Modulation transfer of the human eye as a function of retinal eccentricity.

We measured the monochromatic image quality of the eye across a wide visual field (120 degrees), with natural pupil (4 mm) and accommodation (3 diopters). The method is based on the acquisition and the posterior processing of double-pass aerial images of a point source imaged on the retina, which was kept at a fixed distance from the eye at all retinal eccentricities. The two-dimensional modulation transfer functions (MTF's) computed from the aerial images show that astigmatism is the dominant monochromatic aberration in both the fovea and the periphery and is also the major cause of variability among individuals. We found a slower decline in optical quality with eccentricity than had been found by previous measurements. Our foveal results are in close agreement with those of Campbell and Gubisch [J. Physiol. (London) 186, 558-578 (1966)], but off-axis optical quality is much better than found previously by Jennings and Charman [Am. J. Optom. Physiol. Opt. 55, 582-590 (1978); Vision Res. 21, 445-454 (1981)]. The optical system of the eye seems to follow a wide-angle lens design: the optical quality in the center (fovea) is not particularly good (it is far from the diffraction limit at this pupil size), but the modulation transfer function remains roughly constant for a wide visual field.