Patent ID: 6666857
Filing Date: 2003-12-23
Classification: A61F

Abstract:
A system combining wavefront eye measurement and multi-loop feedback-controlled scanning photoablation under controlled real-time topography comprising:A high pulse rate laser to produce a narrow pulsed beam having an ultraviolet wavelength capable of ablating the anterior cornea of the eye; a continuous wave laser forming a narrow continuous beam of visible or infrared light, this continuous beam being coaxially aligned with said pulsed beam to form a combined beam; a beam directing means comprising linear actuators to dynamically control a two-axis tiltable mirror, tilting said tiltable mirror about a pivot point in order to reflect said combined beam to a stationary parabolic mirror, said parabolic mirror having said pivot point as its focal point, from said parabolic mirror, said combined beam being reflected into collimated beams, each collimated beam able to be directed to any point of the cornea, each collimated beam position being determined by a distinct tiltable mirror position, said tiltable mirror position being measured by two tiltable mirror position detectors; a beam splitter means to separate said collimated beams into collimated pulsed beams and collimated continuous beams, said collimated continuous beams being reflected by said beam splitter to a two dimensional controlled-photosensor, the collimated pulsed beams being transmitted through the beam splitter to the cornea, said controlled-photosensor detecting positions of impingement of the collimated continuous beams in a plane normal to said collimated continuous beams, said positions of impingement on said controlled-photosensor having a one-to-one correspondence to positions of impingement of the collimated pulsed beams on the cornea; a raster-videokeratography means to project a pattern upon the cornea, selected pulses of said pulsed beam being diverted to a beam expander, said expander producing a slightly diverging beam, said diverging beam passing through a Ronchi bar grating to produce a diffusely reflected vertical bar pattern on the cornea, said pattern, after reflection from a dielectric or dichroic mirror, is then imaged by a field-flattening aspherical lens onto a two-dimensional ultraviolet (UV) sensor, said aspherical lens providing sharp focussing of said pattern over the entire cornea on said UV sensor, said UV sensor being comprised of rows of horizontal linear charge coupled devices (CCD's), said rows being about equal in number to the bars in said bar grating, said UV sensor so designed to maximize measurement accuracy of the pattern while minimizing measurement time; an eye-movement detection means consisting of a scleral mask, said mask adapted to adhere to the sclera of the eye, said mask bearing reference markings, said markings being imaged by a focussing lens onto a segmented charge coupled device (SCCD); transepithelial ablation detection means using said focussing lens to image a fluorescent 460 nm pattern produced by pulsed beam ablation of the corneal epithelium, said 460 nm pattern being imaged on a regular charge coupled device (CCD), said regular CCD having a uniform two-dimensional pixel distribution; a wavefront measurement means using a low spatial coherence light source in place of the pulsed laser beam, said low spatial coherence light source being collimated into narrow low coherence beams, said light source using said beam directing means to form a plurality of light spot images on the fundus of the eye, said spot images being focussed through said focussing lens onto the regular CCD; a feedback control means for controlling both said collimated pulsed beams and said low coherence beams comprising both passive and active analog devices and digital processor devices.