Ophthalmic method for laser surgery of the cornea

• US 5,507,741 A
• Filed: 01/20/1988
• Issued: 04/16/1996
• Est. Priority Date: 11/17/1983
• Status: Expired due to Term

• Current Assignee: Amo Manufacturing Usa, Llc (Johnson & Johnson)
• Original Assignee: VISX Incorporated
• Inventors: L'Esperance, Francis A. Jr.
• Primary Examiner(s): Shay, David M.
• Application Number:
  US07/146,045
• Time in Patent Office: 3,009 Days
• Field of Search: 128/303.1, 128/395, 128/847, 319/121.6, 319/121.67, 319/121.68, 319/121.69, 319/121.72, 319/121.73-121.75
• US Class Current: 606/5
• CPC Class Codes: A61B 2017/306 holding by means of suction
• CPC Class Codes: A61B 2018/20351 Scanning mechanisms
• CPC Class Codes: A61B 2018/20355 Special scanning path or conditions, e.g. spiral, raster or providing spot overlap
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 9/00804 Refractive treatments
• CPC Class Codes: A61F 9/00817 Beam shaping with masks
• CPC Class Codes: A61F 9/00819 with photoablatable masks
• CPC Class Codes: A61F 9/009 Auxiliary devices making contact with the eyeball and coupling in laser light, e.g. goniolenses apparatus for eye examination A61B3/0008
• CPC Class Codes: B23K 26/08 Devices involving relative movement between laser beam and workpiece
• CPC Class Codes: B23K 26/082 Scanning systems, i.e. devices involving movement of the laser beam relative to the laser head

Abstract

The invention contemplates an inventory of disposable elements adapted for selective placement in the path of laser-beam delivery to the cornea. Each of the disposable elements carries a membrane which is opaque to the laser beam and which is designedly subject to ablation when exposed to the laser beam, the thickness of the membrane being a precharacterized function of local area such that a given laser-beam course of exposure will require greater or lesser time to locally ablate the membrane and thus permit laser-beam exposure past the membrane and into correspondingly localized ablating impingement with the cornea. Stated in other words, varying-spot size at the cornea is achieved by a time-release function of the membrane, on a predetermined area-controlled basis that is designed to achieve the diopter change specifically identified with each particular selectable element.

Claims

1. The method of making a precharacterized accessory for use in the path of delivery of an ultraviolet laser beam to perform a curvature-changing sculpture of the anterior surface of a cornea, wherein the accessory comprises a plane-parallel plate of substrate material that is transparent to ultraviolet radiation, and an ablatable membrane layer carried by said plate for expendable use in providing a predetermined ablative sculpture of the optically used central area of the anterior surface of the cornea, said membrane being opaque to ultraviolet radiation and having a central circular area of varying thickness which is a function of radius between central inner and radially outer limits of the circular area, the thickness ranging from zero at one of said limits to maximum at the other of said limits, said membrane being of such maximum thickness within said circular area as to require, for a given intensity of ultraviolet radiation, a predetermined total exposure to achieve total ablation of said maximum thickness, said predetermined total exposure being that which is predetermined to achieve a given maximum stroma-penetration depth for a given sculpturing recurvature of the anterior surface of a cornea exposed to ultraviolet radiation via transmission through said plate;

which method comprises preparing said plate with a uniformly thick membrane layer on one plane surface thereof, the material of said membrane layer being opaque to ultraviolet radiation, and exposing a central area of said layer to selective ultraviolet radiation and attendant ablative photodecomposition in a volumetric removal of membrane material and with full depth penetration at one locality within said central area, and essentially zero depth penetration at another locality within said central area, such that a predetermined thickness profile is established between said localities.

2. The method of claim 1, in which the thickness variation ranges from essentially zero thickness at the center of said area, to maximum thickness near the peripheral limit of said central area.

3. The method of claim 1, in which the thickness variation ranges from maximum thickness at the center of said area, to essentially zero thickness near the peripheral limit of said central area.

4. The method of claim 1, in which the thickness variation in said central area ranges from maximum thickness along an alignment through the center and across said central area, to essentially zero thickness at equal and opposite maximum lateral offsets from said alignment.

5. The method of claim 1, in which the thickness variation in said central area ranges from minimum thickness along an alignment through the center and across said central area, to essentially said maximum thickness at equal and opposite lateral offsets from said alignment.

7. The method of claim 1 or claim 6, in which the ultraviolet radiation is characterized by a beam having circular symmetry about a central axis of incidence with said membrane layer.

6. The method of making a precharacterized accessory for use in the path of delivery of an ultraviolet laser beam to perform a curvature-changing sculpture of the anterior surface of a cornea, wherein the accessory comprises a substrate having a flat surface which is a reflector of ultraviolet radiation, and an ablatable membrane layer carried by said surface for expendable use in providing a predetermined ablative sculpture of the optically used central area of the anterior surface of the cornea, said membrane being opaque to ultraviolet radiation and having a central elliptical area of varying thickness which is a function of radius between central inner and radially outer limits of the elliptical area, the thickness ranging from zero at one end of said limits to maximum at the other of said limits, said membrane being of such maximum thickness within said elliptical area as to require, for a given intensity of ultraviolet radiation, a predetermined total exposure to achieve total ablation of said maximum thickness, said predetermined total exposure being that which is predetermined to achieve a given maximum stroma-penetration depth for a given sculpturing recurvature of the anterior surface of a cornea exposed to ultraviolet radiation via transmission via reflection from said surface;

which method comprises preparing said plate with a uniformly thick membrane layer on said flat surface, the material of said membrane layer being opaque to ultraviolet radiation, and at an acute angle of incidence directionally exposing a central area of said layer to selective ultraviolet radiation and attendant ablative photodecomposition in a volumetric removal of membrane material and with full depth penetration at one locality within said central area, and essentially zero depth penetration at another locality within said central area, such that a predetermined thickness profile is established between said localities, and said angle of incidence being such in relation to the major;

minor axis relation of said elliptical area as to determine a circular beam section in the reflection from said elliptical area.