Q. I suffer from a hiatal hernia and have been unable to find any information about this condition. What exactly is it? What causes it, and what can I do to relieve the pain and discomfort? Would you please discuss diet, medications and other treatments for this problem.

A. Hiatal hernia is the old name for what doctors now call reflux esophagitis, otherwise commonly known as heartburn. Physicians and patients have both had some misconceptions about what a hiatal hernia is, and to understand this condition properly takes knowing some anatomy.

Hiatal refers to an opening, and a hernia is an abnormal protrusion of a part of the body -- usually the intestines -- through some opening. In this case, the opening is in the diaphragm -- the muscle of breathing between your lungs and abdomen. The hernia involves the upper part of your stomach, normally tucked just under the diaphragm. In some people, this part of the stomach slips or "herniates" through the diaphragm, and lies partially above it, something that shows up on an x-ray of the stomach (an "upper GI").

Doctors used to think that this abnormal position of the stomach, by itself, led to symptoms of heartburn, caused by stomach acid flowing back up the esophagus, the lower end of the food tube that connects to the stomach. We've since learned that it's not the hiatal hernia itself causing the problem, it's the sphincter, or check-valve, at the junction of the lower esophagus and stomach that matters.

If this sphincter is working properly, stomach acid stays where it belongs; if not, the acid irritates and inflames the lower esophagus, causing esophagitis and the well-known symptoms of heartburn -- a burning pain that rises up the front of the chest and a sour taste in back of the mouth. Some people with this condition can have chest pain similar to that from angina or heart trouble.

So, rather than the diaphragm working as a barrier to "reflux," or backflow, of stomach acid, it's the esophageal sphincter that performs this task. In fact, many people have a hiatal hernia and no symptoms at all, while others have a stomach in a normal position -- but a poorly functioning sphincter -- and terrible heartburn.

To treat reflux esophagitis heartburn, you usually start by avoiding those things that impair

the proper functioning of the sphincter, causing it to open and let stomach acid flow back up the esophagus. Alcohol, smoking and certain foods, such as fatty foods and chocolate, are known to do this; if you find that other foods consistently give you heartburn, avoid those also. Contrary to popular belief, spicy foods don't seem to affect the sphincter and need not be avoided.

Other measures you can try before using medications include wearing loose clothing (to avoid pressure on the stomach), lose weight if overweight and -- for nighttime heartburn -- don't eat before bedtime and sleep with the bedposts at the head of the bed elevated on bricks. Avoid bending over at the waist if this brings on your heartburn.

Antacids work by neutralizing stomach acid; sucralfate (Carafate) forms a protective coating over inflamed tissues and speeds healing. A new class of drugs, which includes Tagamet and Zantec, works by stopping the production of acid by the stomach. These are usually used for severe cases of reflux. Another medication for resistant cases is Reglan, which works by increasing the muscle tone of the sphincter, making it close up. As a last resort for the few people with very severe symptoms not helped by medications, surgery can be done to keep stomach acid from flowing back up.

Q. My left eye has been twitching intermittently for the past couple of days. This has happened once before and went away by itself. What's causing this? Is there anything I can do to make it stop?

A. An occasional twitch in the eye, without other symptoms, is most likely a harmless, though annoying occurrence. Doctors aren't sure what causes this twitching, but something seems to temporarily irritate a nerve to the eye muscles. I don't know of any treatment to make it stop, but it should clear up by itself, as it did last time you had it.

Simple eye twitching, which many people experience from time to time, is much different from the rare but serious eye muscle disorder called blepharospasm (blepharo comes from the Greek word for eyelid). This affliction forces victims into spasms of eye shutting, sometimes contorting other face muscles as well.

Affecting about 50,000 Americans, blepharospasm seems to respond to a novel treatment, injection of the eyelid muscles with a tiny amount of the deadly botulinum toxin, the substance that causes botulism food poisoning. This treatment, invented by a San Francisco ophthalmologist, is currently awaiting federal approval.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington. Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered individually.