The electro-oculogram in central retinal vein occlusion.

As part of a prospective masked study, the electro-oculogram (EOG) was recorded from 28 patients within 48 days of developing central retinal vein occlusion (CRVO). The EOG light peak/dark trough ratio (Lp/Dt) x 100 was significantly lower in the affected than in the unaffected eyes of patients (p < 0.001), and abnormally low in absolute terms in 20 patients (71%). All unaffected fellow eyes had a normal EOG ratio. The mean Lp amplitude of affected eyes was significantly smaller than that of unaffected eyes (p < 0.001), whereas the differences in mean Dt amplitudes between affected and unaffected eyes were not statistically significant. The Lp amplitude in the affected eye was 48% or less of that in the unaffected eye in the eight patients (29%) who developed rubeosis iridis during the 9 month follow-up, and in six others. No patient whose Lp amplitude in the affected eye was greater than 48% of that in the unaffected eye, developed rubeosis. It is concluded that the Lp amplitude is abnormal in patients with acute CRVO. The degree of this abnormality bears a relation to the development of rubeosis, which might prove a useful indicator of whether to institute or withhold panretinal photocoagulation.     

The EOG in rheumatoid arthritis

In untreated rheumatoid arthritis 20% of the patients has a EOG Lp/Dt ratio lower than the lower 5% limit calculated for normal patients. The EOG is more often disturbed in a long-standing chloroquin-induced retinopathy than in the acute phase of intoxication, the reason being progression from a maculopathy to a tapeto-retinal degeneration. The subnormal EOG in rheumatoid arthritis might be due to an auto-immune process against rhodopsin and uveal pigment. Withdrawal of synthetical antimalarial agents in cases suspected of an early drug-induced retinopathy based on EOG subnormality may enhance the underlying rheumatoid process thus causing a further decrease of the EOG. The EOG therefore is not a method of choice in detecting an early chloroquin-induced retinopathy.     

Vigabatrin: longterm follow-up of electrophysiology and visual field examinations

BACKGROUND: To report the results of repeated electrophysiological and visual field examinations in patients with vigabatrin-associated visual field loss (VGB-VFL) and the relationship between these electrophysiological findings, the cumulative dose of vigabatrin and the extent of visual field loss. METHODS: Twenty-two eyes of 11 patients with VGB-VFL were studied. All patients underwent surgery for therapy-resistant epilepsy. Repeated electro-oculograms (EOGs) and flash electroretinograms (ERGs) were made and the cumulative dose of vigabatrin and the visual field loss were recorded after a period of 37-47 months. RESULTS: The visual field loss was stable in patients who had stopped vigabatrin at the time of the first examination. There was a slight increase in VFL in patients who continued vigabatrin. During the second EOG and ERG, abnormalities in scotopic and photopic a-wave latencies and in scotopic b-wave amplitude were found in more than 50% of patients. Only b-wave latency became normal, while EOG, a-wave latency, a-wave amplitude and b-wave amplitude stayed abnormal. The amount of VFL and the cumulative dose of vigabatrin were statistically correlated with the b-wave amplitude, mainly photopic, found during the first and second examinations. CONCLUSION: After 4 years, EOG, flash ERG and visual field loss had not improved in patients with VGB-VFL. The statistically significant correlation found during the first examination between the amount of VFL and the cumulative dose of vigabatrin with the (mainly photopic) b-wave amplitude remained constant.     

Electrophysiological findings in familial exudative vitreoretinopathy

Three patients in a family with familial exudative vitreoretinopathy (FEVR) were studied especially electrophysiologically. Two cases showed abnormal ERG, namely reduction of amplitude of oscillatory potentials, a and b wave of bright white flash ERG, scotopic and photopic b waves. One case showed reduced Light peak/Dark trough ratio of EOG. Next, the electrophysiological findings of cases with FEVR reported in the literature were analyzed. The result was that FEVR has electrophysiological varieties but a statistical significant relationship between electrophysiological findings and visual acuity. That is, cases with abnormal ERG or EOG have more impaired visual acuity than normal ones. Furthermore, there was a tendency that eyes with abnormal ERG or EOG showed more disturbed color vision and advanced fundus findings than normal ones. These results seemed to be understandable by anatomically characteristic fundus feature of FEVR.presented at the 6th Meeting of the International Society of Genetic Eye Disease and 3rd International Symposium on Retinoblastoma, Amsterdam, the Netherlands, May 1–3, 1986.     

