Cataracts and glaucoma are conditions that affect the eye and cause vision loss, but while cataracts gradually cause a painless loss of transparency, glaucoma can affect vision slowly and subtly or quickly and painfully. A cataract forms when changes in the lens, the part of the eye where light is focused, cause cloudiness and prevent light from passing through. Glaucoma is a condition in which increased pressure inside the eye damages the optic nerve, which carries visual information to the brain. If left untreated, glaucoma causes blindness that is irreversible, unlike vision loss caused by cataracts that can be treated by 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 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 as new fluid is made, is prevented from flowing out when the small drainage channels become blocked. The pressure inside the eye increases and causes damage to the optic nerve.
Many people with glaucoma are thought to have optic nerve weakness that makes damage more likely, and in some people the pressure in the eye may even appear to be within normal limits, but nerve damage still occurs. This is known as normal tension glaucoma. Glaucoma is treated with eye drops that lower the pressure inside the eye, and laser treatment or surgery may be used if drug treatment fails.
Cataracts and glaucoma can be treated surgically, but when vision loss from cataracts can be reversed, vision loss due to glaucoma cannot. Surgical treatment of cataracts is usually recommended as soon as cataract symptoms interfere with daily life. The symptoms of cataracts and glaucoma are quite different, and although glaucoma leads to a slow loss of the external field of vision that is difficult to notice, cataracts can cause blurred vision and a dazzling effect from bright lights. Acute glaucoma, which occurs suddenly, causes rapid vision loss along 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 the part of the eye containing the channels may be removed. The result can be positive for both cataracts and glaucoma if the conditions are successfully diagnosed and treated. In the case of glaucoma, early diagnosis is important, and regular eye tests are required to detect the condition and stop progressive vision loss.