January - Glaucoma Awareness Month
Loss of peripheral vision due to retinal damage resulting from excessively high intraocular pressure. Ocular pressure is related to how much fluid filters out of the eye, as compared with the amount that enters the eye from the blood. Interference with the fluid outflow due to blockage builds pressure, as does too much inflow. Two types are known: Open angle-when the canal is open but gets blocked so as to let out too little fluid is one type. The other is anatomical in that the canal is closed and is not letting fluid leave the eye efficiently. Both types lead to excessive pressure in the eye.
Pressure in the eye is measured using an instrument called a tonometer, a sensitive device that measures pressure as millimeters of mercury. Greater than 20 mm of Hg is considered to be hazardous. To detect peripheral retinal damage and instrument measures "visual fields" is used. Vision over the whole retinal surface is determined. If the pressure in the eye remains above normal permanently, the peripheral retina develops swollen areas so as to destroy peripheral vision. Much visual loss results often.
Presently, there is no known cure for glaucoma, but several medications are available to reduce the intraocular pressure and protect against the risk of peripheral vision loss. The risk of developing glaucoma is increased with advanced aging and increase in people with high blood pressure and cataracts. In some patients vision can be partially improved with the use of contrast-enhancing eyeglasses. This disease is a major cause of visual impairment in people.
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