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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.

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.

Anti-red auto-antibodies were found in 69 out of 892 000 blood donors aged between 20 and 60 years, 63 of whom were followed for up to five years. This would suggest an overall incidence of 1 in 13 000 members of a "normal" population. Uncontrolled methyl-dopa treatment could be incriminated in 25% of cases. Only 10% of autoimmune subjects had slight confirmed anaemia, but 72% had biological evidence of red cell destruction (i.e. hyper-reticulocytosis, elevated serum bilirubin levels and shortened red cell life span), which demonstrates the presence of subclinical autoimmune haemolytic disease in apparently normal people. The anti-red cell auto-antibodies were of the IgG type in 97% of the subjects and were associated with various anti-tissue antibodies in 41%, thus pointing to a multisystem autoimmune disorder. In most cases the abnormality persisted or spontaneously regressed during the observation period, but long-term follow-up is required to determine whether asymptomatic red cell autoimmunization is harmless or potentially dangerous.