Eyesight tests for glaucoma
If you have glaucoma, high pressure inside the eye causes damage to the optic nerve, leading to loss of vision and blindness. Around 1 in 50 people in the UK over 40 have some form of glaucoma, and the risk of glaucoma increases as we get older. The most common form of glaucoma is open-angle or chronic glaucoma, which happens when the tubes that drain fluid from the eyes become partly blocked. Because the fluid cannot drain, the pressure in the eye increases, damaging the optic nerve and the nerves in the retina. If glaucoma is found early and treated, this can prevent damage to your vision.
In an eyesight test for glaucoma, the optician puffs air onto the surface of the eye to measure the intraocular pressure – the pressure inside the eye. Other eyesight tests for glaucoma include checking your peripheral vision as a problem with this is often the first sign of glaucoma. You will be asked to look at a main light and then watch for spots of light coming into your field of view over a few minutes, activating a counter whenever you see a spot of light appear. A computer plots your responses and can detect if you have any ‘blind areas’ in your peripheral vision.
Eyesight tests for macular degeneration
Eyesight tests such as the Amler test can diagnose age-related macular degeneration (AMD). AMD occurs when the macula, an area on the retina that helps with accurate vision, becomes damaged or distorted by an overgrowth of blood vessels. As AMD progresses, central vision is lost, making it hard to read or to recognise faces. The Amsler test involves looking at a grid of squares with a dot in the middle – if the grid seems distorted when you stare at the central dot this may indicate AMD.
Eyesight tests for other conditions
During the eyesight test, the optometrist will examine your retina using a slit lamp. This can detect the first signs of undiagnosed diabetes, and monitor the progression of diabetic retinopathy, a common cause of blindness in people with diabetes. Changes in the retina that are also visible during eyesight tests may also indicate the early signs of high blood pressure. The optometrist also uses the slit lamp to look for cataracts and corneal ulcers. Optometrists can diagnose and treat a number of eye conditions including infective conjunctivitis, allergic conjunctivitis, superficial eye injuries, blepharitis and dry eye.