This research adhered to the tenets of the Declaration of Helsinki. Sixty-two patients with emmetropia who had no previous ocular abnormalities and who had never undergone ocular surgery were tested. We measured 15 left eyes and 47 right eyes. These measurements were taken into account for subsequent calculations, and the signs were corrected for pupil decentration and horizontal coma (C1 3) to avoid mirror symmetry. Mean age of the subjects was 42.5 ± 14.7 years (range, 19–69 years). All subjects performed the test session with a natural pupil. Only subjects with pupil diameters larger than 5 mm, when measured with an HS aberrometer, were included. An image of one eye for each subject (containing pupil and limbus margins) was taken with two different instruments, a corneal topographer (Medmont E300; Medmont, Camberwell, Australia) and an HS–based wavefront sensor instrument (COAS; Asclepion-Meditec-Zeiss, Jena, Germany), in their normal operation routines. The image from the topographer also contained the Placido rings used to obtain elevation values, centered on the corneal reflex. The pupil and corneal limbus image from the HS sensor was taken with the alignment camera at the same time the apparatus was used to measure ocular aberrations. Because this camera was used mainly as an aid to alignment, the image was not especially bright, which presented some sensitivity problems and noise. Three images were taken with this instrument to ensure repeatability. However, the topographer camera presented bright, good-quality images, and only one image was taken after a preliminary screening for erroneous images.