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Posted on 05-03-2016

Diagnosing Glaucoma Through Testing
 

Glaucoma, considered the “sneak thief of vision,” is a series of eye conditions that result from a buildup of pressure inside the eye that can lead to vision problems and even blindness. Often inherited, it is most common among older people. Unless you are at special risk for glaucoma that indicates the need for earlier or more frequent testing, your eye doctor will check for it every 2 to 4 years before age 40, 1 to 3 years between age 40 to 54, every one to two years from age 55 to 64, and every 6 to 12 months after age 65. Your optometrist or ophthalmologist will run a series of tests to chart any building pressure.

How Glaucoma Affects The Eye

In a normal eye, aqueous humour inside the eye circulates as newly produced fluid pushes the old fluid out through a mesh-like channel. If the fluid cannot pass through the eye, it builds up to form glaucoma. Persistent or intermittent pressure on the retinal nerve fibers and optic nerve is what threatens vision. The condition can also result from severe eye infection, blockage of ocular blood vessels, inflammation of the eye, injury to the eye, and even eye surgery for another purpose. Most patients report that it occurs in both eyes, although it is often worse in one or the other.

There are two major types of glaucoma – open angle and angle closure glaucoma. In open angle glaucoma, the most common type, the fluid does not flow through the trabecular meshwork, the drain of the eye. In angle closure glaucoma the angle between the iris and the cornea becomes so narrow that fluid cannot pass through to drain.

Common Glaucoma Tests

To test for glaucoma, ocular professionals dilate the eyes and use a variety of techniques to test in five areas:

  • Tonometry tests the inner pressure of the eyes by using a device called a tonometer to detect pressure, after applying pressure from a small device or a puff of warm air. Normal pressure readings are in in the 12 to 22 HG (millimeters of mercury) range, but the doctor may do further testing if the pressure level is over 20 HG.
  • Ophthalmoscopy or a dilated eye exam tests the color and shape of the optic nerve by expanding the pupil and shining a brilliant light into it that magnifies the optic nerve so the doctor can see it better.
  • Perimetry or a visual field test checks the entire field of vision both straight ahead and on the side to ensure the rate at which your glaucoma has affected it.
  • Gonioscopy examines the angle in the eye where the iris and cornea meet by placing a handheld contact lens with a mirror on it that enables the doctor to see what type of glaucoma might be present.
  • Pachymetry measures the thickness of the cornea with the probe (packymeter) placed on the front of the eye to determine whether the thickness of the cornea is obscuring accurate eye pressure reading.

Testing Leads To Treatment

The first two tests, tonometry and ophthalmoscopy, are part of any glaucoma checkup, while the others are conducted if case problems are detected. For someone suspected of having glaucoma, the series of tests confirm the diagnosis and help the physician determine a treatment plan, which often includes eye drops, laser surgery, or microsurgery. While these treatments cannot restore vision loss, frequent examinations and treatment can stop the spread of the problem.

Testing for glaucoma is an important part of your eye exam. To schedule your annual exam and glaucoma test, call for an appointment today at Eye Site of Texas in Katy at 281.644.2010 or in Memorial at 713.984.9144.

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