What Causes Glaucoma in the Eyes?

Glaucoma is a set of diseases that cause optic nerve damage. As noted on the Foundation of the Academy of Ophthalmology website, glaucoma is the second leading cause of blindness in the United States. Glaucoma may develop in people with either high eye pressure or with normal eye pressure but depending on the type of glaucoma one has, the cause of the damage may be different.

Features

• The role of the optic nerve is to carry images from the retina to the brain. When there is enough damage to the optic nerve, loss of vision is possible. Unfortunately, this vision loss is irreversible. The exact cause of the damage to the optic nerve in glaucoma is not fully known but most research suggests that it relates to mechanical forces and/or decreased blood flow to the optic nerve.

Primary open-angle glaucoma

• In primary open-angle glaucoma, the most common form of glaucoma, there is a gradual increase in eye pressure which then causes damage to the optic nerve. The drainage system may not function properly and may lead to the increase in eye pressure. Whether the high pressure causes mechanical damage to the optic nerve or affects the amount of blood flow to the nerve is not fully known at this time. Vision loss in patients with primary open-angle glaucoma generally is painless and slow; patients may not notice the visual changes until they are very profound.

Angle-closure glaucoma

• A rarer form of glaucoma is angle-closure glaucoma. In this form of glaucoma, the drainage system of the eye (the angle formed by the iris and the cornea) becomes closed. This closure may be caused by a narrow angle naturally or by cataract formation and can be acute (sudden) or chronic (occurring over time). In people with naturally narrow angles who have not been diagnosed, dilation of the pupils for a routine eye exam can cause angle closure. Unrelated to the actual cause of the closure, this blockage causes a dangerous increase in eye pressure; in acute angle-closure glaucoma, blindness can result within twenty-four hours.

Normal-tension glaucoma

• Some people develop optic nerve damage while maintaining normal eye pressure. This type of glaucoma is called normal-tension or low-tension glaucoma. The complete reason for this is unknown; some researchers feel that these patients have optic nerves that are more sensitive. Others suggest that changes to the blood vessels supplying the optic nerve may reduce blood flow and contribute to the damage.

Other causes

• There are other causes of glaucoma as well. Patients who suffer blunt trauma to the eye may develop traumatic glaucoma; an injury to the drainage angle may cause an increase in eye pressure. Another form of glaucoma, pigmentary glaucoma, occurs when pigment granules from the iris block the drainage angle. Exfoliation syndrome occurs when whitish material gathers in the angle and interferes with drainage of the eye. There are also a variety of genetic syndromes that include glaucoma. Although much is known about the causes of glaucoma, there is more to be learned.