Familial thrombophilia and retinal vein occlusion

To perform a pilot study on the prevalence of familial thrombophilia in all cases of retinal vein occlusion with no known risk factors.

Over the 1 year study period 71 patients presented with a new diagnosis of retinal vein occlusion (age 28-90 years). Fifty-five (77%) were excluded because of local predisposing factors. The remaining 16 (23%) had a full risk factor history taken and blood investigations of rheological factors and thrombophilia including tests for the factor V Leiden mutation, prothrombin G20210A allele and hyper-homocystinemia.

Of those with no local predisposing factors, 3 patients had antiphospholipid antibodies, 3 had raised fibrinogen levels, 4 had hyper-homocystinemia and 1 was heterozygous for the Leiden mutation. Other lifestyle risk factors such as obesity, smoking and a positive family history of venous thrombosis were not uncommon. No patient had the prothrombin G20210A variant.

It seems likely that several risk factors, both genetic and acquired, need to be present for thrombosis to occur. In investigating a new patient with a retinal vein occlusion one should test for hypertension, glaucoma and diabetes mellitus. Estimation of plasma viscosity and a full blood count are cheap investigations which may reveal neoplasia or vasculitis, and lipid levels should be estimated. In a young patient or one with an unexpected vein occlusion and a personal or family history of thrombosis, a hypercoagulable state may rarely be identified. This additional testing should include testing for antiphospholipid antibodies and a full thrombophilia screen including the factor V Leiden mutation, homocysteine and the prothrombin variant as part of a clinical trial. Until the role of these markers in thrombosis is better defined in relation to causation of retinal vein occlusion and treatment has been shown to improve outcome, we can not recommend them for routine testing. If a hereditary defect is found, referral should be made to a hematologist and consideration given to anticoagulation and screening of family members to prevent further thrombotic episodes. Retinal vein occlusions are multifactorial in origin except in rare cases.