How do I know if I have glaucoma?
Glaucoma can be difficult to detect, especially early in the disease. It cannot be diagnosed with one test alone; several tests are required, each contributing unique information like pieces of a puzzle. These include:
Eye pressure measurement
Eye pressure (intraocular pressure) is the major risk factor for glaucoma, and is the only factor that can be controlled or modified. Mostly glaucoma is due to high eye pressure, however some forms of glaucoma are associated with normal eye pressure. The measurement of eye pressure is critical for the evaluation of glaucoma and assessment of the effect of treatments. For your comfort, anaesthetic medications will be administered to numb the eye and ensure the pressure measurement is painless.
Visual Field Test
This test involves bright and dim lights shone in your peripheral vision - you will be asked to click a button each time you see a light. This is used to generate a map of peripheral vision sensitivity for each eye. These maps may show signs of peripheral visual loss due to glaucoma. They can also be used to monitor for progression of Glaucoma over time.
Optic nerve fibre layer OCT analysis
The OCT is a perfectly safe laser scan of the back of your eye that generates a 3-dimensional image of the optic nerve and surrounding structures. Glaucoma changes the shape and appearance of the nerve; the OCT detects such changes early and can be useful for diagnosing glaucoma. Serial OCT measurements can be used to monitor for progression of glaucoma over time.
Corneal thickness measurement
The cornea is the clear window at the front of your eye. Eye pressure is measured by depressing the cornea and evaluating degree of depression. This can be influenced by corneal thickness as well as eye pressure. Knowing the thickness of your cornea helps in the assessment of your eye pressure.
Optic nerve viewing by an expert
Glaucoma causes characteristic changes of the optic nerve when viewed through the eye using a magnifying lens. These changes can be subtle and difficult to detect; it is best to have the nerves viewed by a trained specialist to properly assess your glaucoma risk.
Do I need to these tests repeated?
Some patients have a very low risk of developing glaucoma. They only need the eye pressure checked yearly. Other patients may have some glaucoma-like changes on testing, but not enough to indicate glaucoma. They may develop glaucoma in the future, and the tests should be repeated more frequently. Patients with definite glaucoma should be seen regularly and have the appropriate tests repeated. This is to check that the treatment is working sufficiently to control the disease.