1. A method for displaying successive image frames on a display, the method comprising: processing image data containing the successive image frames to identify features in an image frame and to display the image frame to a user with two or more of the identified features highlighted; manually selecting one of the identified features by a user; determining a portion of a subsequent image frame in which the selected feature is likely to be present; and if the selected feature is found in the portion of the subsequent image frame, displaying the subsequent image frame to change the position of the selected feature.