Parents need not wait until their children start kindergarten to have their eyes tested for vision problems.

Children under the age of 5 should undergo screening so that any signs of amblyopia (lazy eye), strabismus (crossed eyes) or other visual impairment can be detected and possibly corrected, according to the U.S. Preventive Services Task Force.

The panel advises doctors to incorporate vision screening into each well child care exam or check-up. Their new recommendation statement is published in the Annals of Family Medicine.

Up to 10 percent of all preschoolers have some type of visual impairment caused by refractive error (nearsightedness or farsightedness), lazy eye, crossed eyes or astigmatism.

If left uncorrected, researchers say, a condition such as amblyopia may affect a child’s performance in school, learning ability and later self image. Amblyopia may also increase his or her future risk of total blindness.

Yet signs of amblyopia and other vision problems are often “very subtle,” task force chair Dr. Ned Calonge, chief medical officer of the Colorado Department of Public Health and Environment told Reuters Health.

“Parents of young children may not…notice any concerns,” he said. If vision screening is not included in regular check-ups, parents “may not be able to detect these things,” - although Calonge suspects many doctors do already test their patient’s sight.

While Calonge and the other task force members did not find any evidence to show that regular screening leads to better vision in preschoolers, they found some evidence that intense screening may indeed do the job.

In a United Kingdom-based study, infants and toddlers who underwent vision screening six times between 8 and 37 months had less amblyopia and better vision than those who were screened only once, at 37 months. Youngsters who did not pass a vision screening test were referred to a hospital for further testing and treatment.

The task force also found sufficient evidence that early treatment of crossed eyes, cataracts and other factors that interfere with normal vision may prevent lazy eye. Further, several studies have shown that up to 95 percent of people with lazy eye have better vision after treatment.

As for which screening test should be used, the task force recommends that doctors take the child’s age into consideration. Specially trained individuals may be able to use automated techniques to conduct vision tests in children under age 3, for example, since that age group is more challenging to assess than the more verbal and cooperative older children.

Instead of reading letters from an eye chart, these youngsters can undergo photoscreening, which involves photography of the pupil to diagnose any vision problems, or a light reflex test in which doctors look for crossed eyes by observing the light’s reflection on the cornea, to make sure it reflects in the same place in the child’s left and right eye.

To detect lazy eye, doctors can perform a cover test, using one of their hands to cover a child’s eye and then taking the hand away. That way they can see if and when the lazy eye realigns itself to focus on the same object as the other eye. This particular test can be performed as soon as an infant develops the ability to focus on an object, Calonge said.

Although the task force did not find any studies indicating that vision screening leads to permanent harm, they warn that potential harms may include the labeling of a child as vision impaired. Also, it may entail extra costs incurred by further screenings.

Still, they conclude, “the benefits of screening are likely to outweigh any potential harms.”

The U.S. Preventive Services Task Force is sponsored by the U.S. Department of Health and Human Service’s (HHS) Agency for Healthcare Research and Quality.

SOURCE: Annals of Family Medicine, May/June 2004.