Methods and apparatus for laser sculpture of the cornea

Sculpture apparatus for making a uniform-depth constant-area ablated removal of corneal tissue in preparation for reception of a corneal transplant in an optically used area of the anterior surface of the cornea of an eye, said apparatus comprising laser means for producing a tissue-ablating output beam on a central axis of beam delivery to said area, the intensity distribution of laser-beam projection on said axis exhibiting substantially the same profile of fall-off in all radially outward directions from said axis, whereby for a given exposure of only said beam to said area, a curvature-decreasing change is effected at the anterior surface of the cornea, with depth of tissue-ablating penetration greatest at the center of said area and with penetration depth exhibiting substantially the same fall-off in all radially outward directions from the center of said area, and controllable means for variably limiting the sectional area of said beam at impingement with the cornea, said controllable means including (a) a zoom-lens system and (b) at least one indexible mask having a plurality of annular mask apertures of progressively changing inner radius, and control means connected to said laser means and to said controllable means for so controlling zoom-lens setting for each of a plurality of indexed apertures of said mask as to produce a curvature-increasing change, to the extent that a net uniform-depth ablation of corneal tissue is achieved to said greatest depth over at least said optically used area.

Sculpture apparatus for operation upon the anterior surface of the cornea of an eye, said apparatus comprising laser means for producing a tissue-ablating output beam and controllable means for variably limiting the sectional are of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum optically used area to be ablated and being symmetrical with respect to an axis of beam-projection to the cornea, and flux-density distribution across the beam-projection axis being at maximum near the beam-projection axis and diminishing with distance away from the beam-projection axis;

• said controllable means including;
• (a) at least one indexible mask having a plurality of circular mask apertures of progressively changing radius;
• (b) at least one indexible mask having a plurality of annular mask apertures of progressively changing inner radius;
• and
• (c) control means connected to said laser means and to said controllable means for so controlling the successive use of said masks as to produce a uniform-depth ablation of corneal tissue at least over said optically used area.

Sculpture apparatus for operation upon the anterior surface of the cornea of an eye, said apparatus comprising laser means for producing a tissue-ablating output beam and controllable means for variably limiting the sectional area of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum optically used area to be ablated and being symmetrical with respect to an axis of beam-projection to the cornea, and flux-density distribution across the beam-projection axis being at maximum near the beam-projection axis and diminishing with distance away from the beam-projection axis;

• said controllable means including:
• (a) at least one masking means for producing circular-spot delivery of progressively changing radius;
• (b) at least one masking means for producing annular-spot delivery of progressively changing inner radius;
• and
• (c) control means connected to said laser means and to said controllable means for so controlling the successive use of said respective masking means as to effect at least a predetermined depth of stroma-penetration over the entire optically used area of the cornea as well as a predetermined anterior-surface contour.

Sculpture apparatus for curvature-correcting operation upon the anterior surface of an eye, said apparatus comprising laser means for producing a tissue-ablating output beam and controllable means for variably limiting the sectional area of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum curvature-correcting area to be ablated and being symmetrical with respect to a beam-projection axis which coincides with the optical axis of the eye, the intensity of laser-beam projection being limited per unit time to ablate but a fraction of a predetermined maximum depth of ablation into the stroma region of the cornea, said controllable means including (a) a zoom-lens system and (b) an indexible mask having a plurality of mask apertures of progressively changing area, and control means connected to said laser means and to said controllable means for so controlling zoom-lens setting for each of an indexed plurality of the apertures of said mask as to produce a relatively smooth variation of the sectional area of said beam at impingement of the cornea with an accompanying diopter change in the cornea, said relatively smooth variation being as compared with the stepped variation produced by use of the mask alone, the number of mask apertures and the relation of area change between one and the next mask aperture through the progression of area change being selected for limitation of requisite zoom-lens magnification to the range 1:1.414 or less, for each of the indexed positions of said mask, whereby the variation in energy density at the cornea is within the range 1:2.

Sculpture apparatus for curvature-correcting operation upon the anterior surface of the cornea of an eye, said apparatus comprising pulsing laser means for producing a succession of tissue-ablating pules in an output beam and controllable means for variably limiting the sectional area of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum curvature-correcting area to be ablated and being symmetrical with respect to a beam-projection axis which coincides with the optical axis of the eye, the intensity of laser-beam projection being such that corneal-tissue ablation per pulse is but a fraction of desired maximum ablation into the stroma region of the cornea, said controllable means including (a) a zoom-lens system and (b) an indexible mask having a plurality of mask apertures of progressively changing area, and control means connected to said laser means and to said controllable means for so variably controlling zoom-lens setting for each of an indexed plurality of apertures of said mask as to deliver a plurality of pulses in the course of zoom-lens variation for each of said indexed plurality of mask apertures whereby to achieve a relatively smooth variation of the sectional area of said beam at impingement on the cornea with an accompanying diopter change at the cornea, said relatively smooth variation being as compared with the stepped variation produced by use of the mask alone, the number of mask apertures and the relation of area change between one and the next mask aperture through the progression of area change being selected for limitation of requisite zoom-lens magnification to the range 1:1.414 or less, for each of the indexed positions of said mask, whereby the variation in energy density at the cornea is within the range 1:2.

