Our results in a comprehensive way showed that CRAO patients, compared with controls without thromboembolic events in medical history, are characterized by having laboratory and genetic thrombophilic risks factors, including higher prevalence of protein C deficiency, lower free protein S levels, presence of antiphospholipid antibodies, factor V Leiden mutation, and hyperhomocysteinemia. The gene discussed is PROS1; the disease is hyperhomocysteinemia.