Abstract: Disclosed are head-mounted personal multimedia systems and visual assistance devices thereof, which are featured with a diopter adjustment unit to configurably provide various diopters for the user's eye(s) to watch. In order to watch clearly the picture displayed by a fixed-range display surface, the user's eyes can perform physiological accommodation movements in response to the diopters dynamically configured by the diopter adjustment unit, so that the eye fatigue could be prevented.