Medical Conditions: Effect on Iris Recognition

A first investigation into the effects of cataract surgery and pupil dilation on iris recognition performance is presented. Images from 3 patients were acquired before cataract surgery and two weeks afterwards. Successful iris segmentation was achieved in all cases despite additional specular reflections in the pupil due to the artificial lens. No visible change in iris structure was noticed and automatic matching of pre and postoperative images produced correct identification is all cases. To analyze the effect of dilation, images from 11 subjects were captured before administration of drops and fifteen minutes afterwards. Significant changes in pupil structure were observed with time and the deformation was found to be non-elastic in most cases. A novel shape-description method was used to model irregular pupil outlines, since conventional circle-based localization methods proved inadequate. Despite accurate localization, highly deformed irises failed to match correctly and the CRR obtained was only 86.67%. The results question the widely used assumption of elastic iris deformation and indicate that further research is required to develop a more realistic description of the behavior of iris structure upon dilation.