Sculpture apparatus for curvature-correcting operation upon the anterior surface of the cornea of an eye, said apparatus comprising laser means for producing a tissue-ablating output beam and controllable means for variably limiting the sectional area of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum curvature-correcting area to be ablated and being symmetrical with respect to a beam-projection axis which coincides with the optical axis of the eye, the intensity of laser-beam projection being limited per unit time to ablate but a fraction of a predetermined maximum depth of ablation into the stroma region of the cornea, said controllable means including (a) a zoom-lens system and (b) an indexible mask having a plurality of mask apertures of progressively changing area, and control means connected to said laser means and to said controllable means for so controlling zoom-lens setting for each of an indexed plurality of the apertures of said mask as to produce a relatively smooth variation of the sectional area of said beam at impingement on the cornea with an accompanying diopter change at the cornea, said relatively smooth variation being as compared with the stepped variation produced by use of the mask alone, said mask being one of a plurality of circular discs which are in axially separated array and which are so connected to said control means as to be separately indexible about the same axis of index rotation, each of said discs having a differently characterized progression of apertures of varying beam-transmitting sectional area, and one of the apertures of each disc having an opening area as to avoid beam-section limitation upon the beam-section-limiting ability of any aperture of any other disc of said plurality.

Sculpture apparatus for curvature-correcting operation upon the anterior surface of an eye, said apparatus comprising pulsing laser means for producing a succession of tissue-ablating pulses in an output beam and controllable means for variably limiting the sectional area of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum curvature-correcting area to be ablated and being symmetrical with respect to a beam-projection axis which coincides with the optical axis of the eye, the intensity of laser-beam projection being such that corneal-tissue ablation per pulse is but a fraction of desired maximum ablation into the stroma region of the cornea, said controllable means including (a) a zoom-lens system and (b) an indexible mask having a plurality of mask apertures of progressively changing area, and control means connected to said laser means and to said controllable means for so variably controlling zoom-lens setting for each of an indexed plurality of pulses in the course of zoom-lens variation for each of said indexed plurality of mask apertures whereby to achieve a relatively smooth variation of the sectional are of said beam at impingement on the cornea with an accompanying diopter change at the cornea, said relatively smooth variation being as compared with the stepped variation produced by use of the mask alone, said mask being one of a plurality of circular discs which are in axially separate array and which are so connected to said control means as to be separately indexible about the same axis of index rotation, each of said discs having a differently characterized progression of varying beam-transmitting sectional area, and one of the apertures of each disc having an opening of such sufficiently large beam-transmitting sectional area as to avoid beam-section limitation upon the beam-section-limiting ability of any aperture of any other disc of said plurality.

Sculpture apparatus for curvature-generating operation upon the anterior surface of the cornea of an eye, said apparatus comprising laser means for producing a tissue-ablating output beam and controllable means for variably limiting the sectional area of said beam at impingement of the cornea, the area variation being over a range which at least includes a maximum optically used area to be ablated and being symmetrical with respect to a beam-projection axis which coincides with the optical axis of the eye, said controllable means including (a) a zoom-lens system and (b) at least one indexible mask having a plurality of mask apertures of progressively changing area, and control means connected to said laser means and to said controllable means for so controlling zoom-lens setting for each of an indexed plurality of apertures of said mask as to produce a relatively smooth variation of the sectional area of said beam at impingement of the cornea with an accompanying diopter change at the cornea, said relatively smooth variation being as compared with the stepped variation produced by use of the mask alone, the number of mask apertures and the relation of area change between one and the next mask aperture through the progression of area change being selected for limitation of requisite zoom-lens magnification to the range 1:2 of less, for each of the indexed positions of said mask, whereby the variation in energy density at the cornea is within the range 1:4.

