Objective technique for the determination of monochromatic aberrations of the human eye

The subjective crossed-cylinder aberroscope method of Howland and Howland [J. Opt. Soc. Am. 67, 1508 (1977)] has been modified by the addition of a beam splitter and a camera to permit direct photographic recording of the distorted retinal image of the aberroscope grid. The ocular aberration can then be deduced from direct measurements of the grid distortion. Preliminary results on 11 subjects confirm earlier findings that comalike, third-order aberrations are more important than spherical or other fourth-order aberrations in degrading the retinal image and for the average subject, the diffraction-limited pupil size is approximately 3 mm. This new objective method for measuring wave aberration yields significantly less variance in population estimates of the coefficients of the wave-aberration polynomial than that of the previous subjective method.