Glaucoma is a disease of the eye most often caused by increased fluid pressure in the eye, called intraocular pressure, that results in optic nerve damage and leading to blindness if left undetected and untreated. The most common type of the disease is open angle glaucoma. Primary open angle glaucoma (POAG) is the occurrence of the disorder in the absence of other disease.
Risk Factors for Glaucoma
Glaucoma is the leading cause of blindness in African-Americans in the United States, and this ethnic group is five times more likely to have the disease than Caucasians. However, anyone with a family history of glaucoma, anyone over the age of 60 years, and anyone with myopia, unusually high intraocular pressure, diabetes, or high blood pressure are at risk.
What Is Primary Open Angle Glaucoma?
In POAG, the fluid in the front chamber of the eye, known as the aqueous humor, does not drain properly from the eye. The fluid carries nutrients around the iris to the cornea, which lacks blood vessels in order to stay transparent and allow light to pass through. A drainage system, the trabecular meshwork, is present at the angle where the cornea and iris meet, allowing the fluid to leave the chamber. If the fluid does not drain properly, it builds up, increasing the pressure in the eye. This pressure can damage the optic nerve, causing vision problems and, eventually, blindness.
The inability to drain is not yet nailed down to a single cause. It is thought to be due to a number of different factors. One possibility is a structural defect in the drainage system. Another possibility is a problem with the cells in the trabecular meshwork. A third possibility is enzyme dysfunction. Treatment usually consists of alleviating the intraocular pressure and preventing further damage, including regular eye drops and surgery, as well as more controversial alternative treatments. Early detection and treatment is necessary for preventing vision loss.
Glaucoma Symptoms and Diagnosis
There are usually no symptoms of POAG as the pressure begins to build in the eye. Eventually, the peripheral vision may become cloudy. This side blindness then progresses to tunnel vision and a loss of visual acuity. Regular eye exams are key to early detection.
A full eye exam contains many components that can detect glaucoma:
- tonometry - measures the intraocular pressure
- dilated eye exam - allows the ophthalmologist to view the retina and ensure the optic nerve is not damaged
- visual field test - measures the peripheral vision
A summary of glaucomas is available at Less Common Forms of Glaucoma
For more information on what is currently known about POAG, visit The Glaucoma Foundation and National Eye Institute
Alicia Mae Prater - Alicia received her doctorate in Experimental Pathology in 2007. She has been a freelance writer and scientific editor since 2008.
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