Glaucoma is a disease in which the optic nerveis damaged, leading to progressive, irreversible loss of vision. It is often,but not always, associated with increased pressure of the fluid in the eye.
The nerve damage involves loss of retinalganglion cells in a characteristic pattern. There are many differentsub-types of glaucoma but they can all be considered as a type of opticneuropathy. Raised intraocular pressure is a significant riskfactor for developing glaucoma (above 22 mmHg or 2.9 kPa). One personmay develop nerve damage at a relatively low pressure, while another person mayhave high eye pressurefor years and yet never develop damage. Untreated glaucoma leads to permanentdamage of the optic nerve and resultant visualfield loss, which can progress to blindness.
Glaucoma can be divided roughly into two main categories, "openangle" and "closed angle" glaucoma. Closed angle glaucoma canappear suddenly and is often painful; visual loss can progress quickly but thediscomfort often leads patients to seek medical attention before permanentdamage occurs. Open angle, chronic glaucoma tends to progress more slowly andthe patient may not notice that they have lost vision until the disease hasprogressed significantly.
Glaucoma has been nicknamed the "sneak thief of sight" becausethe loss of vision normally occurs gradually over a long period of time and isoften only recognized when the disease is quite advanced. Once lost, thisdamaged visual field can never be recovered. Worldwide, it is the secondleading cause of blindness. It is also the first leading cause of blindnessamong African Americans. Glaucoma affects 1 in 200 people aged fifty andyounger, and 1 in 10 over the age of eighty. If the condition is detected earlyenough it is possible to arrest the development or slow the progression withmedical and surgical means.
Signs and symptoms
There are rarely any symptoms in the early stages of the disease so regulareye checks by qualified professionals are important. Ophthalmologists andoptometrists will diagnose glaucoma on the basis of intraocular pressure,visual field tests and optic nerve head appearance.
Patients will sometimes notice patchy loss of peripheral vision or reducedclarity of colours and these people may benefit from a review by an eyespecialist.
Symptoms of angle closure glaucoma can include pain in or around the eyeball, headache, nausea or vomiting and visual disturbances, for example halosaround lights. In some cases there are no symptoms.