A head-mounted device (10) may include optical assemblies (20) for presenting images to a user. Motors (48) may be used to adjust the spacing between the optical assemblies (20) to accommodate different interpupillary distances. Gaze trackers (50) may be used to make interpupillary distance measurements and eye relief measurements. Adjustments to the positions of the optical assemblies (20) may be made by the motors (48) based on the interpupillary distance measurements and eye relief measurements.