Abstract

Pupil centration is important for retinal image quality. Both the principal line of sight and the optical axis of a centered optical system pass through the center of the entrance pupil. However, we know that the eye is not, in general, a centered optical system. The eye suffers from a variety of regular and irregular aberrations. Howland and Howland¹ have indicated that coma, in spite of much intersubject variability, is the predominant monochromatic source of image degradation. Coma is a pupil position dependent aberration. Attempts to map the wavefront aberration across the pupil have shown local wavefront irregularities with very marked inter-subject differences. For an axial object point the wavefront aberration of the eye is rarely symmetrical about the pupil center^2,3. Walsh and Charman² reported that, although Howland and Howland could deduce no direct influence of pupil centration, asymmetry of the wavefront aberration in an eye can produce marked degradation in the modulation transfer function (MTF) even with slight decentrations of the pupil. These authors also found that in two eyes an improved MTF could be produced with an appropriately decentered pupil. Campbell et.al.³ have found both subjects with coma induced by pupil position and coma independent of pupil position.

© 1991 Optical Society of America