Laser surgery device and method

• US 6,454,761 B1
• Filed: 01/30/1995
• Issued: 09/24/2002
• Est. Priority Date: 01/30/1995
• Status: Expired due to Fees

• Current Assignee: Philip D. Freedman
• Original Assignee: Philip D. Freedman
• Inventors: Freedman, Philip D.
• Primary Examiner(s): Shay, David M.
• Application Number:
  US08/380,639
• Time in Patent Office: 2,794 Days
• Field of Search: 606/2, 606/3-7, 606/10-17, 600/407, 600/425, 600/473, 600/476
• US Class Current: 606/5
• CPC Class Codes: A61B 18/20 using laser
• CPC Class Codes: A61B 2018/00636 Sensing and controlling the application of energy
• CPC Class Codes: A61B 2018/00642 with feedback, i.e. closed loop control
• CPC Class Codes: A61B 3/102 for optical coherence tomography [OCT]
• CPC Class Codes: A61F 2009/00851 Optical coherence topography [OCT]
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 9/00804 Refractive treatments

Abstract

Laser surgery is controlled by interferometry.

Claims

1. A method of treating biological tissue by laser surgery, comprising detecting a limit or location of surface or mass of biological tissue by a process of interferometry and controlling the laser treating of said biological tissue according to the detected limit or location of surface or mass.

2. The method of claim 1, comprising controlling a method of radial keratotomy.

3. The method of claim 1, comprising detecting said extent of said surface or mass of biological tissue by a process of optical coherence tomography.

4. The method of claim 1, wherein said controlling step comprises controlling a laser beam irradiator according to an ablating plan constructed according to said detecting step.

5. The method of claim 4, wherein said controlling step comprises controlling a laser beam irradiator according to an ablating plan constructed according to said detecting step and (i) by detecting ablating incision by said process of interferometry, (ii) by detecting ablating incision by an intermittent pulse from said laser beam irradiator or (iii) by a combination of detecting ablating incision by said process of interferometry and by an intermittent pulse from said beam irradiator.

6. The method of claim 1 for ablating biological tissue, comprising:

(A) detecting the limits of a surface plane of biological tissue by scanning the tissue with a phase modulated measurement beam; and

(B) ablating the limits of the surface plane of tissue according to said detecting step.

7. The method of claim 6 comprising successively detecting limits of layers of tissue while successively ablating the limits of said layers of tissue.

8. The method of claim 1, comprising:

(A) projecting an interference light beam onto a multilayer target of biological tissue;

(B) detecting the interference light beam reflected by said multilayer target to provide an interferogram;

(C) evaluating said multilayer target on the basis of said interferogram; and

(D) controlling the laser treating of said biological tissue according to said evaluating step.

9. The method of claim 8, comprising:

(A) synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof to produce an interference light beam and projecting said interference light beam onto a multilayer target of biological tissue;

(B) detecting the interference light beam reflected by said multilayer target to provide an interferogram;

(C) evaluating said multilayer target by performing Fourier transform on said interferogram to provide a reflection spectrum filtered to provide a spatialgram; and

(D) controlling the laser treating of said biological tissue according to the spatialgram provided in said evaluating step.

10. The method of claim 9, comprising conducting a sequence of steps (A), (B) and (C) to provide the thickness and the boundary state of a layer of said biological tissue and controlling said laser treating of biological tissue according to thickness and boundary state of the layer.

11. The method of claim 10, comprising constructing a three dimensional image of said biological tissue according to said sequence of steps and comparing said three dimensional image of said tissue to a standard to provide an ablating plan and controlling the laser treating of said biological tissue according to said ablating plan.

12. The method of claim 1, comprising:

(A) projecting a phase modulated measurement beam onto a target of biological tissue and projecting a reference beam onto a reference target;

(B) combining a reflected reference beam reflected from said reference target with a reflected measurement beam reflected by the target of biological tissue;

(C) evaluating a phase difference between the reflected reference beam and the reflected measurement beam; and

(D) controlling the laser treating of said biological tissue according to said evaluating step.

13. The method of claim 12, comprising repeating said steps (A), (B) and (C) to provide a set of repetitively detected phase differences that are evaluated by a comparison with a representation of a standard of biological tissue.

