Patent ID: 6325792
Filing Date: 2001-12-04
Classification: A61B,A61F

Abstract:
A method for performing a lamellar keratectomy on tissue of a cornea, whereby a partial thickness lamellar disc of tissue is freed from surrounding corneal tissue, said method comprising the steps of:generating a pulsed laser beam by a pulsed laser apparatus, said beam having pulses having a duration in a range of about 10 femptoseconds to about 2 picoseconds;said pulses having an energy density at a point of interaction in a material of less than 5 .mu.J/(10 .mu.m).sup.2 ;said pulses having a wavelength transmissive in eye tissue;Wherein the wavelength is in one of a group of ranges consisting of about 400 nm to about 1900 nm, about 2.1 .mu.m to about 2.8 .mu.m, and longer than about 3.1 .mu.m;said beam having up to approximately 100,000 pulses per second;wherein a lasing medium of the pulsed laser apparatus is a broad gain bandwidth laser;wherein the lasing medium of the pulsed laser apparatus uses lasing ions such as titanium, chromium or neodymium (for example, Ti.sub.3 :Al.sub.2 O.sub.3, Cr:LiSrAlF.sub.6, Nd:YLF, or similar lasers);focusing the laser pulses at a selected interaction point in the material;wherein the selected interaction point has a diameter in a range of about 1 .mu.m to about 30 .mu.m;positioning the laser pulses within a selected portion of the material;determining a position of the laser pulses within the material;controlling the diameter of the laser pulses;determining the diameter of the laser pulses;controlling the intensity of the laser pulses;determining the intensity of the laser pulses;controllably blocking the laser pulses from the material;directing the laser beam to a selected start position within the cornea;scanning a laser spot through the corneal tissue in a predetermined manner such that the lamellar disc of the tissue to be removed is outlined and freed from the surrounding corneal tissue by ablating scanned tissue along a path scanned;whereby an edge shape of the partial thickness lamellar disc is varied as desired for specific applications by altering the path of the scanning spot as it traverses from within the cornea to finally exit the cornea anteriorly.