Prognostic value of initial electroretinogram in central retinal vein obstruction

We retrospectively studied the correlation between the initial electroretinogram (ERG) recordings and the final visual acuities (VA) of 47 patients with central retinal vein obstruction (CRVO) after follow-up of more than 1 year. The a- and b-wave amplitudes and the b/a ratio with white flash were significantly larger in patients with good vision (VA > 20/200) than in those with poor vision (VA < 20/200). The b/a ratio and b-wave amplitude with white flash showed sensitivity and specificity of more than 78% for visual prognosis. The latest VA was <- 20/200 in all 20 patients with a subnormal b-wave amplitude and in all 15 with b/a ratio < 1.05. These results suggest that the ERG recorded soon after (CRVO) onset correlates strongly with visual prognosis.     

Dominantly inherited cystoid macular edema.

Four patients of Greek ancestry had dominantly inherited cystoid macular edema. Characteristics of this syndrome include the following: an early onset and prolonged course of cystoid changes in the macula, followed by atrophy of the macula in later stages. Some patients also show leakage of fluorescein from the optic disc capillaries, subnormal EOG Lp/Dt ratios, elevated rod dark adaptation thresholds, red-green and blue-yellow color deficiencies, normal ERG findings, hyperopia, peripheral pigmentary retinopathy, and vitreous opacities. Dominantly inherited cystoid macular edema is a distinct genetic trait among the dominantly inherited macular dystrophies.     

Electroretinogram parameters at presentation as predictors of rubeosis in central retinal vein occlusion patients

This report evaluates the prognostic value of parametric electroretinography (ERG) techniques in the development of rubeosis in central retinal vein occlusion (CRVO). An ERG protocol was followed on the initial clinic visit for 21 CRVO patients. None of these patients had neovascular complications or any treatment before the ERG examination. The ERG data were used to define an intensity-response (I-R) function, b-wave to a-wave peak ratio (b/a-wave ratio), and 30-Hz b-wave implicit time. A Naka-Rushton function was fitted to the I-R data to obtain values for maximum saturated response (Rmax) and for the log of the half-saturation intensity (log K). The authors' results show that ERG parameters relating both to the effective number of responding retinal elements and to the sensitivity of responding elements have significant prognostic value. Unexpectedly high predictive values were found for the Rmax and b/a ratio, parameters thought to correlate with the effective number of responding elements, compared with log K and 30-Hz implicit time, parameters thought to relate more closely to retinal ischemia. A multiple discriminant analysis, combining information from these ERG parameters, allowed separation of CRVO patients in whom rubeosis would develop from those in whom it would not, with a false-positive rate of only 14%.     

Retinal pigment epithelial dysfunction in human immunodeficiency virus-infected patients with cytomegalovirus retinitis

