On a visit to my ophthalmologist for what I thought would be a routine eye examination, he took the pressure in my eyes, sat back and said, “The pressure is 22 in both your eyes. Last year at this time it was 11. We’ll have to watch this. You may be developing glaucoma.”

I had just become what the medical profession calls a “glaucoma suspect.”

Glaucoma refers to a group of diseases that can produce blindness. It damages the optic nerve, leading to progressive, irreversible vision loss. Glaucoma affects one in 200 persons aged 50 and older, and one in ten over the age of 80. People with glaucoma may or may not have an elevated intraocular pressure (IOP), that is, too much pressure inside their eyeballs, which is what my doctor had just discovered in me.

Glaucoma usually, but not always, begins with increased IOP. Many things can cause it, but the bottom line is always the same. The abnormal pressure pinches the optic nerve. Like blinders on a horse, the stress first affects peripheral vision. Little by little it reduces the field of vision until, finally, all sight is destroyed. Glaucoma is treatable but no cure exists. It can lead to a great deal of vision loss before it is diagnosed. Any routine eye examination should include eye pressure tests, which is a simple procedure. Normal readings range from 10 to 21.

The most common form of the disease is open angle glaucoma. Normally the front part of our eyes, the space between the cornea and the lens, is filled with a fluid, the aqueous humor. The aqueous humor is produced in the eye and drains out to maintain a constant pressure. Sometimes, for reasons that are not well understood, it does not drain out properly. This increases pressure inside the eye, damaging the optic nerve. In some people the first sign of open angle glaucoma is not increased pressure inside the eyeball but an enlarged cup-disc ratio. This refers to changes at the back of the eye where the optic nerve leaves the eyeball.

Closed angle glaucoma occurs when the iris, the colored part of the eye, and the lens block the movement of fluid inside the eye. Normal eyes have a system of tiny canals, called the trabecular meshwork, located between the cornea and the iris. Excess fluid drains out through these little canals, re-entering the bloodstream through another tiny channel called Schlemm’s canal. For various reasons the iris, located directly in front of the lens, may fall forward, blocking “the angle,” as the drainage system is called. Hence the name, “closed angle,” or “narrow angle” glaucoma. The effect is the same as in open angle glaucoma—pressure builds up causing damage to the optic nerve. Untreated, severe vision loss and even blindness can occur from either form of the disease. Closed angle glaucoma can be an emergency situation if the blockage causes a sudden increase in pressure with rapid damage to the optic nerve.

Sometimes a child is born with glaucoma, or it develops in the first few years of life. Such infantile glaucoma may be caused by a birth defect that developed because of an infection during the mother’s pregnancy, such as rubella. It may also be an inherited condition. Sometimes lost vision can be restored in cases of infant glaucoma. Congenital glaucoma, the kind present at birth, almost always requires surgery to repair the defect.

Secondary glaucoma is increased intraocular pressure as a result of some other condition. It may develop after an eye injury, after eye surgery, from a tumor in the eye, or as a complication of diabetes. As we age, the lens in the eye becomes increasingly opaque, which signals cataract development. If it also thickens in this process, it may close the drainage angle, resulting in symptoms of glaucoma.

Glaucoma treatment is aimed at lowering pressure in the eyes. Treatment options include various medicines, laser treatments, and surgery. The medicines may be pills, eye drops, liquid taken by mouth, or, in emergencies, intravenously. In most cases, eye drops are tried first. Some of the medicines decrease the amount of fluid produced by the eye. Other medicines increase the amount of fluid that drains out of the eye. People with glaucoma will probably have to use the prescribed medicines for the rest of their lives. Surgery to restore drainage may become necessary if no combination of eye drops can be found that lowers eye pressure enough to prevent damage.

Your first line of defense against glaucoma is early detection. The older you are, the more necessary it is to see an eye specialist, perhaps as often as once a year. Insist that the doctor take the pressure in both of your eyes. If the number is elevated, further insist that close observation be started. Do not risk loss of vision through failure to keep your guard up against glaucoma. My ophthalmologist and I have been holding the fort with no vision loss for more than a decade now. May your outcome be as happy.