Uniform-radiation caustic surface for photoablation
OwnerRobert F. Smithinventor
Life of this patent
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Abstract
A simultaneously generated caustic surface comprised of high energy photons is created for the purpose of ablating organic materials to within optical accuracies. The apparatus and method are principally for modifying, in vivo, the anterior cornea of the eye to effect refractive correction thereof. A catadioptric system in tandem with a continuously adjustable system of lenses provides a range of spherical or aspherical caustic curvatures throughout which range relatively uniform radiation intensity is maintained over the entire caustic. Ablation monitoring uses both visual and interferometric means; control is performed using interferometry in conjunction with a computer controlled excimer laser.
Claims24
A method having a surface area, a desired curvature, and of substantially creating a caustic surface of uniform intensity radiation using a catadioptric device comprising at least one axicon lens, each having a surface and a surface area, and a mirror, said method comprising the steps of:
- selecting:
- (1) a starting coordinate point corresponding to a minimum radial distance from a optical axis for the mirror of said catadioptric system;
- (2) a ratio of the surface area of the axicon lens, of said catadioptric system, to the surface area of said caustic;
- (3) the desired curvature of said caustic;
- calculating positions of rays through said axicon corresponding to tangential rays which form said caustic that maintain said ratio of areas constant;
- varying slopes of said axicon rays so that intersection with said corresponding caustic tangential rays produces the locus of coordinate points of a meridional cross section of said mirror subject to a law of reflection;
- calculating said coordinate points for at least one surface of at lease one of said axicon lens to produce a desired set of axicon rays subject to the law of refraction.
A method of photoablative keratectomy comprising the steps of:
- selecting a desired corneal surface and adjusting an optical device thereby for producing a caustic surface of substantially uniform intensity radiation capable of ablating to said desired corneal surface;
- aligning a photoablative laser coaxially with said optical device and said corneal surface;
- controlling extraneous movement of said corneal surface;
- activating said laser and onto said corneal surface until said corneal surface is ablated to a desired curvature.
An apparatus for ablating a surface of a corneal surface to produce a predefined optical surface thereon, said apparatus comprising:
- a source producing a collimated beam of ablative radiation means for directing said collimated beam coupled to said source;
- an optical device coupled to said means for directing said collimated beam, said optical device consisting of a decollimator containing lenses, said decollimator including means for creating a decollimated beam, said decollimator coupled to a means for directing said decollimated beam into a system, said system comprising means for forming a continuous, simultaneous three-dimensional caustic surface of substantially uniform intensity, said system also including means for continuously adjusting said caustic surface over a range of curvatures;
- an axial advancing means coupled to said system for bringing said caustic surface into proximity with said corneal surface to progressively ablate the corneal surface to a desired curvature;
- a support and control means coupled to the optical device for maintaining said material in alignment with said optical device.
Dependencies are inferred from the claim text.