OBJECTIVE: Prior clinical observations led the authors to examine electrophysiologic measures of retinal (electroretinogram [ERG]) and retinal pigment epithelial (electro-oculogram [EOG]) function in patients infected with human immunodeficiency virus (HIV) who either had or did not have cytomegalovirus (CMV) retinitis in order to determine if the ERG or EOG measures were differentially affected in CMV retinitis. DESIGN: Cross-sectional study. PARTICIPANTS: Forty-one HIV-infected patients (20 with and 21 without CMV retinopathy) were evaluated. INTERVENTION: ERGs and EOGs were recorded. Patients' fundi were evaluated by indirect ophthalmoscopy or fundus photography. MAIN OUTCOME MEASURES: The ERG a- and b-wave amplitudes and EOG light/dark amplitude ratio (L/D ratio) from the eyes of all patients were compared with values 2 standard deviations from the mean of a normal sample. The area of the retinal lesions was estimated from fundus photographs or from careful drawings made during indirect ophthalmoscopy. RESULTS: The majority of the eyes (64.5%) of the patients with CMV retinitis had subnormal L/D ratios, and most eyes (95%) of patients without CMV retinitis had normal L/D ratios. Only six eyes (four with and two without CMV retinopathy) had subnormal a-wave amplitudes, and there was no significant correlation between a-wave amplitude and the L/D ratio for patients with CMV retinitis. Most eyes (80.6%) of the patients with CMV retinitis had subnormal b-wave amplitudes, but there was no significant correlation between b-wave amplitude and L/D ratio in the patients with CMV retinitis. In three patients with CMV retinitis selected to exemplify the range of effects on the ERG and EOG, the b-wave amplitude loss was roughly proportional to the area of retina visibly affected in indirect ophthalmoscopy. One patient had a nonrhegmatogenous retinal detachment. CONCLUSIONS: Middle retinal function, as reflected in the b-wave amplitude, and retinal pigment epithelial function, as reflected in the L/D ratio, were both compromised in CMV retinitis, but the effect on function in the two layers of the retina appeared independent because there was no significant correlation between the L/D ratio and b-wave amplitude. The decrease in L/D ratio was not secondary to loss of photoreceptor function and probably represents a dysfunction of the retinal pigment epithelium because there was no significant correlation between a-wave amplitude, which was normal in most cases, and L/D ratio. The inner retinal pathology of CMV retinitis is visible clinically and was associated with decreases in b-wave amplitude in this and previous studies. The significant independent retinal pigment epithelial dysfunction demonstrated in this study may be an important predisposing factor to retinal detachment in CMV retinitis.     

Effect of metoclopramide, dopamine receptor blocker, on the EOG light peak]

We studied the effects of metoclopramide hydrochloride (MTCL), a D2-selective dopamine receptor antagonist, on the electro-oculograms (EOGs) in 10 eyes of 5 healthy volunteers and on the electroretinograms (ERGs) in 6 eyes of 3 volunteers. MTCL was given intravenously after 15 minutes of dark adaptation. The L/D ratio of EOG was 2.13 +/- 0.14 (mean +/- SE) before the administration of MTCL. After the administration of MTCL, the dark-adapted EOG amplitudes increased transiently. MTCL significantly depressed the L/D ratio to 1.60 +/- 0.07 (p less than 0.01). The a- and b-wave amplitudes of the flash ERG decreased by 12% and 11% respectively. However, the OP2 and OP3 amplitudes of oscillatory potential increased by 23% and 19% respectively. The implicit times of all waves mentioned above tended to be prolonged. This study shows that a blockade of D2-dopamine receptor supresses the EOG light peak. Further investigations are needed to clarify the exact mechanism of this effect.     

Electroretinogram b-wave implicit time and b/a wave ratio as a function of intensity in central retinal vein occlusion.

The ability of electroretinogram (ERG) b-wave implicit time and b/a wave ratio to predict iris neovascular response was analyzed as a function of stimulus intensity over a 3.6 log unit intensity range in 39 patients with central retinal vein occlusion (CRVO). Predictive power for CRVO patients was evaluated using ROC area at intensities of 1.23, 1.83, 2.43, and 3.03 effective log quanta/rod, where reliable data for both parameters were obtainable from most patients. The relative predictive power of b-wave implicit time and b/a wave ratio were shown to vary with stimulus intensity. The predictive power of b-wave implicit time, as measured by ROC area, declined to below significance at high intensity (above 1.83 log quanta/rod), while b/a wave ratio performed best at middle intensities (1.83 and 2.43 log quanta/rod) and not as well at high and low intensities. Further analysis of statistical behavior of both ERG parameters was obtained from the t statistic. Insight into the mechanism influencing predictive power of b-wave implicit time was derived from measurements on normal adults and CRVO patients with response data taken at high intensities. These results suggest that an optimal stimulus intensity range can be found for these ERG parameters in the evaluation of CRVO.     

