Head-mountable display apparatus and methods

A head mountable display apparatus includes a display unit to display one or more images to a user wearing the HMD. A first optical element and a second optical element each configured to direct light from the one or more images displayed by the display unit for viewing by a respective eye of the user. A first input unit to receive user information for the user indicative of a separation of the user's eyes. This may be manually inputted by the user or detected automatically. A second input unit receives a user input, this maybe a rotatable unit which is mechanically or electronically couple to an adjustment unit. An adjustment unit adjusts a current separation of the first and second optical elements responsive to the user input. The display unit is configured to display a first image 1400 comprising one or more indicators 1410, 1420 indicative of the current separation of the first and second optical elements with respect to the separation of the user's eyes.