There is provided an ocular image capturing device comprising an ocular image generating module operable to generate an image of a subject's eye based on light reflected from the eye, and a determination module arranged to determine whether or not at least a portion of a pupil region of the generated image is within a predetermined permissible region within the generated image, and to generate a signal that is indicative of the determination, the pupil region being an image of at least a portion of the pupil of the eye.