The electro-oculogram as an aid in the diagnosis of uveal melanoma

The electro-oculogram (EOG) in the 64 patients with a melanoma of the choroid or ciliary body was compared to the EOG in 11 patients with choroidal metastasis, 11 patients with choroidal naevi and 27 patients with a rhegmatogenous retinal detachment. Using the Dt and the Lp/Dt-ratio, 87.5% of the melanomas could be diagnosed correctly whereas choroidal naevus and retinal detachment were diagnosed correctly in 72.7% and 70.4% of the cases respectively. Choroidal metastases never were classified correctly. Accompanying retinal detachment, tumour volume or a break through Bruch's membrane had no influence on the EOG in the melanoma patients. An important advantage of the method is that it can be used irrespective of the condition of the other eye. Combined with ophthalmoscopy, ultrasonography and fluorescein-angiography the EOG can be an additional aid in the differential diagnosis of malignant melanoma of the choroid and ciliary body.     

Electroretinogram b/a wave ratio improvement in central retinal vein obstruction.

The electroretinogram (ERG), especially the b/a wave ratio, is considered a good indicator of retinal ischaemia in central retinal vein obstruction (CRVO). Seven CRVO patients who showed b/a wave ratio improvement from < 1.0 [negative type (-) ERG] to > or = 1.0 and one from 1.07 to 1.53 were studied. Three mechanisms of change were observed: firstly, the b-wave amplitude increased without an a-wave amplitude decrease (group A, n = 2); secondly, the b-wave amplitude increased with an a-wave amplitude decrease (group B, n = 4); and, thirdly, both decreased, but the a-wave amplitude decreased more markedly (group C, n = 2). In group A, the visual acuities improved markedly. In group B, the visual acuities improved in two cases in which the b-wave amplitude reached the normal range; the visual acuities did not improve in two cases in which the b-wave amplitude did not reach the normal range. In group C, the visual acuities remained poor. The negative (-) ERG or significantly reduced b/a wave ratio is associated with ischaemic CRVO and did not occur because of the filtering effect of the haemorrhage, which may reduce the stimulus light for the ERG. Improvement of the reduced b/a wave ratio with an increased b-wave amplitude was accompanied by improvements in fundus appearance and visual acuity in CRVO. The results suggest that the retinal ischaemia in CRVO, as revealed by the ERG and fluorescein angiogram, may be reversible in some cases.     

Correlation of electroretinographic and fluorescein angiographic findings in unilateral central retinal vein obstruction

Background: In central retinal vein obstruction (CRVO), electroretinogram (ERG) abnormalities and extensive retinal capillary dropout (CD) in the fluorescein angiogram (FA) are good indicators of retinal ischemia. We retrospectively studied patients with unilateral CRVO and compared the ERG and FA results Methods: Single white flash ERG, photopic ERG, scotopic ERG and flicker ERG were recordered in 30 cases of unilateral CRVO. We analyzed the correlation between the ERG results and the presence/absence of extensive CD Results: The ERG b/a-wave amplitude ratios, photopic and scotopic b-wave amplitudes, and flicker amplitudes were significantly smaller (P<0.05) in eyes with extensive CD (n=12, 40%), than in eyes without (n=18, 60%). When the photopic or scotopic b-wave amplitudes were normal or supernormal, extensive CD on FA was absent in all eyes. When the b/a-wave ratios were 1.0 or when the b-wave amplitudes with white flash or flicker amplitudes were normal or supernormal, extensive CD was present in less than 32% of eyes Conclusion: These results suggest that the ERG results, especially the b/awave amplitude ratio, are significantly correlated with the presence/absence of CD on FA in CRVO.     

Symptomatic and asymptomatic visual loss in patients taking vigabatrin.

PURPOSE: To investigate the clinical, perimetric, and electrophysiologic findings in patients with visual field loss on long-term treatment with the antiepileptic medication vigabatrin. DESIGN: Consecutive observational case series. PARTICIPANTS: Forty-one consecutive subjects taking vigabatrin referred for screening ophthalmologic assessment were studied. Twelve subjects with evidence of peripheral visual field constriction are presented. METHODS: Twelve subjects with evidence of peripheral visual field constriction on 60-4 perimetry underwent central 30-2 and blue-on-yellow (B/Y) perimetry, as well as electroretinography (ERG), electro-oculography (EOG), and visual-evoked potential (VEP) testing. MAIN OUTCOME MEASURES: Visual acuity; fundus abnormalities; visual field loss; and ERG, EOG, or VEP abnormalities were the main outcome measures. RESULTS: Eight of the 12 subjects with constricted visual fields were asymptomatic. The central 30-2 perimetry demonstrated bilateral visual field constriction in 9 of 12 patients and the B/Y perimetry in 8 of 9 patients tested. Of the ten patients tested electrophysiologically, four had abnormal ERGs, five had abnormal EOGs, and three had delayed VEPs. CONCLUSIONS: The incidence of visual field constriction in patients taking vigabatrin may be higher, and asymptomatic visual field loss more common, than reported previously. The authors postulate a possible Muller cell dysfunction in the peripheral retina. Patients taking vigabatrin should have regular peripheral visual field examinations.     

