COLUMBUS, Ohio -- Young children with vision problems can be quickly and accurately identified with a simple, inexpensive screening test, according to a recent study.

In experiments at Ohio State University's College of Optometry, scientists found that 3-year-old children can complete a simple test measuring their stereoacuity -- a type of depth perception.

Further, the scientists found that this stereoacuity test is a better vision screening tool than standard tests of visual clarity and refractive error. (Refractive error is a measure of nearsightedness, farsightedness and astigmatism.)

"The stereoacuity test shows excellent potential as a single vision screening method that effectively identifies children needing further visual attention," said Paulette P. Schmidt, associate professor of optometry and physiological optics at Ohio State and author of the study.

The vision screening methods most commonly used today are based on measurements of visual clarity, Schmidt said. But these screening tests often fail to pick up unusual vision problems.

Today, as a result of faulty screening, nearly three out of every four childhood cases of amblyopia -- also called "lazy eye" -- go undetected, Schmidt said.

Another widely used vision screening test is the Modified Clinic Technique (MCT), Schmidt said. The MCT includes measures of visual clarity, refractive error, eye coordination and eye health and is 95 percent accurate in identifying people with vision problems. But Schmidt says it has disadvantages.

"The MCT is time-consuming and takes a high degree of professional skill to administer," she said. "Lay volunteers don't have the expertise to do it."

Some vision researchers are developing a high-tech vision screening test for children called photoretinoscopy. But the equipment necessary to administer this test costs from $2,500 to $20,000, Schmidt said.

The stereoacuity screening test has none of these disadvantages, Schmidt said.

"The stereoacuity test is short, which is important in testing children," she said. "It's simple, it can be administered by lay people and it's inexpensive. The whole test package costs about $100. And it's accurate."

Schmidt's study, which was published in the journal Optometry and Vision Science, included 30 children about 3 years of age who were at high risk of developing vision problems. Before being tested, each child played with a pair of "sunglasses" and a toy letter E. For the stereoacuity test, a first-year optometry student gave the child Polarized glasses to wear and presented two cards. When viewed through Polarized glasses, one card had a three-dimensional E; the other did not. The researcher asked the child to point to the card that had a three-dimensional E "popping out."

This test was repeated four times at a distance of 1.5 meters. After this testing session, an optometrist came into the room and repeated the test. Each child then received a comprehensive vision exam, which also included individual tests of visual clarity and refractive error.

The results:

_ Almost 87 percent of the children completed the stereoacuity screening test in both sessions. "This shows that a test of stereoacuity can be done effectively with 3-year-old children," Schmidt said.

_ Overall, the stereoacuity screening test was superior to tests of visual clarity and refractive error in correctly identifying those children with vision problems -- and those without. Also, the stereoacuity test showed the highest level of agreement with the results of the vision exam. "Stereoacuity was the single most effective screening procedure," Schmidt said.

_ The first-year optometry student and optometrist agreed in their screening evaluations of the children 73 percent of the time. "This shows that even people with little training can correctly administer this screening test," Schmidt said.

Schmidt hopes the stereoacuity screening test will ultimately lead to earlier identification of children with vision problems.

"In children, there are critical periods of vision development," she said. "For example, vision develops very rapidly over the first three or four years of a child's life. During this period, the cells in the visual cortex (the seeing brain) respond only when both eyes process the same bit of information. When a child goes through this period with 'lazy eye' or 'turned eye', these cells are not activated. These cells may cease to function and the child may never be able to regain the function in them."

"It's so important to identify children with vision problems or potential vision problems while they're still in that critical three- to four-year period," she said. "If we can identify them then, vision can still be corrected."

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Contact: Paulette P. Schmidt, (614) 292-1113

Written by Kelly Kershner, (614) 292-8308