Sculpture apparatus for curvature-correcting operation upon the anterior surface of the cornea of an eye, said apparatus comprising laser means for producing a tissue-ablating output beam and controllable means for variably limiting the sectional area of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum curvature-correcting data to be ablated and being symmetrical with respect to a beam-projection axis which coincides with the optical axis of the eye, the intensity of laser-beam projection being limited per unit time to ablate but a fraction of a predetermined maximum depth of ablation into the stroma region of the cornea, said controllable means including (a) a zoom-lens system and (b) an indexible mask having a plurality of mask openings of progressively changing area, and control means connected to said laser means and to said controllable means for so controlling zoom-lens setting for each of an indexed plurality of the openings of said mask as to produce a relatively smooth variation of the sectional area of said beam at impingement on the cornea with an accompanying diopter change at the cornea, said relatively smooth variation being as compared with the stepped variation produced by use of the mask alone, said controllable means further including means for varying the intensity of the laser beam, said last-mentioned means being so continuously coordinated with the control of zoom-lens setting as to compensate for flux-density dilution as a function of instantaneous zoom-lens magnification.

Sculpture apparatus for curvature-correcting operation upon the anterior surface of the cornea of an eye, said apparatus comprising pulsing laser means for producing a succession of tissue-ablating pulses in an output beam and controllable means for variably limiting the sectional area of said beam at impingement on the cornea, the area variation being over a range which at least includes a maximum curvature-correcting area to be ablated and being symmetrical with respect to a beam-projection axis which coincides with the optical axis of the eye, the intensity of laser-beam projection being such that corneal-tissue ablation per pulse is but a fraction of desired maximum ablation into the stroma region of the cornea, said controllable means including (a) a zoom-lens system and (b) an indexible mask having a plurality of mask openings of progressively changing area, and control means connected to said laser means and to said controllable means for so variably controlling zoom-lens setting for each of an indexed plurality of openings of said mask as to deliver a plurality of pulses in the course of zoom-lens variations for each of said indexed plurality of mask openings whereby to achieve a relatively smooth variation of the sectional area of said beam at impingement on the cornea with an accompanying diopter change at the cornea, said relatively smooth variation being as compared with the stepped variation produced by use of the mask alone, said controllable means further including means for varying the intensity of the laser beam, said last-mentioned means being so continuously coordinated with the control of zoom-lens setting as to compensate for flux-density dilution as a function of instantaneous zoom-lens magnification.

The method of using a tissue-ablating laser beam to remove a wound of stroma-penetrating depth from the anterior surface of a damaged cornea without net change in curvature of the optically used area of the cornea, said method comprising the steps of:

• (a) determining the circular area that is both centered on the optical axis of the cornea and large enough to embrace both the superficial wound and the optically used area;
• (b) removing epithelium from said circular area and smoothly filling the wound with substance having laser-ablatable response comparable with that of corneal tissue;
• (c) performing a curvature-reducing procedure involving laser-beam exposure and control with varying radius of circular-spot delivery centered on the optical axis, wherein the radius varies throughout said circular area, and wherein depth of ablating penetration into the stroma on the optical axis is to a predetermined depth at least corresponding to that of the wound;
• and
• (d) performing a curvature-increasing procedure involving laser-beam exposure and control with varying inner radius of annular-spot delivery centered on the optical axis, wherein the annular spot has an outer radius at least matching that of the procedure of step (c), and wherein the curvature increasing procedure is continued until it achieves maximum penetration to said predetermined depth.

The method of using a tissue-ablating laser beam to remove a wound of stroma-penetrating depth from the anterior surface of a damaged cornea without net change in curvature of the optically used area of the cornea, said method comprising the steps of:

• (a) determining the circular area that is both centered on the optical axis of the cornea and large enough to embrace both the superficial wound and the optically used area;
• (b) removing epithelium from said circular area and smoothly filling the wound with substance having laser-ablatable response comparable with that of corneal tissue;
• (c) performing successive curvature-changing procedures involving laser-beam exposure and control with varying size of spot delivery centered on the optical axis, one of said procedures involving varying radius of circular-spot delivery and the other of said procedures involving varying inner radius of annular-spot delivery;
• and
• (d) the respective procedures of step (c) being of such relative duration as collectively to achieve at least said stroma-penetrating depth and to avoid a net change in curvature of the anterior surface of the cornea.

The method of using a tissue-ablating laser beam (i) to remove a wound of stroma-penetrating depth from the anterior surface of a damaged cornea which also requires curvature correction, and (ii) concurrently to effect a predetermined curvature correction in the optically used area of the cornea, said method comprising the steps of:

• (a) determining the circular area that is both centered on the optical axis of the cornea and large enough to embrace both the superficial wound and the optically used area;
• (b) removing epithelium from said circular area and smoothly filling the wound with substance having laser-ablatable response comparable with that of corneal tissue;
• (c) performing successive curvature-changing procedures involving laser-beam exposure and control with varying size of spot delivery centered on the optical axis, one of said procedures involving varying radius of circular-spot delivery and the other of said procedures involving varying inner radius of annular-spot delivery;
• and
• (d) the respective procedures of step (c) being of such predetermined relative duration as collectively to achieve at least said stroma penetrating depth and to achieve said predetermined curvature correction.