Retinal vascular occlusions may involve both arteries and veins. Far more common are retinal vein occlusions. They occur when a retinal vein becomes obstructed by an adjacent blood vessel. This causes hemorrhage in the retina, which can result in swelling and lack of oxygen to the retina and sometimes glaucoma. Symptoms vary in severity from one person to another and are dependent on whether the central retinal vein or a branch retinal vein is involved. For a branch vein, the sudden onset of blurred vision or a missing area of vision is symptomatic. For a central vein occlusion, severe loss of central vision is characteristic. Common risk factors for vascular occlusion are hypertension, diabetes and cardiovascular disease.

Patients who suffer from a branch vein occlusion generally notice a gradual improvement in their vision as the hemorrhage resolves. Because the macula is often affected, recovery from a central vein occlusion is more difficult. It is important for follow-up care to be given in either of these cases to treat any complications. If areas of the retina have been oxygen-deprived, laser surgery may be used to prevent the growth of delicate vessels that could break, bleed or cause glaucoma.