AIM: To determine the smartphone use patterns and effects of smartphone use on accommodation and convergence system of the eyes among Malaysian teenagers. METHODS: A total of 62 participants aged between 13 and 17y were involved. A self-administered questionnaires containing 12 items was used to evaluate the smartphone usage patterns. This was followed by an eye examination, involving a battery of accommodation and convergence assessments before and after the smartphone use. The data analysis comprised descriptive statistics, paired t-test, and correlation coefficients. RESULTS: The use of smartphones is at a high level and at an optimal distance daily, with more than 6h a day watching video films, games, and completing school projects. Majority of the participants not reported eye strain factors and eye prescription changes with the use of digital devices. The use of a smartphone continuously for 30min was found to significantly decrease amplitude of accommodation, accommodative facility, and positive relative accommodation (P<0.001). Meanwhile, the lag of accommodation parameters and negative relative accommodation increased with the use of smartphones significantly (P<0.001). The near point of convergence (NPC) and distance and near negative fusional vergence decreased significantly (P<0.001). The NPC parameter was found to have a weak negative association with the frequency of smartphone use (R=-0.276, P<0.05). CONCLUSION: Frequent and continuous use of smartphones have increased visual stress and resulted in weakness of accommodation and vergence functions. Therefore, frequent break is mandatory when using a smartphone and appropriate visual hygiene, the 20-20-20 rule (every 20min, view something 20 feet away for 20s) are required during smartphone use to maintain visual function.