What is glaucoma?

Glaucoma is a group of serious eye diseases that can damage the optic nerve, can worsen over time, and can lead to permanent blindness.1 A leading cause of blindness worldwide, over 64 million people across the globe have glaucoma, and this number is expected to increase over the next few decades.2 There is no cure for glaucoma at this time, but treatment can slow or halt the progression of the disease.3

What are the symptoms of glaucoma?

Most people do not know they have glaucoma right away. It usually takes a while for symptoms to develop.As the disease progresses, people with glaucoma may slowly start to lose their side vision (also called peripheral vision).3

Glaucoma in its advanced stages can lead to full vision loss.3

Pain, nausea, redness of the eye, and blurred vision are symptoms of an acute glaucoma and should be treated immediately by a physician.3

What causes glaucoma?

What is intraocular pressure? Why is it important?

Glaucoma usually occurs when pressure builds up inside the eye. This pressure is called intraocular pressure, or IOP. The level of IOP in the eye depends on how much fluid is coming into the eye and how much fluid leaves the eye. The fluid in the eye that is responsible for IOP is called aqueous humor.4

Aqueous humor is formed in the ciliary body and drains through two pathways- through the trabecular pathway or through the uveoscleral pathway. If too much aqueous humor comes in, or if not enough flows out through one or both pathways, IOP can increase to levels that damage the optic nerve.4

Normal IOP usually ranges between 12-22 mg Hg. Not all patients with high IOP will have glaucoma, and not all patients with glaucoma have high IOP. 5

What are the most common types of glaucoma?

There are two main types of glaucoma: open-angle glaucoma and angle-closure glaucoma.4 A specific type of open-angle glaucoma- called normal-tension glaucoma- involves damage to the optic nerve even though IOP is normal.6

Open-angle glaucoma (OAG)

Open-angle glaucoma is the most common type of glaucoma in the United States. Around 80% of people who have glaucoma have open-angle glaucoma.4 In OAG, the path for aqueous humor to drain out of the eye is open, but the flow of aqueous humor is too slow. It is as if the drain, known as the angle, were clogged. This slowness causes an increase in IOP that can damage the optic nerve.3

Angle-closure glaucoma (ACG)

Angle-closure glaucoma is more common in Asian countries and in people of Asian descent.4 ,7 In ACG, the flow of aqueous humor out of the eye is blocked, or closed off, by a part of the eye called the iris.4

Who is at risk for having glaucoma?

Because most people do not know if they have glaucoma right away, it is important to know who is at risk. 4 Early detection can mean early treatment which could lead to better outcomes.3

People with the following characteristics should ask their doctor if they are at increased risk for glaucoma4:

  • Older age (over the age of 60 years, though glaucoma can occur in younger people, as well)3
  • A family member who has had glaucoma
  • Black race or Mexican ethnicity3
  • Use of certain medicines called corticosteroids
  • High IOP
How is glaucoma diagnosed?

Doctors use a number of tests to decide whether a person has glaucoma. Some of these tests may include the following.3

  • Visual acuity test.

    The patient reads letters of different sizes on a chart. This helps the doctor understand how well the patient can see from different distances.

  • Visual field test.

    There are many ways that the patient’s field of vision can be tested. Some of these tests involve looking into a machine and telling the doctor what is seen. Other tests may involve the doctor sitting in front of the patient and asking them to describe what they see on the far sides of their field of vision.

  • Dilated eye exam.

    The doctor places drops into the eye to dilate (or widen) the pupil. This allows for more light to enter the eye. The doctor can then look into the eye for signs of damage to the optic nerve. The drops used in this test may make vision blurry for a few hours.

  • Tonometry.

    IOP is an important part of glaucoma. This test measures IOP using a tool called a tonometer. The doctor will place drops into the eye that will cause it to be numb. Then, the doctor will puff a small, painless burst of air onto the eye. The tonometer measures the response of the eye to the puff of air.

  • Pachymetry.

    In this test, the doctor will place drops into the eye that will cause it to be numb. He or she uses a tool that uses ultrasonic waves to measure the thickness of the cornea. A thin cornea may put someone at higher risk for glaucoma.3

What can I expect if I have been diagnosed with glaucoma?

When symptoms of glaucoma occur, it is normal to feel anxious, worried, or sad. People with glaucoma may even have trouble sleeping.8 Vision loss from glaucoma can have an effect on quality of life. Activities that used to be easy may become a struggle.4

The healthcare team can help patients find ways to cope with glaucoma. They can also help with emotional concerns or problems with daily living that occur because of vision loss. People with glaucoma should not be afraid to talk with their healthcare team about all aspects of glaucoma support.

There may be local support groups that meet in-person to help members cope with the effects of glaucoma. There are also groups online such as the Glaucoma Research Foundation or, where people with glaucoma can talk with each other and provide advice and support. People with glaucoma can also ask their doctor if they need help finding a support group that works for them.

  1. McMonnies CW. Glaucoma history and risk factors. J Optom. 2017;10:71-8.
  2. Tham YC, Li X, Wong TY, et al. Global prevalence of glaucoma and projections of glaucoma burden through 2040. Ophthalmology. 2014;121(11):2081-90.
  3. Facts about glaucoma. National Institutes of Health (NIH) National Eye Institute. 2015. Published September, 2015. Accessed 6 May 2019.
  4. Weinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma. JAMA. 2014;311(18):1901-11.
  5. Tsai JC. High eye pressure and glaucoma. Glaucoma Research Foundation (GRF). 2017. Published October 29, 2017. Accessed 6 May 2019.
  6. Radhakrishnan S. Questions and Answers: Normal-tension glaucoma. Glaucoma Research Foundation (GRF). Published 2019. Accessed 6 May 2019.
  7. Goel M, Picciani RG, Lee RK, et al. Aqueous humor dynamics: A review. Open Ophthalmol J. 2010;4:52-9.
  8. Agorastos A, Skevas C, Matthaei M, et al. Depression, anxiety, and disturbed sleep in glaucoma. J Neuropsychiatry Clin Neurosci. 2013;25(3):205-13.