What are the tests for glaucoma?
Glaucoma can result in severe vision loss, making early detection vital in order to mitigate the potential impact.
For this reason, there are five tests regularly used to diagnose the condition and you are advised to get frequent eye checks, particularly as you get older. Here are the primary tests for establishing whether or not you have glaucoma:
Tonometry measures inner-eye pressure using a device called a tonometer. The optometrist may use drops to numb the eye, depending on which technique they choose to use. They then apply a small amount of pressure to the eye either with a warm puff of air or a tiny device.If you exceed the typical range for eye pressure, it is a sign of glaucoma. A normal pressure range is considered to be between 12 and 22 mm Hg, which refers to millimetres of mercury - a standard eye pressure measurement. However, eye pressure varies from person to person, so this test is often not enough to diagnose the condition on its own.
This test will reveal whether you have any damage to your optic nerve due to glaucoma. Your optometrist may need to apply eye drops, which will dilate the pupil, allowing them to examine the optic nerve.If the optic nerve looks unusual in shape or colour and the pressure of your eye is higher than the normal range, it is likely you will be asked to do more glaucoma tests, including gonioscopy and perimetry.
Gonioscopy is typically a test used to define what type of glaucoma you have. It is a diagnostic exam that checks the angle of where the iris (the coloured part of the eye) meets the cornea (the transparent dome at the front of the eye) to see whether it is narrow and closed or open and wide. Eye drops will be used to numb the area, after which a hand-held contact lens will be placed on the eye. A mirror in the lens will be able to show the optometrist whether the angle is closed and blocked, which is a symptom of acute glaucoma, or open and wide - a symptom of chronic glaucoma.
This examination helps to produce a map of your field of vision. In other words, it will be able to check whether your eyesight is already being affected by glaucoma.You will be asked to look directly ahead and indicate when a moving light passes your peripheral vision. Sometimes, there will be a delay in seeing the light when it crosses your blind spot, but this is normal and does not mean your eyesight is fading. It is also likely that once you have been diagnosed with glaucoma, you will be asked to have visual field tests a couple of times a year to evaluate whether your eyesight is deteriorating.
Pachymetry is a simple, painless test that measures the thickness of the cornea. Your optometrist will gently place a probe called a pachymeter against the front of your eye to do this. The exam will help diagnosis of glaucoma because the thickness of the cornea has an impact on eye pressure readings. This means it can be used in conjunction with tonometry to gain a more accurate diagnosis and guide future treatment. Pachymetry only takes a minute or so with each eye, so it is likely your optometrist will suggest an exam in conjunction with other tests.
While there may seem to be a lot of diagnostic tests for glaucoma, it is always advisable to be as thorough as possible when detecting the condition. In fact, you may be referred to a glaucoma specialist if a number of the above tests are completed and the results are inconclusive.