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Glaucoma is an eye disease in which progressive damage to the optic nerve occurs. The optic nerve connects the eye to the brain. As the optic nerve is slowly damaged, characteristically-shaped blind areas develop that can progress to loss of vision or even total blindness, usually painlessly.
Open angle glaucoma (also called chronic open angle glaucoma and chronic simple glaucoma) is the most common type, accounting for about 90 percent of all glaucoma. It usually affects both eyes, though one eye may be involved earlier or more severely than the other. It usually does not occur until middle life, though sometimes younger individuals are affected. The condition tends to be hereditary. It is not contagious and not related to cancer. The high pressure in the eyes is not the same as high blood pressure.
What Causes Open Angle Glaucoma?
Glaucoma may be caused by a problem in the eye's fluid drainage system.
A clear fluid called aqueous humor (or simply aqueous) fills the anterior chamber, a compartment at the front of the eye between the cornea and the iris. Aqueous is produced and circulated in the anterior chamber to supply essential nutrients to the eye and keep a normal, gentle pressure within it.
The pressure is maintained within a narrow range by a control system that delicately balances the production and drainage of aqueous from the anterior chamber.
The drainage channels - the trabeculum filter and the Canal of Schlemm - are located near the "angle," a wedge-shaped space in the anterior chamber that encircles the iris, where it meets the edge of the cornea.
Increased pressure can occur when either the drainage of the aqueous is weakened, or the production is increased, or both. If the pressure stays much above a normal level for enough time, the delicate blood supply and fibers in the optic nerve are likely to be damaged.
Examination and Diagnosis
As part of the routine eye examination, the pressure within your eyes is checked by a painless test called tonometry. Depending on the type of tonometer used, you may be given anesthetic eyedrops. An elevated pressure is one sign that you may have glaucoma, but it alone will not tell if you do have glaucoma - in other words, tonometry cannot tell for sure that glaucoma is present or that the pressure needs treatment.
A diagnosis of open angle glaucoma can be made only by a thorough examination in which various eye functions and certain structures inside the eye are evaluated. OCT measures several structural areas of the eye. A visual field test measures the function of the eye. The inside of the eye is examined with several instruments. A gonioscope - which is a special type of contact lens with built-in mirrors that allow a view into the angle structures - is placed on the eye so the condition of the drainage channels can be studied. The retina and optic nerve are examined with an ophthalmoscope or biomicroscopy.
If the optic nerve does not appear to be damaged and there is no loss of visual field evident, a mildly increased eye pressure may not need to be treated. However, it does need to be examined regularly to watch for any developing changes.
Treatment
The goal of treatment is to lower the eye pressure. Almost always, this can be accomplished by the regular use of prescription eyedrops. Some of these work by improving the filter drainage mechanism; others lower the production of aqueous.
Even when medications are faithfully used, they are sometimes unable to stop the disease from progressing. Then, laser surgery may be recommended to make tiny new openings in the drainage channels. This procedure, called laser trabeculoplasty (LTP), can lower the pressure, sometimes dramatically, though it still might need to be supplemented with medications. Even when LTP is successful, it is not always a permanent solution; months or years later, pressure may again rise to dangerous levels.
If all other therapy combinations have not been successful, filtration surgery may be recommended. The most common of these procedures, called trabeculectomy, is the surgical creation of a new drainage channel. There are other surgical procedures, which can provide even greater drainage, if needed, to reduce the ocular pressure and save vision.
Surgery always has risks and side effects. If it becomes necessary in your case, those risks will be carefully explained to you along with the potential benefits.
Glaucoma is usually a lifetime problem. Never assume that you have been cured, and do not stop treatment unless you have been told to do so. Left untreated, this disease can cause total blindness. On the other hand, proper treatment and regular checkups can help you to preserve your precious eyesight for the rest of your life.
Glaucoma
