Retinal Vein Occlusions
A retinal vein occlusion occurs when a blood vessel next to the retinal vein pushes up against it, or when the retinal artery – which lays on top of the vein – becomes heavy and applies a large amount of pressure to the vein, blocking the blood flow away from the retina. The latter is associated with high blood pressure. A blockage in the vein can occur in one of two places. A central retinal vein occlusion (CRVO) occurs in the main vein of the eye, near the optic nerve. This type of retinal vein occlusion affects the whole retina. A branch retinal vein occlusion (BRVO) occurs when a smaller branch off of the main vein becomes blocked. A BRVO affects a much smaller part of the retina.
A blocked vein causes hemorrhages in the retina, as well as swelling of the retina and decreased oxygen flow to the retina. It is also possible for blood and fluid to leak into the retina. A retinal vein occlusion can also cause a macular edema, which is swelling of the macula. A macular edema causes a decrease in vision.
Blurred vision occurs with a retinal vein occlusion, usually due to the leakage of fluid into the macula. The symptoms of a retinal vein occlusion often have a sudden onset. In cases of central retinal vein occlusion, pain in the eye may be experienced. This is due to an increase in pressure associated with the vein blockage.
Neovascularization, or abnormal blood vessel growth, is often associated with a retinal vein occlusion. These abnormal vessels that form in the retina are very fragile and break easily, leaking blood or fluid into the vitreous. Neovascularization can cause you to see spots, or floaters, and if severe enough, can also cause the retina to pull away from its position at the back of the eye.
There are several factors that put people at an increased risk for developing a retinal vein occlusion. Those with diabetes, glaucoma, high blood pressure, blood disorders, and cardiovascular disease are at an elevated risk.
If a BRVO occurs in one eye, there is an increased risk that a retinal vein occlusion will occur in the other eye. The best way to prevent this is to control your health conditions (diabetes, hypertension) that may contribute to a retinal vein occlusion. If you experience any of the symptoms of a retinal vein occlusion, see a retina specialist immediately.
A retina specialist can detect a retinal vein occlusion by directly examining the retina using an ophthalmoscope. Also, a fluorescein angiogram may be performed. (see angiogram)
There is no cure for a retinal vein occlusion, but treatments can be done to improve the secondary complications. Laser surgery can treat a macular edema and prevent the growth of abnormal blood vessels. Laser surgery procedures can improve vision, but vision will not be returned to normal.