Requirements for segmented correctors for diffraction-limited performance in the human eye.

Wavefront correctors have yet to provide diffraction-limited imaging through the human eye's ocular media for large pupils (>/= 6 mm).To guide future improvements in corrector designs that might enable such imaging, we have modeled the performance of segmented piston correctors in conjunction with measured wave aberration data of normal human eyes (mean=34.2 yr; stdev= 10.6 yr). The model included the effects of pupil size and wavelength in addition to dispersion, phase wrapping, and number and arrangement of facets in the corrector. Results indicate that </= 100x100 facets are needed to reach diffraction-limited performance for pupils up to 8 mm (extrapolated) at 0.6 microm wavelength. Required facet density for the eye was found to be substantially higher at the pupil's edge than at its center, which is in stark contrast to the requirements for correcting atmospheric turbulence. Substantially more facets are required at shorter wavelengths with performance highly sensitive to facet fill. In polychromatic light, the performance of segmented correctors based on liquid crystal technology was limited by the naturally occurring longitudinal chromatic aberration of the eye rather than phase wrapping and dispersion of the liquid crystal. Required facets to correct defocus alone was found highly sensitive to pupil size and decentration.