Partially Open-Angle Glaucoma
Approximately one percent of all Americans have this form of glaucoma, making it the most common form of glaucoma in our country. It occurs mainly in the over 50 age group.
There are no symptoms associated with POAG. The pressure in the eye slowly rises and the cornea adapts without swelling. If the cornea were to swell, which is usually a signal that something is wrong, symptoms would be present. But as this is not the case, this disease often goes undetected. It is painless, and the patient often does not realize that he or she is slowly losing vision until the later stages of the disease. However, by the time the vision is impaired, the damage is irreversible.
In POAG, there is no visible abnormality of the trabecular meshwork. It is believed that something is wrong with the ability of the cells in the trabecular meshwork to carry out their normal function, or there may be fewer cells present, as a natural result of getting older. Some believe it is due to a structural defect of the eye´s drainage system. Others believe it is caused by an enzymatic problem. These theories, as well as others, are currently being studied and tested at numerous research centers across the country.
Glaucoma is really about the problems which occur as a result of increased IOP. The average IOP in a normal population is 14-16 millimeters of mercury (mmHg). In a normal population pressures up to 20 mmHg may be within normal range. A pressure of 22 is considered to be suspicious and possibly abnormal. However, not all patients with elevated IOP develop glaucoma-related eye damage. What causes one person to develop damage while another does not is a topic of active research.
As we mentioned earlier, this increased pressure can ultimately destroy the optic nerve cells. Once a sufficient number of nerve cells are destroyed, blind spots begin to form in the field of vision. These blind spots usually develop first in the peripheral field of vision, the outer sides of the field of vision. In the later stages, the central vision, which we experience as `seeing,´ is affected. Once visual loss occurs, it is irreversible because once the nerve cells are dead, nothing can restore them at the present time. Later on, we will talk about the many ways your eye doctor can detect glaucoma in its earliest stages — before any visual damage occurs.
POAG is a chronic disease. It may be hereditary. There is no cure for it at present, but the disease can be slowed or arrested by treatment. Since there are no symptoms, many patients find it difficult to understand why lifelong treatment with expensive drugs is necessary, especially when these drugs are often bothersome to take and have a variety of side effects.
Taking medications regularly, as prescribed, is crucial to preventing vision-threatening damage. That is why it is important for you to discuss these side effects with your doctor. The two of you need to act as a `team´ in the battle against glaucoma. Later on, we will discuss the medications commonly prescribed and their side effects.