The invention relates to a method for measuring a characteristic of an eye of a subject, the method comprising: providing a fixation target for a subject to view； ascertaining a diameter of a pupil of the eye of the subject while the subject views the fixation target； adjusting a brightness level of the fixation target to a selected brightness level corresponding to the ascertained diameter of the pupil of the eye； and objectively measuring at least one characteristic of the eye of the subject while the subject views the fixation target at the selected brightness level.
