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.
There are two main types of glaucoma: open-angle glaucoma and angle-closure glaucoma. Though there are two types, the cause of each type is the same – your eye is unable to drain the fluid that needs to be drained.
The more common of the two types is open-angle glaucoma, which is sometimes called wide-angle glaucoma. In this case, the drain work in the eye looks normal, but for one reason or another, it is not draining the fluid as it should.
Angle-closure glaucoma is caused when the structure of the drain path between the iris and the cornea is too narrow. This structure of the eye is also linked to causing farsightedness and cataracts because fluid can build up quite suddenly. The reason for this is unknown for now, but many doctors believe it is because of genetics. Those who develop glaucoma in old age suffer from blocked channels that are unable to drain the fluid. Often, parents of those with glaucoma also had glaucoma. Aside from being hereditary, glaucoma can also be triggered by traumatic events in the eye such as being bluntly hit, severe eye infections, chemical injuries, blocked blood vessels, and inflammatory related issues
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 descent are 3 to 6 times as likely as White people to develop glaucoma and the disease is the leading cause of irreversible blindness in Black people who 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.
The current ophthalmic standard tests for eye pressure are not sufficient to diagnose glaucoma. It is important also to look directly at the optic nerve after pupil dilation, and a test of the person's peripheral vision is needed. It is advisable to check for glaucoma at ages 35 and 40, and then every 2 or 3 years until 60.