glaucoma

Condition in which pressure inside the eye (intraocular pressure) is raised abnormally as excess fluid accumulates. It occurs when the normal outflow of fluid within the chamber of the eye (aqueous humour) is interrupted. As pressure rises, the optic nerve suffers irreversible damage, leading to a reduction in the field of vision and, ultimately, loss of eyesight.

The most common type, chronic glaucoma, usually affects people over the age of 40, when the trabecular meshwork (the filtering tissue at the margins of the eye) gradually becomes blocked and drainage slows down. The condition cannot be cured, but, in many cases, it is controlled by drug therapy. Laser treatment to the trabecular meshwork often improves drainage for a time; surgery to create an artificial channel for fluid to leave the eye offers more long-term relief. A tiny window may be cut in the iris during the same operation.

Acute glaucoma is a medical emergency. A precipitous rise in pressure occurs when the trabecular meshwork suddenly becomes occluded (blocked). This is treated surgically to remove the cause of the obstruction. Acute glaucoma is extremely painful. Treatment is required urgently since damage to the optic nerve begins within hours of onset.

During routine eye examinations, the ‘air puff’ test serves to measure the the intraocular pressure and detect glaucoma at an early stage.