Smartphone Application: Repeatability and Validity in Estimating Manifest Strabismus on Children and Adolescents.

Abstract

Purpose : We performed a prospective clinical study to compare the test-retest reliability of the newly developed strabismus application (App) in estimating horizontal strabismus magnitude and compare measurements to the clinical standard of eye alignment measure the unilateral prism cover test (PCT).

Methods : Data was collected from 35 patients (20 females, mean 10.51 ± 3.18 years) with manifest horizontal strabismus estimated by unilateral PCT (20 esotropes and 15 exotropes) and 32 control subjects (18 females, mean 9.15 ± 2.64 years) with no manifest horizontal deviation (0 to 3 exophoria) by alternate PCT. At least two good captures with the strabismus App were needed to be included for analysis. The mean strabismus measurement from the App and unilateral PCT was compared using paired t-test. Test-retest reliability was assessed using Bland-Altman plots and 95% limits of agreement (LOA) for the strabismus App and for strabismus App scores to unilateral PCT. Pearson correlation and regression analyses were also used to compare App measure and PCT.

Results : Failure of the App to capture data was noted in 3 strabismus and 2 control subjects. For controls the mean difference between the App and PCT was 1.4 prism diopters (Δ) (95% LOA: 3.4 to -1.3Δ). The mean strabismus measures was significantly less (P<0.001, 95% CI:-4.94 to -1.38Δ) in the App (mean = 20.90Δ ±10.38) compared to PCT (mean = 24.06Δ±11.55). Strabismus App showed strong test-retest reliability (correlation coefficient: 0.987; 95%CI: 0.97-0.99); mean difference was 2.18Δ±5.0; 95% LOA for test-retest reliability was –7.6 to 11.98Δ. Strabismus App strongly correlated with PCT (correlation coefficient: 0.987; 95%CI: 0.97 -0.99); mean difference was -3.02Δ±5.0; 95% LOA was –12.81 to 6.79Δ. App measurements were on average lower than the PCT (slope=0.86, intercept = -0.8, R²= 0.97, p<0.001) with root mean squared error of 4.4Δ diopters.

Conclusions : The smartphone strabismus app is a repeatable test, providing results that are comparable though not an exact match with the clinical standard of eye alignment measure the PCT. However the results show potential as a reliable test for screening.

This is a 2020 ARVO Annual Meeting abstract.