Laser beam and ablating apparatus and related method

• US 5,624,436 A
• Filed: 01/28/1994
• Issued: 04/29/1997
• Est. Priority Date: 01/29/1993
• Status: Expired due to Term

• Current Assignee: Nidek Company Limited
• Original Assignee: Nidek Company Limited
• Inventors: Nakamura, Takua, Sugiyama, Kazuharu
• Primary Examiner(s): Shay, David M.
• Application Number:
  US08/187,735
• Time in Patent Office: 1,187 Days
• Field of Search: 219/121.6, 219/121.73, 219/121.74, 219/121.75, 219/121.8, 606/2, 606/3, 606/5, 606/10-19
• US Class Current: 606/12
• CPC Class Codes: A61B 2017/00707 Dummies, phantoms; Devices simulating patient or parts of patient
• CPC Class Codes: A61B 2017/00725 Calibration or performance testing
• CPC Class Codes: A61B 2218/006 for smoke evacuation
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61F 9/00804 Refractive treatments

Abstract

An ablation apparatus for ablating by laser beam including a laser beam providing means for providing laser beam to ablate an object to be processed into a desired form, a light beam delivering optical system for delivering the laser beam to the object to be processed, an ablation area changing diaphragm for changing ablation area on the object to be processed, and a control device for controlling the motion of the ablation area changing diaphragm, the ablation apparatus comprising instructing device for instructing the controlling device to form a curved surface with a first optical characteristic on the rate reference object which has a known ablation rate as to an ablation rate of the object to be processed, measuring device for measuring a second optical characteristic of the curved surface actually formed on a rate reference object in accordance with control by the controlling device, input device for inputting the second optical characteristic measured by the measuring device, and correcting device for calculating an ablation rate with respect to the object to be processed based on a comparison between the second optical characteristic input by the input device and the first optical characteristic whereby a driving information of the ablation apparatus is corrected.

Claims

1. An ablating apparatus, comprising:

a controller;

a laser beam source coupled to and governed by the controller;

an optical system responsive to a laser beam from the laser beam source for directing the laser beam along a path to an ablation area position of a first object to be ablated;

means disposed in the laser beam path responsive to the controller for changing the position of the ablation area of the first object to be ablated,

a second object for positioning in the path of the laser beam, said second object having a known ablation rate relative to the first object to be ablated;

first means coupled to the controller for instructing said ablation area position changing means and the laser source to ablate the second object by forming a curved surface having a first refractive power;

means coupled to the controller for measuring the first refractive power of the curved surface of the second object to obtain a second measured refractive power; and

means coupled to the measuring means for inputting the measured second refractive power to the controller said controller also including means for comparing the first refractive power to the second measured refractive power, and second means for controlling the laser source and the ablating area position changing means to ablate the first object by forming a curved surface based upon the comparison between the first and second refractive power.

2. An ablation apparatus according to claim 1, wherein the ablation area position changing means comprises a diaphragm with a variable aperture.

3. An ablation apparatus according to claim 1, wherein the measuring means includes a lensmeter for measuring the refractive powers.

4. An ablation apparatus according to claim 1, wherein the first object is a cornea and the second means is for changing curvature of said cornea.

5. An ablation apparatus according to claim 1, wherein the second object is transparent.

6. An ablation apparatus according to claim 5, wherein the second object is made from polymethyl metacrylate (PPMA).

7. A cornea operating apparatus for irradiating an eye to be ablated by a laser beam to correct a refractive error of the eye, the apparatus comprising:

a laser source for emitting a laser beam having a Gaussian distribution in a direction of beam cross section;

an optical system coupled to the laser source for irradiating the laser beam emitted from said laser source along a path and onto a surface of the cornea of the eye to be ablated;

scanning means positioned on the path of the optical system for scanning the laser beam in the direction of Gaussian distribution;

means coupled to a driving control means for determining an error in ablation rate between a refractive power of a simulated lens and a predetermined reference refractive power, the simulated lens being a reference object ablated by said optical system prior to and in place of the cornea of the eye being ablated; and

said driving control means being governed by said determined error in the ablation rate for controlling output power of the laser beam emitted from the laser source and for controlling the scanning of the laser beam by said scanning means.

