Glaucoma usually occurs in people over the age of 40. This may be one reason why early detection of glaucoma is difficult. Many people think that some loss of vision is just part of growing older and so don’t bother to see a doctor about their eye problems.
There are several types of glaucoma. Rarely, congenital glaucoma can occur in infants and even unborn babies. Another form, called acute angle closure glaucoma, results in very rapid elevation of pressure within the eye. It can cause severe pain in the eye, often along with nausea, vomiting and rapid blurring or loss of vision. The most common type of glaucoma is Progressive Open Angle Glaucoma, or POAG.
POAG is found in one of every 200 people in their sixties and between four and five of every 100 people in their nineties. Some are at greater risk than others, particularly women. Since the disease can be inherited, those with relatives affected by glaucoma are more likely to develop it. People with diabetes, the very near-sighted, those with poor blood circulation or of African or Asian ancestry are also at greater risk.
The trouble with POAG is that there are no symptoms. Vision problems become noticeable only in the later stages of the disease, usually after major damage has been done and sight has been permanently affected. It would seem that someone losing sight would quickly notice a problem. Yet with glaucoma, changes are often so minor that years pass before loss of vision becomes apparent. When we look directly at an object, we use our central vision. Since our mind focuses on the object, any loss of central vision is noticed immediately. Glaucoma causes a loss of peripheral vision and often goes unnoticed, as objects to the side are not at the centre of attention. As vision loss due to glaucoma progresses, one’s field of vision becomes more and more constricted. Eventually only a small central area of vision remains, similar to looking through a small tube or tunnel. Finally even this small amount of vision may be lost, resulting in blindness.
The exact reasons are not well understood. Though more factors are at play in glaucoma than just pressure elevation, they are not well understood either. Lowering the pressure in the eye helps prevent further vision loss in this disease. The pressure is related to the flow of aqueous fluid within the eye. Our eyes continuously produce this fluid, which circulates through the eye and drains away through a filtering system. Anything that upsets the balance between fluid production and drainage can cause pressure to rise within the eye.
In progressive open angle glaucoma, the filtering system appears to be blocked, causing a decrease in drainage fluid from the eye. The amount of fluid in the eye increases, leading to higher pressure.
Treatment is aimed at either decreasing the amount of fluid produced or increasing drainage. In most cases medication is all that is needed to lower pressure to safe levels. Medication may be in the form of eye drops or, less commonly, pills. If pressure cannot be controlled by medication, a small operation (laser treatment), can be performed to create new drainage for the fluid in the eye.
Raised pressure inside the eye is not related to high blood pressure. Unless the pressure in the eye increases rapidly, it cannot be felt. Usually pressure increases so slowly that it does not cause pain or headache. In most cases it is impossible to know if you have glaucoma unless you see a doctor.
Your family doctor can do a preliminary screening of your eyes and decide whether or not you should see an ophthalmologist. An ophthalmologist is a medical eye specialist who will examine your eyes and do some simple, painless tests to measure the pressure in your eyes and check your field of vision. Not everyone with raised pressure requires treatment. Some only need to have their eyes checked regularly. Your ophthalmologist will be able to advise what is right for you.
Glaucoma can be treated and loss of vision can be prevented. Although vision lost to glaucoma cannot be regained, further loss can be stopped. Talk to your doctor about having regular eye check-ups to detect small problems before they become big ones