An Overview of Glaucoma

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Glaucoma refers to a group of diseases that cause damage to the optic nerve. Containing more than a million nerve fibers, the optic nerve connects the eye to the brain. This important nerve is responsible for carrying images to the brain.

The optic nerve fibers make up a part of the retina that gives us sight. This nerve fiber layer can be damaged when the pressure of the eye (intraocular pressure) becomes too high. Over time, high pressure causes the nerve fibers to die, resulting in decreased vision. Vision loss and blindness will likely result if glaucoma is left untreated.

What to Know About Glaucoma - Illustration by Michela Buttignol

Verywell / Michela Buttignol


Glaucoma has been nicknamed the “sneak thief of sight” because it often goes undetected and causes irreversible damage to the eye. There are usually no symptoms in the early stages of the disease. Many people have glaucoma but are not aware of it, making it a very scary, silent eye disease.

As the disease progresses, vision seems to fluctuate and peripheral vision fails. If left untreated, vision can be reduced to tunnel vision and eventually, total blindness.


Glaucoma usually occurs when fluid in the eye builds up, causing higher pressure than the eye can withstand. The canal responsible for draining this fluid becomes plugged, preventing proper drainage.

In other cases, the eye may produce more fluid than normal and simply cannot be drained fast enough, producing higher intraocular pressure. Researchers do not know exactly what makes some people more prone to this problem.

Other causes may include trauma, genetic disorders and low blood flow to the optic nerve.

Risk Factors

Having high intraocular pressure increases the risk of developing glaucoma. Black people 40 years of age and older have the highest risk. Anyone over 60 years of age is at increased risk, especially Latinx people. Women are at higher risk than men.

Furthermore, those with a family history of glaucoma are at higher risk of developing glaucoma. Having systemic diseases such as diabetes, high blood pressure and heart problems also increase your risk. Other risk factors include nearsightedness and direct trauma to the eye.


There are two major types of glaucoma: chronic glaucoma, also known as primary open-angle glaucoma (POAG)—and acute closed-angle glaucoma.

  • Chronic glaucoma: Open-angle glaucoma damages the eye with no warning signs. It is the most common type of glaucoma and is often referred to as the “silent type.” Damage occurs over time, usually without notice.
  • Acute closed-angle glaucoma: Closed-angle glaucoma happens quickly. An “attack” may produce a red, painful eye and symptoms such as facial pain, headache, blurry vision, rainbow-colored halos around lights, nausea, and vomiting. It is a severe medical emergency.

How It's Diagnosed

Your eye doctor may use tonometry or gonioscopy to test for glaucoma.

  • Tonometry: A key test in glaucoma diagnosis is tonometry. A tonometer measures intraocular pressure.
  • Gonioscopy: Gonioscopy may be performed to look at the angle of the eye to detect if it is open or closed. An inspection of the health of the optic nerve is also important in assessing any damage that may have occurred because of glaucoma. If damage is suspected, the doctor may measure your overall visual field with a computerized perimeter or analyze your nerve fiber layer with scanning laser ophthalmoscopy.

Treatment Options

The goal of glaucoma treatment is to reduce eye pressure to a level at which no more damage occurs.

  • Treatment is given in the form of prescription eye drops and, occasionally, oral systemic drugs.
  • Laser treatment has been shown to work just as well as medicines to prevent more damage from occurring.
  • In certain cases in which medication or laser procedures do not achieve this goal, surgery is helpful.
  • Many times therapy includes a combination of these treatments.

It is important to understand that glaucoma cannot be cured, but can be controlled. Unfortunately, vision loss caused by glaucoma cannot be reversed.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Eye Institute. Glaucoma.

  2. Davis BM, Crawley L, Pahlitzsch M, Javaid F, Cordeiro MF. Glaucoma: the retina and beyond. Acta Neuropathol. 2016;132(6):807-826. doi:10.1007/s00401-016-1609-2

  3. Hu CX, Zangalli C, Hsieh M, et al. What do patients with glaucoma see? Visual symptoms reported by patients with glaucoma. Am J Med Sci. 2014;348(5):403-409. doi:10.1097/MAJ.0000000000000319

  4. American Academy of Ophthalmology. What is glaucoma? Symptoms, causes, diagnosis, treatment.

  5. National Eye Institute. Glaucoma data and statistics.

  6. Lee SY, Bae HW, Kwon HJ, Seong GJ, Kim CY. Utility of Goldmann applanation tonometry for monitoring intraocular pressure in glaucoma patients with a history of laser refractory surgery. PLoS One. 2018;13(2):e0192344. doi:10.1371/journal.pone.0192344

  7. Ahmad S. Glaucoma suspects: a practical approach. Taiwan J Ophthalmol. 2018;8(2):74. doi:10.4103/tjo.tjo_106_17

  8. Wu A, Khawaja AP, Pasquale LR, Stein JD. A review of systemic medications that may modulate the risk of glaucoma. Eye (Lond). 2020;34(1):12-28. doi:10.1038/s41433-019-0603-z

  9. Gazzard G, Konstantakopoulou E, Garway-Heath D, et al. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (Light): a multicentre randomised controlled trial. Lancet. 2019;393(10180):1505-1516. doi:10.1016/S0140-6736(18)32213-X

By Troy Bedinghaus, OD
Troy L. Bedinghaus, OD, board-certified optometric physician, owns Lakewood Family Eye Care in Florida. He is an active member of the American Optometric Association.