What is Glaucoma?|
Glaucoma is one of the leading causes of preventable blindness and is often called the "sneak thief" of sight because the most common type causes no symptoms until vision is already damaged. That's why the best way to prevent vision loss from glaucoma is to know your risk factors and have medical eye examinations at appropriate intervals.
What causes glaucoma?
Many people know that glaucoma has something to do with pressure inside the eye - the intraocular pressure (IOP). Pressure builds up in the eye when the clear liquid which normally flows in and out of the eye, is prevented from draining properly. The resulting increase in pressure within the eye can damage the optic nerve. Ophthalmologists used to think that high intraocular pressure was the main cause of optic nerve damage in glaucoma but we now know that even people with "normal" IOP can experience vision loss from glaucoma - so-called "normal tension glaucoma". Elevated IOP is still considered a major risk factor for glaucoma, though, because studies have shown that the higher the IOP is, the more likely optic nerve damage is to occur.
Most people who have glaucoma don't notice any symptoms until they begin to lose some vision.
As optic nerve fibers are damaged by glaucoma, small blind spots may begin to develop, usually in the side - or peripheral - vision. Many people don't notice the blind spots until significant optic nerve damage has already occurred. If the entire nerve is destroyed, blindness results.
Open Angle Glaucoma and Angle Closure
Open Angle Glaucoma
The most common form of glaucoma is open-angle glaucoma. In open-angle glaucoma, the eye fluid, that normally flows through the pupil into the front section of the eye's interior, cannot get through the eye's filtration area to the normal drainage canals. This causes a buildup of pressure in the eye (intraocular pressure, or IOP), which can damage the optic nerve and lead to vision loss.
Angle Closure Glaucoma
In angle-closure glaucoma, the normal drainage canals are blocked when the area between the iris and the cornea is not open. This condition can be chronic (progressing slowly or occurring persistently) or acute (occurring suddenly). Acute angle-closure glaucoma, does produce noticeable symptoms. In angle-closure glaucoma, there is a rapid buildup of pressure in the eye (intraocular pressure-IOP), which may cause any of the following:
- blurred vision
- severe eye pain
- haloes (which may appear as rainbows) around lights
- nausea and vomiting
Angle-closure glaucoma is a rare, but serious, form of the disease and is considered a medical emergency as vision loss can occur within hours of the onset of the problem. If you have any of these symptoms, call your physician or ophthalmologist immediately. Unless treated quickly, blindness can result. Chronic angle-closure glaucoma, like open-angle glaucoma, may cause vision damage without symptoms. Although angle-closure glaucoma is unusual, people of Asian ancestry are at higher risk of developing it. As with other forms of glaucoma, age and family history are also risk factors, and the problem seems to occur in older women more often than others.
"Normal (or low) tension" glaucoma is an unusual and poorly understood form of the disease. In this type of glaucoma, the optic nerve is damaged even though the patient's intraocular pressure is consistently within a range usually considered normal.
Childhood glaucoma is rare, and starts in infancy, childhood or adolescence. Like open-angle glaucoma, there are few, if any, symptoms in the early stage, and blindness can resu