1. A computer-implemented method comprising: obtaining an eye image; determining a location of a center of an iris in the eye image; generating a polar eye image based, in part, on the location of the center of the iris in the obtained eye image; determining, using one or more processors, locations of one or more of an inner eye corner and an outer eye corner in the polar eye image; determining one or more role angles based on the determined locations of the one or more of the inner eye corner and the outer eye corner in the polar eye image, the one or more role angles comprising a roll angle corresponding to a difference between a location of the center of the iris in the polar eye image and the location of one of the inner eye corner or the outer eye corner in the polar eye image; and storing, in a storage unit, the one or more role angles as biometric sample features.