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Gonioscopy is an eye test that may be performed to diagnose glaucoma, a potentially serious eye disorder that could lead to loss of vision. The test is typically done with a special lens to properly examine the angular area where the cornea and iris come together. While a gonioscopy can be quite painless, a topical anesthetic is often put into the patient's eye to ease any discomfort. The test takes a few minutes, and is usually conducted in the doctor’s office.
Glaucoma is a condition that can develop when a naturally secreted fluid known as aqueous humor accumulates in the eye raising internal pressure in the eye. Sometimes an obstruction that prevents drainage of the fluid could cause the problem. In some cases, the eye produces greater amount of fluid than normal, which may not get cleared away quickly, resulting in higher internal or intraocular pressure.
There are different types of glaucoma. In the more prevalent form called primary open angle glaucoma, intraocular pressure tends to increase gradually, whereas in the closed angle form of glaucoma, pressure can increase quite quickly. If the pressure is higher than the level that the eye can withstand it might damage the optic nerve, which relays visual information from the eye to the brain. Thus, one may suffer from decreased vision and over time from blindness if glaucoma is not treated.
A gonioscopy is one of the diagnostic tests that could help detect glaucoma. The test enables the ophthalmologist to look at and assess the angle where the cornea and the iris converge. This region is the outlet from which the aqueous humor normally leaves the eye.
Gonioscopy can indicate if the drainage angle is accessible, has narrowed, or blocked. The test could assist the doctor in diagnosing the form of glaucoma, determining the underlying cause, and ascertaining damage to the area. A grading system is often referred to for interpreting the test findings based on the variations in angle width.
An ophthalmologist may perform the procedure with a goniolens. There are different types of lenses used for gonioscopy, and they may have one or more mirrors. Typically, during the test the specialized lens is positioned delicately onto the surface of the eye, and a fine beam of light is directed into the eye. Before the procedure, the ophthalmologist usually numbs the eye with anesthetic eye drops.
Those who wear contact lenses are generally advised to take off their lenses prior to the test. Usually, lenses can be worn again an hour after the test or once the effect of the eye drops is diminished. Another precautionary measure that may be recommended is to avoid rubbing one’s eyes for about twenty minutes following the gonioscopy.