• PURPOSE: To compare two established visual acuity protocols: the Amblyopia Treatment Study HOTV (ATS HOTV) visual acuity protocol and the Electronic-Early Treatment of Diabetic Retinopathy Study (E-ETDRS) protocol, in children aged 5 to 12 years. • DESIGN: Prospective cohort study. • METHODS: Crowded HOTV optotypes and crowded ETDRS optotypes were presented to 236 consecutive children aged 5 to 12 years using an electronic visual acuity tester (Palm handheld, personal computer, and monitor). Twenty-three percent of the children were classified as amblyopic, 35% as having uncorrected refractive error, 36% as normal, and 6% as other. Visual acuity test results were converted to logarithm of minimal angle of resolution (logMAR) units for analysis. • RESULTS: In developmentally normal children (n = 230), testability was 100% for HOTV in 5- to 12-year-olds and 100% for E-ETDRS in 7- to 12-year-olds. The E-ETDRS testing could be completed in 52% of 5-year-olds and in 87% of 6-year-olds. Visual acuity performance was better when measured by HOTV compared with E-ETDRS (median difference 0.06 logMAR [three letters on a chart with five letters/line], P = .0001), and the difference was found in normal eyes, eyes with refractive error, and amblyopic eyes. • CONCLUSIONS: The ATS HOTV protocol yields slightly better visual acuity performance compared with E-ETDRS in 5- to 12-year-olds, but on average by less than a logMAR level. This systematic difference is important when a physician changes testing modality as a child matures and should be considered when interpreting the results of recent and ongoing clinical trials in amblyopia.
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