Central Retinal Vein Occlusion Eyes Research Articles

Establishing an experimental rat model of photodynamically-induced retinal vein occlusion using erythrosin B.

To develop a reliable, reproducible rat model of retinal vein occlusion (RVO) with a novel photosensitizer (erythrosin B) and study the cellular responses in the retina. Central and branch RVOs were created in adult male rats via photochemically-induced ischemia. Retinal changes were monitored via color fundus photography and fluorescein angiography at 1 and 3h, and 1, 4, 7, 14, and 21d after irradiation. Tissue slices were evaluated histopathologically. Retinal ganglion cell survival at different times after RVO induction was quantified by nuclear density count. Retinal thickness was also observed. For all rats in both the central and branch RVO groups, blood flow ceased immediately after laser irradiation and retinal edema was evident at one hour. The retinal detachment rate was 100% at 3h and developed into bullous retinal detachment within 24h. Retinal hemorrhages were not observed until 24h. Clearance of the occluded veins at 7d was observed by fluorescein angiography. Disease manifestation in the central RVO eyes was more severe than in the branch RVO group. A remarkable reduction in the ganglion cell count and retinal thickness was observed in the central RVO group by 21d, whereas moderate changes occurred in the branch RVO group. Rat RVO created by photochemically-induced ischemia using erythrosin B is a reproducible and reliable animal model for mimicking the key features of human RVO. However, considering the 100% rate of retinal detachment, this animal model is more suitable for studying RVO with chronic retinal detachment.

The Effect of Antivascular Endothelial Growth Factor Therapy on the Development of Neovascular Glaucoma after Central Retinal Vein Occlusion: A Retrospective Analysis

Purpose. Ischemic central retinal vein occlusion (CRVO) eyes are at high risk of developing neovascular glaucoma (NVG). Our purpose is to investigate the effect of anti-VEGF therapy for macular edema after CRVO on the development of neovascular glaucoma (NVG) in ischemic CRVO eyes. Methods. This is a retrospective case series of 44 eyes from 44 patients with CRVO treated with anti-VEGF therapy for macular edema. The primary outcome was the development of NVG. Results. Of the 44 eyes, 14 eyes had ischemic CRVO, and 30 eyes had nonischemic CRVO. Nonischemic eyes received a mean of 8.4 anti-VEGF doses, over mean follow-up of 24 months. One nonischemic eye (3.3%) developed NVD but not NVG. The 14 ischemic eyes received a mean of 5.6 anti-VEGF doses, with mean follow-up of 23 months. Of these 14 ischemic eyes, two eyes (14%) developed iris neovascularization and 3 eyes (21%) developed posterior neovascularization. Three of these 5 eyes with neovascularization progressed to NVG, at 19.7 months after symptom onset, on average. Conclusion. Anti-VEGF therapy for macular edema may delay, but does not prevent, the development of ocular NV in ischemic CRVO. Significant risk of NVG still exists for ischemic CRVO eyes.

Enhanced Depth Imaging Optical Coherence Tomography of the Choroid in Central Retinal Vein Occlusion

To evaluate subfoveal choroidal thickness in patients with central retinal vein occlusion (CRVO) using enhanced depth imaging optical coherence tomography. Retrospective observational study. We measured bilateral subfoveal choroidal thickness, averaged for 100 scans, in 36 patients (mean age, 66 ± 15 years; 26 women and 10 men) with unilateral CRVO by using the enhanced depth imaging methods of the Spectralis optical coherence tomography system. Twenty-two patients were treated with intravitreal bevacizumab (1.25 mg/0.05 mL), and subfoveal choroidal thickness was measured before and after treatment. Statistical analysis was performed to compare subfoveal choroidal thickness of CRVO and fellow eyes and to compare subfoveal choroidal thickness before and after intravitreal bevacizumab. Mean subfoveal choroidal thickness measured in 36 eligible eyes of 36 patients was 257.1 ± 83.2 μm, which was significantly greater than that in fellow eyes (222.6 ± 67.8 μm; P < .01, paired t test). There was strong correlation between CRVO eyes and fellow eyes (r = 0.79, P < .01). Mean subfoveal choroidal thickness after intravitreal bevacizumab was 227.7 ± 65.1 μm, which was significantly thinner than that before intravitreal bevacizumab therapy (266.9 ± 79.0 μm; P < .01, paired t test). Subfoveal choroidal thickness of CRVO eyes was significantly greater than that of fellow eyes and decreased significantly after intravitreal bevacizumab treatment. Enhanced depth imaging optical coherence tomography can be used to evaluate choroidal involvement in CRVO and may assist noninvasive diagnosis and management of this disease.

