Algorithm for Purkinje images I and IV and limbus centre localization

Purpose: To develop a fast and reliable image processing algorithm for the extraction of Purkinje reflection data for measurement of ocular alignment with standard PC hardware. Methods: Purkinje images I and IV are specular reflections of light sources, the positions of which are proportional to eye rotation. Fast histogram-based thresholding and gradient techniques were used to localize Purkinje images I and IV, the pupil centre and the limbus centre in images obtained with near infrared light. Results and Conclusions: Execution time was 500 ms per eye. A set of 540 images was evaluated of which 94% were automatically analysed. (C) 1997 Elsevier Science Ltd.