Aberrations and relative efficiency of light pencils in the living human eye.

We propose a new method for ray tracing in the living human eye. It consists of delivering a narrow light pencil from an unexpanded laser beam and recording the integrated energy and position of the aerial image formed by the outgoing beam (after reflection off the retina and passage through the fully open pupil of the eye and camera lens). The lateral displacement of the aerial image is proportional to the geometrical aberration (displacement) of the incoming ray at the retina. In addition, its integrated energy is proportional to retinal reflectance that is highly directional [related to the Stiles-Crawford (SC) effect and to the effective pupil transmittance]. This method permits us, by delivering rays through different equispaced positions at the pupil plane, to sample the complex pupil function: its magnitude is a measure of the effective pupil transmission and its phase is the wave aberration. Experimental results, aberrations, and reflectometric directionality for four subjects are consistent with previous findings.