Retinal vein occlusion is a condition where one of the veins in the retina becomes blocked. This blockage can lead to vision problems because it prevents blood from flowing properly, causing fluid to leak into the retina. Symptoms may include blurred vision or sudden vision loss, depending on the severity of the occlusion. There are two main types of retinal vein occlusion: central retinal vein occlusion (CRVO) and branch retinal vein occlusion (BRVO). CRVO affects the main vein, while BRVO affects smaller branches. Risk factors include high blood pressure, diabetes, and high cholesterol, which can damage blood vessels over time.