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

To report testability and test-retest reliability of the SpotChecks contrast sensitivity (CS) test in amblyopic and nonamblyopic eyes of children with unilateral amblyopia.

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.

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.

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.

Clinicaltrials.Gov, registered 14 July 2022, NCT05462821.