Clinical Validation of a Novel Smartphone Application for Measuring Visual Acuity in Adults

Abstract

Purpose : It is well known that best-corrected visual acuity (BCVA) practically does not change during accommodation. Thus, it should be possible to measure BCVA by situating an appropriately scaled test within the subject’s interval of clear vision. This can be achieved by means of a mobile device placed at a handheld distance. In an effort to address the need for an accurate tool for the measurement of BCVA, the purpose of the present study was to clinically validate BCVA measures obtained with VisionApp by comparing them to the gold standard.

Methods : BCVA was measured in n=48 eyes using VisionApp installed in four electronic devices. The app displayed a Landolt C optotype and utilized a 4-force choice procedure loosely based on the FrACT (Freiburg Visual Acuity & Contrast Test). The angular size of the optotype was automatically scaled as a function of the face-to-screen distance, which was continuously measured by means of the front camera. Results were compared to clinical BCVA measurements taken using a standard ETDRS chart placed at 10 feet (3 m). To assess the similarity of measurement methods, a statistical analysis was performed based on a two-tailed, paired t-test.

Results : The t-test revealed no significant difference in measured VA (p = 0.415), with a mean difference between clinical and app measurements of less than one letter (0.005 logMAR). The Bland-Altman analysis showed that the mean difference between measurement methods was 0.05 LogMAR (95% CI), with a standard deviation of 0.153.

Conclusions : The high agreement in measurements of BCVA between the app and the gold standard facilitates home monitoring for adult patients providing ophthalmologists with a reliable and accessible method to communicate BCVA results remotely between providers and patients. Further studies are needed to validate the results in children.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.