Effect of Higher Order Aberrations on Image Quality in the Human Eye

Abstract

Though measurements of the wave aberrations of the human eye have been made with several techniques1-3, there remains considerable uncertainty about the contribution of higher order aberrations to the optical quality of the human eye4. Knowledge of very high order aberrations is important, for example, because they may limit resolution in fundus imaging. We have constructed a wavefront sensor based on the Hartmann-Shack principle3 to measure the contribution of higher order aberrations in a number of eyes. A point source from a 632.8 nm laser is imaged on the retina and the light reflected from the retina returns through the pupil of the eye. A two-dimensional array of lenslets is conjugate with the eye's pupil, dividing the wavefront exiting the eye into a large number of individual beams. The light from each lenslet is focused on a CCD array, produced an array of spots. Fig. 1a shows the regular array of spots that would have been obtained from a perfect eye with no aberrations; Fig. 1b shows the distorted array of spots obtained with a real human eye. Aberrations in the eye's optics cause displacements in the positions of the spots from which the wavefront error of the eye can be reconstructed.