Thousands of Americans have been blinded by glaucoma, a disease that comes on gradually, without warning, and may affect anyone over the age of 40. But it can be detected by a simple check.
Blindness comes on slowly, without warning, without any obvious symptoms, often until it is too late. When visual loss has taken place, there is no medicine or operation that will correct the damage.
Between one and two percent of people over the age of 40 already have glaucoma, whether they are aware of it or not – and many are totally ignorant of what is going on inside their eyes.
But fortunately, simple tests are available which can quickly give an indication if the disease is probable. For this reason, everyone 40 and over should regularly have an eye-check known as tonometry carried out.
Screening centers routinely include this in their general examination. Many family doctors and all eye specialists perform the test which is simple, painless, and accurate.
If every patient was checked for glaucoma when he visited his physician, say on an annual basis, then the risks to the community in general would be markedly reduced.
Dr. Daniel Vaughan, associate professor of ophthalmology at the University School of Medicine in San Francisco, told doctors recently:
All physicians should participate in the diagnosis of glaucoma by making tonometry and ophthalmoscopy a part of the routine physical examination of all patients old enough to co-operate. It should be done routinely, and all doubtful cases referred to an ophthalmologist for confirmation and management.
There are two main kinds of glaucoma. Open-angle glaucoma is the most common and accounts for 90 percent of cases. Acute or angle-closure glaucoma accounts for only five percent, and is much more dramatic and often presents itself as ar immediate emergency with startling symptoms that demand urgent attention.
The open-angle type is chronic and may smolder on for many years. It affects both eyes and progresses insidiously. There are often no subjective early symptoms the patient is aware of, and by the time he notices them, it is often too late for treatment to be effective.
The basic lesion in glaucoma is a gradual build-up in the pressure of fluid in the front part of the eye, in the area between the cornea (the transparent window of the eve), and the lens which sits close behind it.
The Iris (the colored part of the eye) separates this compartment into an anterior chamber (front) and a posterior chamber (rear). In the center of the iris is the pupil, through which light passes, traversing the lens which is directly behind it, and through another fluid-filled compartment called the vitreous, and finally on to the light-sensitive sheet at the back of the eye, called the retina.
At the base of the iris, and completely encircling it, is the ciliary body. This has several functions. It enables the iris to expand or contract, according to the amount of light coming to the eye. This makes the pupil smaller or larger, in a similar way that the light entering a camera can be varied by stopping its iris up or down.
Another function of the ciliary body is the production of the fluid called aqueous which actively circulates in the front part of the eye, then toward the periphery of the eye, to be collected by tiny tubes.
If the production of fluid is excessive, or if the collecting tubes are detective (from whatever reason, and commonly age plays a part), pressure builds up in this part of the eye.
Gradually, this pressure is exerted on the back part of the eye. The light-sensitive retina is very susceptible to constant pressure increases. Little by little, its effectiveness becomes impaired, and gradually it ceases to function. Peripheral vision is the first to suffer. With sustained pressure, this increases until large areas of the retina no longer have their normal power, and the eye begins to go blind.
It might be years before a patient becomes aware of the disability. Suddenly he might notice that side vision has gone. He might be involved in an accident by not seeing a car coming from a side street.
Treatment, once a diagnosis is made, is usually effective. It involves the regular use of eye drops called miotics. This facilitates the outflow of aqueous by increasing the efficiency of the outflow channels. It is not known exactly how this happens.
Many drugs are used, and each specialist has his own choice. Pilocarpine placed in each eye five times a day is popular. Physostigmine may also be used, sometimes in combination with Pilocarpine. Adrenaline drops are popular again, and these seem to reduce the production of aqueous by the ciliary body.
Oral medication is also used if drops do not adequately control the pressure. A family of drugs called carbonic anhydrase inhibitors is often used. It seems these may reduce aqueous production by 40 – 60 percent. Although there is a risk of these producing kidney stones, many consider this risk worthwhile, particularly if it can obviate eye surgery, which is the only alternative if medical measures fail.
The less common but more dramatic form of glaucoma is the acute or angle-closure form. Here, the anterior chamber angle is suddenly blocked, preventing aqueous from escaping. The build-up of pressure is sudden. Severe pain and sudden visual loss are the two dramatic symptoms.
Medical attention is often instituted promptly and heavily in an effort to reduce pressure as an urgent prelude to surgery. An operation called peripheral iridectomy is carried out, and this is often successful.