Baseline Characteristics and Response to Treatment of Participants With Hemiretinal Compared With Branch Retinal or Central Retinal Vein Occlusion in the Standard Care vs COrticosteroid for REtinal Vein Occlusion (SCORE) Study

To compare baseline characteristics and treatment response of participants with hemiretinal vein occlusion (HRVO) with those of participants with branch retinal vein occlusion (BRVO) or central retinal vein occlusion (CRVO) in the Standard Care vs COrticosteroid for REtinal Vein Occlusion (SCORE) Study. Eyes were randomized to standard care, 1 mg intravitreal triamcinolone acetonide, or 4 mg intravitreal triamcinolone acetonide. Standard care was observation in the SCORE-CRVO trial and grid photocoagulation in the SCORE-BRVO trial. The HRVO eyes were enrolled in the SCORE-BRVO trial. Baseline characteristics, changes in visual acuity and center point thickness, safety outcomes, and number of treatments were compared among HRVO, BRVO, and CRVO participants. At baseline, HRVO eyes were intermediate between BRVO and CRVO eyes in area of retinal thickening, area of fluorescein leakage, visual acuity, and center point thickness. No differences in visual acuity change from baseline to 1 year were noted between standard care groups for HRVO and BRVO. Within triamcinolone-treated eyes, HRVO eyes did not differ from BRVO eyes in visual acuity change, but HRVO eyes fared better than CRVO eyes. There were no differences in center point thickness change between standard care groups for HRVO and BRVO, nor were there differences across the 3 disease entities for triamcinolone-treated eyes. There were no differences in frequency of protocol treatments and adverse events. The HRVO participants were similar to BRVO and CRVO participants regarding most demographic characteristics, with fundus findings intermediate between BRVO and CRVO. In the SCORE Study, HRVO was treated as BRVO; HRVO eyes responded to treatment similarly to BRVO eyes, and there was no difference among the 3 disease entities in frequency of protocol treatments and adverse events. clinicaltrials.gov Identifier: NCT00105027.

Significant Correlation between Electroretinogram Parameters and Ocular Vascular Endothelial Growth Factor Concentration in Central Retinal Vein Occlusion Eyes

Central retinal vein occlusion (CRVO) leads to retinal ischemia, which then induces an upregulation of vascular endothelial growth factor (VEGF). The aim of this study was to determine whether a significant correlation exists between the ocular VEGF levels and the amplitudes and implicit times of different components of the electroretinogram (ERG) in eyes with a CRVO. The medical records of the 20 consecutive patients who had macular edema secondary to CRVO and were examined at the Nagoya University Hospital from November 2008 to February 2010 were reviewed. Because all the patients were scheduled to receive an intravitreal injection of bevacizumab (IVB), it was possible to collect samples of the aqueous humor before the IVB. The correlation between the different components of the ERGs and the VEGF concentration in the aqueous was determined. The mean VEGF concentration of the aqueous humor was 416 pg/mL with a range of 100-1260 pg/mL. The b/a ratio of the single flash ERGs (P = 0.049; ρ = -0.45), implicit times of the cone a-wave (P = 0.028; ρ = 0.50), cone b-wave (P = 0.0059; ρ = 0.63), and 30 Hz flicker ERGs (P = 0.0058; ρ = 0.63) were significantly correlated with the VEGF concentration in the aqueous. The significant correlations between the different components of the ERGs and the aqueous VEGF concentration indicate that full-field ERGs can be used to detect the CRVO patients at a high risk of developing neovascularization of the iris.

SCORE Study Report #11: Incidences of Neovascular Events in Eyes with Retinal Vein Occlusion

