Effects of screen size on smartphone functionality and usability for stroke patients with hemiparalysis.

[Purpose] The effect of screen size on smartphone functionality and usability for patients with stroke, considering both the non-dominant and dominant hand smartphone usage, was investigated in this study. [Subjects and Methods] Thirteen patients with stroke participated in this study-five pre-non-dominant hand users and eight pre-dominant hand users. The smartphone screen sizes used were 4.2, 4.5, and 5.6 inches. Usability was assessed in terms of discomfort experienced during dragging operations, which was self-reported using a four-point Likert scale. Functionality was assessed in terms of completion time and the frequency of errors in the task requiring users to quickly touch numbers 0 through 9 in order on the keypad. [Results] For all three screen sizes, a significant difference between the dominant and non-dominant hands was found in usability, completion time, and frequency of errors. For dominant hand users, differences in usability and completion time were found among the three screen sizes. Among the three screen sizes, no difference in the frequency of errors was found in either of the groups. [Conclusion] This study will be useful as basic research on usability and functionality with stroke patients using only pre-non-dominant or pre-dominant hand.