What is glaucoma?

Glaucoma is a general term used to describe a group of eye disorders that damage the optic nerve. It's the most common form of optic nerve damage leading to vision loss. In most cases, fluid builds up in the front part of the eye. This extra fluid puts pressure on the eye, gradually damaging the optic nerve. This pressure is known as intraocular pressure (IOP), or eye pressure.

Some people have normal eye pressure and still get glaucoma. Untreated or poorly controlled glaucoma can lead to permanent and irreversible vision loss and blindness.

What is the optic nerve?

Your optic nerve plays a crucial role in vision. It sends signals from the retina (neural tissue in the back of your eye, like the film of an old-fashioned camera) to the brain. Your brain relies on these signals to create images.

How common is glaucoma?

Glaucoma is a common age-related eye problem that affects an estimated three million Americans. Globally, it is the second leading cause of blindness after cataracts.

Who might get glaucoma?

Glaucoma can affects people of all races and genders, but the risk increases with age. African Americans and Latinos are much more likely to get glaucoma than other races, and they tend to develop the disease earlier in life. Asian and Inuit populations are also more susceptible to a specific form of glaucoma known as angle closure glaucoma.

People with diabetes are twice as likely to get glaucoma. Other risk factors include:

What are the types of glaucoma?

There are several types of glaucoma, including:

  • Open-angle: This type is the most common, affecting up to 90% of Americans who have glaucoma. It occurs when tiny deposits build up in the eye’s drainage canals, slowly clogging them. The canals appear to be open and functioning normally. But over months or years, the deposits cause fluid to build up and put pressure on the optic nerve. The disease can go unnoticed for years because most people don’t have symptoms.
  • Closed-angle: Also called angle-closure or narrow-angle glaucoma, this rare type often comes on suddenly (acute). It occurs when the angle between the iris (the colored part of the eye that controls light exposure) and cornea (clear outer part of the eye) is too narrow. As a result, the drainage canals become blocked, preventing aqueous fluid from leaving the eye and causing an acute elevation in eye pressure. Symptoms, including eye pain and headaches, can be severe and require immediate medical attention.
  • Normal-tension: As many as one in three people have optic nerve damage even when eye pressure is normal or not very high. Experts aren’t sure what causes normal-tension glaucoma, which is also called normal-pressure or low-tension glaucoma. This type is more common among Asians and Asian Americans.
  • Congenital: Some babies are born with drainage canals that don’t form properly in the womb. Your healthcare provider might notice a baby’s glaucoma symptoms at birth. Or signs may become noticeable during childhood. This condition is also known as childhood, infantile or pediatric glaucoma.

Does glaucoma affect both eyes?

Most people develop glaucoma in both eyes, although the disease initially may be worse in one eye. With open-angle glaucoma, one eye may have moderate or severe damage, while the other eye may be mildly affected. Over time, the disease damages both eyes.

People with closed-angle glaucoma in one eye have a 40% to 80% chance of developing the same type of glaucoma in the other eye within five to 10 years.

Symptoms and Causes

What causes glaucoma?

Glaucoma can occur without any cause, but is affected by many factors. The most important of which is the intraocular eye pressure. Your eyes produce a fluid called aqueous humor that nourishes them. This liquid flows through the pupil to the front of the eye. In a healthy eye, the fluid leaves through a drainage canal located between the iris and cornea.

With glaucoma, the drainage canals become clogged with microscopic deposits. The fluid has nowhere to go, so it builds up in the eye. This excess fluid puts pressure on the eye. Eventually, this elevated eye pressure can damage the optic nerve leading to glaucoma.

What are the symptoms of glaucoma?

Signs of open-angle glaucoma tend to come on subtlety and gradually. That makes them easy to miss. Many people with open-angle glaucoma have no noticeable symptoms early on, which makes it incredibly important to have routine eye exams to detect this disease in its earlier stages. Because glaucoma damage is irreversible, early detection and treatment is crucial to prevent blindness.

Closed-angle glaucoma has more severe symptoms that tend to come on suddenly.

With any type, you may experience:

  • Eye pain or pressure.
  • Headaches.
  • Rainbow-colored halos around lights.
  • Low vision, blurred vision, narrowed vision (tunnel vision) or blind spots.
  • Nausea and vomiting.
  • Red eyes.

