Validating Rules for Defining No Improvement of Visual Acuity in Childhood Amblyopia

PURPOSE. When treating amblyopia, it is important to define when visual acuity (VA) is no longer improving (i.e., stable) because treatment decisions may be altered based on this determination. METHODS. Simulated observed VAs, incorporating measurement error, were compared with simulated true VAs to determine false-positive and false-negative rates for stable VA for six rules (using single VA or test/retest measurements, with or without averaging, over two or three visits). Four HOTV VA profiles were modeled: stable or improving VA over time with each of patching and spectacles. RESULTS. Across six rules and two treatments, when true VA was stable, false-negative rates for stability ranged from 26% to 67%; when true VA was improving, false-positive rates for stability ranged from 0% to 38%. Single VA measurements at consecutive visits had a false-negative rate of 30% with patching and 29% with spectacles, a false-positive rate of 38% with patching and 35% with spectacles. Averaging two VA tests at each visit slightly increased the false-negative rate (35% with patching and 36% with spectacles), while reducing the false-positive rate (22% with patching and 21% with spectacles). CONCLUSIONS. Comparing false-negative and false-positive rates for stability across rules allows selection of the most appropriate rule for clinical practice or research. When considering less desirable treatments, a rule with a lower false-negative rate is preferable, whereas a rule with a lower false-positive rate would be preferred when it is important to correctly classify improving VA.