Glaucoma in the Eye

Glaucoma is a general name for a group of eye diseases that damage the optic nerve of the eye. Glaucoma prevents the eye from sending accurate visual information to the brain.

 

Usually associated with gradual, but sometimes sudden, increases in pressure within the eyeball glaucoma can result in partial or total blindness over time. The damage caused by glaucoma is irreversible, and it is currently the second leading cause of blindness in Americans over age 40 in the United States.

 

What are the Symptoms of Glaucoma?

Glaucoma often is called the "silent thief of sight," because most types typically cause no pain and produce no symptoms until noticeable vision loss occurs. For this reason, glaucoma often progresses undetected until the optic nerve already has been irreversibly damaged, with varying degrees of permanent vision loss.

 

What Causes Glaucoma?

There are many theories about the causes of glaucoma, but the exact cause is unknown. Although the disease is usually associated with an increase in the fluid pressure inside the eye, other theories include lack of adequate blood supply to the nerve. Following are the different types of glaucoma and their potential causes.

 

 • Primary open-angle glaucoma. This is the most common form of glaucoma. Damage to the optic nerve is slow and painless. Those affected can lose a large portion of vision before they notice any vision problems. 

One theory about its development is that the eye's drainage system becomes inefficient over time. This leads to an increased amount of fluid and a gradual buildup of pressure within the eye. Another theory about the cause of this type of glaucoma is that there is poor blood flow (perfusion) to the optic nerve. Other theories also exist.

 

 • Angle-closure glaucoma. This type of glaucoma, also called closed-angle glaucoma or narrow-angle glaucoma, is a less common form of the disease. It is a medical emergency that can cause vision loss within a day of its onset.

It occurs when the drainage angle in the eye (formed by the cornea and the iris) closes or becomes blocked. Many people who develop this type of glaucoma have a very narrow drainage angle. With age, the lens in the eye becomes larger, pushing the iris forward and narrowing the space between the iris and the cornea. As this angle narrows, the fluid in the eye is blocked from the drainage system. Therefore the fluid builds up and eye pressure increases.

Angle-closure glaucoma can be chronic (progressing gradually) or acute (appearing suddenly). The acute form occurs when the iris completely blocks fluid drainage. When people with a narrow drainage angle have their pupils dilated, the angle may close and cause a sudden increase in eye pressure. Although an acute attack often affects only one eye, the other eye may be at risk of an attack as well.

 

 • Secondary glaucoma. This type of glaucoma results from an injury or other eye disease. It may be caused by a variety of medical conditions, medications, physical injuries and eye abnormalities. Infrequently, eye surgery can lead to secondary glaucoma.

 

 • Normal-tension or low-tension glaucoma. In this form of glaucoma, eye pressure remains within the "normal" range, but the optic nerve is damaged nevertheless. It is not known why this happens.

 

How is Glaucoma treated?

Glaucoma treatment is aimed at reducing pressure in the eye. Regular use of prescription eye drops are the most common and often the first treatment. Some cases may require systemic medications, laser treatment or other surgery. While there is not yet a cure for glaucoma, early diagnosis and continuing treatment can preserve eyesight.

 

 • Medications. A number of medications are currently available to treat glaucoma. Typically, medications reduce elevated pressure in the eye. A single medication or a combination of medications may be prescribed. The type of medication may change if it is not reducing pressure enough or if the patient is experiencing side effects.

 

 • Surgery. Procedures include laser treatment, making a drainage flap in the eye, inserting a drainage valve, or destroying the tissue that creates the fluid in the eye. All procedures aim to reduce the pressure inside the eye when medication is not sufficient. Surgery cannot reverse vision loss.

 

 • Laser surgery. Laser trabeculoplasty helps fluid drain out of the eye. A high-energy laser beam stimulates the structure that drains fluid from the eye (the trabecular meshwork) so that fluid drains more efficiently. The results may be somewhat temporary, and the procedure may need to be repeated in the future.

 

 • Conventional surgery. If eye drops and laser surgery aren't controlling eye pressure, you may need a trabeculectomy. This filtering microsurgery creates a drainage flap. Fluid can then percolate into the flap and later drain into the vascular system.

 

 • Drainage implants. Drainage valve implant surgery may be an option for adults with uncontrolled glaucoma or secondary glaucoma or for children with glaucoma. A small silicone tube is inserted in the eye to help drain fluid.