Near-sightedness, also called "myopia," is one of the most common medical problems, and affects almost one in three American kids. Most parents rely on routine school-based eye exams to pick up the problem. And because many pediatricians don't focus on the eyes (just like teeth, that body part is neglected during their training), parents often get left in the dark about healthy vision habits. These five critical lessons should help shed some light on the issue.

Take this unexpected scenario: In Tennessee, local Lions Clubs volunteers helped screen over 100,000 preschool children for eye problems from 1997 to 2003 at health fairs. If the child failed the simple screening test, he or she was referred to an eye doctor for a professional eye exam. Now, you'd think the experts could tell which kids who failed really had problems, and prescribe glasses only to kids who really needed them. But here's the catch: Almost 25 percent of kids who ultimately had no eye problems were still given glasses along the way.

What was going on? As described in a 2004 research article from Vanderbilt University, it turns out that almost one in three preschoolers who then saw an optometrist got glasses, while only one in fifty seeing a pediatric ophthalmologist did. Thus, it seemed very likely that optometrists had a strong tendency to over-prescribe glasses to young children.

The first critical lesson for parents: Before fitting a very young child—like a preschooler—for glasses, make sure a medical doctor is involved.

Now suppose your child sees the right professional and gets glasses appropriately. Some parents worry that using glasses, like a crutch, makes the body lazier and weaker. Thus, they encourage their kids to wear glasses "only when they need them"— for example, to see the blackboard.

Unfortunately, this seemingly reasonable practice actually worsens myopia. A few years ago, researchers made 47 Malaysian grade-school children wear glasses that fully corrected their vision, while another 47 wore glasses that weren't full strength. The science was clear: after two years, though both groups worsened, kids who were fully corrected had about 33 percent better uncorrected eyesight (for savvy parents out there: the difference was one-quarter diopter).

Second lesson: If properly prescribed, glasses should be worn regularly.

Once kids get glasses, the sad truth is that myopia almost invariably gets worse year after year, before finally stabilizing in the late teen years. People have tried all kinds of schemes to slow the progression, including herbal remedies and eye movement exercises. Many doctors believed that wearing hard contacts might "re-mold" kids's eyes. But in 2004, a major clinical trial concluded that using rigid gas permeable contact lenses failed to stop myopia progression. Using bifocal glasses to stop the progression in children also didn't have much impact, based on the 2003 COMET trial of the practice (they did help a little). The overall results were disappointing; it was hoped these therapies would be better.

But there is also good news, involving eye drops called atropine. In 2006, researchers in Singapore (where myopia is epidemic— 80 percent of young people wear glasses or contacts) published a fascinating study. Taking almost 400 school-kids with myopia, they tested the nightly drops in one eye, and left the other eye alone. After two years, incredibly, the treated eyes had no progression, compared to the untreated eye. Though there are certainly some unknowns (for example, whether the benefit is permanent, a risk of allergies, and side-effects of having dilated eyes), the drops may suggest a promising way to prevent myopia progression.

Third lesson: If you want to stop myopia progression, ask your eye doctor about the research involving atropine drops and get your doctor's opinion on them.

Parents may also wonder how to prevent myopia in the first place. It's not clear why some kids get it, thought some studies link it to prolonged exposure to sunlight (and summer births) and "near-work" like reading. (For example, myopia worsens in 90 percent of University of Pennsylvania law students.) An intriguing 1999 study in the publication Nature found that having a room or night light on chronically in children less than 2 years of age roughly quadrupled the probability of later myopia. To be sure, the science is still unclear on this finding.

Fourth lesson: Try to have your infant or young child sleep in a room without artificial light, and encourage breaks during periods of near-work.

In the end, of course, myopia is easily treated, since needing glasses or contact lenses isn't the worst thing in the world. And with the advent of laser-assisted eye surgery like LASIK, the problem can be cured once children are grown. Though high myopia, even when treated, carries a slightly higher risk of glaucoma and retinal injuries, these complications are uncommon in most people. So, while lessons one through four above are important, don't forget the fifth and final lesson.

Fifth lesson: Remember that even if your child gets myopia, he or she will probably lead a healthy life.

The opinions expressed in this article are those of the author and do not necessarily reflect the opinions of iVillage.

Dr. Darshak Sanghavi is assistant professor of pediatrics at the University of Massachusetts Medical School and the author of A Map of the Child: A Pediatrician's Tour of the Body. His Web site is DarshakSanghavi.com