Abstract: The present invention provides a method of diagnosing, or developing or monitoring a treatment regime for, an ocular condition in a subject based on detected physical behaviour in a tear film, or lack of tear film, in the subjects eye, the method comprising the steps of: (a) capturing from the subjects eye at least a first captured data set; (b) identifying at least a first comparative data set; (c) analysing the at least a first captured data set relative to the at least a first comparative data set, thereby detecting physical behaviour in the tear film; and (d) diagnosing, or developing or monitoring a treatment regime for, the ocular condition based on the detected physical behaviour of the tear film. Also provided are methods of selecting contact lenses, of evaluating the effects of wearing a contact lens, and of determining preferable wearing periods of contact lenses and rest periods from wearing contact lenses by subjects.