Because serum VEGF levels have been found to be increased in BD patients and correlated with ocular disease with demonstrated VEGF gene polymorphisms [42], VEGF may therefore have contributed to the elevated NO levels along with an additional risk factor for the development of retinal vaso-occlusive disease and neovascularization, resulting in poor visual outcome in such patients. The gene discussed is VEGFA; the disease is Behcet disease.