Glaucoma is a complicated disease in which there is damage to the optic nerve, associated with a buildup of fluid pressure inside the eye (aqueous humour), leading to progressive and irreversible vision loss. The optic nerve carries visual information from the eye to the brain. Glaucoma is the second leading cause of blindness and unfortunately, approximately 10% of people with glaucoma who receive proper treatment still experience loss of vision. Glaucoma tends to be inherited and may not show up until later in life. It most often occurs in people over age 40, although a congenital or infantile form of glaucoma exists. People with a family history of glaucoma, African Americans over the age of 40, and Hispanics over the age of 60 are at an increased risk of developing glaucoma. Other risk factors include thinner corneas, chronic eye inflammation, and using medications that increase the pressure in the eyes. This increased intraoccular pressure, damages the optic nerve, leading to glaucoma which will cause permanent loss of vision. Without treatment, glaucoma can cause total permanent blindness within a few years. Glaucoma has been called the "silent thief of sight" because the loss of vision often occurs gradually over a long period of time, and symptoms only occur when the disease is quite advanced.
Reasons for the pressure rise in the eye.
Glaucoma usually occurs when pressure in your eye increases. The front part of the eye is filled with a clear fluid called aqueous humor. This fluid is always being made behind the colored part of the eye (the iris). Normally, this fluid, flows out of the eye through a mesh-like channel at the front of the eye in an area called the anterior chamber angle. If this channel becomes blocked, fluid builds up, causing glaucoma.
Types of Glaucoma
There are four types of glaucoma:
• Open-angle (chronic) glaucoma
• Angle-closure (acute) glaucoma
• Congenital glaucoma
• Secondary glaucoma
Open-angle glaucoma: Also called wide-angle glaucoma, is the most common type of glaucoma. It accounts for 90% of glaucoma cases in the United States. The cause is unknown. It tends to run in families. People of African descent are at particularly high risk for this disease. It is painless and does not have acute attacks. The structures of the eye appear normal, but fluid in the eye does not flow properly through the drain of the eye, called the trabecular meshwork. The only signs are gradually progressive visual field loss, and optic nerve changes (increased cup-to-disc ratio on fundoscopic examination).
Angle-closure (acute) glaucoma: This usually occurs abruptly due to a rapid increase of pressure in the eye because the exit of the aqueous humor fluid is suddenly blocked. This causes a quick, severe, and painful rise in the pressure in the eye. Closed-angle glaucoma accounts for less than 10% of glaucoma cases in the United States. Its symptoms may include severe eye pain, nausea, redness in the eye, seeing colored rings (halos) around lights, blurred vision, very high intraocular pressure (>30 mmHg), nausea and vomiting, suddenly decreased vision, and a fixed, mid-dilated pupil. It is also associated with an oval pupil in some cases. Dilating eye drops and certain medications may trigger an acute glaucoma attack. This condition is an ocular emergency, and medical attention should be sought immediately, as severe vision loss can occur quickly.
Congenital glaucoma: This is seen in babies. It is usually inherited. It is present at birth and is caused by abnormal eye development.
Secondary glaucoma: Factors triggers secondary glaucoma include; Drugs such as corticosteroids, eye diseases such as uveitis, Systemic diseases, trauma.
Examinations & Tests
• A detailed history
• Visual acuity measurements
• Opthalmoscopy: Examines the shape and color of the optic nerve.
• Tonometry : Examines the inner eye pressure
• Pachymetry: Examines the thickness of the cornea
• Visual field testing.
Glaucoma is not curable, and vision lost cannot be regained. With medication and/or surgery, it is possible to halt further loss of vision. The goal of treatment is to reduce eye pressure and this depends on the type of glaucoma.
For open-angle glaucoma, combinations of eye drops are given.
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