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Vision Screening Programs Important in Early Detection of Amblyopia By Dr. Paulette Schmidt Vision disorders are the most frequently occurring handicapping conditions in childhood in the United States. How is this possible? First, children do not know how they should see, so they do not tell us that they cannot see. Second, vision problems usually do not hurt. Third, it is not possible to identify vision problems simply by looking at a child. Amblyopia is an important cause of visual impairment; it originates in childhood and, if undetected and untreated, prevents a child’s full visual development. Amblyopia can result in permanent vision loss. Further, before amblyopia treatment can begin, children with or at risk for amblyopia must be detected. Amblyopia occurs in as many as one in 20 children. An estimated 75,000 to 200,000 three-year-old children in the United States have amblyopia. Children with amblyopia are at 16 times the risk for blindness in their good eye in comparison to children with normal vision. Amblyopia poses a significant public health problem in the United States. The Healthy People 2010 Program, a federal program designed to improve health care of children, targets an increased participation of preschool-age children in vision screening programs to detect amblyopia early when treatment is most effective. In Scandinavia, as the result of vision screening programs in which all preschool-age children have their vision tested, the occurrence of amblyopia has been reduced by 90 percent. Vision screening tests are not diagnostic and are not a substitute for comprehensive eye examinations. However, with accepted treatment for amblyopia established, amblyopia meets the inclusion criteria for detection in public health screening programs. In the absence of comprehensive eye examinations for all children, amblyopia is targeted for early detection through vision screening programs. Vision screening is a quick, simple public health strategy to detect children with or at risk for eye disorders. Vision screening does not provide a diagnosis or treatment; vision screening identifies those with or at risk for a vision disorder. Vision screening is typically conducted by a nurse or trained layperson. With an increased emphasis on screening for amblyopia among preschool-age children, use of effective vision screening tests is essential. Uncorrected farsightedness (hyperopia) and/or astigmatism are both a type of refractive error. Uncorrected farsightedness (hyperopia) and/or astigmatism and eye misalignment (strabismus) are the most frequent causes of amblyopia. Further, eye misalignment is frequently caused by uncorrected farsightedness (hyperopia). Therefore, screening for amblyopia must use tests known to be effective in detecting refractive error. The effectiveness of screening tests used to detect amblyopia was scientifically established by the VIP Study, funded by the National Eye Institute of the National Institutes of Health and conducted in five U.S. cities. Results reported by VIP included the best tests for use in preschool vision screening and which tests perform poorly; vision screenings conducted by trained lay people were found to be similar to those conducted by trained nurses and eye doctors when standardized training and testing procedures were used. Eleven vision screening tests were evaluated in the VIP Study: three tests of refractive error, three tests of visual acuity, three tests of eye alignment, and two photoscreeners (tests of refractive error plus eye alignment). Over 4,500 preschool-age children had their vision screened. Results varied tremendously in terms of the effectiveness of the tests for detecting amblyopia and risk factors for amblyopia (refractive error and eye misalignment). Further, vision screening tests that targeted detection of refractive error were found to be particularly effective in amblyopia detection among preschool-age children. Regardless of who performed the test, effective tests include the Retinomax Autorefractor and SureSight Vision Screener. Photoscreeners were found less accurate than the autorefractors in screening for refractive error. Amblyopia detection was especially effective when lay screeners used the Single crowded LEA Symbols Visual Acuity Screening Test at five feet. In summary, amblyopia is an important cause of visual impairment in childhood with continued impact in later life. Vision loss due to amblyopia is preventable. Detection of amblyopia is targeted through vision screening programs. As the result of the VIP Study, the most effective vision screening tests for use in detecting amblyopia in preschoolers have been scientifically established. Parents should ask whether amblyopia screening programs are available in their local communities. Parents should also check to see whether the most effective vision screening tests for amblyopia detections are being utilized. Further information about the VIP Study is available at http://optometry.osu.edu/research/vip or www.nei.nih.gov.
This web site is funded by The Ohio Department of Health, Bureau of Child and Family Health Services, Save Our Sight Program. |