Glaucoma is a form of optic neuropathy (disease of the optic nerve). The optic nerve is made up of many nerve fibers (like an electric cable with its numerous wires), and transmits images to the brain. In glaucoma, nerve fibers are damaged, which can result in vision loss.
Most cases of glaucoma are associated with an elevated pressure inside the eye, known as intraocular pressure (IOP). When the aqueous humor (a clear liquid that normally flows in and out of the eye) cannot drain properly, pressure builds up. The resulting increase in IOP can damage the nerve fibers.
The most common form of glaucoma is primary open-angle glaucoma, in which the aqueous fluid is blocked from flowing out of the eye at a normal rate through a drainage system called the trabecular meshwork . Most people who develop primary open-angle glaucoma notice no symptoms until their vision is impaired.
Approximately 20% of glaucoma patients have normal IOP, a condition known as normal tension glaucoma. Therefore the diagnosis of glaucoma is not solely based on IOP measurement, but consists of careful evalution of the optic nerve and other eye structures. This requires a dilated exam and other tests including visual field testing, nerve fiber layer analysis, optic nerve photography, examination the trabecular meshwork with a special contact lens (gonioscopy), and corneal thickness measurement (pachymetry).
Ocular hypertension is a condition that can lead to open-angle glaucoma. When the IOP is above normal, the risk of developing glaucoma increases. Several risk factors affect whether you will develop glaucoma, including the IOP level, family history, age, steroid medication, African-american ancestry, and decreased corneal thickness. If your risk is high, your eye doctor may recommend treatment to lower your IOP, even without definite optic nerve damage.
In angle-closure glaucoma, the iris (the colored part of the eye) obstructs the drainage of aqueous fluid, leading to an increase of IOP. In acute angle-closure glaucoma IOP increases suddenly. This situation requires emergent intervention because optic nerve damage and vision loss can occur within hours. Symptoms can include nausea, vomiting, seeing halos around lights, and eye pain. If this happens, your eye doctor will perform a procedure called laser iridotomy, which makes a small opening in the iris to relieve the obstruction.
Childhood glaucoma, which starts in infancy, childhood, or adolescence, is rare. Like primary open-angle glaucoma, there are few, if any, symptoms in the early stage. Blindness can result if it is left untreated. Like most types of glaucoma, childhood glaucoma may run in families. Signs of this disease include:
- clouding of the cornea (the clear front part of the eye);
- tearing; and
- an enlarged eye.
A “glaucoma suspect” is an individual with one or more risk factors for glaucoma devlopment, or when the diagnosis is in doubt. Such individuals need close monitoring.
The goal of glaucoma treatment is to lower your eye pressure sufficiently to prevent or slow further vision loss. Treatment usually consists of eye drops, but can include laser treatment, or surgery to create a new drain in the eye (filtration surgery). Glaucoma is a chronic disease that can be controlled but not cured. It is one of the leading causes of blindness in this country. Early detection is critical, as the condition is usually asymptomatic early in its course. Once symptoms occur, the disease is already far advanced. Ongoing monitoring (every three to six months) is needed to watch for changes. The doctors at Eye Care of Maine have a great deal of experience in diagnosing and treating glaucoma patients, using the very latest technology.
For more information on Glaucoma:
National Eye Institute (opens in a new window)
See What Glaucoma Looks Like (opens in a new window)
Glaucoma Research Foundation (opens in a new window)
The Eye Digest (opens in a new window)