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HRT Nerve Fiber Analyzer is a new exam that may help to physicians to detect earlier changes and more sensitive objective changes to individuals who may have or have glaucoma. The test is objective, and fast. More than that, the HRT is able to determine if you have glaucoma prior to your experiencing any vision loss.

Intraocular pressures are only one way of detecting glaucoma. Many individuals have glaucoma with normal pressures and also need to be treated. Another test which is used to detect glaucoma is perimetry (visual field) testing which measures vision already lost. Often this test is used to follow the progression of glaucoma. This test is based on the patients responses. Some tests can be unreliable. The GDx exam offers another method by which glaucoma can be evaluated and followed. The test is very fast and usually takes less than 5 minutes. The pupil does not have to be dilated and the results can be obtained quickly. The chin is supported and the patient looks straight ahead and focuses on the light indicated. A very safe, invisible laser scans the back of the eye and acquires an image in less than one second. The only other way we have of evaluating the nerve is by dilating the patient and looking at the details of the optic nerve head.

The exam from the GDx prints a color coded “thickness map” of the nerve fiber layer at the back of your eye. This information can assist the doctor to get objective values on the early changes which may help to determine if you have glaucoma. It also helps to follow patients who have already been diagnosed with glaucoma.

The bright colors represent a thick nerve fiber layer, darker colors depict areas where the nerve fiber layer is thinner. The blue color is normally seen at the 3 and 6 o’clock position. The 12 and 6 o’clock positions should show bright colors (reds and yellows.)

The thickness map is dark, indicating thinning of the nerve fiber layer. In this picture, the nerve is represented by the circle. Around the nerve however the color is all blue. This represents a very thin nerve fiber layer in the 360 degrees. This individual has very advanced nerve fiber layer loss and is consistent with advanced glaucoma.

The GDx can be used to track the progression of eye disease and it can help to determine if you have glaucoma. The GDx can be used on periodic times during the year to see if there are any changes which have not been seen on the visual field or through the dilated examination when evaluating the optic nerve head. Patients who are at risk for glaucoma should have a GDx done as a baseline in conjunction with a thorough eye examination by a physician. For a definition of at risk patients, please click here. Insurance The GDx is covered by Medicare in the state of Illinois and by most insurance companies. Please ask for payment options if your insurance doesn’t cover the exam, or if you have no insurance. (Excerpts of this document taken from Laser Diagnostic Technologies, Inc, GDx pamphlet copyright 1998.)


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