In most cases, retinal vein occlusion causes some degree of permanent vision loss, but the effect is usually minor if the individual had sharp vision before the blockage developed, according to Merck Manual. The person is also more likely to retain normal vision if the occlusion blocked a branch, rather than the central vein. Roughly 80 percent of people who have poor visual acuity before the occlusion either experience little to no improvement or develop further vision impairment.
In about 33.3 percent of all cases, patients experience gradual improvement in the eye, but it may take up to a year to fully assess the recovery, Cleveland Clinic states. The inner surface at the back of the eye is the retina, which contains nerve cells that convert incoming light into signals that help the brain process images. Retinal vein occlusion occurs when a clot blocks the central retinal vein or an offshoot branch, cutting off blood and oxygen supply to the retinal nerve cells. The veins are unable to draw blood away from the retina, and tissue damage occurs in areas that are not able to receive blood and nutrients. People with high blood pressure, high cholesterol or diabetes have a higher risk of developing the condition.
Fluid buildup and swelling in the retina, known as macular edema, is a major complication that increases the chance of suffering permanent vision loss, according to Cleveland Clinic. Another obstacle is neovascular glaucoma, which occurs when the restricted blood flow causes new blood vessels to form and create harmful pressure inside the eye.