Branch retinal vein occlusion
The eye is like a photographic camera. It has the lens and an opening in front that help in the focusing of the objects on the retina. The retina is a thin membrane that is sensitive to the light, as the film in the photographic camera. The macula is found in the center of the retina, where the light focuses. It is responsible for what we see in front of us, for activities such as writing and reading and for the perception of colors. The rest of the retina is responsible for the peripheral vision.
The retina is nourished by the blood flow, which provides the nutrients and the oxygen that the nerve cells need for proper operation. When there is a blockage in the veins of the retina then we have what we call a retinal vein occlusion.
Branch retinal vein occlusion is the blockage of the small veins of the retina. (When there is blockage of the central vein of the retina it is called Central retinal vein occlusion).
Branch retinal vein occlusion often occurs when the arteries of the retina that are thickened by atherosclerosis (hardening of the arteries) cross and press on the retinal veins resulting in closing them. When the vein is closed the nerve cells in this area of the retina may suffer significant losses. Because the macula, the part of the retina responsible for central vision, is affected by the occluded veins part of central vision may be lost.
The most common symptom of Branch retinal vein occlusion is loss of vision or blurring of part or all of the vision in one eye. It is painless and can occur suddenly or gradually over a period of several hours or days. Sometimes there is a sudden and complete loss of vision. Branch retinal vein occlusion almost always occurs in one eye only.
It is associated with aging and usually occurs in people aged 50 years and older. Hypertension is usually associated with it. People with diabetes are at increased risk for Branch retinal vein occlusion. Approximately 10-12 % of people with Branch retinal vein occlusion have also glaucoma and atherosclerosis.
The measures used to prevent Branch retinal vein occlusion are similar to those of coronary heart disease and include:
If you have sudden vision loss you should visit an ophthalmologist. First he will measure the vision in both eyes, he will examine the pupillary reflex, he will measure the intraocular pressure and will perhaps examine your visual fields. Then he will put drops in both your eyes to dilate the pupils and examine the retina. You will have to wait for about half an hour for the drops to work. You will have blurred vision for a few hours and you will be sensitive to the light afterwards and therefore you should not drive home after the examination. Then a special contact lens will be put on your cornea to examine the retina and the macula. Your ophthalmologist will ask you to do a fluorescein angiography (intravenous injection of a dye and pictures of the retina taken with a camera) and an Optical Coherence Tomography test (taking tomographic images of the retina using light) to assess the macula and to see if there is edema (swelling) or leaking of the retina due to the vein occlusion. In addition, you will need tests to determine the levels of sugar and cholesterol in your blood. People under 40 should be checked for blood clotting problems.
Because there is no cure for Branch retinal vein occlusion, the main objective is to stabilize vision by closing the vascular leak. Treatment includes laser and injections.
Discovering what causes the occlusion is the first step in treatment. Your ophthalmologist may recommend a waiting and observation period after diagnosis. During the course of the disease, many patients will experience swelling in the central region of the macula. This swelling, called macular edema, can last for more than a year.
The treatment for macular edema is laser. Laser is a light beam that can be focused on the retina with high precision. Thus we can close the leaking retinal blood vessels. Laser is done in the clinic and is usually painless. After you have drops put in your eyes to dilate the pupil you sit on the slit lamp, a special contact lens is put on the cornea to help focus the laser on the retina and you will see many strong flashes of light. The treatment for the leaking blood vessels doesn't last long and its main objective is to stabilize vision by closure of the leaking blood vessels that prevent the macula from functioning properly.
It has been found that injection of a substance (eg Lucentis etc) into the eye that inhibits the abnormal blood vessels and reduces leakage is able to stop the progression of the disease and improve vision. These injections are performed in theatre painlessly under sterile conditions and they must often be repeated at intervals of 1-2 months. A small device may also be injected into the eye releasing slowly over several months cortisone into the eye and thereby reducing the swelling of the retina.
If you have any questions about your disease or its treatment do not hesitate to consult your doctor, who will discuss it with you in detail.