Levels of homocysteine may be increased by dietary habits, prescription medicines, or enzymatic mutations affecting homocysteine metabolism.43 The results of meta-analyses confirm total homocysteine to be an independent risk factor for RVO.21,44 Loewenstein et al.45 investigated the prevalence of genetic mutation in the enzyme methylentetrahydrofolate reductase (MTHFR) whose impaired activity may lead to hyperhomocysteinemia. Here, MTHFR is linked to hyperhomocysteinemia.