Strong vision depends on many factors, not least of which is the health of the optic nerve—a bundle of nerve fibers that transfers information from the eyes to the brain. Glaucoma is a group of conditions that damage the optic nerve, but what are the causes and risk factors?

What causes glaucoma?

Your eye produces a fluid called aqueous humor, which bathes the eye and brings it nutrients. After doing its job, this fluid normally drains out through mesh-like tissue located at the angle where your iris and cornea meet. Internal pressure on the eye increases when the fluid builds up, either due to overproduction or blocked drainage. 

Each type of glaucoma is differentiated by the cause of the inadequate drainage and heightened pressure. 

The primary types of glaucoma include:

• Open-angle glaucoma: The drainage angle formed by the cornea and iris remains open, but the trabecular meshwork is partially blocked. This causes pressure in the eye to gradually increase. 
• Angle-closure glaucoma: The iris bulges toward the front of the eye, blocking the drainage angle formed by the cornea and iris. People who already have narrow drainage angles are at higher risk of angle-closure glaucoma. Angle-closure glaucoma can be chronic or acute. An acute case is considered a medical emergency.
• Normal-tension glaucoma: Damage occurs even if your eye pressure is within normal range. Experts think this may be due to a sensitive optic nerve, or insufficient blood supply to the nerve caused by health issues that affect circulation.
• Pediatric glaucoma: Incomplete or incorrect development of eye drainage systems in utero can result in children being born with glaucoma. The optic nerve can also sustain damage from an underlying health condition.
• Pigmentary glaucoma: Granules of pigment from your iris flake off and clog the drainage channels in your eye. Jogging and impact sports can also disturb granules and cause them to resettle in areas that affect drainage, sometimes temporarily.

What are risk factors for glaucoma?

Increased internal eye pressure, or intraocular pressure (IOP), from any cause can elevate your risk for glaucoma. 

Studies have determined, however, that the following factors can also place you at a higher risk:

• age 60 and up (though glaucoma can occur at any age);
• black, Asian, or Hispanic ancestry;
• close family history of glaucoma;
• certain health conditions (diabetes, heart disease, hypertension, and sickle-cell anemia);
• corneas that are thin at the center;
• extreme nearsightedness or farsightedness;
• eye injury or eye surgery; and
• extended corticosteroid use.

Most forms of glaucoma progress slowly and with no noticeable symptoms in the early stages. Without regular eye checkups, glaucoma often goes undiagnosed until considerable damage has already been done. Existing impairment cannot be reversed, but if the disease is identified and treated early, further vision loss can often be prevented.

*Mayo Clinic. (2020). Glaucoma: Symptoms and Causes.