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Introduction: Previous studies have reported that an elevated plasma homocysteine level is a risk factor for vascular disease. The aim of this study is to determine whether hyperhomocysteinemia is a risk factor for retinal vein occlusion (RVO) and whether it is a prognostic factor., Patients and Methods: The plasma homocysteine level was measured in 101 patients and compared to the plasma homocysteine level of controls. The relation between plasma homocysteine level and the other known risk factors of retinal vein occlusion was studied, as well as the correlation between the clinical outcome of the RVO and the plasma homocysteine level., Results: The mean plasma homocysteine level was significantly higher in the 101 RVO patients than in the 29 controls (11.9 mmol/l vs 8.6, p<0.001). We found no relation between plasma homocysteine and other risk factors of vascular disease except for the hematocrit level. Hyperhomocysteinemia was more frequent in the ischemic forms and in bilateral RVO, but the difference was not statistically significant., Conclusions: Hyperhomocysteinemia seems to be an independent risk factor for RVO and was more frequent in severe RVO, but our study did not evidence an association with a severe prognosis. Vitamin therapy can decrease homocysteinemia but its efficacy in the prevention and in the treatment of RVO remains to be demonstrated.

Purpose: Epidemiological studies have shown a significant correlation between increased levels of lipoprotein (a) and coronary and cerebral vascular diseases. Lipoprotein (a) presents a striking homology with plasminogen and may therefore complete with binding of plasminogen at fibrin and at the endothelial cell surface, leading to fibrinolytic system dysfunction. The aim of this work is to study the relationship between increased levels of Lp(a) and retinal vein occlusion., Methods: 132 consecutive patients with retinal vein occlusion were screened for lipoprotein (a) level. They also underwent initial and final visual acuity measurement, fluorescein angiography and blood tests including glucose, cholesterol and triglyceride levels, apolipoprotein A1 and B, protein electrophoresis, coagulation tests. Lipoprotein (a) results were compared with those of 52 age, sex and cardiovascular risk factors-matched controls., Results: Lipoprotein (a) values were significantly higher in the retinal vein occlusion group than in the control group (p = 0.05). Elevated lipoprotein (a) (> 0.1 g/l) levels were observed more often in retinal vein occlusion patients (61%) than in the controls (42%; p < 0.02). No correlation was found in retinal vein occlusion patients between high levels of lipoprotein (a) and a severe form of retinal vein occlusion. Lipoprotein (a) levels were similar in central vein and branch vein occlusion patients., Conclusion: Lipoprotein (a) has been shown to be correlated with cardiovascular disorders and may also be involved in retinal vein occlusion, probably by dysfunction of the fibrinolytic system. However, it does not seem to be a prognostic factor of retinal vein occlusion and its role has to be elucidated in further studies.

Background: The prognosis of retinal vein occlusion is highly unpredictable because nonischemic types may convert into ischemic types within the first months. This study was designed to identify epidemiologic characteristics of the different types of retinal vein occlusion, their visual outcome, and their prognostic factors., Methods: The authors analyzed prospectively the data from patients who have had retinal vein occlusion with complete medical and biologic examination, including fluorescein angiography, and a 1-year follow-up., Results: One hundred seventy-five retinal vein occlusion eyes consisted of 120 central retinal vein occlusions (CRVO), 7 hemicentral occlusions, and 48 branch occlusions. In initially nonischemic CRVO eyes, retinal ischemia developed in 54%. The study of prognostic factors in the CRVO group showed that older age, male sex, and the number of risk factors (systemic vascular risk factors and glaucoma) were correlated with a poor visual outcome and with the development of retinal ischemia, as well as baseline visual acuity, initial extent of retinal ischemia, and rheologic findings (hematocrit, fibrinogen, and erythrocyte aggregation levels). Logistic regression underlined the prognostic role of sex, the number of risk factors, erythrocyte aggregation, and initial clinical features. Persistent macular edema was shown to be associated with hyperlipidemia and cardiovascular history, and inversely correlated to glaucoma., Conclusion: Because clinical characteristics of CRVO may worsen, the authors' results provide a basis to predict visual outcome by taking into account epidemiologic and rheologic findings. A careful follow-up of these patients is recommended.

Hemorheologic factors probably play a role in the pathogenesis and prognosis of retinal vein occlusion. Accordingly, we designed a prospective, randomized, double-masked study to evaluate the effect of troxerutin, a rheologic drug, on retinal vein occlusion. Fifty-three patients were included, 27 with central retinal vein occlusion and 26 with branch retinal vein occlusion. They were randomly assigned for treatment with either troxerutin or a placebo. All subjects were similar in age, gender, associated diseases, hemorheologic values, and clinical severity of the retinal vein occlusion. At the end of follow-up, members of the troxerutin-treated group, as compared with the placebo group, showed significant improvement in visual acuity (P = .03), macular threshold (P = .01), retinal circulation times (P = .04), and macular edema (P = .05). Furthermore, they had diminished progression of ischemia (P = .05) and decreased red blood cell aggregability (P = .006) when compared with the controls. These encouraging preliminary results obtained with a rheologic treatment attest to the pathogenic role of blood viscosity in retinal vein occlusion and suggest that a large-scale randomized study should be conducted.

