Objective measurements of digital habits in a university population and their relationship with refraction and axial length

To evaluate the relationship between myopia and potential "myopiagenic" digital habits (excessive screen time, near face-device distance or low ambient light level). 82 university students (21 ± 3 years) underwent a comprehensive optometric examination, including subjective refraction and axial length (AL) measurements. Digital habits were objectively measured using a mobile application (app) capturing screen time, face-device distance, ambient light level and number of interruptions larger than 20″ per day (called "events"). The collection of 40 M data points showed mean values: 57 ± 40 min of daily screen time, 355 ± 67 mm of face-device distance, 305 ± 215 lux of ambient light level and 52 ± 32 events. No correlation was found between spherical equivalent refraction (SER) and digital habits. Particularly, SER was more negative for greater screen times, nearer face-device distances, lower light levels or more events. AL was inversely correlated with SER decrease. Correlation coefficients were very weak (R < 0.14) in all cases. The app quantified smartphone-based digital habits in a university population. The study revealed weak correlations between digital habits and myopia, indicating that longer-duration studies in a greater population are needed to obtain powerful correlation coefficients.