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.     

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.     

The a- and b-wave latencies as a prognostic indicator of neovascularisation in central retinal vein occlusion

To evaluate the prognostic value of ERG in cases of central retinal vein occlusion (CRVO) regarding the development of neovascularisation (NV), we studied 20 patients with unilateral CRVO. Half of them were allocated in the perfused group and the other 10 finally developed NV and were allocated in the non-perfused group. Flash ERG was recorded from all patients. Our findings suggest that b-wave latency is the most reliable parameter in predicting NV, followed by the a-wave latency. The b/a wave amplitude of ERG ratio does not seem to be suitable for clinical use. This revised version was published online in July 2006 with corrections to the Cover Date.     

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%.     

Cup/disk ratio in branch retinal vein occlusion.

Recent reports have been attempted to evaluate, without obtaining a positive result, whether the reduction in size of the optic disc may influence the pathogenesis of central retinal vein occlusion. Cup/disc ratios in the fellow eye of 67 patients with branch retinal vein occlusion were compared with the ratios of 67 controls matched to cases for age, sex and refractive defect. There was no significant difference between cup/disc ratios of the two groups. These results suggest that the anatomical features of the optic disc are of no importance in the development of branch retinal vein occlusion.     

Thrombophilia as a risk factor for central retinal vein occlusion

Central retinal vein occlusion is associated with systemic conditions, such as arterial hypertension, diabetes, hypercholesterolemia, but also with certain hypercoagulability states (thrombophilia). Growing evidence indicates, that the presence of antiphospholipid antibodies and elevated plasma homocysteine levels predispose to central retinal vein occlusion. In younger patients, factor V Leiden (Arg506Gln) could increase the risk of this disease. Other probable causes of thrombophilia related to retinal vein occlusion include increased levels of plasminogen activator inhibitor 1 and lipoprotein (a), which impair fibrinolysis.     

"二步法"激光诱导脉络膜视网膜静脉吻合术治疗兔视网膜中央静脉阻塞的视觉电生理变化

目的评价“二步法”激光诱导脉络膜视网膜静脉吻合术(laser-induced chori-oretinal venous anastomosis,LCRVA)治疗实验性视网膜中央静脉阻塞(central retinal veinocclusion,CRVO)的有效性。方法青紫蓝兔30只,8只(16眼)设为正常对照组,其余22只(44眼)采用光动力学方法建立双眼的CRVO模型。CRVO模型成功后,对双眼CRVO兔(15只),随机选1眼先后用倍频Nd:YAG激光器和Nd:YAG激光器分别在选定部位击破Bruch膜及相邻的静脉壁,以建立视网膜静脉与脉络膜血管之间的吻合通道;对侧眼作为CRVO对照眼;4只单眼CRVO兔中,2只为LCRVA治疗组,另2只为CRVO对照组。于术前1d,术后4h、1d、3d、1周、2周、3周、4周、8周、12周和16周各时间点,分别进行ERG检测。结果34眼(77.3%,15只兔双眼,4只兔单眼)一次性建立了CRVO模型。对其中的17眼行LCRVA,每眼击射2个点。经眼底荧光素血管造影检查证实,在8眼(47.0%)中的11个点(32.4%)存在功能性吻合。CRVO对照组较正常对照组在各时间点主要表现为ERG b波潜伏期延长,振幅下降。经LCRVA治疗后2~3周,b波振幅呈恢复趋势,与CRVO对照组有显著性差异(P<0.05)。OPs波振幅与ERG b波呈现相似变化。ERGa波变化不明显。结论兔CRVO眼的视网膜功能明显受损,LCRVA可一定程度减轻CRVO对视功能的损害。     

Optociliary veins and central retinal vein occlusion.

In a follow up of 94 patients with central retinal vein occlusion (CRVO) whose onset had taken place less than 1 year earlier, optociliary veins (OCVs) were found in 7.4% at first examination. Among the 79 eyes in which the fundus of the eye was very visible after a follow up of more than 1 year OCVs were found in 30.4%, showing a late development of OCVs in many cases of CRVO. No difference was found in the occurrence of OCVs between non-ischaemic and ischaemic forms of CRVO. The visual acuity of the eyes with CRVO that developed OCVs was not significantly different from the visual acuity of the eyes without OCVs. Thus, the presence of OCVs in CRVO does not seem to be associated with better visual prognosis.     

Leuprolide acetate and central retinal vein occlusion.

