Glaucoma

Glaucoma is a disorder that damages the optic nerve, leading to progressive, irreversible vision loss.

Glaucoma is typically associated with high pressure within the eye, although it can occur with normal pressure. How the high pressure damages the cells of the optic nerve is unknown.

Glaucoma is one of the most common causes of vision loss among older people in the United States.

Glaucoma is classified as open-angle (chronic) or closed-angle (acute). Open-angle glaucoma is much more common than is closed-angle glaucoma. In both kinds, people who have had glaucoma in one eye are likely to develop glaucoma in the other eye. And either kind can cause blindness if left untreated. Blindness often can be prevented, however, with the use of eye drops and surgery that decrease eye pressure.

For additional detail on this topic, see How Glaucoma Occurs.

Causes

In most cases, the underlying cause of glaucoma is unknown, although both open-angle and closed-angle glaucoma tend to run in families. Glaucoma occurs more commonly among older blacks, Asians, and Eskimos (Inuits); people who have difficulty seeing near and far objects (hyperopia); people who have diabetes; and people who have used corticosteroids for a long time.

In rare cases, glaucoma results from damage to the eye caused by infection, inflammation, a tumor, large cataracts or surgery for cataracts, injury, or other conditions that keep fluid from draining freely from the eye, leading to increased eye pressure and optic nerve damage (secondary glaucoma).

Symptoms

Open-angle glaucoma is painless and causes no early symptoms. The most important symptom is the development of blind spots, or areas of vision loss, over months to years. The blind spots slowly grow larger and merge. Vision loss occurs so gradually that it is often not noticed until much of it is lost. Side (peripheral) vision is usually lost first; central vision is lost last. The changes may progress to the point where only a small central island of vision remains, in which the person can see straight ahead perfectly but becomes blind in all other directions (sometimes referred to as tunnel vision). If glaucoma is left untreated, eventually even central vision can be lost, resulting in total blindness.

Closed-angle glaucoma causes abrupt onset of severe pain in and around the eye, headache, redness, blurred vision, rainbow-colored halos around lights, and sudden vision loss. Nausea and vomiting may occur in response to the increased eye pressure. Closed-angle glaucoma is considered a medical emergency, because if left untreated, blindness can occur as quickly as 2 to 3 hours after the start of symptoms.

Diagnosis

An eye doctor performs a complete eye examination, which includes measuring pressure in the eye, inspecting the optic nerve for damage, testing peripheral vision for blind spots, and inspecting drainage canals in the eye. Because older people can develop glaucoma and lose vision without knowing it, they should undergo a comprehensive screening eye examination every 1 to 2 years.

Treatment

The goal of treatment is to prevent the onset of vision loss or to stop its progression.

Eye drops are the primary treatment for open-angle glaucoma. These include beta-blockers, such as betaxolol and timolol; carbonic anhydrase inhibitors, such as brinzolamide and dorzolamide; prostaglandin-like drugs, such as bimatoprost and latanoprost; alpha agonists, such as apraclonidine and brimonidine; and cholinergic drugs, such as carbachol and pilocarpine. They either decrease production or increase drainage of fluid in the eye. Although generally safe, the drops may cause side effects in the eye or throughout the body.

An older person may find it difficult or impossible to self-administer eye drops because of arthritis or a neurologic condition, such as a tremor. In such cases, an alternative device, such as an eyedropper with an oversized bulb, may be necessary. Alternatively, a caregiver can administer the drops. Carbonic anhydrase inhibitors can be taken by mouth to lower eye pressure, but their use is limited because of frequent side effects.

Surgery or laser therapy is almost always needed if the person has closed-angle glaucoma. These treatment methods may also be needed for people with open-angle glaucoma if eye drops cannot effectively control eye pressure, if they cannot be used, or if they cause serious side effects. Surgery and laser therapy aim to improve fluid drainage by opening drainage canals or creating new ones. Although generally safe, surgery or laser therapy may not always achieve the desired level of eye pressure and occasionally causes a temporary increase in eye pressure or inflammation and bleeding within the eye. Surgery or laser therapy may need to be repeated to achieve the desired level of eye pressure. Eye drops to lower eye pressure may be needed even after surgery or laser therapy. Cataracts may develop or progress as a result of surgery for glaucoma.

Treatment of secondary glaucoma may include antibiotic or antiviral eye drops for infection, corticosteroid eye drops for inflammation, and surgery for a tumor or cataract.

Outlook

There is no cure for open-angle glaucoma. Therefore, eye drops must be used for the rest of the person's life. In addition, regular checkups are needed for monitoring eye pressure, optic nerve health, and areas of vision seen out of each eye (visual field testing). Surgery and laser therapy can cure closed-angle glaucoma in many people, but regular checkups for monitoring and eye drops may still be needed in some people.