Heidi D. Nelson, M.D., M.P.H.; Peggy Nygren, M.A.; Laurie Huffman, M.S.; David Wheeler, M.D.; Andrew Hamilton, M.S.; Steven Teutsch, M.D., M.P.H.; Jonathan Klein, M.D., M.P.H.
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In 2001, the U.S. Preventive Services Task Force (USPSTF) developed draft recommendations on screening for visual impairment in children younger than age 5 years, drawing on systematic reviews of the evidence trials and well-conducted observational studies. The evidence pertaining to this topic was originally summarized for the USPSTF in a manuscript covering publications on screening for visual impairment through the end of 1999.1 To help the USPSTF finalize their draft recommendations, the literature review was updated through June 2003, focusing on the randomized controlled trial (RCT) evidence that served as the basis for the draft recommendations.
This update of the evidence, written in 2003, focuses on the question of whether screening for amblyopia and associated conditions in children younger than age 5 years leads to better vision outcomes. This question has been added to the analytic framework from the original evidence review (Figure 1, 14 KB).1 The other key questions in the original evidence review were not systematically reviewed for this update. However, new RCTs that address treatment effectiveness and performance of screening tests in the context of a screening program are cited here, since there is now more evidence of their effectiveness than was available in 2001. Only RCTs were systematically reviewed for this brief update.
References suggested by experts or professional organizations following the review of the 2001 report were reviewed for inclusion. In addition, the research team used the search strategies from the 2001 report, and developed appropriate update search strategies for MEDLINE® (1999-June 2003) and the Cochrane systematic review and RCT registry databases (1999-June 2003) (Appendix).
Captured titles and/or abstracts were downloaded and imported into the EndNote® program to create a vision screening update library. Titles and/or abstracts were reviewed using specific inclusion and exclusion criteria (Appendix). Full text papers were retrieved for RCTs of screening for amblyopia that included children aged 5 years and younger, and included a followup assessment with appropriate vision outcomes. Studies were excluded if they were not RCTs, did not include children aged 5 years or younger, or included only high-risk populations (i.e., those with low birth weight). Eligibility criteria were reapplied to the full-text articles.
Information on the number and characteristics of participants, definition of amblyopia, screening tools and screening intervals, interventions, and results was abstracted from included studies.
Criteria developed by the USPSTF were used to rate study quality (Appendix). Information on randomization, maintenance of comparable groups, attrition, and analysis was dually reviewed by research team members. Disagreements on quality ratings were discussed until consensus was reached. Studies rated as being of "good" or "fair" quality are mentioned in this update of the evidence.
Two hundred and fifty-four abstracts and titles were identified; 42 full-text articles were retrieved for additional review: 10 from suggestions of experts and professional organizations, 28 from the MEDLINE® search, and 4 from the Cochrane searches. Of these papers, 2 fair-quality studies (1 trial, 2 publications) met inclusion criteria for screening for amblyopia in preschool children (Table 1). Although not the focus of this review, 6 additional studies assessed the sensitivity and specificity of preschool screening tools, and 3 compared treatment interventions for preschool amblyopia (RCT described in Table 2). Quality ratings for the studies described in this update of the evidence are in Table 3.
A recently published, nested RCT of screening was rated as being of fair quality by USPSTF criteria. From the Avon Longitudinal Study of Parents and Children (ALSPAC) based in southwest England, 3,490 children born during the last 6 months of the cohort study were randomized into an intensive, visual-screening group or control group.2 Children in the intensive group were invited to participate in screenings at a research clinic at 8, 12, 18, 25, 31, and 37 months of age. During the screenings, an orthopist conducted an examination and a battery of tests appropriate to the age of the child. Children in the control group were offered similar testing by an orthopist at age 37 months only. All children received the usual recommended surveillance by their general practitioners and health visitors and were offered screening for reduced visual acuity by a school nurse at school entry (aged 4-5 years). Any child failing an acuity test or cover test was referred to the hospital eye service. All children were invited to a final vision assessment at age 7.5 years. Amblyopia was defined in 2 different ways (Table 1).
Amblyopia at age 7.5 years was less prevalent in the intensive screening group than in the control group (Amblyopia A: 1.45% vs 2.66%, P = 0.06; Amblyopia B: 0.63% vs 1.81%, P = 0.02). The cumulative incidence of amblyopia in each group was similar. Residual amblyopia was more likely in the control group (despite treatment) than in the intensive group. Mean visual acuities in the worse-seeing eye were better for children in the intensive group who had been treated for amblyopia than for treated children in the control group (0.15 vs 0.26 LogMAR units, P < 0.001). A higher proportion of children who were treated for amblyopia had been seen in the eye clinic before the age of 3 years in the intensive group than in the control group (48% vs 13%, P = 0.0002).
