Disclosed is a head mountable device (2) for measuring eye movement. The head mountable device (2) comprising: a frame (4)； a camera system (6) comprising a first camera, wherein the camera system (6) is configured to obtain a first set of images (8) of a first eye (20) of a user； a first liquid crystal display (LCD) shutter (10) configured to control passage of light (13) to at least part of the first eye (20) based on a first control signal (12), the first LCD shutter (10) is configured to operate in a first primary mode and a first secondary mode, where passage of light (13) through the first LCD shutter (10) in the first secondary mode is restricted relative to the first primary mode.
