1. A system for modifying an eye, comprising: a light source comprising a plurality of light elements; a photodetector; an optical system for directing light from the light elements reflected by a surface of the eye onto the photodetector, the photodetector configured to produce a signal comprising a plurality of images of at least some of the plurality of light elements, each image corresponding to a location on the surface of the eye; a memory including programming code for processing the signal produced by the photodetector; and a processor for executing the programming code and outputting shape data for use in calculating a treatment plan for a corneal refractive procedure on the eye; wherein the programming code comprises instructions for determining the shape data based on a combination of zonal reconstruction and polynomial fitting using the plurality of images.