Accuracy and precision of a sphero‐cylindrical over‐refraction app for smartphones

Purpose To evaluate the accuracy and precision of a web‐based smartphone app designed to measure sphero‐cylindrical over‐refraction. Methods A total of 307 healthy young subjects (22.5 ± 3.4 years) underwent clinical subjective refraction. In addition to each subject's refractive correction, spherical and cylindrical errors from −1.50 to 0.00 D were randomly induced so that their sum did not exceed −2.50 D, thereby generating a clinical over‐refraction. Seven different IOS and Android‐based smartphones were used. A new app showing tripole rescaling stimuli in blue or red light was used. Each subject used one smartphone to measure their induced over‐refraction subjectively, obtaining an app over‐refraction finding. Differences between the app and clinical over‐refraction were analysed across 675 values. Results The mean difference between the app and clinical over‐refraction in terms of power vector components ± limits of agreement was 0.17 ± 0.84 D for M ( p < 0.0001), 0.01 ± 0.42 D ( p = 0.28) for J 0 and −0.01 ± 0.32 D ( p = 0.33) for J 45 . The corresponding values for sphere and cylinder were 0.16 ± 0.80 D ( p < 0.0001) and 0.01 ± 0.85 D ( p = 0.40), respectively. The sphere and cylinder measurements obtained by the app differed from the expected values by no more than 0.50 D in 85% of cases. Conclusions The accuracy and precision of the over‐refraction obtained by the app was slightly lower than standard clinical subjective refraction in terms of inter‐examiner repeatability and comparable to measurements obtained using objective methods. The app shows the potential to perform sphero‐cylindrical over‐refractions reliably.