Electro-oculogram in patients with neurofibromatosis type 1

Purpose: The electro-oculogram (EOG) is a powerful test to evaluate the functional status of the retinal pigment epithelium (RPE). Clinically detectable changes of the RPE desribed in neurofibromatosis type 1 (NF-1) patients include combined hamartoma of the retina/RPE and congenital hypertrophy of the RPE. The goal of this study was to determine whether the function of RPE as measured by EOG is also changed in individuals with NF-1. Patients: Studies were undertaken in 20 patients with clinically diagnosed NF-1 and compared to 16 normal healthy controls. Methods: Standard EOG and flash ERG recordings were performed in accordance with International Society for Clinical Electrophysiology of Vision (ISCEV) standards. Results: In NF-1 patients the Arden indexes of the EOG test were significantly higher primarily due to the lower values of dark troughs. Supernormal EOGs were present in 60% of NF-1 patients in comparison to the control group mean +2 SD. No one patient showed so high abnormalities during flash ERG examination. Conclusions: Dysfunction of the RPE may be characteristic feature of individuals with NF-1.     

Electro-oculogram of Retinal Vein Occlusion

Twenty five cases, including 26 eyes with retinal vein occlusion (RVO) were examined by means of the electro-oculogram. The results showed that 23 of the 26 eyes suffering from RVO exhibited abnormalities of the electro-oculogram (EOG). The potential difference and Arden ratio in the RVO eyes were lower than those in the normal eyes (P<0.01). The more the visual acuity of ill eyes was decreased, the higher the abnormal rate of EOG in ill eyes was. 14 eyes had the visual acuity less than 0.1, whose EOGs were abnortmal. Six eyes had the visual acuity from 0. 2 to 0. 4, in which the EOGs of 5 eyes were abnormal. Six eyes had the visual acuity more than 0. 5, a-mong which the EOGs of 4 eyes were abnormal. Based on the above observations, it may be considered that the circulatory disturbance resulting from RVO damages not only the internal layer but also the external layer of the retina. We suggest that EOG is a useful method for distingquishing lesions caused by RVO and may reflect the functional condition     

Visual field and electrophysiological abnormalities due to vigabatrin

The purpose of this study was to determine the electrophysiological changes in patients using the anti epileptic drug vigabatrin and to correlate these findings with the previously reported risk for visual field loss in these patients. In 1998 the neurologists of both involved hospitals referred all patients on vigabatrin medication for ophthalmological examination to the outpatients clinics. Of the 33 patients whom were referred to our outpatient clinics, four had to be dropped from the study because of disability to perform the examinations the remaining 29 patients were included in the study. Standard ophthalmological investigations were carried out, and contrast sensitivity, visual field (Humphrey 30-2 and Esterman or Octopus 32), colour vision (panel D15), ERG and EOG according to ISCEV standards were tested. 18 patients continued the medication and 11 stopped taking the drug during the study. Nine of the patients who stopped the drug were followed during at least half a year afterwards, this group will be described in the combined article `Electro ophthalmic recovery after withdrawal from vigabatrin' (Graniewski and Van der Torren, this issue). The electro-ophthalmological findings in the group of 29 patients were correlated with the visual fields and the daily and cumulative dosages of vigabatrin. Of the patients, 32% showed no visual field constriction at all; from these patients 64% had EOG and/or ERG changes. Of the patients with slight to marked visual field constriction, 90% presented EOG and/or ERG changes. Significant correlation between daily dosages of vigabatrin and visual field defects was shown as well as between visual field defects and rod and cone b wave amplitude reductions. Cumulative vigabatrin dosages presented a significant correlation with EOG ratio and ERG rod b-wave amplitude. Conclusively EOG and ERG testing were found to be even an more accurate way to monitor the direct vigabatrin effect on the outer retina and is possible different from the visual field testing.     

