Systems, methods and apparatus are provided through which in some aspects an ocular scene is imaged and changes in the ocular scene relative to a calibration image, are tracked. In one aspect, an imaging instrument includes an eyepiece, a light source operable to project light, an imaging system operable to image an ocular scene; and a processing system operable to receive a set of calibration images, and further operable to capture an image of the imaged ocular scene associated with a calibration image. In another aspect, a method to track changes in an ocular scene includes receiving a set of calibration images, receiving a set of landmarks on each calibration image, capturing a set of images of an ocular scene, associating each captured image with a calibration image, and detecting landmarks on each captured image wherein each detected landmark corresponds to a landmark on the associated calibration image.