The veins of the retina return blood from the retina to the general circulation. While the arteries bring oxygen-rich blood to the eye, the veins take oxygen-poor blood out of it. A blockage in the veins causes blood to back up and pool there. Blockages can occur at various points in the system, causing blood to spill into the surrounding retina. This can happen either acutely-- which is a total block, causing sudden symptoms of vision loss-- or gradually, which is a partial block that progresses slowly over months or even years. These clots are usually the result of damage to the blood vessels from hypertension, diabetes, inflammations, or a blood condition. There are two types of retinal vein clots: central and branched. Central retinal vein blockages occur where all the branch veins empty into a common vessel at the level of the optic nerve. Damage to the macular (MACK-you-lur), or central, region in the retina can cause swelling and permanent vision loss. A branch retinal vein blockage occurs in either of the two main branches of the central retinal vein, usually in people suffering from hypertension, cardiovascular disease, or diabetes. In both types of vein clots, laser treatment has been shown to be effective in both limiting the damage from some vein clots, as well as in preventing complications. A careful examination of the retina by a medical doctor is essential to managing retinal vein clots. It's also necessary in order to detect and treat any underlying medical problems.
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