The causes of CRVO aren't clear. Experts do know that people get CRVO if they have a blood clot or reduced blood flow out of the central retinal vein (the main vein that helps blood flow away from the retina). When the retina doesn't get enough blood flow, it also doesn't get enough oxygen.
Central retinal vein occlusion (CRVO) is a common retinal vascular disease, and its incidence increases with age. The primary risk factors for CRVO are hypertension, hyperlipidemia, and diabetes, and it mostly affects individuals > 60 years old.