14. The method of claim 13, further comprising constructing an image of said biological tissue from said set of repetitively detected phase differences and comparing said image to a representation of a standard to construct an ablating plan for said laser treating step (D).

15. The method of claim 14, comprising focusing a treatment laser beam on the said biological tissue according to said evaluating step to achieve selective surgery of said biological tissue according to repetitively detected phase differences.

16. The method of claim 12, wherein step (A) comprises (i) projecting said measurement beam to successively survey layers along an axis substantially perpendicular to the projection of said beam or (ii) projecting said measurement beam to successively survey layers substantially parallel to the projection of said beam and constructing a cross-sectional image of the entire mass of target tissue from evaluating the phase difference step (C).

17. The method of claim 16, comprising (a) surveying a plane of said target tissue by successively projecting said measurement beam onto a plane of said target region having X-Y axes to define said plane, (b) successively surveying a next plane incrementally displaced along a Z axis perpendicular to said X-Y axes, and (c) repeating step (b) to provide a three dimensional image for comparing to a standard to construct an ablating plan.

18. The method of claim 12, comprising determining an absolute distance to the target of biological tissue according to steps (A), (B), and (C);

and (i) projecting an interference light beam onto the target of biological tissue;

(ii) detecting the interference light beam reflected by said target of biological tissue to provide an interferogram; and

(D) controlling the laser treating of the biological tissue according to said absolute distance and said interferogram.

19. A laser surgery device, comprising:

laser beam irradiator for applying a laser beam to a target region of biological tissue;

interferometer for projecting a light beam onto said target region of biological tissue, including a detector for receiving a reflected interference beam from said target region, detecting a phase difference of said interference beam and providing an electrical signal according to said phase difference; and

a controller responsive to said electrical signal for controlling an output of applied laser beam from said laser beam irradiator.

20. The laser surgery device of claim 19, wherein said controller comprises a processor that compares said electrical signal to a standard, constructs an ablating plan according to the comparison and controls the output of applied laser beam from the laser beam irradiator according to the ablating plan.

21. The laser surgery device of claim 19, wherein said controller comprises a processor that compares said electrical signal to a standard and determines factors of total power intensity, pulse duration, repetition rate or position of a light guide for said laser beam irradiator and controls the output of applied laser beam from the laser beam irradiator according to the determined factors.

22. The laser surgery device of claim 19, wherein said interferometer comprises:

(A) an optical source comprising a multimode laser diode that provides a light beam having a range of stable wavelengths;

(B) a lens element that focuses the light beam onto a beam splitter that splits said light beam to provide a reference beam and a measurement beam;

(C) a focusing system for receiving the reference beam and focusing the reference beam onto a phase modulating element that provides a phase modulation to the reference beam;

(D) a focusing system for receiving the measurement beam and focusing the measurement beam onto a measurement region that reflects said measurement beam;

(E) polarizer that receives a reflected reference beam from the phase modulating element and a reflected measurement beam from said measurement region and collapses the differently polarized reference and measurement beams onto a common polarization; and

(F) a lens system that injects the reference and measurement beams to the detector.

23. The laser surgery device of claim 19, wherein said interferometer comprises:

(A) an optical source for emitting a light beam in a predetermined wave number region;

(B) beam splitter for transforming the emitted light beam into a transmitted beam and a reflected beam;

(C) mirrors for reflecting said transmitted and reflected beams in different paths said beam splitter for synthesizing an interference beam from said reflected beams; and

(B) an emitter that emits said interference beam onto said target region of biological tissue.

24. The laser surgery device of claim 23, including Fourier transformer for performing Fourier transform to provide a spatialgram from said phase difference that is converted into said electrical signal.

25. The laser surgery device of claim 23, including Fourier transformer for performing Fourier transform to provide a reflection spectrum, filtering means for filtering the reflection spectrum, complex power reverse Fourier transformer for performing power reverse Fourier transform on the reflection spectrum filtered to provide a spatialgram and a processor for evaluating the target region on the basis of the electrical signal converted from the spatialgram and said laser beam irradiator is responsive to the evaluator.