Method for performing ophthalmic laser surgery

  • US 4,732,148 A
  • Filed: 07/31/1986
  • Issued: 03/22/1988
  • Est. Priority Date: 11/17/1983
  • Status: Expired due to Term
First Claim
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1. The method of using an ultraviolet laser beam to change optical properties of an eye by selectively ablating the anterior surface of the cornea with penetration into the stroma to achieve a volumetric removal of corneal tissue, which method comprises confining the laser beam to a maximum-area circular section producing a spot which is centered on and equal to the area of the cornea to be subjected to ablation, adjusting the intensity of laser-beam projection to a limited level at which resultant corneal-tissue ablation per unit time is to an ascertained elemental depth which is but a fraction of a predetermined maximum ablation depth into the stroma, directing the adjusted beam to the cornea in the context of reflection to define a central circular region within the confined beam, said directing step being by reflection to the anterior surface and for that period of time which will accomplish at least some ablative penetration to the predetermined maximum ablation depth, whereby laser-beam impingement upon the cornea is a circle having an outer diameter determined by the central circular region;

  • and, in the course of said period of time, varying the diameter of said central circular region to thereby vary the outer diameter of the spot at corneal impact, said diameter variation proceeding in a range within said maximum-area circular spot;

    whereby the cornea is impacted with greatest cumulative ablating penetration per unit area at the central region of the ablated area and with ablative penetration decreasing with increasing radius to the outer portion of the ablated area, whereby a myopia-correcting change in the anterior surface may be effected by volumetric removal of corneal tissue.

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