UNC Health Care
graphic of eye ball

Six Causes of Sudden Vision Loss

One second you can see clearly, and the next your vision fades to black. Sudden vision loss is scary—and sometimes irreversible. That’s why it’s important to seek help right away.

Joshua Hardin, MD, a UNC Health Care ophthalmologist, explains six conditions that can cause sudden vision loss. If you experience any of the following symptoms, make an appointment with your doctor immediately.

Dry Eye Disease

In dry eye disease, you don’t produce enough tears to lubricate the eye. It’s a common condition, but people don’t always realize it can be serious.

“The vision loss from dry eye can be more profound than a person thinks,” Dr. Hardin says. “If left untreated, it can cause corneal scarring and permanent vision loss.”

Symptoms of dry eye include scratchy, irritated eyes, fluctuating vision that improves with rest or blinking, excessive tearing episodes and an overall reduction in vision.

Over-the-counter eye drops can ease these symptoms, but if irritation persists, it’s time to see a doctor. Your provider may prescribe medications that work like artificial tears or reduce eye inflammation. In severe cases, your doctor may suggest a procedure to close your tear ducts to reduce tear loss or therapies aimed at improving the function of the oil glands along the eyelid margin.

Cortical Cataracts

Cataracts, or the yellowing or whitening of the lens of the eye, are common as people age. Vision loss associated with cataracts typically happens over time, but some types of cataracts can affect vision more abruptly.

Cortical cataracts start at the outside of the lens and spread across the rest of the lens. “Sometimes when they grow across the center of the lens, they can cause a sudden decline in vision over the span of a few weeks,” Dr. Hardin says.

Other symptoms of cataracts include glare, difficulty reading in low-light conditions, and a general deterioration in both near and distance vision that is not correctable with glasses.

If you have cataracts, your doctor may perform surgery to remove them.

Wet Macular Degeneration

The retina, or the back wall of the inside of the eye, receives and translates light into electrical signals that travel to the brain and are interpreted as sight. At its center is the macula, the area of the retina that processes high-contrast vision that allows people to perform daily activities such as reading or driving.

In macular degeneration, the photoreceptors of the macula that process vision start to thin and die as deposits, called drusen, form under the retina and interrupt nutrient flow to the weak receptors.

Most cases of macular degeneration are gradual, happen as part of the aging process, and slowly progress. This is called “dry” macular degeneration. However, in 10 percent of cases, the condition will progress to “wet” macular degeneration, where fluid from blood vessels trying to restore nutrients is leaked into the retina.

“That fluid causes an immediate substantial reduction in vision,” Dr. Hardin says. “It also causes vision distortion, particularly wavy images.” If the fluid is not addressed with treatment, it can cause profound scarring and irreversible vision loss.

When you’re diagnosed with macular degeneration, you are given an Amsler grid, a tool that can detect if the condition has changed from dry to wet. You look at the center of the grid with each eye. If the lines appear wavy, it could be a sign of wet macular degeneration.

If you do see wavy lines, make an appointment with your doctor within a week. Your provider will start you on eye injections every four to six weeks to dry up the fluid and prevent scarring. Between injection periods, it’s important to continue to look at the Amsler grid to monitor for progression, Dr. Hardin says. If you see changes in the grid before your next injection date, make an earlier appointment.

Retinal Tears or Detachment

The retina is made up of very thin layers that can tear or pull away from the back of the eye, called detachment.

Retinal tears and detachment are often associated with a condition called posterior vitreous detachment (PVD), a normal part of aging where the vitreous jelly that fills the eye and gives it its shape pulls away from the retina.

“PVD happens in a majority of people over 50, around 80 percent plus,” Dr. Hardin says. “For a small group of people, during this pulling, the vitreous can pull a hole in or tear the retina.”

Injury can also cause a tear or detachment. Symptoms include seeing flashes of light, many new floaters that may appear like snow falling, or a black curtain coming across the eye and wiping out vision.

If not recognized early, a small retinal tear or detachment can progress and lead to permanent vision loss. If you experience any of these symptoms, visit your ophthalmologist right away.

Treatment of a retinal tear or detachment depends on its severity. If you have a tear, your doctor may use laser surgery to weld the retina back together. If you’re experiencing a tear with a small detachment, your doctor may inject an air bubble into your eye to push the retina back in place, and then use a laser to repair the tear. If there is a larger detachment, your doctor may recommend more extensive surgery.

Giant Cell Arteritis (GCA)

Giant cell arteritis (GCA) is a common condition in the elderly in which the blood vessels around the scalp are inflamed. (It’s also called temporal arteritis.) The temporal artery on the side of the head is most commonly affected, which causes headaches and tenderness. The ophthalmic artery and small arteries that feed the optic nerve, which connects the eye to the brain, also can be affected. When these arteries are inflamed, blood flow to the optic nerve is blocked, damaging the optic nerve and leading to irreversible vision loss that can happen over the course of hours, one eye at a time.

If you experience this type of vision loss, it’s important to see a doctor right away. “If GCA is not recognized and treated, it can cause full blindness in both eyes, as well as damage to the vessels that feed the brain,” Dr. Hardin says.

After a GCA diagnosis is confirmed, usually by biopsy of the temporal artery, your doctor will start you on a steroid to preserve what’s left of your vision.

“If people come in with temporal headaches, we can prevent vision loss in both eyes,” Dr. Hardin says. “But most often people come in with vision loss in one eye, so our efforts are to spare vision in the fellow eye.”

Central Retinal Artery Occlusion

Central retinal artery occlusion is a stroke to the eye. When this happens, it can cause instantaneous vision loss that is rarely recovered, Dr. Hardin says.

The central retinal artery supplies blood to the optic nerve and retina. In central retinal artery occlusion, “an embolus of some kind—plaque from an artery, a platelet aggregate or something floating in the blood—gets lodged in the central retinal artery and closes it off,” Dr. Hardin says.

“When people come in with this condition, we send them directly to the emergency room to be admitted for stroke treatment,” Dr. Hardin says. “Although they’ve only had a stroke to the eye, they are at risk for brain stroke as well, because the vessels of the brain are likely to be affected, if not at the same time, then at some point in the future.”

People who experience central retinal artery occlusion most likely have other stroke risk factors—such as plaque in the carotid arteries of the neck or atrial fibrillation—  an irregular heartbeat—or a blood clotting disorder.

Depending on the severity of the occlusion, your doctor may try to recover vision loss by significantly reducing eye pressure, massaging the eye, or applying laser to the plaque. But unfortunately, Dr. Hardin says there is little evidence to support these treatments, and vision loss is usually permanent.

To keep your eye health in check and prevent vision loss, don’t forget to schedule regular eye exams with your ophthalmologist.


Experiencing vision loss or need to schedule an eye exam? Find an ophthalmologist near you.