1. A system for diagnostically evaluating the health of tissue within the fundus of an eye, which comprises: a laser source for generating a laser beam, said laser beam having a plurality of laser pulses, wherein each laser pulse has a first wavelength and a pulse duration less than approximately two hundred femtoseconds; an optical assembly for focusing each laser pulse to a focal point in the fundus, with the focal point being characterized by a spot size having a diameter of approximately two microns, wherein the laser pulses of the first wavelength illuminate tissue to induce a second harmonic generation (SHG) response of a second wavelength, by photon conversion, when the laser beam is incident on anisotropic tissue in the fundus, with said SHG response of the second wavelength being used to create an image; a means for detecting the SHG response; and a computer for evaluating the image of the SHG response in comparison with a template for healthy tissue to determine the health of the fundus tissue.