Compared to previous studies only one genetic factor was determined as a risk factor for RVO and other genetic factors including factor V H1299R and V Leiden, β-fibrinogen G455A, PAI-1 4G/5G, ACE I/D, HPA1, prothrombin G20210A, factor XIII Val34Leu, MTHFR A1298C and C677T polymorphisms, activated protein C and S, antithrombin III deficiency, antiphosolipid and anticardiolipin antibodies, hyperhomocysteinemia may be possible other risk factors and it is necessary to investigate these genetic factors for RVO in large scale study groups . The gene discussed is HPSE; the disease is hyperhomocysteinemia.