Refraction correction with custom shaping by inner corneal tissue removal using a microjet beam

Abstract

The present invention provides a new approach to reshaping of the cornea, e.g., for refraction change, using multiple, displaced planar cuts and a custom shaping template. Large refractive change and/or substantial tissue removal can be obtained by a two-cut approach to reshaping of the cornea to a desired shape using a template or applanator. The process begins with a planar template being applied to the cornea. The template includes one or more moveable sections or cams positioned to provide an overall flat contact surface with the cornea. Then, a first cut is made by a water microjet producing a hinged flap. The first cut is parallel to but displaced from the anterior cornea surface in contact with the template. Then the template cam or cams are repositioned to change the shape of the cornea surface in situ in preparation for the second cut. The hinged flap is not moved; it remains in contact with the stromal bed. The second cut is along the same path as the first cut. However, since the cornea has been reshaped, the second cut defines a separate cut line in the cornea. As a result of the first and second cuts, a body of internal tissue defined by the relative paths of the first and second cuts through the corneal tissue can be removed from the cornea to thereby shape the cornea and provide refractive correction. This enables a large range of accurate refractive correction and/or therapeutic tissue removal by directly controlling the geometry of the volume of tissue removed from the interior of the cornea.

1 . Apparatus for removing inner corneal tissue comprising: 
 a vacuum template adapted to contact an anterior surface of a cornea and operable to produce at least two configurations thereby to maintain the anterior surface of the cornea in at least two respective shapes;    a fluid beam producing device for producing a fluid beam; and    a beam scan guide for scanning said fluid beam across said cornea.    
     
     
         2 . Apparatus according to  claim 1  wherein said vacuum template is further adapted to engage said anterior surface of said cornea by including a vacuum guard and a stationary template, wherein said vacuum guard surrounds said stationary template and said vacuum template further includes a gap between said vacuum guard and said stationary template and a means for applying a vacuum to said gap, thereby securing the cornea against the vacuum template.  
     
     
         3 . Apparatus according to  claim 1  wherein said vacuum template is further adapted to engage said anterior surface of said cornea by including a vacuum guard and a stationary template, wherein said vacuum guard surrounds said stationary template in a snug fit, said stationary template includes a plurality of grooves and said vacuum template further includes a means for applying a vacuum to said plurality of grooves, thereby securing the cornea against the vacuum template.  
     
     
         4 . Apparatus according to  claim 1  and further comprising a control unit for controlling the configurations produced by said vacuum template.  
     
     
         5 . Apparatus for removing inner corneal tissue comprising: 
 a vacuum template adapted to contact an anterior surface of a cornea, said vacuum template including at least one piston which moves in a direction perpendicular to the plane defined by the direction of the fluid beam and the direction of scanning in order to produce a plurality of configurations and, whereby the anterior surface of the cornea is adaptable to a plurality of respective shapes reflecting the plurality of configurations of said piston;    a fluid beam producing device for producing a fluid beam; and    a beam scan guide for scanning said fluid beam across said cornea.    
     
     
         6 . Apparatus according to  claim 5  wherein said vacuum template includes a plurality of pistons and each of said plurality of pistons is adaptable to move in a direction perpendicular to the plane defined by the direction of the fluid beam and the direction of scanning and to maintain contact with the anterior surface of the cornea, and, for each of said plurality of pistons, the direction of movement is opposite from the direction of movement of at least one other of said plurality of pistons and the magnitude of movement is different than the magnitude of movement of at least one other of said plurality of pistons, whereby the anterior surface of the cornea is changed to a custom shape reflecting the custom shape of said plurality of pistons.  
     
     
         7 . Apparatus according to  claim 6  and further comprising a control unit for controlling the movement of each of said plurality of pistons in a direction perpendicular to the plane defined by the direction of the fluid beam and the direction of scanning, to the anterior surface of the cornea in situ.  
     
     
         8 . Apparatus according to  claim 6  wherein the cross-section of said plurality of pistons forms a honeycomb.  
     
     
         9 . Apparatus according to  claim 6  wherein said plurality of pistons includes gaps in between each of said plurality of pistons and further including and a means for applying a vacuum to said gaps, thereby securing the cornea against said plurality of pistons.  
     
     
         10 . Apparatus according to  claim 6  wherein said plurality of pistons includes a deformable disc at one end for contacting the anterior surface of the cornea and smoothing the height transitions in between adjacent ones of said plurality of pistons.