To investigate in The Standard Care versus COrticosteroid for REtinal Vein Occlusion (SCORE) Study: (1) incidences of neovascular events and retinal capillary nonperfusion (abbreviated as "nonperfusion"), and their relationship with treatment groups; (2) neovascular incidences by nonperfusion status; and (3) pertinent baseline factors for their potential risk for neovascular events. Two multicenter, randomized clinical trials, 1 evaluating participants with central retinal vein occlusion (CRVO) and the other evaluating participants with branch retinal vein occlusion (BRVO). At 36 months, data were available for 81 participants with CRVO and 128 with BRVO. Standard care (observation or grid photocoagulation) versus 1 or 4 mg intravitreal triamcinolone. Neovascularization of the iris (NVI), neovascular glaucoma (NVG), disc or retinal neovascularization (NVD/NVE), preretinal or vitreous hemorrhage (PRH/VH), and nonperfusion. The cumulative 36-month incidences for CRVO and BRVO eyes, respectively, were 8.5% and 2.4% for NVI or NVG; 8.8% and 7.6% for NVD/NVE or PRH/VH. There were no differences in incidences of neovascular events or risk of nonperfusion when comparing the 3 treatment groups within diseases. For CRVO at 36 months, 16.6% of eyes with ≥5.5 disc areas of nonperfusion versus 4.0% of eyes with <5.5 disc areas of nonperfusion developed NVG (P = 0.0003); for BRVO at 36 months, 14.6% versus 2.4% developed NVD/NVE (P<0.0001). Similar results were noted for most other neovascular events. Nonperfusion was the only significant baseline factor for neovascularization in BRVO, with the risk of a neovascular event increasing with greater disc areas of nonperfusion, and the highest risk noted at ≥5.5 disc areas. In the SCORE Study, triamcinolone treatment was not associated with lower incidences of neovascular events or nonperfusion status compared with observation or grid photocoagulation. Cumulative 36-month incidences for most neovascular events were significantly higher for nonperfused than perfused eyes. Greater baseline disc areas of nonperfusion increased the risk of neovascularization in BRVO but not CRVO eyes, possibly owing to obscuration of retinal capillary details caused by dense hemorrhage at baseline for CRVO eyes. Increased risk of neovascularization was noted below the historical threshold of 10 disc areas of nonperfusion for retinal vein occlusion.

Oxygen Saturation in Central Retinal Vein Occlusion

To test whether oxygen saturation is affected in retinal blood vessels in patients with central retinal vein occlusion (CRVO). Prospective observational case series. Oxygen saturation of hemoglobin was measured in retinal blood vessels in 10 patients with unilateral CRVO. The duration of CRVO before measurement was from 1 day to about 6 months. Two patients were excluded because of poor quality of oximetry images. The spectrophotometric retinal oximeter is based on a fundus camera. It simultaneously captures images of the retina at 605 nm and 586 nm and calculates optical density (absorbance) of retinal vessels at both wavelengths. The ratio of the 2 optical densities is approximately linearly related to hemoglobin oxygen saturation. Mean oxygen saturation was calculated for first- and second-degree arterioles and venules in both eyes of each patient. The mean oxygen saturation of hemoglobin in retinal venules was 49% ± 12% (mean ± SD, n = 8) in eyes affected by CRVO and 65% ± 6% in unaffected fellow eyes (P = .003). The mean arteriolar oxygen saturation was 99% ± 3% in CRVO eyes and 99% ± 6% in the fellow eyes. Venular oxygen saturation was variable within and between CRVO eyes. Oxygen saturation in retinal venules is lower in eyes with CRVO than in fellow eyes and there is considerable variability within and between CRVO eyes. Arteriolar saturation is the same in CRVO and fellow eyes. Retinal oxygenation is disturbed in CRVO.

Natural History of Visual Outcome in Central Retinal Vein Occlusion

To investigate systematically the natural history of visual outcome in central retinal vein occlusion (CRVO). Cohort study. Six hundred sixty-seven consecutive patients (30 patients had both eyes involved resulting in 697 eyes) with CRVO first seen in the authors' clinic from 1973 through 2000. At the first visit, all patients underwent a detailed ophthalmic and medical history and a comprehensive ophthalmic evaluation. Visual evaluation was carried out by recording visual acuity, using the Snellen visual acuity chart, and assessing visual fields with a Goldmann perimeter. The same ophthalmic evaluation was performed at each follow-up visit. Central retinal vein occlusion was classified into nonischemic (588 eyes) and ischemic (109 eyes) types at the initial visit based on functional and morphologic criteria. Visual acuity and visual fields. Of the eyes first seen within 3 months, visual acuity was 20/100 or better in 78% with nonischemic CRVO and in only 1% with ischemic CRVO (P < 0.0001), and visual field defects were minimal or mild in 91% and 8%, respectively (P < 0.0001). Final visual acuity, on resolution of macular edema, was 20/100 or better in 83% with nonischemic CRVO and in only 12% with ischemic CRVO (P < 0.0001), and visual field defects were minimal or mild in 95% and 18%, respectively (P < 0.0001). On resolution of macular edema, in eyes with initial visual acuity of 20/70 or worse, visual acuity improved in 59% with nonischemic CRVO, with no significant (P = 0.55) improvement in ischemic CRVO. Similarly, on resolution of macular edema, in eyes with moderate to severe initial visual field defect, improvement was seen in 86% of nonischemic CRVO eyes, but no significant (P = 0.83) improvement was seen in eyes with ischemic CRVO. In nonischemic CRVO, development of foveal pigmentary degeneration, epiretinal membrane, or both, was the main cause of poor final visual acuity. This shows that initial presentation and the final visual outcome in the 2 types of CRVO are entirely different. A clear differentiation of CRVO into nonischemic and ischemic types, based primarily on functional criteria, is crucial and fundamental in determining visual outcome. Visual outcome is good in nonischemic CRVO and poor in ischemic CRVO.

