Glaucoma is a group of eye diseases that are usually characterized by damage to the optic nerve and gradual vision loss that starts with losing peripheral (side) vision. People who have high eye pressure are at higher risk for glaucoma. There are several different types of glaucoma. Each type of glaucoma is different — but most have no early symptoms, so it’s important to get tested regularly, especially if you are at higher risk.

Open-angle glaucoma is the most common type in the United States, where 9 in 10 people with glaucoma have the open-angle type. Many people don’t have any symptoms until they start to lose their vision, and people may not notice vision loss right away. Researchers aren’t sure what causes open-angle glaucoma, but it may be caused by pressure building up in your eye. If the fluid in your eye can’t drain fast enough, it creates pressure that pushes on a nerve in the back of your eye (the optic nerve). Over time, the pressure damages the optic nerve, which affects your vision. This can eventually lead to blindness — in fact, open-angle glaucoma causes almost 2 in 10 cases of blindness in African Americans. People with high blood pressure are also at higher risk for this type.

Normal-tension glaucoma is a type of open-angle glaucoma that happens in people with normal eye pressure. About 1 in 3 people with open-angle glaucoma have the normal-tension type. You may be at higher risk for normal-tension glaucoma if you: are of Japanese ancestry, have a family history of normal-tension glaucoma, have had certain heart problems, like an irregular heartbeat or have low blood pressure. Experts don’t know what causes normal-tension glaucoma, but research shows that treatments that lower eye pressure can help slow the disease and stop vision loss.

Angle-closure glaucoma, also called narrow-angle or acute glaucoma, is a medical emergency. Go to the doctor or emergency room immediately if you suddenly have: Intense pain in your eye, nausea, red eyes and blurred vision. In this type of glaucoma, the outer edge of the iris (the colored part of your eye) blocks fluid from draining out of the front of the eye. The fluid builds up quickly, causing a sudden increase in eye pressure. If it’s not treated, angle-closure glaucoma can cause blindness in just a few days. An ophthalmologist can use laser treatment and give you medicine to help the fluid drain. This can lower eye pressure and protect your vision. Your doctor might treat both eyes to prevent future problems, even if you only have angle-closure glaucoma in one eye. Another type of angle-closure glaucoma, sometimes called slow or chronic angle-closure glaucoma, happens more slowly and might not have any symptoms.

Some babies are born with congenital glaucoma. About 1 out of 10,000 babies born in the United States have a defect (problem) in the eye that keeps fluid from draining normally. In these cases, you can usually notice the symptoms right away. Children with congenital glaucoma: Have cloudy eyes Are sensitive to light, make extra tears, may have eyes that are larger than normal. Surgery works very well to treat congenital glaucoma. If a pediatric ophthalmologist does surgery early enough, children with congenital glaucoma usually won’t have any permanent vision loss. Several other types of glaucoma can also develop in children. Any glaucoma that affects babies or children is called pediatric glaucoma.

Neovascular glaucoma happens when the eye makes extra blood vessels that cover the part of your eye where fluid would normally drain. It’s usually caused by another medical condition, like diabetes or high blood pressure. If you have neovascular glaucoma, you may notice: pain or redness in your eye and vision loss. This type of glaucoma can be hard to treat. Doctors need to treat the underlying cause (like diabetes or high blood pressure) and use glaucoma treatments to lower the eye pressure that results from it.

Pigmentary glaucoma or pigment dispersion syndrome happens when the pigment (color) from your iris (the colored part of your eye) flakes off. The loose pigment may block fluid from draining out of your eye, which can increase your eye pressure and cause pigmentary glaucoma. Young, white men who are near-sighted are more likely to have pigment dispersion syndrome than others. If you have this condition, you may have blurry vision or see rainbow-colored rings around lights, especially when you exercise. Doctors can treat pigmentary glaucoma by lowering eye pressure, but there currently isn’t a way to prevent pigment from detaching from the iris.

Exfoliation glaucoma (sometimes called pseudoexfoliation) is a type of open-angle glaucoma that happens in some people with exfoliation syndrome, a condition that causes extra material to detach from parts of the eye and block fluid from draining. Recent research shows that genetics may play a role in exfoliation glaucoma. You are at higher risk if someone else in your family has exfoliation glaucoma. This type of glaucoma can progress faster than primary open-angle glaucoma, and often causes higher eye pressure. This means that it’s especially important for people who are at risk to get eye exams regularly.

Uveitic glaucoma can happen in people who have uveitis, a condition that causes inflammation in the eye. About 2 in 10 people with uveitis will develop uveitic glaucoma. Experts aren’t sure how uveitis causes uveitic glaucoma, but they think that it may happen because uveitis can cause inflammation and scar tissue in the middle of the eye. This may damage or block the part of the eye where fluid drains out, causing high eye pressure and leading to uveitic glaucoma. In some cases, the medicines that treat uveitis may also cause uveitic glaucoma, or make it worse. This is because corticosteroid drugs may cause increased eye pressure as a side effect.