Glaucoma Tests
Tonometry
The tonometry test measures the inner pressure of the eye. This is a routine test for glaucoma. The patient will be sitting upright and drops are used to numb the eye. Then the doctor will use a special device that measures the eye’s pressure. But there are problems with some of the devices and the standard deviation of studies by the Augenklinik der Universitat Tubingen has resulted in disturbing results on many of the devices used in this country. According to H. Landenberger and T. Schlote study, the Goldmann tonometry, which is photographed here. The results of measurement of the intraocular pressure with the Goldmann tonometry should not be used for clinical management of patients with glaucoma since the results are not accurate. The probability of success, defined as Goldmann tonometry-recordings within +/- 3 mmHg of the Goldmann tonometry recordings, was less than 53 % between 5 and 20 mmHg and less than 30 % between 20 and 30 mmHg. Note: for a full copy of the study, please see Schloteand Landenberger,[Intraocular Pressure Difference in Goldmann Applanation Tonometry versus a Transpalpebral Tonometer TGDc-01"PRA" in Glaucoma Patients.] [Article in German]I
You should be concerned with the equipment you eye doctor uses. For instance, the highest diagnostic precision to differentiate between normal eyes and early glaucomatous eyes - even before any visual field defect has been confirmed with a Heidelberg Retina Tomograph .
Ophthalmoscopy
Ophthalmoscopy is an examination of the back part of the eyeball (fundus), which includes the optic disc, retina, choroid, and blood vessels.The ophthalmoscope is an instrument with a small light on the end.. This helps the doctor look at the shape and color of the optic nerve. There are three different types of ophthalmoscopy. They are director ophthalmoscopy, indirect ophthalmoscopy, and slit-lamp ophthalmoscopy
Direct ophthalmoscopy: You will be seated in a darkened room. The examiner performs this common examination by projecting a beam of light from an ophthalmoscope, an instrument about the size of a flashlight, through the pupil to view the back of the eyeball. The magnification obtained by using the direct ophthalmoscope occurs because the eye itself is a simple magnifier. The rotating lenses incorporated in the instrument are used to compensate for the refractive error of the examiner or the patient being examined.
Slit-lamp ophthalmoscopy: You will be seated at the same instrument used in examining the front part of the eye. An additional lens will be held close to the eye to enable the doctor to see the fundus. This has the advantage of a stereoscopic view in addition to the magnification of direct ophthalmoscopy. The view is much wider than that of direct ophthalmoscopy, but not as wide as indirect ophthalmoscopy.
Indirect ophthalmoscopy
You will either lie or sit in a semi-reclining position. The examiner performs this examination by holding the eye open. The examiner wears an instrument on the head resembling a miner's light. While holding the eye open and using a hand-held instrument, the examiner shines a very bright light into the eye. Some pressure may be applied to the eyeball using a small, blunt instrument, and you will be asked to look in various directions. This examination takes between 5 and 10 minutes. The bright light will be uncomfortable, but the test is not painful. This examination requires more skill and time than the other forms of ophthalmoscopy, but has the advantage of allowing the doctor to see the entire retina. If the pressure in the eye is not in the normal range, or if the optic nerve looks unusual, then one or two special glaucoma tests will be done. These two tests are called perimetry and gonioscopy.
Perimetry
The perimetry test is also called a visual field test. During this test, you will be asked to look straight ahead and then indicate when a moving light passes your peripheral (or side) vision. This helps draw a "map" of your vision. There are two tests: Kinetic and threshold static automated perimetry
With "kinetic" perimetry, a trained perimetrist moves the stimulus; stimulus brightness is held constant. The limits of the visual field are mapped to lights of different sizes and brightness. With threshold static automated perimetry, a computer program is selected. The most commonly used one tests the central 30° of the visual field using a six degree spaced grid. This is accomplished by keeping the size and location of a target constant and varying the brightness until the dimmest target the patient can see at each of the test locations is found. These maps of visual sensitivity, made by either of these methods, are very important in diagnosing diseases of the visual system.
Gonioscopy is a painless eye test that checks if the angle where the iris meets the cornea is open or closed, showing if either open angle or closed angle glaucoma is present. Gonio lenses permit observation of the angle by eliminating the cornea as a refracting surface by placing a concave surface against the cornea. This allows visualization of the angle using obliquely inclined mirrors.