The presence of eyeglasses worn by a human subject is detected regardless of whether the subject's head is viewed frontally or in profile. Image data within search windows defined relative to the subject's eye is processed to form linear representations of edge boundaries. Angles formed by intersections of the linear representations are determined and used as a basis for determining if eyeglass lenses are present. When prescribed eyeglass components are detected, the eye detection and tracking routines are configured accordingly.