Laser apparatus and method for refractive surgery

Abstract

An ultrashort pulsed laser instrument is used to perform refractive surgery. The invention operates in ablative and incisional modalities. In the ablative mode, spiral ablation disks consisting of individual laser pulses are produced at high scanning speeds. Ablation profile may be produced in cornea by stacking and arranging multiple ablation disks to produce a specified shape change. Placement of ablation disks is assisted by an optical tracking and control system that compensates for eye motion. A preferred embodiment allows for ablative corrections to be performed on non-planar posterior surface of a laser cut flap affixed to registration platen, thereby avoiding exposing the eye interior to high radiant power. Laser cut and contrast agent dyed fiduciary marks may serve as reference features for the optical tracking system. Incisional procedures, such as corneal flaps for LASIK, may also be performed.

I claim: 
     
         1 . A laser instrument comprising:
 a laser source generating a laser pulse train of ultrashort duration pulses;   an optical processing module configured to control and modulate said laser pulse train;   a scanning beam delivery module for scanning in three dimensions the focal point of said laser pulse train;   a focusing optics module for focusing said laser pulse train onto biological tissue for the purpose of removing said tissue;   an optical tracking system for detecting relative lateral and axial motions between said laser pulse train and said tissue; and   a means for adjusting and compensating the delivery of said laser pulse train to said tissue using said optical tracking system to correct for said lateral and axial motions   wherein the laser pulse train of ultrashort duration pulses produce a discrete ablation sequence, and wherein a wavelength and intensity of the laser source remain unchanged during the production of the ablation sequence.   
     
     
         2 . The laser instrument of  claim 1 , wherein the instrument removes a designated volume of said biological tissue through a series of discrete ablative sequences. 
     
     
         3 . The laser instrument of  claim 1 , wherein the scanning beam delivery module comprises optical scanning elements operating with a linear scan rate of at least 0.5 meter/second. 
     
     
         4 . The laser instrument of  claim 1 , wherein the optical tracking system comprises one or more digital cameras and one or more optical radiation sources illuminating the surgical field. 
     
     
         5 . The laser instrument of  claim 1 , further comprising an axial position optical sensing module configured to detect a position of a tissue interface by the measurement of light intensity collected from the focusing optics module. 
     
     
         6 . The laser instrument of  claim 5 , wherein the size of a signal detected by the axial position optical sensing module is related to the distance between a tissue interface and a position of the focusing optics module. 
     
     
         7 . The laser instrument of  claim 1 , wherein the instrument produces ablative tissue removal in a series of discrete ablative sequences, said ablative sequences occurring in a time interval matched to a characteristic period associated with motion of said tissue. 
     
     
         8 . The laser instrument of  claim 1 , wherein the instrument produces ablative tissue removal in a series of discrete ablative sequences, said ablative sequences timed to allow said optical tracking system to correct said relative motion in a manner that allows said ablative sequences to occur with an acceptable amount of said relative motion. 
     
     
         9 . The laser instrument of  claim 1 , wherein the optical tracking system comprises:
 a first image based tracking system for motion normal to the laser optical axis; and   a second optical system for motion parallel to the laser optical axis.   
     
     
         10 . The laser instrument of  claim 1 , wherein the optical tracking system relies upon fiduciary marks produced by a first process step of creating precise incisions and a second process step of introducing a contrast agent substance to be preferentially located at or in said precise incisions. 
     
     
         11 . The laser instrument of  claim 1 , wherein the optical tracking system relies upon fiduciary marks produced by a first process step of creating precise incisions using said laser instrument, said precise incisions having widths sufficiently narrow to not materially affect human vision. 
     
     
         12 . The laser instrument of  claim 2 , wherein each ablation sequence is comprised of a spiral ablation array forming a disk having a characteristic depth and a characteristic diameter. 
     
     
         13 . The laser instrument of  claim 12 , wherein the characteristic diameter of each ablation sequence characteristic diameter is less than  1  millimeter. 
     
     
         14 . The laser instrument of  claim 12 , wherein the characteristic diameter and the characteristic depth of each ablation sequence are equal. 
     
     
         15 . The laser instrument of  claim 1 , wherein the means for adjusting and compensating the delivery of said laser pulse train to said tissue using said optical tracking system to correct for said lateral and axial motions comprises an ablation assist arm mounted on a motion control system, wherein the ablation assist arm comprises an aperture plate. 
     
     
         16 . The laser instrument of  claim 1 , further comprising a manifold to apply a hydrating fluid to the biological tissue. 
     
     
         17 . The laser instrument of  claim 1 , wherein the means for adjusting and compensating the delivery of said laser pulse train to said tissue using said optical tracking system to correct for said lateral and axial motions comprises a registration platen connected to a micro-positioning subsystem.