Myopia, the most common refractive error, occurs when the eyes cannot focus and see near objects clearly. Research has shown a correlation between digital technology usage and the onset or exacerbation of myopia. This study uses an on-line survey and an objective screen time data derived from smartphones as biosensors to assess the effects of smartphone usage on myopia severity among students at the Faculty of Medicine in Montenegro. Out of 206 survey responses, 70 participants submitted a screenshot showing either a daily summary or a detailed weekly breakdown of phone activity. The study employed the Mann-Whitney U test to examine the median differences between the groups (M) (N = 64 eyes) and students from other programs (O) (N = 76 eyes), and Pearson’s correlation coefficient to explore potential correlations between the diopter and other variables. The results showed: medical students had higher levels of myopia (p = 0.002) and studied more hours per day compared to students from other programs (p < 0.001). Among medical students, more study hours were associated with less severe myopia (p = 0.021). For non-medical students, higher screen time between midnight and 6 AM correlated with worse myopia (p = 0.004), while higher screen time between 6 PM and midnight was associated with less severe myopia (p = 0.010). Our findings suggest that myopia among medical students may be influenced by factors beyond total study hours, while late-night screen use appears to exacerbate myopia in non-medical students. These results highlight the importance of controlled screen exposure particularly at night, as strategies to mitigate myopia progression.