Electrophysiological similarities between two eyes with X-linked recessive retinoschisis

Electroretinograms (ERG) and electro-oculograms (EOG) were studied in 88 eyes of 44 male patients with X-linked recessive retinoschisis. Differences of fundus appearance, ERG, and EOG between the eyes of each patient were analyzed. Fundus abnormalities were symmetrical in 77.3% of the cases. The amplitude of the ERG a-wave was normal in 26.1% and was abnormally low in 73.9%. The amplitude of the b-wave was below normal in all eyes; thus a small b-wave/a-wave ratio, which is characteristic of X-linked recessive retinoschisis, was observed in every case. The light peak to dark trough (LP/DT) ratio of the EOG was normal in 90.8% of the cases. The relative electrophysiological differences between the two eyes were calculated and showed that a-wave amplitude was not different between eyes in 75.0% of the cases; b-wave amplitude was not different in 77.3% of the cases; b-wave/a-wave ratio was symmetrical in 93.2% of the cases; and the LP/DT ratio was consistent between eyes in 86.8% of the cases. These results suggest that in most cases of X-linked recessive retinoschisis the fundus appearance, ERG, and EOG are similarly affected in both eyes of the patient.     

Electroretinogram interpretation in central retinal vein occlusion.

The authors report electroretinogram (ERG) data from the initial clinic visit of 39 patients with central retinal vein occlusion (CRVO). No patient had signs of neovascular complications or had received treatment at the time of the ERG examination. Area under the receiver operating characteristic (ROC) curve was used to compare effectiveness of the 4 ERG parameters (Rmax, Log K, b/a wave ratio, and 30 Hz implicit time) in separating those patients who went on to iris neovascularization from those who did not. Rmax is the maximum saturated b-wave amplitude and Log K is the half saturation constant of the Naka-Rushton curve fit to the intensity response data. Discriminant scores, derived using multiple discriminant analysis, were calculated for the total patient groups, CRVO eye alone, and intereye difference. These scores also were compared with the four individual ERG parameters using ROC analysis. Parameters based on amplitude of ERG response, Rmax, and b/a wave ratio are as effective predictors of neovascular response as those interpreted as indicators of retinal sensitivity, such as 30Hz implicit time or Log K. The authors present evidence that loss of b-wave amplitude is not necessarily associated with irreversible loss of inner retinal function.     

Early panretinal photocoagulation for ERG‐verified ischaemic central retinal vein occlusion

Purpose: We have previously shown that photopic cone b‐wave implicit time ≥35.0 ms in 30 Hz flicker electroretinography (ERG) predicts ocular neovascularization (NV) in central retinal vein occlusion (CRVO). Here, we evaluate the effects of early panretinal photocoagulation (PRP) in patients with ERG‐verified ischaemic CRVO. Methods: Patients with CRVO, admitted to our department between 2000 and 2008, were classified as having ischaemic or non‐ischaemic CRVO based on the ERG‐results. In a first group of 71 patients, 18 patients had ischaemic CRVO and were assigned to standard treatment that is regular examinations and PRP as soon as NV was found. In a consecutive group of 65 patients, 18 patients with ischaemic CRVO received early PRP. In this group, ERG was performed on average 6 weeks after the first symptoms of CRVO. The patients underwent PRP as soon as possible after the ERG‐examination, and the treatment was completed within one to three sessions. Results: Twelve patients in the standard treatment group developed neovascular glaucoma during a mean period of 5 months after the CRVO. In the early treatment group, one patient developed subtle iris rubeosis 7 months after PRP. Otherwise, none of the patients showed any signs of ocular NV, and the intraocular pressure remained within normal range, without the necessity of supplementary medication, during a mean follow‐up of 41 months. Conclusions: This study indicates that ocular NV in patients with CRVO can be predicted by photopic 30 Hz flicker ERG and that early PRP in ERG‐verified ischaemic CRVO could be suggested as standard treatment.