What is a vein occlusion?
A Retinal Vein Occlusion (RVO) is a blockage of one of the small blood vessels which drains blood from the retina. A Branch Retinal Vein Occlusion (BRVO) affects a small area of the retina while a Central Retina Vein Occlusion (CRVO) affects the entire retina. When the blood flow is interrupted, the affected retina is "starved" of oxygen and important nutrients. This may cause an area of blurriness or a blind spot close to the central vision.
What causes it?
A vein occlusion is often caused by hardening of the retinal arteries (arteriosclerosis). In the retina, the artery and the vain lie very close to each other. If the artery is thickened and hardened, it can press on the neighboring vein and impede the blood flow. The blood flow becomes turbulent, a clot forms and then a blockage takes place. After a blockage, the vein becomes "leaky" and can leak fluid into the retina. The retina is like a sponge, it soaks up the extra fluid, and becomes thick and swollen. If the central part of the retina becomes swollen, it is termed macular edema.
What are the symptoms?
Many times a RVO will affect the macula. This is the part of the retina which we use for central visual tasks such as reading, watching tv or recognizing faces. The central vision may be blurry or there may be an area of darkening or greyness. Sometimes the vision change is so mild, that it is not noticed at first. While for other people, there is an abrupt change to the vision. Occasionally, a vein occlusion leads to bleeding within the eye. If this happens, the main symptom is a shower of new floaters.
With aging, everyone develops some degree of arteriosclerosis. Some conditions which accelerate these changes and put you at higher risk are high blood pressure, diabetes, smoking, and high cholesterol. Other less common causes are vasculitis (inflammation of blood vessels), estrogen medication (oral contraceptives), and blood disorders which create a pro-clotting environment.
What is the treatment?
When there is a blockage of the vein, there is no way to remove the clot. However, side effects of the blockage (eg macular edema) can be treated. The best treatment for macular edema currently, is an intravitreal injection of an anti-VEGF medication (please see anti-VEGF). This medication is injected into the eye by your retina specialist at the hospital. Lucentis is now covered for vein occlusions in Saskatchewan. It only lasts in the eye for 4 weeks, so monthly injections are required initially. On average, 6-7 injections will be required in the first year of treatment. With these injections, further visual loss may be prevented and for some, lost vision may be recovered.
In some scenarios, your retina specialist may choose to treat this condition with laser as well or in place of the injections. Laser treatment is safe and can be done at the office. It is also effective at reducing swelling and stabilizing the retina after a vein occlusion. Laser does leave tiny retinal scars, so it is reserved for cautious use by your physician.
In certain situations, a RVO can lead to bleeding within the eye (vitreous hemorrhage). If the bleeding is mild, then anti-VEGF treatment is very useful. However, if the bleeding is severe then retina surgery may be required. With a vitrectomy, your surgeon can remove the blood and then apply laser to the affected part of the retina. With most RVO’s, surgery is not required. Your specialist will discuss which treatment option is best for your eye.
What is the recovery?
A RVO creates a permanent change to the retinal blood flow. With our treatment we are treating the side effects, but not the root cause of the problem. As such, the treatment can be short term or long term. Regular follow-up examinations are required to monitor the condition and to watch for macular swelling. Occasionally, a similar problem may occur in the other eye. If this happens, it is important to contact your retina specialist promptly.