You can temporarily lose your vision, totally or partially, due to another condition. The possible causes and what you should do depend on whether you can see at all.
If you have sudden total, or near-total, vision loss, it’s an emergency. You need to call 911, see your eye doctor or maybe even a specialty ophthalmologist immediately, or go to an ER right away, because you have a short window of time to get it diagnosed and treated. Don’t wait to see if it goes away.
If you have partial vision loss, a migraine is the most likely reason. But there are other, less common, causes that need prompt treatment to save your sight.
You’ll want to know what the causes are and what to do if it happens.
Sudden Total or Near-Total Vision Loss
It can happen if a clot creates a blockage in your retinal artery. Your doctor may call it “central retinal artery occlusion” or “branch retinal artery occlusion.” It also means you’re at risk for a stroke or heart attack. It can happen if you get a blood clot that clogs a blood vessel in the eye. It’s similar to how a clot can trigger a heart attack if plaque in your coronary arteries breaks off and forms a clot. If the same thing happened in your brain, it would be an “ischemic” (clot-triggered) stroke.
Clots can cause temporary blindness in one eye, usually lasting 20 to 30 minutes. It often seems like a curtain of darkness falls (doctors call this “amaurosis fugax”). Without prompt treatment, this blockage may cause permanent blindness.
Your doctor may prescribe a medicine to break up the clot. Some cases need angioplasty, a procedure to reopen the blockage in the blood vessel. And it’s also a wake-up call to lower your risk of a heart attack or stroke.
Temporary, Partial Vision Loss
If you have partial vision loss, the causes include:
Migraines: These are, by far, the most common cause of short-term, partial vision loss. When you get a migraine, you may have “aura” that affects the vision in both of your eyes. You may see flashing lights, shimmering spots, or blind spots.
A retinal migraine affects only one eye. This rare condition causes partial or total blindness for a short period, usually 10 to 30 minutes. It typically comes before or during a headache. It is totally harmless to you and your vision.
Retinal vasospasm: Like migraine, this condition can cause temporary vision loss. Treatment can fully restore your sight.
When a blood vessel in your retina tightens, it causes a vasospasm. This cuts down on blood flow, which can bring on temporary vision loss in one eye. Various conditions can lead to a vasospasm. These include a retinal migraine, atherosclerosis, and high blood pressure.
If you have a retinal vasospasm, your doctor may recommend aspirin or a type of medicine called a calcium-channel blocker to relieve it. You’ll also work with your doctor to manage whatever caused the retinal vasospasm in the first place.
Closed-angle glaucoma: When your eye’s iris bulges, it can prevent fluid from draining properly. This builds up pressure in your eye. You’d have a lot of discomfort, nausea, short-term blurred vision, halos, or blindness in one eye. Your doctor will look for a slightly enlarged pupil that doesn’t react to light. Without prompt treatment, it can cause permanent blindness.
Medicine you take as an eyedrop or as a pill, such as prostaglandins or beta-blockers, can help ease the pressure in your eye. If that doesn’t work, you may need an operation called an iridotomy. The surgeon makes a tiny hole in your iris, which lets the fluid drain and eases the pressure.
Giant cell arteritis: This condition isn’t common, but it’s an important cause of vision loss in people older than 50.
This disease causes inflammation in the linings of your arteries, particularly those in your head. Symptoms include head pain, scalp tenderness, jaw pain, fever, and fatigue. Giant cell arteritis also triggers vision loss, usually in one eye. Without treatment, it can result in permanent blindness in a week or two.
Your doctor will probably first give you a corticosteroid, such as prednisone. You’ll likely feel better within a few days, but you may need to keep taking the drug for 1 or 2 years. A drug called tocilizumab is also approved to help treat giant cell arteritis.
These are very unlikely to be the cause of temporary vision loss.
Retinal vein occlusionis when a vein in the retina gets blocked, often due to a blood clot. It can lead to a buildup or leak of fluid in the eye, as well as swelling. Some people have bouts of temporary vision loss leading up to this condition. It’s more likely to happen in people who have diabetes and health problems that affect blood flow, such as high blood pressure.
Your doctor may inject corticosteroids to control the inflammation. You may also need another type of drug called an anti-vascular endothelial growth factor or laser treatment to cut the fluid buildup.
Epileptic seizures: For about 5% to 10% of people with epilepsy, their seizures affect their occipital lobe, the part of the brain that controls vision. As a result, this disease can prompt vision loss during and after a seizure. If you have epilepsy, your doctor will recommend treatment to help prevent this and other complications.
Papilledema: This is a condition where pressure in the brain causes your optic nerve to swell. This can lead to vision changes, such as double vision, blurriness, and short-term blindness. It usually lasts for a few seconds. Other symptoms include headaches and vomiting. Papilledema may be the result of a tumor, abscess, or blood clot. High blood pressure, an infection, and certain medications can also put pressure on the brain.
Uhthoff phenomenon: This affects only people with multiple sclerosis (MS) -- and it’s rare even among them. MS damages nerves, and it can make them more sensitive to heat. With Uhthoff phenomenon, a rise in your body temperature worsens your symptoms. It lasts less than a day. You can lose your vision in one or both eyes. You may also feel weaker, number, or dizzier than usual. Triggers for the condition include exercise, a fever, a hot bath, sun exposure, and stress. Your MS treatment should help prevent this and other complications.