Earlier data from the ALSPAC study,3 rated to be of fair quality, evaluated the number of children from each group confirmed to have strabismus or amblyopia before the age of 37 months. Sensitivities of individual tests within the intervention program were also evaluated. The intensive screening group detected more children with amblyopia than the control group (1.6% vs 0.5%, P < 0.01). Screening in the intensive group was more specific than in the control group (4.5% false-positive results vs 7.5%, P < 0.01). The cover test and visual acuity test were always more than 99-percent specific, but had poor sensitivity until age 37 months. Before age 37 months, photorefraction was found to be more sensitive than acuity testing. The cover test, with either photorefraction or acuity testing at 37 months, provided the best sensitivity and specificity (82%-84% sensitivity; 97%-98% specificity; 63%-73% positive predictive value [PPV]; 99% negative predictive value [NPV]).
The Amblyopia Treatment Study (ATS), rated to be of good quality, is an RCT that evaluated patching versus atropine treatment in 409 children aged 3 to 7 years with moderate amblyopia.4 Children were recruited from community- and university-based practices throughout North America. Visual acuity testing was conducted using an ATS protocol administered by a study-certified tester. Seven days later, children were randomly assigned to patching or atropine treatment. Patching treatment included wearing a patch for 6 hours a day. Atropine treatment used atropine sulfate 1 percent, 1 drop per day. Adjustments in treatment were made based on patient responses and study criteria. followup visits occurred at 5, 16, and 26 weeks (primary outcome).
In both the patching and the atropine group, visual acuity in the amblyopic eye significantly improved from baseline to 6 months. In the patching group, the mean change in visual acuity was 3.16 lines (95% confidence interval [CI], 2.95-3.37). In the atropine group, the mean change in visual acuity was 2.84 lines (95% CI, 2.61-3.07). The mean treatment group difference in 6-month logMAR acuity was 0.034 (95% CI, 0.005-0.064). Seventy nine percent of the patching group and 74 percent of the atropine group met the criteria for treatment success (95% CI for differences in percentages, -4% to 13%).
At 6 months, visual acuity in the sound eye was decreased from baseline by 1 line in 7 percent of the patching group and in 15 percent of the atropine group. Visual acuity was decreased by 2 or more lines in 1 percent of the patching group and in 9 percent of the atropine group (P < 0.001). Both treatments were well-tolerated. Atropine had a slightly higher degree of acceptability, as indicated by a parental questionnaire and better adherence than patching.
Important RCTs have been published about screening for amblyopia in children since the literature review represented in the 2001 summary of evidence considered by the USPSTF. These studies, summarized in Table 4, specifically fill evidence gaps outlined by the USPSTF.
1. Kemper A, Harris R, Lieu T, Homer C, Whitener BL. Screening for Visual Impairment in Children 0 to 5 Years. Systematic Evidence Review No. 27 (Prepared by the Research Triangle Institute-University of North Carolina Evidence-based Practice Center under Contract No. 290-97-0011). Rockville, MD: Agency for Healthcare Research and Quality. May 2004. (Available at: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hstat3.chapter.33443).
2. Williams C, Northstone K, Harrad RA, Sparrow JM, Harvey I; ALSPAC Study Team. Amblyopia treatment outcomes after screening before or at age 3 years: follow up from randomised trial. BMJ 2002;324(7353):1549.
3. Williams C, Harrad RA, Harvey I, Sparrow JM; ALSPAC Study Team. Screening for amblyopia in preschool children: results of a population-based, randomised controlled trial. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood. Ophthalmic Epidemiol 2001;8(5):279-95.
4. Pediatric Eye Disease Investigator Group. A randomized trial of atropine versus patching for treatment of moderate amblyopia in children. Arch Ophthalmol 2002;120:268-78.
This update of the evidence and the updated recommendations of the USPSTF are available through the AHRQ Web site (http://www.preventiveservices.ahrq.gov) and through the National Guideline Clearinghouse™ (http://www.guideline.gov).
Disclaimer: The authors of this article are responsible for its contents, including any clinical or treatment recommendations. No statement in this article should be construed as an official position of the U.S. Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.
This document is in the public domain within the United States. For information on reprinting, contact Randie Siegel, Director, Division of Printing and Electronic Publishing, Agency for Healthcare Research and Quality, 540 Gaither Road, Rockville, MD 20850. Requests for linking or to incorporate content in electronic resources should be sent to: info@ahrq.gov.
Current as of May 2004
Internet Citation:
U.S. Preventive Services Task Force. Screening for Visual Impairment in Children Younger than Age 5 Years: Update of the Evidence. May 2004. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/3rduspstf/visionscr/vischup.htm
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