What is retinal vein occlusion?
The eye is often compared to a camera. The front of the eye contains a lens that focuses images on the inside of the back of the eye. This area, called the retina is covered with special nerve cells that react to light.
Nerve cells need a constant supply of blood to deliver oxygen and nutrients. Most people understand what happens in a “stroke.” A small blood clot blocks the flow of blood through one of the arteries in the brain, and the area that is not getting blood becomes damaged. This same type of damage can happen anywhere in the body, not just the brain.
When the flow of blood from the retina is blocked, it is often because of a retinal vein occlusion. If this happens, the nerve cells of the retina can die and vision may be lost. Because all of the blood from the retina drains through one large vein, a blockage of that vein can affect all the vision in that eye.
What types of Vein Occlusions?
1- Branch Retinal Vein Occlusion (BRVO)–only small branch of the retinal vein is blocked. Affects a certain segment of the retina.
2- Central Retinal Vein Occlusion (CRVO)–the entire trunk of the retinal vein is blocked. Affects the entire retina.
Both conditions can cause loss of vision.
Why do people get retinal vein occlusion?
Retinal vein occlusion happens when a blood clot blocks the vein. Sometimes it happens because the veins of the eye are too narrow. It is more likely to occur in people with diabetes, high blood pressure, high cholesterol levels, or other health problems that affect blood flow.
How does the doctor know whether someone has a retinal vein occlusion?
The symptoms of retinal vein occlusion range from subtle to very obvious. There is painless blurring or loss of vision. It almost always happens in just one eye. At first, the blurring or loss of vision might be slight, but it gets worse over the next few hours or days. Sometimes there is a complete loss of vision almost immediately.
If these symptoms occur, it is important to schedule an appointment with your doctor as soon as possible. Retinal vein occlusion often causes permanent damage to the retina and loss of vision. It can also lead to other eye problems.
How is retinal vein occlusion treated?
Unfortunately, there is no way actually to unblock retinal veins. However, the doctor can treat any health problems that seem to be related to the retinal vein occlusion.
Vision may come back in some eyes that have had a retinal vein occlusion. About one-third have some improvement, about one-third stay the same and about one-third gradually improve, but it can take a year or more to learn the final outcome.
In some cases, the blocked vessels will lead to fluid accumulation and swelling in the retina like a sponge absorbing water. In some patients with certain patterns of vein occlusion, this fluid may be treated with:
1- Focal laser photocoagulation
2- Injections in the eye with medicines such as Avastin, Lucentis, and/or Steroid medicine in the eye.
3- Implantable device that is injected in the eye that releases small amount of a medicine called Dexmethasone (another type of steroid). The name of this implant is Ozurdex.
4- Combination of all the above treatments
All these treatment options are done in the office and are painless procedures. Patients do usually experience some discomfort, but this usually resolves within hours.
What are the complications that may occur if treatment is not performed?
Sometimes the retinal vein occlusion will cause a dangerous condition called neovascular glaucoma. In neovascular glaucoma, abnormal blood vessels start growing inside the eye, and the pressure in the eye starts increasing. This can permanently destroy all vision in the eye. It can also cause significant pain and cause the eye to deteriorate physically.
If this condition seems likely to develop, your doctor might recommend a treatment called panretinal laser photocoagulation.
What happens in laser photocoagulation?
In laser photocoagulation, the surgeon focuses a laser beam onto a small spot on the retina where the abnormal blood vessels are growing. The laser beam heats up that spot, creating a tiny burn in the blood vessels, which stops their growth or leads to fluid resorption.
This treatment is usually effective in stopping the growth of the blood vessels and fluid leakage, but it will not bring back any vision that has been lost. Unfortunately, there is no known way to reverse the damage that is done by the more severe forms of retinal vein occlusion and neovascular glaucoma. The goal of treatment is to prevent further damage and possible loss of the eye itself. There are new drugs being used in some patients to treat new blood vessels or leaking fluid. Microscopic quantities of the drugs are injected into the eye. The treatments are new so ask your eye doctor about the latest information.