Background: Impaired visual acuity is common in preschool-aged children. Screening for impaired visual acuity in primary care settings could identify children with vision problems at a critical period of visual development and lead to interventions to improve vision, function, and quality of life.
Purpose: To assess the effects of screening for impaired visual acuity in primary care settings in preschool-aged (1 to 5 years) children.
Data Sources: We searched Ovid MEDLINE from 1950 to July 2009, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews through the third quarter of 2009. We supplemented electronic searches with reviews of reference lists of relevant articles and solicited additional citations from experts.
Study Selection: We selected randomized trials and controlled observational studies that directly evaluated screening for impaired visual acuity in preschool-aged children. To evaluate indirect evidence on screening, we also included studies on the diagnostic accuracy of screening tests for impaired visual acuity used in primary care settings, and randomized trials and controlled observational studies that reported clinical outcomes associated with treatments for impaired visual acuity due to refractive error, amblyopia, or amblyogenic risk factors (visual acuity, quality of life, functional capacity [including school performance], or adverse events).
Data Extraction: One investigator abstracted data and a second investigator checked data abstraction for accuracy. Two investigators independently assessed study quality using methods developed by the U.S. Preventive Services Task Force.
Data Synthesis: No randomized trial evaluated outcomes of preschool vision screening compared with no screening. One large, fair-quality randomized trial nested within a population-based cohort study found that repeat orthoptist screening from ages 8 to 37 months was associated with reduced likelihood of amblyopia at age 7.5 years compared with one-time orthoptist screening at age 37 months on one of two definitions of amblyopia. A large, prospective cohort study from this population found that one-time orthoptist screening at age 37 months was associated with no significant difference in risk for amblyopia at age 7.5 years compared with no screening. No study evaluated school performance or other functional outcomes.
No screening test was consistently associated with both high (>90 percent) sensitivity and specificity. In the largest study to directly compare the diagnostic accuracy of different screening tests, differences in likelihood ratio estimates and diagnostic odds ratios for 10 different screening tests were generally small, with the exception of the Random Dot E stereoacuity test, which was associated with a lower diagnostic odds ratio. Diagnostic accuracy of preschool vision tests did not clearly differ in children stratified by age, though testability was generally lower in children ages 1 to 3 years, with the potential exception of the MTI photoscreener.
Three fair- or good-quality trials of preschool-aged children with amblyopia or unilateral refractive error found that treatment (patching and/or eyeglasses) resulted in small (<1 line on the Snellen eye chart) improvements in visual acuity in the amblyopic or worse eye compared with no treatment after 5 weeks to 1 year of follow-up. One trial found larger benefits in the subgroup of children with worse baseline visual impairment. No trial evaluated effects of treatment on school performance or other measures of function. Evidence on whether age has an impact on effectiveness of treatment is mixed. Amblyopia treatments were associated with reversible visual acuity loss in the nonamblyogenic eye in some studies. Evidence on adverse psychosocial effects and effects of suboptimal compliance with amblyopia treatments is limited.
Limitations: We excluded nonEnglish-language studies, could not evaluate for publication bias because of the small numbers of trials, included studies of screening in community-based settings, and did not construct outcomes tables.
Conclusions: Direct evidence on effectiveness of preschool vision screening for improving visual acuity or other clinical outcomes remains limited and does not adequately address whether screening is more effective than no screening. In terms of indirect evidence, a number of screening tests appear to have utility for identification of preschool-aged children with vision problems, and treatments for amblyopia or unilateral refractive error (with or without amblyopia) are associated with mild improvements in visual acuity compared with no treatment. Additional studies are needed to better understand effects of screening compared with no screening, to clarify the risk for potential unintended harms from screening (such as use of unnecessary treatments), and to define the optimal time at which to initiate screening during the preschool years.