An optical coherence tomography (OCT) system for imaging a retina applies a user specific focus correction to focus a sample arm light beam on the user's retina. An OCT image detector generates an OCT signal. A control unit monitors the OCT signal, controls a reference arm optical path length adjustment mechanism to identify a length of the reference arm optical path for which the OCT signal corresponds to an OCT image of the retina, and varies an operational parameter of the sample arm light beam focus mechanism over a range, while maintaining the length of the reference arm optical path for which the OCT signal corresponds to the OCT image of the retina, to identify a focus correction for the user, based on the OCT signal, for application to the sample arm light beam.