ngle-closure glaucoma affects nearly half a million people in the United States. In China and surrounding countries, it is more common than open-angle glaucoma. There is a tendency for this disease to be inherited. It is more common in hyperopes (far-sighted people).

In people with a tendency to angle-closure glaucoma, the anterior chamber is smaller than average. As mentioned earlier, the trabecular meshwork is situated in the angle formed where the cornea and the iris meet. In most people, this angle is about 45 degrees. The narrower the angle, the closer the iris is to the trabecular meshwork. As we age, the lens routinely grows larger. The ability of aqueous humor to pass between the iris and lens on its way to the anterior chamber becomes decreased, causing fluid pressure to build up behind the iris, further narrowing the angle. If the pressure becomes sufficiently high, the iris is forced against the trabecular meshwork, blocking drainage, similar to putting a stopper over the drain of a sink. When this space becomes completely blocked, an angle-closure glaucoma attack (acute glaucoma) results.

Acute angle-closure glaucoma

Unlike POAG, in which IOP increases slowly, in acute angle-closure, it increases suddenly. This sudden rise in pressure can occur within a matter of hours and become very painful. If the pressure rises high enough, the pain may become so intense that it can cause nausea and vomiting. The eye becomes red, the cornea swells and clouds, and the patient may see haloes around lights and experience blurred vision.

If the attack goes untreated, scarring of the trabecular meshwork may occur and result in permanent glaucoma, which is much more difficult to control. Cataracts may also develop. Damage to the optic nerve may occur quickly and cause permanently impaired vision.

Many of these sudden “attacks” occur in darkened rooms, such as movie theaters, which cause the pupil to dilate. Acute stress is another predisposing condition. When the pupil dilates, the contact between the lens and the iris is maximized. This further narrows the angle and may trigger an attack. A variety of drugs can also cause dilation of the pupil and lead to an attack of glaucoma. These include anti-depressants, cold medications, antihistamines, and some medications to treat nausea.

Acute glaucoma attacks are not always full blown. Sometimes a patient may have a series of minor attacks. A slight blurring of vision and haloes (rainbow-colored rings around lights) may be experienced, but without pain or redness. These attacks may end when the patient enters a well lit room or goes to sleep-two situations which naturally cause the pupil to constrict, thereby allowing the angle to open spontaneously.

An acute attack is an emergency condition. If the pressure is not relieved within a few hours, vision can be permanently lost. An acute attack may be stopped with a combination of drops which constrict the pupil, and drugs that help reduce aqueous production. When IOP has dropped to a safe level, laser iridotomy is the treatment of choice. This is an outpatient procedure in which a laser beam is used to make a small opening in the iris, allowing aqueous to pass directly from the posterior chamber to the anterior chamber. Since it is common for the other eye also to have a narrow angle, laser iridotomy on the unaffected eye is done as a preventative measure.

Routine examination using a technique called gonioscopy can predict one's chances of developing angle-closure. A special lens which contains a mirror is placed lightly on the front of the eye and the width of the angle examined visually. Patients with narrow angles can be warned of early symptoms, so that they can seek immediate treatment.

Chronic angle-closure glaucoma

Not all people with angle-closure experience an acute attack. Many develop what is called chronic angle-closure glaucoma (aka creeping angle-closure glaucoma). In this case, the iris gradually closes over the drain, causing no overt symptoms. When this occurs, scars slowly form between the iris and the drain and the IOP will not rise until there is a significant amount of scar tissue formed-enough to cover the drainage area. If the patient is treated with medication, such as pilocarpine, an acute attack may be prevented, but the chronic form of the disease may still develop.

© Leo D. Bores, MD, 1996 — 2002