The spherical aberration of the eye.

The spherical aberration of the eye was measured by placing a series of centered annular apertures over the eye pupil, and determining the optimum spectacle correction for each aperture. A “double star” was used as a test object. Accommodation was controlled by reflecting a second test object into the field of view. The three eyes examined had positive (undercorrected) spherical aberration when unaccommodated; in one case 2 diopters at the pupil margin. The aberration was reduced with increasing accommodation and in one case became negative at high accommodation. Homatropine reduced the spherical aberration of two of the three eyes examined. A historical review of previous work is given.