be appropriate. Jpn J Ophthalmol 2004;48:208–214 © Japanese Ophthalmological Society 2004