Changes of photopic negative response in retinal vein occlusion

Objective To observe the changes of photopic negative response (PhNR) of electroretinography (ERG) in patients with retinal vein occlusion (RVO).Methods A total of 30 patients (30 eyes) with retinal vein occlusion (RVO) diagnosed by indirect ophthalmoscopy and fundus fluorescein angiography (FFA) were selected;the unaffected fellow eyes of the patients and another 25 healthy agematched individuals (50 eyes) were cllected as the normal control.All of the patients underwent the examination of visual acuity,visual field,and flash-ERG (FERG);the normal control ones underwent FERG.In the 30 patients with RVO,there were 14 with central RVO (CRVO) and 16 with branch RVO (BRVO).According to the disease history and results of FFA,the patients were divided into 3 time groups:＜1 month,1-3 months,and＞3 months;according to the types of RVO,the patients were divided into ischemic and non-ischemic group.The amplitude of PhNR and other parameters were analysed.The relationship among the amplitude of PhNR and RVO types and time course were analyzed.Results The amplitude of PhNR in the CRVO and BRVO eyes was (28.20±5.8) and (36.96±4.71) μV,respectively;those in the unaffected fellow and control eyes was (61.25±3.93) and (59.33±16.92) μV,respectively;the amplitude of PhNR was significantly smaller in the CRVO and BRVO eyes than those in the unaffected fellow or control eyes (F=10.69 and 9.80,P＜0.001;F=9.69 and 9.75,P＜0.001).The amplitude of PhNR in ischemic and non-ischemic group in CRVO eyes was (22.77±15.73) and (36.63±12.91)μV,respectively;the difference between the two groups was significant(t=6.54,P＜0.01).The amplitude of PhNR in ischemic and non-ischemic group in BRVO eyes was (32.39±13.22) and (46.73±10.43)μV,respectively;there was no significant difference between the two groups (t=2.12,P＜0.05).The amplitude of PhNR was (24.58±14.60) and (27.94±15.73)μV,respectively,in CRVO and BRVO eyes with＜1 month disease course;was (50.39±13.80) and (58.69±12.43)μV in those with 1-3 months disease course;and was (25.40±19.94) and (34.48±16.72)μV in those with＞3 months diseases course.Significant difference was found between the 1-3 months group and＞3 months group in CRVO eyes (F=4.30,P＜0.01).Conclusions The amplitude of PhNRs was significantly smaller in RVO eyes than those in the unaffected fellow or control eyes .The amplitude of PhNR amplitude of ischemic type was smaller than that of non-ischemic type.The amplitude of PhNR has descending,ascending,and descending tendency during the disease courses. Key words: Electroretinography/utilization; Retinal vein occlusion/diagnosis

Increased retinal toxicity of intravitreal tissue plasminogen activator in a central retinal vein occlusion model

Intravitreal injection of tissue plasminogen activator (tPA) is used to treat several ocular conditions, although excessive doses of intravitreal tPA cause retinal toxicity. Toxicity may increase in the ischemic retina, such as in central retinal vein occlusion (CRVO), because tPA toxicity to neural tissues increases under ischemic conditions. We investigated tPA toxicity to the retina in a CRVO rat model. CRVO was induced in pigmented rats with rose Bengal-assisted laser photothrombosis. One hour after CRVO induction, 3 microl of tPA (0.075, 0.75, 3, or 7.5 microg) was injected intravitreally. Eyes that did not receive laser treatment, which served as non-CRVO controls, received tPA (0.75, 3, or 7.5 microg). The same amount of balanced salt solution (BSS) was injected as a nondrug control. Eyes were enucleated at 12 hours after injection, and terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling (TUNEL) staining was performed to evaluate retinal cell apoptosis. The number of TUNEL-positive cells increased in a dose-dependent manner in both non-CRVO and CRVO group and significantly (P = 0.002) increased when 0.75, 3, or 7.5 microg of tPA was injected into the CRVO eyes. When comparing the number of TUNEL-positive cells between the eyes with and without CRVO that received the same treatment, apoptosis significantly increased in CRVO eyes. Retinal toxicity associated with intravitreally injected tPA can increase in a dose-dependent manner and be exacerbated in CRVO eyes, suggesting that the dose of tPA should be reduced when tPA is used to treat eyes with CRVO.

