How is glaucoma diagnosed?
There are many tests that can be carried out by your eye doctor to determine whether or not you have glaucoma. Regularly having your eyes checked over by a specialist is the best way to avoid glaucoma. Diagnosing glaucoma early on, allows treatment to begin to preserve your sight. Because open angle closure glaucoma has little to no symptoms, many tests may be required to be undertaken, before reaching a final diagnosis.
This is a test that helps to determine the pressure inside your eye called intraocular pressure. Elevated pressure within the eye is known to cause damage to the optic nerve. Your eye doctor will place eye drops into your eye that works as an anesthetic. The tonometer machine is placed in front of you, where you can comfortably rest your chin and forehead against the padded support. A slit lamp is moved into position to focus on the center of your eye. The tonometer device on the lamp then presses slightly against your cornea. The reaction to this slight pressure is then measured by the tonometer sensor. This test is essential in diagnosing glaucoma. The eye pressure result recorded by what is called millimeters of mercury or mmHg.
Visual Field Test (Perimetry test)
If you are found to have higher than average readings of mmHg in the tonometer pressure test, your doctor will next want to determine if any damage has occurred to the optic nerve, as a result of that elevated pressure. This type of test measures how well you respond to certain objects or lights appearing on a screen in front of you. You will look inside a bowl-shaped instrument that is called a perimeter, with your forehead and chin resting on a padded support.
The test is performed on one eye at a time, where you press a button as soon as you see a flashing object within the window. If you missed an object or flash, this will be recorded on the computer, determining if you have any peripheral loss of vision or otherwise. Any peripheral vision loss is linked to damage to the optic nerve. You can expect the visual field test to last around 10 to 20 minutes. The visual field test is a type of test that can be used repeatedly in the future, in order to help monitor your glaucoma. This is especially important if your doctor believes you are in the early stages of this condition and is vital for preserving vision. Of course, this test also helps to determine the level of treatment you will receive.
Gonioscopy is a type of test that specifically examines how fluid drains from your eye via tiny canals. Much like the tonometer test, a slit lamp is used along with the eye drops that act as an anesthetic. A contact lens is placed on the eye and a beam of light is used to determine the angle in which the lens sits. If the test shows that the angle between your cornea and iris is not within normal measures, then your doctor can determine how this affects the drainage of fluid from your eye. Essentially, your doctor will be able to tell if the drainage angle is open or closed.
Pachymetry is important for measuring the thickness of your cornea. Generally, those with less thickness in the cornea, are found to be at greater risk of developing glaucoma. Most advanced modern tests are carried out by way of hand-held ultrasound technology. Your doctor will place anesthetic eye drops into your eye, before carefully placing a pachymetry probe tool against the center of your cornea. An ultrasound wave will then measure the thickness of your cornea. This is considered to be a very quick and easy evaluation.