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?

When the optic nerve gets damaged, glaucoma is the result. Blind spots will develop in your field of vision as the optic nerve deteriorates slowly over time. Doctors have yet to fully understand why optic nerve damage is usually connected to increased pressure in the eye, commonly known as intraocular pressure (IOP).

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 a tissue, called the trabecular meshwork, which is located at the angle where the cornea and iris meet.

An increase in eye pressure occurs when the fluid builds up, either due to overproduction or blocked drainage. When there is too much fluid, it can’t flow out of the eye as it normally would, and this increases your IOP.

In terms of additional glaucoma causes, research shows that glaucoma tends to run in families. Scientists have also identified genes in some people that are connected to high eye pressure and optic nerve damage.

What are the most common types of glaucoma?

Each type of glaucoma is differentiated by the cause of 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 the normal range. Experts think this may be due to either a sensitive optic nerve or insufficient blood supply to the nerve, which is 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. This causes them to resettle in areas that affect drainage, sometimes temporarily.

What are the risk factors for glaucoma?

Increased internal eye pressure 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
• 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.