Repeatability of SpotChecks contrast sensitivity test in macular disease

SpotChecks is an accessible contrast sensitivity test with good repeatability in healthy adults. This study compared its intra-visit repeatability with the near Pelli-Robson test in adults with macular disease.

One eye from 29 adults with macular disease (mean age 71 ± 13 years) underwent high-contrast logMAR acuity and two repeated contrast sensitivity measurements with SpotChecks and Pelli-Robson during one visit. All testing was performed at 40 cm using habitual correction under 110 cd/m² luminance. SpotChecks was scored as the contrast sensitivity at the highest row with two or more errors. Pelli-Robson was scored as (0.05 × the number of correct letters -0.15). Repeatability was defined as 1.96 $\sqrt{2}S$ _w (S_w, within-subject standard deviation), and differences between tests and groups were compared using a bootstrap hypothesis test. Limits of agreement between SpotChecks and Pelli-Robson were assessed with Bland-Altman analysis. Results were compared with previously tested healthy adults.

Mean visual acuity was 0.15 ± 0.13 logMAR. Mean contrast sensitivity (logCS) was 1.51 ± 0.18 for SpotChecks, 1.49 ± 0.18 for Pelli-Robson. Repeatability was identical for SpotChecks and Pelli-Robson (0.17 logCS, p = 0.98) and comparable to normal values (SpotChecks: 0.19 logCS, p = 0.53; Pelli-Robson: 0.17 logCS, p = 0.87). Contrast sensitivity correlated with logMAR acuity (SpotChecks: r = -0.60; Pelli-Robson: r = -0.48; both p < 0.001). Limits of agreement between SpotChecks and Pelli-Robson were 0.03 ± 0.21 logCS. Abnormal contrast sensitivity (>2 SD below normal) was detected in 76% of eyes with SpotChecks and 66% with Pelli-Robson, exceeding 34% identified by logMAR acuity (p < 0.001 and p < 0.02, respectively).

In adults with macular disease and good to mildly reduced visual acuity, SpotChecks demonstrated intra-visit repeatability comparable to Pelli-Robson and healthy individuals. Receiver operating characteristic analysis showed comparable discriminative performance for SpotChecks and Pelli-Robson, both outperforming high-contrast logMAR acuity.