Patent ID: 6287299
Filing Date: 2001-09-11
Classification: A61F

Abstract:
Laser-beam fluence monitoring apparatus for a system for modifying curvature of a cornea of an eye by selective laser photoablation Qf corneal tissue, the system including means for generating a sequence of pulses of laser radiation, a scanner for directing the laser-radiation pulses toward the cornea in an overlapping pattern corresponding to a desired cumulative spatial distribution of laser beam fluence on the cornea for providing a desired cumulative spatial distribution of photoablation of the corneal tissue, and an eye-tracker cooperative with the scanner for changing the direction of the laser radiation pulses to compensate for motion of the eye during corneal curvature modification, the fluence monitoring apparatus comprising:an optical beam-dividing element located between the scanner and the cornea to receive laser-radiation pulses directed by the scanner, the beam dividing element arranged to direct a first fraction of each of the successive laser-radiation pulses received from the scanner along a first optical path to a fixed monitor plate, and transmit a second portion of each of the laser-radiation pulses received from the scanner along a second optical path to the cornea;said monitor plate being a plate of a material which emits fluorescent light in response to irradiation by the laser radiation, in an amount proportional to the amount of the laser radiation;a video camera for providing an electronic image of said monitor plate;image processor means arranged for periodically capturing said electronic image and processing and summing said periodically-captured images to provide an integrated electronic image representative of one of cumulative laser-beam fluence spatial distribution on the cornea above a predetermined photoablation threshold value resulting from the sequence of laser-radiation pulses, and spatial distribution of cumulative ablation depth of corneal tissue resulting from the sequence of laser-radiation pulses; andwherein said processing of said periodically-captured images includes correcting said images to eliminate errors therein due to the eye-motion-compensating pulse-direction changes applied by the scanner.