Background: Retinal venous circulation is characterized by the combination of a low flow state and a high vascular resistance, which would make it particularly dependent on blood viscosity. Erythrocyte aggregation is the chief determinant of blood viscosity at low shear rates. Recent studies have demonstrated increased erythrocyte aggregation in many systemic vascular disorders and also in retinal vein occlusion., Methods: To assess the possible role of abnormal hemorheologic findings in the pathogenesis of central retinal vein occlusion (CRVO), the authors retrospectively studied erythrocyte aggregation and hematocrit and fibrinogen levels in 33 patients with CRVO and without any known risk factors (diabetes, hypertension, smoking, hyperlipidemia, cardiovascular disease, glaucoma). Erythrocyte aggregation was assessed with a light back-scattering method. Results were compared with those of a group of 33 age- and sex-matched controls., Results: Eleven (33%) of the 33 patients with CRVO had abnormal hemorheologic findings. Erythrocyte aggregation was highly significantly increased in the CRVO group when compared with the control group (P < 0.0001), as was the hematocrit level (P < 0.05). In addition, the proportion of patients with abnormal blood rheologic tests was greater (50%) in the subgroup of patients who initially had nonischemic CRVO that worsened into an ischemic CRVO during the follow-up., Conclusion: These data suggest that abnormal hemorheologic findings could affect the pathogenesis of CRVO, and perhaps be predictive of an aggravation. The latter hypothesis needs to be confirmed in a larger, prospective study.

Objective: To assess the prevalence of antiphospholipid antibodies in patients with occlusive retinal vascular disorders., Patients: Seventy-five consecutive patients (44 with central retinal vein occlusions, 24 with branch venous occlusions, five with vasculitis plus branch venous occlusion, and two with arterial occlusions) were screened for antiphospholipid antibodies and compared with a control group composed of outpatients with similar systemic vascular disorders., Results: The antibody assay for one patient was positive for lupus anticoagulant and the antibody assay for three other patients was positive for anticardiolipin antibodies. These four patients had central or branch retinal vein occlusion and presented with several vascular risk factors. Comparison of the retinal vascular occlusion and the control groups showed no difference in the levels of anticardiolipin antibodies or lupus anticoagulant., Conclusions: Antiphospholipid antibodies did not seem to be a feature of retinal vein occlusion, but in rare cases (5%) they may contribute to the occlusive phenomenon. A systematic screening does not seem to be justified, but it may be valuable to test for antiphospholipid antibodies in patients without conventional risk factors and in patients with clotting screen abnormalities, particularly if associated with lupus-like syndrome or other elements of the primary antiphospholipid syndrome.

Reversible aggregation of red blood cells (RBC) plays an important role in determining the flow properties of blood, and is the cause of the increase in blood viscosity at low shear rates. Retinal venous circulation is characterized by the combination of a low flow state and a high vascular resistance which might severely limit its capacity to adjust to high blood viscosity. These characteristics make the venous circulation in the retina particularly dependent on haemorheological factors. To test the possibility that high RBC aggregation could predispose to the onset and development of retinal vein occlusion (RVO), RBC aggregation and disaggregation (SEFAM erythroaggregameter, France) were measured in 64 patients with RVO. Results were compared to those of a group of 64 controls, similar in age, sex, smoking habit and associated pathologies. Increased RBC aggregation was observed in 52% of the patients, and the mean values showed a highly significant elevation of RBC aggregation parameters in RVO patients (+14%) when compared with controls (P less than 0.001). Subgroups were compared to study the influence of site (central versus branch), form (ischaemic versus non-ischaemic), duration and severity of the occlusion on the aggregation parameters. No significant differences were found between these various subgroups. An increase in RBC aggregability and in the shear resistance of RBC aggregates, by predisposing to circulatory stasis, is likely to contribute to the onset of RVO.

Erythrocyte aggregation is one of the principal determinants of blood viscosity at low shear rates (low flow). Anatomical and hemodynamical characteristics make retinal venous circulation particularly dependent on hemorheological factors. Erythrocyte aggregation and other laboratory parameters (haematocrit, fibrinogen, plasma proteins, clotting) were measured in 85 patients presenting with retinal vein occlusion and 64 controls matched for age, sex and vascular risk factors (hypertension, diabetes, smoking). Statistical analysis of the results demonstrated a significant difference between the retinal vein occlusion group an the control group for erythrocyte aggregation (p less than 0.001 for the aggregation index at 10 sec and for the threshold of dissociation). The fibrinogen level, haematocrit and plasma proteins (albumin, IgA, IgG, IgM, total proteins, 2-macroglobulin) were similar in the two groups. No statistically significant difference for erythrocyte aggregation was observed between occlusions of the venous branch and occlusions of the central retinal vein or between ischaemic and non-ischaemic forms. These results suggest that raised erythrocyte aggregation mainly explains the increase in blood viscosity previously demonstrated, and could play a role in the constitution of retinal vein occlusion.

Erythrocyte aggregation (EAg) is one of the principal determinants of blood viscosity at low shearing rates (slow flow). The retinal venous circulation, characterised by a slow circulatory rate and a high resistance to flow, creates a favourable environment for the formation of erythrocyte aggregates. EAg and other laboratory parameters (haematocrit, fibrinogen, plasma proteins, clotting) were measured in 64 patients presenting with retinal vein occlusion (RVO) and 64 controls matched for age, sex, risk factors (HT, diabetes, smoking) and concomitant vascular disease. Statistical analysis of the results demonstrated a significant difference between the RVO group and the control group for fibrinogen (p = 0.03) and erythrocyte aggregation (p = 0.00003 for the aggregation index at 10 sec and p = 0.0002 for the threshold of partial dissociation). The rise in the fibrinogen level alone cannot explain the increased erythrocyte aggregation. These results demonstrate that the increased EAg largely explains the hyperviscosity reported by other authors and suggest that it plays an important role in the pathogenesis of RVO.