Glaucoma is a condition in which the normal fluid pressure inside the eyes (intraocular pressure, or IOP) slowly rises as a result of the fluid aqueous humor - which normally flows in and out of the eye - not being able to drain properly. Instead, the fluid collects and causes pressure damage to the optic nerve (a bundle of more than 1 million nerve fibers that connects the retina with the brain) and loss of vision.
Causes of Glaucoma
While physicians used to think that high intraocular pressure (also known as ocular hypertension) was the main cause of optic nerve damage in glaucoma, it is now known that even persons with normal IOP can experience vision loss from glaucoma. Thus, the causes are still unknown.
Types of Glaucoma
- Open-angle:The fluid that normally flows through the pupil into the anterior chamber of the eye cannot get through the filtration area to the drainage canals, causing a build-up of pressure in the eye
- Low-tension or normal-tension:This type of glaucoma causes optic nerve damage and narrowed side vision.
- Angel-closure:The fluid at the front of the eye cannot reach the angle and leave the eye because the angle becomes blocked by part of the iris.
- Childhood: Develops in infancy, early childhood, or adolescence. Prompt medical treatment is important in preventing blindness.
- Congenital: Occurs in children born with defects in the angle of the eye that slow the normal drainage of fluid.
- Primary:Primary glaucoma cannot be contributed to any known cause or risk factor.
- Secondary:In rare cases, secondary glaucoma is a complication following another type of eye surgery.
Symptoms of Glaucoma
- blurred or narrowed field of vision
- severe pain in the eye(s)
- haloes (which may appear as rainbows) around lights
The symptoms of acute angle-closure glaucoma may resemble other eye conditions. Consult a physician for diagnosis immediately if you notice symptoms, as this type of glaucoma is considered a medical emergency requiring prompt medical attention to prevent blindness.
In addition to a complete medical history and eye examination, your eye care professional may perform the following tests to diagnose glaucoma:
- Visual acuity test - the common eye chart test (see above), which measures vision ability at various distances.
- Pupil dilation - the pupil is widened with eye drops to allow a close-up examination of the eye's retina.
- Visual field - a test to measure a person's side (peripheral) vision. Lost peripheral vision may be an indication of glaucoma.
- Tonometry - a standard test to determine the fluid pressure inside the eye.
Risk Factors for Glaucoma
- race - African Americans are five times more likely to develop glaucoma than Caucasians. In addition, glaucoma is the leading cause of blindness for African Americans.
- age - Persons over age 60 are at more of a risk for developing glaucoma.
- family History - People with a family history of glaucoma are more likely to develop the disease.
- high Intraocular pressure - Persons with an elevated (greater than 21 mm Hg) IOP are at an increased risk.
The National Eye Institute, part of the National Institutes of Health, recommends that anyone in these risk groups receive an eye examination with dilated pupils every two years.
Treatment for Glaucoma
Specific treatment for glaucoma will be determined by your physician based on:
- your age, overall health, and medical history
- extent of the disease
- your tolerance for specific medications, procedures, or therapies
- expectations for the course of the disease
- your opinion or preference
While glaucoma cannot be cured, early treatment can often control it. Treatment may include:
- Conventional surgery - The purpose of conventional surgery is to create a new opening for fluid to leave the eye.
- Laser surgery (also called laser trabeculoplasty) - There are several types of surgical procedures that can be performed with a laser that are used to treat glaucoma, including:
- Trabeculoplasty - In this, most common type of laser surgery to treat open-angle glaucoma, a laser is used to place "spot welds" in the drainage area of the eye (known as the trabecular meshwork) which allows fluid to drain more freely.
- Iridotomy - In this procedure, the surgeon uses the laser to make a small hole in the iris - the colored part of the eye - to allow fluid to flow more freely in the eye.
- Cyclophotocoagulation - A procedure that uses a laser beam to freeze selected areas of the ciliary body - the part of the eye that produces aqueous humor - to reduce the production of fluid.
In some cases, a single surgical procedure is not effective in halting the progress the glaucoma, and repeat surgery and/or continued treatment with medications may be necessary.