For field angles up to 20 deg, the SE, LC, and SC approaches yield very similar sets of aberration coefficients. At all field angles, the SE and LC pupil approaches give descriptions of off-axis wavefront aberration, which, with appropriate manipulation, lead to the same estimates of PSF, modulation transfer function, or other descriptors of retinal image quality. However, in our opinion, within the field that is currently of main clinical interest (up to about 30 deg radius) the circular pupil approaches are preferable to the SE approach, since they are simpler to implement, they may be more easily understood by clinicians, and pupils viewed off-axis may not always be elliptical. As given above, a variation on the SC pupil is possibly the best choice, with a common pupil size across the range of visual field positions not exceeding the minimum semidiameter at any of these positions. For studies extending to field angles , we suggest that the SE approach be used. Since, however, at these large field angles the approximation for the eccentricity of the approximately elliptical pupils becomes poor, it may be better to use the actual eccentricity in the analysis.