Image Processing Algorithms for Aligning an Opthalmologic Device Relative to a Patient's Eye

Abstract: Ophthalmologic devices usually need to be aligned at a specific position relative to a patient’s eye during diagnostic and therapeutic treatment of a patient. Most ophthalmologic devices use manual or semi automatic positioning techniques. However in these kinds of systems the duration and final positioning accuracy of the alignment is highly dependent on the skill of the user. The surgical guidance system (SGS) is a diagnostic ophthalmologic device which is currently developed by the company Wavelight. In order to get rid of user’s influence the system should be aligned automatically with an accuracy of tens of micrometers. The aim of this thesis is to develop and implement image processing algorithms to automatically align the device with respect to a patient’s eye. The positioning was done by using a camera system, a set of light emitting diodes and a motor block. The relative position between device and an eye was determined based on diode reflection in the image of an eye which is illuminated by the diodes. Motor control for adjusting the measurement head in response to the image content was developed and implemented on an experimental setup which has motors for movements in X, Y, and Z directions and where the camera and diodes are mounted on. A full control loop was implemented where the image content is evaluated and motors are moved according to the evaluation.