What are the causes of glaucoma?

Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

Glaucoma is caused by an accumulation of aqueous humor, the fluid in the front of the eye. Normally, aqueous humor can leave the eye where the cornea and iris meet. Sometimes this drainage system is not working well, allowing the aqueous humor to accumulate. This causes excess pressure in the eye and can damage the optic nerve.

Clear liquid called aqueous humor circulates inside the front portion of the eye. To maintain a healthy level of pressure within the eye, a small amount of this fluid is produced constantly while an equal amount flows out of the eye through a microscopic drainage system. (This liquid is not part of the tears on the outer surface of the eye.)
Because the eye is a closed structure, if the drainage area for the aqueous humor — called the drainage angle — is blocked, the excess fluid cannot flow out of the eye. Fluid pressure within the eye increases, pushing against the optic nerve and causing damage.

While most people who have glaucoma may have no idea they have it, and, as a result, the optical nerve is damaged over the years, there are some forms of glaucoma that are far more acute.

Angle-closure glaucoma, also called narrow-angle glaucoma, causes intraocular pressure to increase so rapidly that the onset of debilitating symptoms is swift and prompt treatment is needed.

Unlike open-angle glaucoma, in which the eye-nourishing aqueous humor cannot drain through the trabecular meshwork located at the angle where iris and cornea meet, with angle-closure glaucoma, the aqueous humor never even reaches that draining trabecular meshwork, because the angle is blocked or closed. This rapidly increases intraocular pressure, resulting in very noticeable symptoms like nausea, headaches and blurred vision.

One of the causes of this is thought to be the angle where the iris and cornea meet.

In most people, that is a 45 degree angle. But in some people, that angle is narrower and the iris is very close to the trabecular meshwork, which drains the aqueous humor. But in addition to a narrower angle, angle-closure glaucoma can also be triggered by pupil dilation, because the lens and iris are then in close contact, potentially blocking the trabecular meshwork. This is the reason angle closure glaucoma often occurs in a dark room or when someone is undergoing stress. The pupils dilate in both cases.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.