8. A cornea operating apparatus according to claim 7, wherein the means for determining the error in the ablation rate, comprises:

measuring means for measuring the refractive power of said simulated lens; and

calculating means for calculating the error rate of the ablation rate based on the refractive power of the simulated lens measured by the measuring means and the predetermined reference refractive power.

9. A cornea operating apparatus according to claim 7, wherein said laser source comprises an excimer laser.

10. A cornea operating apparatus according to claim 7, wherein said reference object is made from transparent polymethyl metacrylate resin.

11. A cornea operating apparatus according to claim 7, further comprising ablation plume removing means for removing ablation plume while said reference object is being ablated, the ablation plume being produced from the ablation of the reference object during formation of the simulated lens.

12. A cornea operating apparatus according to claim 7, wherein the means for determining the error in the ablation rate, comprises:

measuring means for measuring the refractive power of said simulated lens; and

calculating means for calculating the error rate of the ablation rate based on the refractive power of the simulated lens measured by the measuring means and the predetermined reference refractive power.

13. A cornea operating apparatus for irradiating an eye to be ablated by a laser beam to correct a refractive error of the eye, the apparatus comprising:

a laser source for emitting a laser beam along a path having a Gaussian distribution in a direction of beam cross section;

beam deflecting means along the path for deflecting a portion of the path of the laser beam emitted from the laser source;

scanning means in a portion of the laser path for scanning the deflected laser beam in the direction of Gaussian distribution;

means disposed in the laser beam path for changing a position of an ablation area on the cornea of the eye to be ablated by the laser beam;

means coupled to a driving control means for determining an error in ablation rate between a refractive power of simulated lens and a predetermined reference refractive power, the simulated lens being a reference object ablated by said optical system prior to and in place of the cornea of the eye being ablated; and

said driving control means begin governed by the error of the ablation rate for controlling output power of the laser beam emitted from the laser source, the scanning of the laser beam and the position of the ablation area.

14. A cornea operating apparatus according to claim 13, further comprising ablation plume removing means for removing ablation plume while said reference object is being ablated, the ablation plume being produced from the ablation of the reference object during formation of the simulated lens.

15. A cornea operating apparatus according to claim 13, wherein said laser source comprises an excimer laser.

16. A cornea operating apparatus according to claim 13, wherein said ablated reference object is made from transparent polymethyl metacrylate resin.

17. A method for ablating to a desired shape an object to be processed positioned in an optical path of a laser beam, comprising the steps of:

positioning a rate reference object, having a known ablation rate, in the optical path of the laser beam;

forming on the rate reference object a curved surface based upon a first refractive power;

removing ablation plume produced by the rate reference object while being irradiated by the laser beam in order to maintain ablation stability;

measuring the formed curved surface to obtain a second refractive power;

comparing the first and second refractive powers;

calculating a rate of ablation for the object to be processed based on the comparison between the first and second refractive powers; and

ablating the object to be processed based on the calculated ablation rate.

18. An ablating method according to claim 17, wherein the step of positioning the rate reference object, comprises positioning a transparent rate reference object.

19. An ablating method according to claim 17, wherein the step of removing the ablation plume comprises:

blowing air over the rate reference object while the object is being irradiated by the laser beam.

20. An ablating method according to claim 17, wherein the step comprises:

measuring the refractive power by a lensmeter.

21. A laser beam ablation method comprising the steps of:

ablating with the laser beam an ablation rate reference object to manufacture a simulated lens;

measuring a refractive power of the simulated lens;

calculating an error rate between the measured refractive power of the simulated lens and a predetermined reference refractive power;

calculating an ablation rate of an object to be ablated based on the calculated error rate of the refractive power; and

ablating the object to be ablated by the laser beam based on the calculated ablation rate.

22. An ablating method according to claim 21, wherein said step of ablating with the laser beam an ablation rate reference object, comprises ablating an ablation rate reference object that includes transparent polymethyl methacrylate resin.

23. An ablating method according claim 21 wherein the step of ablating said object to be ablated includes ablating a cornea.