Blockage of Central Retinal Veins and Branch Retinal Veins
(Retinal Vein Occlusion; Branch Vein Occlusion)
A vein in the retina (the transparent, light-sensitive structure at the back of the eye) may become blocked, causing sudden, painless loss of vision.
The central retinal vein is the main vein that drains blood away from the retina. Blockage may occur in the main vein or in its branches.
Central retinal vein blockage occurs mainly in older people. Risk factors include
Sometimes the cause of the blockage is unknown.
Blockage of the central retinal vein causes severe, painless, and usually sudden loss of vision, but vision loss can also sometimes occur gradually over a period of days to weeks.
Blockage of the central retinal vein may also cause growth of abnormal blood vessels on the retina or iris. Sometimes, these abnormal blood vessels bleed or cause a painful type of glaucoma (called neovascular glaucoma).
Using an ophthalmoscope, doctors can see changes in blood vessels and the retina. If the central retinal vein is blocked, the veins may be engorged (appearing enlarged), bleeding spots may be visible scattered throughout the retina, and the front of the optic nerve may be swollen.
Fluorescein angiography helps determine the extent of damage to the retina and helps the doctor plan treatment. In this test, a doctor injects dye into a vein in the arm and then photographs the retina. The dye makes the blood vessels of the retina show up better in the photograph. Optical coherence tomography (an imaging study) can help show that the retina is swollen, which is common.
Once the retinal vein blockage has been diagnosed, doctors often do tests to identify disorders that could increase the risk of developing blockages. For example, depending on which specific disorders they suspect, doctors may test people for diabetes (by measuring blood sugar or hemoglobin A1C levels), glaucoma (by measuring eye pressure), high blood pressure (by measuring blood pressure), and disorders that cause abnormally thick blood (called hyperviscosity disorders).
How much vision people retain depends mainly on two things:
Most people have some permanent loss of vision.
If the visual acuity is good at the time of retinal vein blockage (usually when only a branch is blocked), it will likely remain good, occasionally near normal. If the visual acuity is poor (for example, worse than 20/200), it will remain poor or worsen in 80% of people. Blockage of the central retinal vein rarely recurs.
Certain drugs can be injected into the eye, or an implant that slowly releases constant levels of a corticosteroid can be injected into the eye. Laser treatment of the leaking blood vessels can also help improve vision for some people with a blockage in a branch of the retinal vein. Although the treatments help restore vision in a number of people, many people have some permanent vision loss. Thus, preventing such blockages by controlling risk factors (for example, high blood pressure, diabetes, and other risk factors for atherosclerosis) is desirable.
Laser treatment may be used to destroy abnormal blood vessels to treat or prevent neovascular glaucoma or prevent further vision loss from bleeding within the eye.