Glaucoma is one of the leading causes of blindness in the U.S.
It is often painless and gradual in onset, so a person may not know there is a problem until a lot of damage has occurred. It is commonly found during routine eye exams.
Glaucoma involves three variables:
There is a fluid inside the eye called the aqueous humor. It is produced, circulates through the eye and must drain out of the eye. If the fluid has difficulty draining out of the eye, it can build up and cause increased pressure. (This is not related to tears which are external to the eye.) In glaucoma, the elevated pressure causes damage to the optic nerve. This usually occurs gradually and painlessly, so people rarely notice it.
Optic Nerve Damage
The optic nerve is the main nerve that carries visual information from the eye to the brain. It is composed of a million tiny fibers. These fibers gradually become damaged as a result of the increased pressure. Often this can be seen when the optic nerve is examined as part of a routine eye exam. Unfortunately, once damage has occurred, it can rarely be reversed.
Vision loss in early glaucoma affects the peripheral or side vision, not the central reading vision. Blind spots gradually develop in the side vision, over months to years, depending on the severity of the glaucoma. Because it is gradual and painless, most people will not notice any change in vision until the blind spots become so large that they begin to affect the central reading vision. Usually by this time the glaucoma is advanced and much of the vision is lost. A special test called a Visual Field can map out these blind spots and monitor any changes over time.
The optic nerve contains healthy, pink nerve tissue surrounding a central white optic cup which contains no nerve tissue. In glaucoma, there is a loss of the healthy nerve tissue and an increase in the size of the optic cup.
As with many diseases, the earlier the detection, the better chance of maintaining vision. The vision lost from glaucoma cannot be restored by glasses or surgery. People at higher risk developing glaucoma include those with trauma to the eye, diabetes, and those with a family history of glaucoma. Black patients are also at increased risk for developing glaucoma. Therefore, routine eye exams are an important part of the diagnosis of glaucoma. Keeping scheduled appointments and taking the medication as prescribed is essential. Glaucoma is not cured by medical or surgical treatment, but is controlled by it.
Types of Glaucoma:
Chronic Open Angle Glaucoma
This is the most common type of glaucoma. Because it is gradual and painless, most patients do not know they have it. It is often detected during a routine eye exam. There is no apparent cause for the increased pressure.
Angle Closure Glaucoma
This is much less common than chronic open angle glaucoma. In this type of glaucoma, the drainage area closes off suddenly causing a dramatic rise in eye pressure over a short period of time. This can cause pain, redness, headache, nausea, vomiting and decreased vision. It is often referred to as a glaucoma attack and can cause blindness if not treated promptly.
Glaucoma can be related to other eye diseases, bleeding, inflammation, trauma or medications. In these cases, the underlying cause must be treated as well as the glaucoma.
Infants can be born with eye abnormalities that cause glaucoma. There can be excessive tearing, light sensitivity, a cloudy cornea or an increase in the size of the eye. Anything suspicious should be evaluated immediately. Treatment usually involves surgery.
Treating the high intraocular pressure of glaucoma involves a variety of drops and/or pills to bring the eye pressure to a safe level. They act to either decrease the aqueous production or increase drainage of the aqueous humor. Medication acts to control the eye pressure, it does not cure it. Therefore, a patient with glaucoma needs to continue on the medication to prevent further damage.
In some patients, medication is not sufficient to control the glaucoma. Laser surgery is done to increase the rate of aqueous humor drainage from the eye. In those patients with angle closure glaucoma, laser surgery is done immediately to relieve the blockage of the drainage area and decrease the eye pressure as quickly as possible.
Some patients require surgery to create a new drainage area and relieve the increased pressure. This is usually done after medication and laser surgery has not decreased the eye pressure to a safe level.