Cataracts and glaucoma are both conditions which affect the eye, and both cause loss of vision, but while cataracts gradually cause a painless loss of transparency, glaucoma can affect vision either slowly and subtly or quickly and painfully. A cataract is formed when changes in the lens, the part of the eye where light is focused, cause clouding and prevent light from passing though. Glaucoma is a condition where increased pressure inside the eye damages the optic nerve, which carries visual information to the brain. If left untreated, glaucoma causes blindness which is irreversible, unlike the loss of sight caused by cataracts, which may be treated using cataract surgery.
Both cataracts and glaucoma are more common in people with diabetes. Glaucoma tends to affect both eyes at the same time, although one may be worse than the other. There are a number of different types of glaucoma, and the most common is known as primary open angle glaucoma, which tends to develop slowly. Fluid in the chamber at the front of the eye, which normally drains away as new fluid is produced, is prevented from flowing out when tiny drainage channels become blocked. Pressure inside the eye increases and causes optic nerve damage.
It is thought many people with glaucoma have a weakness of the optic nerve which makes damage more likely, and in some people the pressure in the eye might even appear to be within normal limits but nerve damage still occurs. This is known as normal tension glaucoma. Glaucoma is treated using eye drops which lower the pressure inside the eye, and laser treatment or surgery may be used if drug treatment fails.
Cataracts and glaucoma can both be treated surgically, but where the visual loss of cataracts can be reversed, sight loss due to glaucoma cannot. Surgical treatment of cataracts is normally recommended as soon as cataract symptoms interfere with everyday life. The symptoms of these conditions are quite different, and while glaucoma leads to a slow loss of the outer field of vision which is difficult to notice, cataracts can cause blurred sight and a dazzling effect from bright lights. Acute glaucoma, which happens suddenly, causes rapid sight loss together with symptoms such as pain, nausea, and blurred vision, with halos seen around lights.
Different surgical methods are used to treat cataracts and glaucoma. Cataracts are removed from the eye and replaced with artificial lenses, while glaucoma surgery may involve using a laser to open blocked drainage channels or part of the eye containing the channels may be removed. The outcome can be positive for both cataracts and glaucoma if the conditions are diagnosed and treated successfully. In the case of glaucoma, early diagnosis is important, and regular eye tests are required to pick up the condition and halt the progressive loss of sight.