context: Your retina is a thin layer of tissue that lines the back of your eyeball. It turns light into signals to the brain, which interprets them as sight. When a vein in the retina becomes blocked, it's called retinal vein occlusion. This can give you blurry vision or even sudden permanent blindness in that eye. It's similar to retinal artery occlusion, which is sometimes called an eye stroke. The damage happens when a blocked vein keeps blood from draining from the retina. That raises pressure inside your eye, which can cause bleeding, swelling, and fluid leaks. Retinal vein occlusions can harm your eye in minutes. Usually, a blood clot blocks the vein. Sometimes, a nearby artery can be a problem. In the retina, arteries and veins cross over each other. When an artery hardens, it can press against a vein and narrow the opening. This causes choppy blood flow, which may lead to clotting. So if you have diabetes, high blood pressure, and other conditions that affect the blood vessels, you're more likely to have retinal vein occlusion. Other things also can raise your odds for the condition: Smoking Being overweight Older age Hardened arteries, called atherosclerosis Glaucoma Lymphoma Leukemia Multiple myeloma Trauma to the eye You may not always know that you're going to have retinal vein occlusion. Almost always, it happens in only one eye. Some people -- especially those with blockage in smaller blood vessels -- have no symptoms. Usually, though, you may notice: Blurry or missing vision in part or all of an eye Dark spots or lines floating in your vision Pain and pressure in the eye If you have any of these symptoms, see a doctor right away. Your doctor will check your eyes and ask about your medical history. She'll put drops in your eyes to open up your pupils. She'll use a tool called an ophthalmoscope to check your retina for signs of blockage or bleeding. Your doctor may also order a test called a fluorescein angiography. You'll get a harmless dye injected into your arm. When it travels through your bloodstream and reaches the retina, a special camera takes pictures of your eye. Your doctor will be able see any fluid leaks in your blood vessels. Sometimes, you may also need a test called optical coherence tomography. You may get drops to dilate your pupils and then a machine scans your eyes with rays of light to make a detailed image of your retina. There's no cure for retinal vein occlusion. Your doctor can't unblock the retinal veins. What she can do is treat any complications and protect your vision. She may recommend: Injections. A drug called anti-vascular endothelial growth factor targets substances that cause fluid buildup in a part of your retina called the macula, which provides your central vision and helps you see details like fine print. This helps to ease swelling. Or your doctor may give you steroid injections in your eye instead. Your doctor will apply a pain-numbing drug first and use a very thin needle, so you shouldn't feel much discomfort. Focal laser therapy. A laser burns and seals off blood vessels near the macula. This keeps them from leaking. The retina does not have pain nerves, so you should not feel much discomfort. Laser surgery: You may need this if you grow new blood vessels in your eye. Your doctor will use a laser to make tiny burns on the retina. It stops the vessels from leaking and growing. These treatments may help you get your vision back. Most people's eyesight will get better after a few months. But some may not see any improvements. Usually, an underlying medical condition brings on a retinal vein occlusion. So it's important to keep your blood pressure, cholesterol, and blood sugar under control. If you have diabetes, get your eyes checked every year. If you take birth control pills, talk to your doctor. Rarely, they can lead to retinal vein occlusion.