Glaucoma is a serious eye disease usually caused by excessive pressure inside the eye, although it can occur with normal eye pressure as well. This damages the retinal nerve fibres, causing permanent deterioration of vision. Glaucoma is the second leading cause of blindness in the world, according to the World Health Organization.
Glaucoma usually develops in the middle-aged or elderly and is the most common cause of blindness. Visual loss usually starts at the periphery and gradually encroaches upon central vision. Damage to the nerve fibers can begin up to six years before symptoms become noticeable, by which time the damage can be significant. While there is no known cure, glaucoma can be managed through early detection and treatment with eyedrops.
Secondary glaucoma refers to any form of glaucoma in which there is an identifiable cause of increased eye pressure. Secondary glaucoma may be caused by an eye injury, inflammation, certain drugs such as steroids and advanced cases of cataract or diabetes. The type of treatment will depend on the underlying cause, but usually includes medications, laser surgery, or conventional surgery. As with primary glaucoma, secondary glaucoma can be of the open-angle or angle-closure type and it can occur in one or both eyes.
Fluid normally moves into and out of the eyeball to keep it nourished and maintain its shape. When this flow becomes blocked the intra-ocular pressure (IOP) can build and cause glaucoma. The common forms of glaucoma start painlessly and without symptoms, but the uncommon forms can produce symptoms like hazy vision, pain in the eye, headache, nausea, vomiting, rainbow halos around lights, or a sudden loss of vision in one eye. Other visual problems due to glaucoma include diminished sensitivity to contrasts, oversensitivity to light, problems with glare and a loss of ability to see fine details.
A gene has been discovered for one of the rarer forms of glaucoma.
Glaucoma is responsible for 20% of blindness in Pakistan and 14% and 11.6%, of blindness in both eyes in the UK and USA, respectively. In the USA, it afflicts about 3 million Americans, but nearly half are unaware they have the disease. More than 120,000 Americans are blind from glaucoma, which accounts for 9% to 12% of all cases of blindness.
Glaucoma occurs most commonly in people over the age of 60. It tends to run in families. Anyone over 40, nearsighted or farsighted people, diabetics, blood relatives of glaucoma patients, steroid users, smokers and people with high blood pressure or who have previously injured their eyes have the highest risk of contracting glaucoma. The incidence of glaucoma is rising as the population ages. People of African extraction are 3 to 6 times as likely as whites to develop glaucoma and the disease is the leading cause of irreversible blindness in blacks. Blacks tend to develop the disease about 10 years earlier than whites.
People are generally not aware of the fairly high risk of glaucoma; in the USA 3 million people have it, but half of them do not yet realize that they have a vision problem. If it is neglected too long, it can blind them. If it is diagnosed early, it can successfully be treated with medicated drops or surgery.