Glaucoma, often does not cause any symptoms and it may be a long time before you realise that you have a problem with your eyesight. Vision loss progresses slowly from the outer rim of the eye (peripheral vision) and involves the central vision and most people do not realise side vision loss as the normal or less affected eye makes up for the loss of vision. Hence regular check-ups for glaucoma are important so that any problems can be detected and treated as early as possible. Early diagnosis and treatment can prevent damage to vision.
Tests for glaucoma
There are several glaucoma tests that may be conducted to confirm glaucoma. The tests are painless and do not take a long time. However all tests should be conducted at the same appointment to ensure that the results are as accurate as possible.
Eye pressure test (tonometry): This test measures the pressure in your eye. An instrument known as tonometer is used to measure the pressure inside your eye. You will be given a small amount of anaesthetic (painkiller) medication in the eyes, and dye would be placed onto your cornea (the transparent layer of tissue that covers the front of the eye). The tonometer is applied to the eyes to measure the intraocular pressure. It can detect elevated pressure in the eye (ocular hypertension or OHT), a very treatable risk factor for chronic open-angle glaucoma.
Central corneal thickness: The thickness of cornea is measured as it is considered to be an affecting factor for how the intraocular pressure gets interpreted.
Gonioscopy: Examination of the front outer edge of eye, between the cornea and the iris (the coloured part of your eye) is known as gonioscopy. The tiny spongy tissue called the trabecular meshwork through which the aqueous humor drains is situated in the angle where the iris and cornea meet. Gonioscopy can help to diagnose if this angle is open or closed (blocked).
Visual field test (perimetry): This test assesses the visual field and can detect missing areas of vision. During the test you will be shown a sequence of light spots to assess which ones you can see. Some light spots assess your peripheral vision (around the sides of your eyeball), which is where vision loss in glaucoma begins. People with damage to vision because of glaucoma may not be able to see the spots in peripheral vision (this indicates that glaucoma has damaged vision).
Optic nerve assessment: Optic nerve carries visual information from the eyes to the brain. An eye drop to enlarge your pupils will be administered and then the eye would be examined using a slit lamp (a microscope with a very bright light). The test can assess whether your optic nerve has been damaged by glaucoma. Damage to the optic nerve is permanent; hence loss of vision is also permanent.