1. A computer-implemented method comprising: capturing, using a light sensor, a plurality of images of a subject including a view of an eye of the subject; determining a reflectance metric by at least one of: measuring a time difference between (i) an occurrence of a flash pulse captured by one or more of the images and (ii) an appearance of a corresponding glare detected on the eye in one or more of the images; and measuring uniformity of a pattern of glare on an outer surface of the eye visible in one or more of the images caused by one or more flash pulses captured by one or more of the images, wherein the uniformity of a pattern of glare on the eye is measured as a ratio of circumference to an area of the glare; and rejecting or accepting the images based on, at least, the reflectance metric.