Risk factors and laboratory workup for retinal vein occlusion
After diabetic retinopathy, retinal vein occlusion (RVO) is the second most common vision-threatening retinal vascular disorder. Depending on the anatomic site of the occlusion, RVO is traditionally classified as branch retinal vein occlusion (BRVO), hemiretinal vein occlusion, or central retinal vein occlusion (CRVO). BRVO occurs at an arteriovenous crossing site where a retinal artery compresses the adjacent vein, whereas CRVO occurs in the central retinal vein as it travels through the lamina cribrosa in the optic nerve head. The pathogenesis of RVO is multifaceted but has been attributed to Virchow's Triad of thrombosis - turbulent blood flow, vascular endothelial cell damage, and hypercoagulability. Known risk factors for developing any RVO include advanced age, metabolic risk factors such as hypertension, hyperlipidemia, atherosclerosis, and elevated body mass index (BMI), and hypercoagulable risk factors including drugs and diseases that increase hypercoagulability such as hyperhomocysteinemia. CRVO risk is specifically increased in individuals with diabetes mellitus, smoking, and ischemic heart disease. Additionally, ocular hypertension or glaucoma has been noted to be a risk factor for CRVO, thought to be due to movement of the lamina cribrosa and subsequent alterations to the anatomy of the retinal vein that passes through it, leading to turbulent blood flow. Ophthalmologists who diagnose patients with a new RVO can work together with the patient's primary care physician to evaluate for and control systemic risk factors such as blood pressure, lipid levels, and blood sugar. Furthermore, in more unusual clinical presentations (i.e., RVO in a young patient, bilateral presentation, or any patient without common risk factors), a more extensive laboratory workup is often obtained to evaluate for systemic vasculitides (syphilis, sarcoidosis, lupus, etc.) or hypercoagulable conditions (antiphospholipid syndrome, Factor V Leiden thrombophilia, or monoclonal gammopathy), among others.