A 63-year-old man suffered a central retinal vein occlusion 2 months after he began taking leuprolide acetate for prostate cancer. Despite control for possible systemic hypertension (126/90 mm Hg) and mild hypercholesterolemia (total cholesterol level =246 mg/dL [range: 16 to 200 mg/dL], high-density lipoprotein level =67 mg/dL [range: 40 to 59 mg/dL], and low-density lipoprotein level =144 mg/dL [range: 0 to 130 mg/dL]), progression of the venous occlusive disease occurred. Leuprolide acetate, which is associated with thromboembolic events and diffuse intravascular coagulation, may be implicated in central retinal vein occlusion.     

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.     

Infrequency of retinal neovascularization following central retinal vein occlusion.

Forty-eight patients with the clinical diagnosis of central retinal vein occlusion and ten surgically enulceated eyes with central retinal vein occlusion documented by histopathologic examination were studied and reviewed. Retinal neovascularization developed in only one of the ten eyes. Rubeosis iridis occurred in 14% (7) of the clinical cases and in all of the histopathologic cases. Ten eyes with neovascular glaucoma, enucleated following central retinal vein occlusion, showed absence of retinal endothelial cells. The absence of retinal capillary endothelial cells is significant in explaining the rare occurrence of retinal neovascularization following central retinal vein occlusion. However, the small number of cases may reflect a biased result. Further studies of more cases over a longer period are required to reach the final conclusion.     

Acute onset of central retinal vein occlusion and retinal detachment.

The simultaneous occurrence of a central retinal vein occlusion and retinal detachment has not been previously reported. Although both are well recognized entities with characteristic appearances, their simultaneous acute onset led to a misdiagnosis in our case report. The need for a complete eye examination in the face of obvious pathology is stressed.     

Systemic considerations in bilateral central retinal vein occlusion.

BACKGROUND: Central retinal vein occlusion (CRVO) is a common cause of visual impairment and can occur at any age. Nonetheless, 90% of patients with CRVO are older than 50 years, and only 10% of CRVO patients are younger than 40 years. Systemic vascular diseases, such as hypertension and diabetes, are common risk factors for the development of CRVO. However, when a patient less than 50 years of age has bilateral and simultaneous central retinal vein occlusions, a hyperviscosity syndrome or inflammatory condition is also suspected. CASE REPORT: This article presents the case of a 40-year-old man with bilateral ischemic CRVO and the differential diagnoses considered, including systemic lupus erythematosus (SLE), antiphospholipid antibody syndrome (APAS), dysproteinemias, and hyperhomocysteinemia. CONCLUSION: When a CRVO is observed in a young patient, more obscure underlying etiologies must be explored. As primary care providers, optometrists need to consider common (and atypical) vascular risk factors for vein occlusion to prevent further ocular morbidity and systemic complications.     

Cilio-retinal arterial circulation in central retinal vein occlusion.

The hypothesis that an occlusion of the central retinal artery is an essential prerequisite for haemorrhage formation after central retinal vein obstruction has been investigated by examining the fundus changes in patients with a cilio-retinal arterial circulation; the findings are at variance with the 'combined occlusion hypothesis'. Comparisons were made between the pathological features in two retinal capillary beds with independent sources of arterial supply--namely, the central retinal and cilio-retinal arteries--but with an obstructed venous drainage channel common to both--namely, the central retinal vein. The importance of intraluminal pressure changes (as distinct from perfusion changes) in the causation of haemorrhages and oedema after venous occlusion is stressed, and the role of arterial disease in the pathogenesis of venous occlusions is distinguished from its role in determining the sequelae of such occlusions.     

Supernormal cone electroretinograms in central retinal vein occlusion.

In 12 successive cases of unilateral central retinal vein occlusion (CRVO), the strongly light-adapted cone electroretinogram (both a- and b-wave) was always slower and larger (supernormal) to long-wave stimuli compared with that of the unaffected eye. This supernormality became less as the level of light adaptation decreased; in the dark-adapted state, long-wave stimuli produced subnormal responses from the affected eye in all but two subjects. This supernormality was not caused by ineffectiveness of the adapting light related to a reduced cone quantal catch because it occurred in the dark. At any one state of adaptation, the supernormality increased with the wavelength of stimulation, paralleling the relative absorption ratio of long-middle wavelength-sensitive cones. This suggests that cones, especially long wavelength-sensitive cones, are less able to reduce their responsiveness to light with increasing levels of light adaptation in a retina affected by CRVO.