Glaucoma is a leading cause of blindness among older people in the U.S. Sometimes called the "silent thief of sight," it can affect a person's sight before they realize they have the disease. Glaucoma is a specific pattern of diseases that damage the optic nerve, which carries images we see to the brain. While there is no known cure, loss of sight is largely preventable if glaucoma is caught early.
What causes glaucoma?
Pressure builds up in the eye when the clear liquid called the aqueous humor, which normally flows in and out of the eye, is prevented from draining properly. This can happen in different ways, depending on the type of glaucoma. The resulting increase in pressure within the eye can damage the optic nerve. Ophthalmologists used to think high intraocular pressure was the main cause of optic nerve damage in glaucoma. However, we now know that even people with "normal" pressure levels can experience vision loss from glaucoma - so-called "normal tension glaucoma."
What are the symptoms?
Glaucoma causes blindness in so many cases because most people do not even notice any problems until some degree of damage has already occurred and some vision lost.
As optic nerve fibers are damaged by glaucoma, small blind spots may begin to develop, usually in the side, or peripheral vision. Many people do not notice the blind spots until significant optic nerve damage has already occurred.
One type of glaucoma (acute angle-closure glaucoma) does not produce noticeable symptoms until it has become a big problem. A sudden build-up of pressure may cause any of the following symptoms: blurred vision, severe eye pain, headache, rainbow haloes around lights, nausea, and vomiting.
Acute angle-closure glaucoma is a rare and severe form of glaucoma. Call your ophthalmologist immediately if you have any of these symptoms.
Different types of glaucoma
Glaucoma most commonly occurs with aging. In open-angle glaucoma, the drainage angle of the eye becomes less efficient with time, and pressure gradually increases.
If this increased pressure results in optic nerve damage, it is known as chronic open-angle glaucoma. This form of glaucoma can damage vision so gradually and painlessly that you are not aware of trouble until the optic nerve is already badly damaged. Over 90 percent of adult glaucoma patients have open-angle glaucoma.
In angle-closure glaucoma, normal drainage canals are blocked when the area between the iris and the cornea is not open. This condition can be chronic (progressing slowly or occurring persistently) or acute (occurring suddenly).
In acute angle-closure glaucoma, intraocular pressure (IOP) increases suddenly due to the buildup of aqueous in the eye.
Chronic angle-closure glaucoma, like open-angle glaucoma, may cause vision damage without symptoms. On the other hand, acute angle-closure glaucoma is considered an emergency situation because optic nerve damage and subsequent vision loss can occur within hours of the onset of the problem.
"Normal (or low) tension" glaucoma is an unusual and poorly understood form of the disease. In this type of glaucoma, the optic nerve is damaged even though the patient's intraocular pressure is consistently within a range usually considered normal.
Childhood glaucoma is rare and starts in infancy, childhood, or adolescence. Like open-angle glaucoma, there are few, if any, symptoms in the early stage, and blindness can result if untreated. Like most types of glaucoma, this type is thought to have a hereditary component.
Congenital glaucoma is a type of childhood glaucoma that usually appears soon after birth, although it can become apparent later in the first year of life. Unlike other childhood glaucomas, congenital glaucoma often has noticeable signs, including tearing, light sensitivity, and cloudiness of the cornea. This type of glaucoma is more common in boys, and can affect one or both eyes.
Detection of glaucoma
Regular eye examination is the best way to detect glaucoma. Doctors check intraocular pressure, inspect the drainage angle, evaluate any optic nerve damage, damage, and test the visual field of each eye.
Risk factors for glaucoma
High IOP alone does not mean that you have glaucoma. Your doctor considers many pieces of information to determine your risk for developing the disease and any appropriate action. The most important of these risk factors include:
- African ancestry
- A family history of glaucoma
- Past injuries to the eye
- A history of severe anemia or shock
Treatment and medicines
Damage caused by glaucoma is, as a rule, not reversible. Glaucoma can be held in check with eye drops, pills, ointments, wafer-like inserts, and laser or surgical operations that can be used to prevent or slow further damage from occurring. Treatment for glaucoma is focused on lowering IOP to a level not likely to further damage the optic nerve. This level varies from person to person and over time.