Method and system for laser treatment of refractive errors using offset imaging

• US 6,203,539 B1
• Filed: 11/12/1997
• Issued: 03/20/2001
• Est. Priority Date: 05/07/1993
• Status: Expired due to Term

• Current Assignee: Amo Manufacturing Usa, Llc (Johnson & Johnson)
• Original Assignee: VISX Incorporated
• Inventors: Shimmick, John K., Telfair, William B., Munnerlyn, Charles R., Glockler, Herrmann J.
• Primary Examiner(s): Shay, David M.
• Application Number:
  US08/968,380
• Time in Patent Office: 1,224 Days
• Field of Search: 606/2-15, 606/17-19
• US Class Current: 606/5
• CPC Class Codes: A61F 2009/00844 Feedback systems
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 2009/00882 based on topography
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61F 9/00804 Refractive treatments
• CPC Class Codes: A61F 9/00806 Correction of higher orders
• CPC Class Codes: A61F 9/00817 Beam shaping with masks

Abstract

An ophthalmological surgery system and method for performing ablative photodecomposition of the corneal surface by offset image scanning. The image of a variable aperture, such as a variable width slit and variable diameter iris diaphragm, is scanned in a preselected pattern to perform ablative sculpting of predetermined portions of a corneal surface. The scanning is performed with a movable image offset displacement mechanism capable of effecting radial displacement and angular rotation of the profiled beam exiting from the variable aperture. The profiled beam is rotated by rotating the aperture in conjunction with the offset displacement mechanism. The invention enables wide area treatment with a laser having a narrower beam, and can be used in the treatment of many different conditions, such as hyperopia, hyperopic astigmatism, irregular refractive aberrations, post ablation smoothing and phototherapeutic keratectomy.

Claims

1. An ophthalmological surgery system for performing selective ablation of a corneal surface of an eye to effect a desired corneal shape, said system comprising:

means for directing a laser beam along a path;

variable aperture means for profiling said beam to produce a variable area profiled beam, said variable aperture profiling means including a variable width slit; and

means for scanning the profiled beam over a predetermined area of the corneal surface while varying the aperture to change the profiled beam in a predetermined manner, said scanning means including means for varying a radial displacement of the profiled beam from an axis of rotation and means for simultaneously varying the angular position of the profiled beam about the axis of rotation in a predetermined manner.

2. The system of claim 1 wherein said variable aperture profiling means includes means for selectively varying the slit width during scanning.

3. The invention of claim 1, further comprising a controller coupled to the variable aperture profiling means and the scanning means, the controller comprising a treatment table having a listing of coordinate references for the profiled beam.

4. The invention of claim 3, wherein the table further comprises a listing of the number of coordinate pulses at each coordinate reference required to effect the desired corneal shape.

5. The invention of claim 1, wherein the scanning means comprises at least one member of the group consisting of a lens, a mirror, and a prism.

6. The system of claim 1 wherein said variable aperture profiling means includes a variable diameter diaphragm.

7. The invention of claim 6 wherein said variable aperture profiling means includes means for selectively varying the diameter of the diaphragm during scanning.

8. The invention of claim 1 wherein said scanning means includes an imaging lens positioned in the path of the profiled beam and means for displacing and rotating said lens means with reference to an axis of rotation.

9. The invention of claim 8 wherein said variable aperture profiling means includes a variable width slit and means for rotating said slit;

and wherein said means for displacing and rotating said lens means and said means for rotating said slit are operationally coupled.

10. The method of performing selective ablation of a corneal surface of an eye to effect a desired corneal shape, said method comprising the steps of:

(a) directing a laser beam along a path;

(b) profiling the beam with a variable width slit to produce a profiled beam;

(c) establishing a center of rotation for the profiled beam;

(d) displacing said profiled beam from the center of rotation by a displacement and varying the displacement of said profiled beam from the center of rotation and

(e) varying an angular position of said profiled beam about the center of rotation to cause said beam to describe a path referenced to the center of rotation.

11. The method of claim 10 wherein said step (b) of profiling includes the steps of varying the slit width in a predetermined manner;

said step (d) of displacing includes the step of varying the displacement of the profiled beam in a manner related to the slit width; and

said step (e) includes the steps of rotating the slit and the profiled beam about the center of rotation in a related manner.

12. The method of claim 10 wherein said step (a) includes the step of operating the laser beam in a pulsed manner;

and wherein said steps (d) of displacing and (e) of varying include the step of repositioning the profiled beam when the laser beam is off.

13. The method of claim 10 wherein said steps (d) of displacing and (e) of varying are performed with an imaging lens placed in the path of the profiled beam.

14. A method of performing selective ablation of a corneal surface of an eye to effect a predetermined hyperopic refractive correction, said method comprising the steps of:

(a) directing a laser beam along a path; and

(b) selectively irradiating the corneal surface of the eye to produce said hyperopic refractive correction by;

(i) intercepting the beam with a variable width slit to produce a profiled beam having an initial width;

(ii) establishing a center of rotation for the profiled beam;

(iii) displacing the profiled beam exiting the slit by an initial amount from the center of rotation;

(iv) rotating the slit and profiled beam by a predetermined angular amount with reference to the center of rotation;

(v) adjusting the slit width;

(vi) displacing the profiled beam exiting the slit by a selected amount; and

(vii)repeating steps (iv)-(vi) until the desired hyperopic correction is completed.

15. The method of claim 14 wherein said steps (iii), (iv) and (vi) are performed with an imaging lens placed in the path of the profiled beam.

