Testability and test–retest reliability of SpotChecks Contrast Sensitivity Test in children with unilateral amblyopia

Purpose To report testability and test–retest reliability of the SpotChecks contrast sensitivity (CS) test in amblyopic and nonamblyopic eyes of children with unilateral amblyopia. Methods Children aged 3–12 years with unilateral amblyopia due to strabismus and/or anisometropia were recruited as part of a randomized trial. SpotChecks was administered twice in the left eye at 8 weeks post‐randomization. This single‐use paper test has a measurable CS threshold range of 0.90 to 2.09 logCS (24 lines, 1 line = 0.05 logCS). Testability was defined as the completion of a pre‐test. Bland–Altman analysis was used to evaluate test–retest reliability. Results In children aged 3–6 years, 81% (117/145) passed the pre‐test: 17 of 34 (50%) 3‐year‐olds, 39 of 46 (85%) 4‐year‐olds, 33 of 37 (89%) 5‐year‐olds, and 28 of 28 (100%) 6‐year‐olds. Fifty‐four of 117 (46%) who passed the pre‐test had matching test pairs for analysis. In children aged 7–12 years, all 45 passed the pre‐test. Twenty‐two of 45 (49%) who passed the pre‐test had matching test pairs for analysis. Among 76 test–retest pairs (40 amblyopic and 36 nonamblyopic eyes), the mean difference (95% CI) was 0.01 (−0.02 to 0.03) logCS and the half‐width of the 95% limits of agreement was ±0.20 (0.16–0.24) logCS. Results were similar between amblyopic and nonamblyopic eyes, as well as within age cohorts. Conclusions Children aged 6–12 years were more likely to be testable. Regardless of age, half of all test–retest pairs were completed incorrectly, possibly due to examiner or participant‐related factors. A greater than 4‐line (0.20 logCS) change on the SpotChecks contrast sensitivity test is required to detect a change in contrast sensitivity function beyond measurement error in children 3–12 years of age with unilateral amblyopia. Trial Registration Clinicaltrials.Gov, registered 14 July 2022, NCT05462821.