A monitoring system for monitoring the visual behavior of a wearer of a head-mounted device, the monitoring system includes: —a least one wearer's visual behavior sensor configured to sense at least one wearer's visual behavior data relating to the visual behavior of the wearer of the head-mounted device, —a communication unit associated with the at least one wearer's visual behavior sensor and configured to communicate the visual behavior data to a wearer information data generating unit, —a wearer information data generating unit configured to: —receive the wearer's visual behavior data, —store the wearer's visual behavior data, and —generate an wearer information data indicative of at least one of: wearer's vision or general health condition of the wearer or wearer's activity or wearer's authentication based, at least, on the evolution over time of the wearer's visual behavior data.