Ocular Surface Temperature in Central Retinal Vein Occlusion: Preliminary Data

To compare ocular surface temperature (OST) measures in patients with central retinal vein occlusion (CRVO) and controls. Thirty-six patients with unilateral CRVO and 54 healthy volunteers were included in the study. OST was evaluated by infrared thermography. In CRVO eyes and in fellow, nonaffected eyes, OST values were lower than in controls (p<0.05). Ischemic CRVO eyes showed lower temperatures than nonischemic ones. Infrared thermography may be helpful in the management of patients with CRVO.

The photopic negative response of the flash electroretinogram in retinal vein occlusion

The photopic negative response (PhNR) has recently been shown to be severely affected in central retinal artery occlusion (CRAO), despite relative preservation of the cone b-wave compared to that in the healthy unaffected fellow eye. The aim of this study was to test how the PhNR of the flash electroretinogram (ERG) is affected in human retinal vein occlusion. PhNR was elicited with red stimuli (1 cd s/m2, 5 cd s/m2, and 7 cd s/m2 with 4 ms duration) and blue background (10 cd/m2). Standard Ganzfeld flash ERG was produced according to the ISCEV standard for the clinical electroretinogram (2004). Sixteen patients with central retinal vein occlusion (CRVO), 14 patients with branch retinal vein occlusion (BRVO), and 16 controls were analyzed. The amplitude of the PhNRs was significantly smaller in the CRVO and BRVO eyes than those in the unaffected fellow or control eyes (p = 0.000). There was a significantly greater reduction of PhNR amplitudes than that of other waves including the OPs, rod b-wave, combined a-wave and b-wave, cone a-wave and b-wave, and 30 Hz flicker ERG. Thus, PhNR amplitude in retinal vein occlusion is severely affected. There is a potential role for PhNR in assessing inner retinal damage and evaluating the effect of treatment.

The capillary blood flow in ischaemic type central retinal vein occlusion: the effect of laser photocoagulation.

To determine the effect of photocoagulation on retinal blood flow (RBF) in eyes with ischaemic type central retinal vein occlusion (CRVO). Retinal blood flow was measured in 12 eyes with CRVO, 12 fellow eyes and 12 eyes of 12 age-matched healthy subjects using the Heidelberg retinal flowmeter (HRF). Microvascular blood flow values (volume, flow, velocity) were recorded from the upper temporal retina and macula. Eyes were re-examined 1 month after photocoagulation. We investigated whether there was a difference in RBF measurements before and after photocoagulation treatment. In eyes with CRVO, mean RBF values (volume, flow and velocity) obtained from the upper temporal retina increased significantly after treatment (paired t-test, p < 0.05). In contrast, mean RBF values from the macula were unaffected by photocoagulation (paired t-test, p > 0.05). Retinal blood flow values from the upper temporal retina obtained from control subjects were significantly higher than the values in eyes with CRVO before and after photocoagulation (unpaired t-test, p < 0.05), but there was no significant difference between control subjects and CRVO patients in RBF values from the macula (unpaired t-test, p > 0.05). Mean RBF values were significantly higher in CRVO patients' fellow-eyes before photocoagulation in the eyes with CRVO (paired t-test, p < 0.05) but were lower than in age-matched healthy control eyes (unpaired t-test, p < 0.05). Macular blood flow did not differ between the eyes with CRVO and fellow eyes (paired t-test, p > 0.05). Laser photocoagulation increased retinal blood flow in eyes with CRVO, but RBF did not reach normal values. Photocoagulation was found to have no effect on RBF in the macular area.