Diagnosis and Tests

How is glaucoma diagnosed?

It’s possible to have glaucoma and not know it. Regular eye exams are important to catch glaucoma or other eye problems. Eye exams can assess optic health and vision loss.

To check for glaucoma, your eye doctor may do one or more of these painless tests:

  • Dilated eye exam to widen pupils and view the optic nerve at the back of the eyes.
  • Gonioscopy to examine the angle where the iris and cornea meet.
  • Optical coherence tomography (OCT) to look for changes in the optic nerve that may indicate glaucoma.
  • Ocular pressure test (tonometry) to measure eye pressure.
  • Pachymetry to measure corneal thickness.
  • Slit-lamp exam to examine the inside of the eye with a special microscope called a slit lamp.
  • Visual acuity test (eye charts) to check for vision loss.
  • Visual field test (perimetry) to check for changes in peripheral vision (your ability to see things off to the side).

Management and Treatment

How is glaucoma managed or treated?

Untreated glaucoma can lead to faster development of permanent vision loss or blindness. Treatments can slow down additional vision loss, but they can’t restore lost vision. It’s important to see your eye doctor right away if you have eye pain, severe headaches or vision problems.

Glaucoma treatments include:

  • Eyedrops/Medication: Prescription eyedrops decrease fluids and increase drainage to alleviate eye pressure. There are many types of eyedrop medications that can be used for this condition. Because glaucoma is a lifelong condition, you may need to use daily eyedrops for life.
  • Laser treatment: Your eye doctor uses a laser (strong beam of light) to help improve fluid drainage from your eye. While the laser can complement the use of eye drops, it may not replace it completely. The results from laser treatments vary, but can last up to five years. Some laser treatments can also be repeated.
  • Surgery: Surgery is another way to help reduce eye pressure. It is more invasive but can also achieve better eye pressure control faster than drops or laser. Surgery can help slow down vision loss, but it can’t restore lost vision or cure glaucoma. There are many types of surgeries for glaucoma, and depending on the specific type and severity, your eye doctor may choose one over another.

What are the complications of glaucoma?

An estimated one in 10 people with glaucoma develop some degree of visual impairment. Blindness is rarer, affecting 5% of people with glaucoma.


How can I prevent glaucoma?

Early detection of glaucoma through routine eye exams is the best way to protect eye health and prevent vision loss. Glaucoma testing should occur every:

  • 1 to 2 years after age 35 for people at high risk.
  • 2 to 4 years before age 40.
  • 1 to 3 years between ages 40 and 54.
  • 1 to 2 years between ages 55 to 64.
  • 6 months to 12 months after age 65.

Outlook / Prognosis

What can I expect if I have glaucoma?

Blindness is a rare complication for people with glaucoma if detected early. However, glaucoma is a chronic and progressive condition that often causes some degree of vision loss over time. The earlier you catch glaucoma and start treatments, the better the odds of saving your vision. Treatments can slow down disease progression and vision loss. If you’re at high risk for glaucoma, regular eye exams are a must.

Living With

When should I call the doctor?

You should call your healthcare provider if you experience:

  • Blurred or low vision.
  • Halos, eye floaters or flashers.
  • Sudden, severe eye pain or headaches.
  • Sensitivity to light.
  • Vision loss.

What questions should I ask my doctor?

You may want to ask your healthcare provider:

  • Why did I get glaucoma?
  • What type of glaucoma do I have?
  • What is the best treatment for the type of glaucoma I have?
  • Are there any treatment risks or side effects?
  • What lifestyle changes can I make to protect my vision?
  • Should I watch for signs of complications?

A note from Cleveland Clinic

While there isn’t a cure for glaucoma, treatments can keep eye pressure under control and prevent vision loss. Eye exams can catch the disease early and save your sight. If you’re at high risk for glaucoma, ask your eye doctor how often you need screenings. If you have glaucoma, it’s important to use daily eyedrops as prescribed. You can also ask your provider about laser treatments and surgery options. With proper care, you can keep glaucoma from worsening and causing irreversible vision loss or blindness.

Last reviewed by a Cleveland Clinic medical professional on 11/05/2020.


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