16. The method of claim 14 wherein the ablation is to be performed in an optical zone and a transition zone of the corneal surface, the transition zone having an outer edge;

wherein the slit has first and second edges; and

wherein said step (iii) is performed such that the edge portion of the exiting profiled beam associated to the first slit edge impinges the optical zone adjacent the center and the edge portion of the exiting profiled beam associated to the second slit edge impinges the transition zone adjacent the outer edge thereof.

17. The method of claim 16 wherein said steps (iv)-(vi) are performed such that the edge portion of the exiting profiled beam associated to the first slit edge impinges the ablation zone at progressively increasing distances from the center thereof and the edge portion of the exiting profiled beam associated to the second slit edge impinges the transition zone adjacent the outer edge thereof.

18. The method of claim 17 wherein said step (iv) of rotating includes the steps of positioning the profiled beam to a position substantially 180°

from an existing position, and then rotating the profiled beam to a subsequent angular position.

19. The method of claim 18 wherein said subsequent angular position is equal to the existing position plus a predetermined incremental amount.

20. A method of performing selective ablation of a corneal surface of an eye to effect a desired corneal shape, said method comprising the steps of:

(a) directing a laser beam toward a variable aperture;

(b) profiling the beam with the variable aperture to produce a variable area profiled beam, wherein said step (b) of profiling includes the step of intercepting the laser beam with a variable width slit and a variable diameter diaphragm; and

(c) scanning the profiled beam over a predetermined area of a corneal surface while varying the aperture to change the profiled beam in a predetermined manner, said step (c) of scanning including the steps of establishing an axis of rotation for the profiled beam, and;

(i) selectably laterally deflecting the beam path from the axis by a displacement amount,

(ii) varying an angular position of the profiled beam about the axis of rotation, and

(iii) varying the displacement amount from the axis in a predetermined manner.

21. The invention of claim 20 wherein said step (c) of scanning includes the step of selectively varying the slit width.

22. The method of claim 20 wherein said step (c) of scanning includes the step of selectively varying the diameter of the diaphragm.

23. The method of claim 20 wherein said step (c) of scanning is performed by scanning the beam over successive arcuate bands in the predetermined area of a corneal surface.

24. The method of claim 20 wherein said step (c) of scanning is performed by scanning the profiled beam over successive annular bands in the predetermined area of the corneal surface.

25. The method of claim 20 wherein said step (c) of scanning is performed by scanning the profiled beam over a predetermined portion of the corneal surface while enlarging the variable aperture.

26. The method of claim 20 wherein said step (c) of scanning is performed by scanning the profiled beam over a predetermined portion of the corneal surface while reducing the variable aperture.

27. The method of claim 20 wherein said step (c) of scanning is preceded by the steps of creating a treatment table containing a listing of coordinate references for the profiled beam and the number of pulses at each coordinate reference required to effect the desired corneal shape, and sorting the listings in the treatment table to establish a scanning pattern for the profiled beam.

28. The method of claim 20 wherein the eye has an anterior corneal surface;

and wherein the corneal surface is the anterior corneal surface.

29. The method of claim 20 wherein the corneal surface is a surface of the cornea exposed by removing the epithelium.

30. The method of claim 20 wherein the corneal surface is the posterior surface of a section cut from the cornea.

31. The invention of claim 20 wherein said step (c) of scanning includes the steps of selectively varying the slit width and selectively varying the diameter of the diaphragm.

32. The invention of claim 20, wherein said step (c) of scanning includes the step of rotating the variable width slit.

33. The method of claim 20 wherein said step (c) of scanning is performed by scanning the profiled beam over a predetermined portion of the corneal surface while alternatively enlarging and reducing the variable aperture.

34. The method of claim 33 wherein the predetermined portion comprises a central zone of the corneal surface.

35. The method of claim 33 wherein the predetermined portion comprises an outer region of the corneal surface.

36. The method of claim 20 wherein said step (c) of scanning is preceded by the steps of establishing an optical zone on the corneal surface in which the desired corneal shape is to be effected, the optical zone having an outer boundary, and establishing a transition zone between the optical zone and a remaining corneal surface, and wherein said step (c) of scanning is performed by scanning the profiled beam over the optical zone and the transition zone to effect the desired corneal shape.

37. The method of claim 36 wherein the transition zone has an inner boundary and an outer boundary;

wherein said variable width slit has inner and outer edges; and

wherein said step (c) of scanning includes the step of maintaining that portion of the profiled beam corresponding to first and second intersections of the diaphragm and the outer edge of the slit adjacent the outer boundary of the transition zone.

38. The method of claim 37 wherein said step (c) is further performed by narrowing the slit width by translating the inner edge of the slit toward the outer edge of the slit.

39. A method of performing selective ablation of a corneal surface of an eye to effect a desired corneal resculpting, said method comprising the steps of:

directing a laser beam toward the cornea along a beam path;

establishing a center of rotation for the beam;

displacing said beam path from the center of rotation by a displacement, wherein the beam has an elongate substantially rectangular beam shape, and wherein the displacing step is performed so that the elongate substantially rectangular beam shape is oriented laterally relative to the center of rotation;

varying the displacement of said beam from the center of rotation;

varying an angular position of said beam about the center of rotation and rotating the elongate substantially rectangular beam shape so that the rotated elongate substantially rectangular beam shape is laterally oriented relative to the center of rotation;

intercepting the beam with a variable diameter iris and a variable width slit, and varying a diameter of the iris and a width of the slit; and

rotating the variable width slit in coordination with the varying of the angular position of the beam, the slit having a first edge movable relative to an opposed second edge, wherein the slit rotating step is performed so that a first elongate side of the beam defined by the first edge of the slit comprises an inner edge oriented toward the axis of rotation and a second elongate side of the beam defined by the second edge of the slit comprises an outer edge oriented toward a peripheral boundary of said desired corneal resculpting.