Colour Doppler Assessment of Blood Flow in Eyes with Central Retinal Vein Occlusion

Purpose: To assess the blood flow changes in eyes with central retinal vein occlusion (CRVO) and compare these values with values of fellow eyes and eyes of normal subjects. Methods: 25 eyes of 25 consecutive newly diagnosed patients with CRVO comprised the study group. Their fellow eyes and those of 25 healthy subjects were the control group. All patients underwent a complete ophthalmological examination. Eyes with CRVO were classified into two groups as non-ischaemic and ischaemic by fundus fluorescein angiography. Colour Doppler imaging was performed with a Toshiba Sonolayer SSH-140A and 7.5-MHz linear array probe. Maximum systolic velocity (V_max), end-diastolic velocity (V_min) and resistive index (R_i) values were noted for each of the central retinal artery (CRA), central retinal vein (CRV) and ophthalmic artery (OA). These parameters were compared with those of the fellow eyes and both eyes of the control group. Results: Mean ages were 63.55 and 61.45 years in the CRVO and control groups, respectively. Age and sex distributions were statistically identical in both groups. When we compared the eyes with CRVO to the control group, no statistically significant difference existed between the two groups with regard to the V_min and R_ivalues of the CRA and CRV. However, V_max values of the CRA and CRV were significantly lower in CRVO eyes when compared to the control group. The CRVO group and control group had similar V_max, V_min and R_i values for the OA. Only the V_max was significantly lower in the CRV in eyes with CRVO when compared to the unaffected fellow eyes. No statistically significant difference could be detected between any of the parameters of CRA, CRV and OA of the ischaemic and non-ischaemic CRVO groups. Conlusions: More data on broader series need to be obtained in order to decide on the practical use of colour Doppler imaging in the differentiation of ischaemic eyes from non-ischaemic eyes in CRVO.

Axial Length and Refraction in Retinal Vein Occlusions

To assess whether axial length and refraction are risk factors for retinal vein occlusion, we measured these parameters in 88 consecutive patients with unilateral branch retinal vein occlusion (BRVO), in 58 consecutive patients with unilateral central retinal vein occlusion (CRVO) and in 50 patients selected as a control group. Patients and controls were free or affected by systemic or local predisposing factors. We compared eyes with CRVO with control eyes, eyes with BRVO with control eyes, and eyes with CRVO with eyes with BRVO. Comparing CRVO eyes and controls, none of the investigated variables was shown to be significant. From the analysis of BRVO eyes versus controls, it resulted that refraction was the only variable which played the role of an independent prognostic factor. When comparing BRVO eyes with CRVO eyes, we found that age was slightly related to the development of BRVO. In conclusion, faulty refraction appeared to be a risk factor for the development of BRVO. We did not find any influence of axial length on the occlusion of retinal veins.

Cone ERG subnormality to red flash in central retinal vein occlusion: a predictor of ocular neovascularisation?

In patients with unilateral central retinal vein occlusion (CRVO), we retrospectively examined whether cone electroretinogram (ERG) subnormality to red flash (ratio of the b-wave amplitude in the CRVO eye to that in the normal fellow eye < 1) found at the time of diagnosis of the CRVO was a predictor of later ocular neovascularisation. Ganzfeld ERG cone and rod responses had initially been obtained in a consecutive series of 21 patients with unilateral CRVO. Patients were re-evaluated 6-55 months later to determine whether ocular neovascularisation had developed. Of the 21 CRVO eyes, 6 (29%) were subnormal to red in the affected compared with the normal fellow eye. At follow-up, all 6 (100%) patients had developed ocular neovascularisation compared with 1 (7%) of the 15 patients who were supernormal to red (p = 0.00013). Cone ERG subnormality to red flash in CRVO eyes compared with normal fellow eyes may be a predictor of later development of ocular neovascularisation.

Vitreous Changes and Macular Edema in Central Retinal Vein Occlusion

The condition of the posterior vitreous was determined in 56 eyes with central retinal vein occlusion (CRVO). Using a life-table analysis, it was studied in 56 eyes. The incidence of posterior vitreous detachment (PVD) in the CRVO eyes at the first vitreous examination did not differ significantly from that in 64 age-matched control eyes. However, the incidence of PVD in CRVO eyes increased from 39.3% at the first vitreous examination to 58.5% after 6 months, and to 69.6% 1 year from the examination. The incidence of PVD in CRVO eyes during follow-up was statistically higher than that of the controls (P = .009). The incidence of PVD after the first vitreous examination was significantly higher in eyes with hemorrhagic retinopathy than in eyes with venous stasis retinopathy (P = .04). In the 34 eyes with macular edema, the edema lasted significantly longer in those with vitreomacular attachment (VMA) at the first examination than in those without VMA at this time (P = .02). VMA may play an important role in the pathogenesis and chronicity of macular edema in CRVO.