Iris registration method in cataract surgery for astigmatic management

Abstract

A method implemented in an ophthalmic laser system to perform iris registration based on two iris images taken with the patient at upright and supine positions, respectively. For each iris image, the iris region is transformed into a rectangular rubbersheet, with the radial and angular coordinates of the iris image respectively mapped to vertical and horizontal coordinates of the rubbersheet. A horizontal one-dimensional log-Gabor transform is applied to the rubbersheet line-by-line. The transformed rubbersheet is binarized line-by-line. The two binary rubbersheets are compared at a series of relative horizontal shifts to determine the horizontal shift value that produces the lowest Hamming distance between the two binary rubbersheets, and the cyclotorsion rotation of the eye between the upright and supine positions is calculated accordingly. Then, while the patient is in the supine position, the laser system treats the eye based on measured astigmatism axis orientation and the calculated cyclotorsion rotation.