Method and apparatus for monitoring laser surgery

• US 6,817,998 B2
• Filed: 03/26/2001
• Issued: 11/16/2004
• Est. Priority Date: 07/23/1999
• Status: Expired due to Fees

• Current Assignee: Leon C. Lahaye
• Original Assignee: Leon C. Lahaye
• Inventors: LaHaye, Leon C.
• Primary Examiner(s): Shay, David M.
• Application Number:
  US09/816,175
• Publication Number:
  US 20010056276A1
• Time in Patent Office: 1,331 Days
• Field of Search: 606/3, 606/5, 606/10-13
• US Class Current: 606/11
• CPC Class Codes: A61B 18/20 using laser
• CPC Class Codes: A61B 2017/00057 Light
• CPC Class Codes: A61B 2018/00636 Sensing and controlling the application of energy
• CPC Class Codes: A61B 2018/00898 Alarms or notifications created in response to an abnormal condition
• CPC Class Codes: A61F 2009/00844 Feedback systems
• CPC Class Codes: A61F 2009/00846 Eyetracking
• CPC Class Codes: A61F 2009/00855 Calibration of the laser system
• CPC Class Codes: A61F 2009/00872 Cornea
• CPC Class Codes: A61F 9/008 using laser
• CPC Class Codes: A61F 9/00804 Refractive treatments
• CPC Class Codes: A61F 9/00814 Laser features or special beam parameters therefor

Abstract

A method and system for laser surgery produces controlled laser pulses and simultaneously verifies that a correct sequence of pulses are being delivered to the patient. A photo detector receives a predetermined portion of the energy of the treatment pulses as they exit the system. A separate monitoring computer compares an output signal from the photo detector with reference information for the treatment sequence. The system is exemplified in an implementation in an ophthalmic laser surgery system.

Claims

1. A method for modifying the cornea of a patient with pulses of laser light in accordance with a treatment sequence comprising the steps of:

generating pulses of laser light;

controlling the pulses of laser light so that selected portions of the cornea are ablated by the pulses in accordance with the treatment algorithm;

during treatment, directing to a photo detector from the last optical element in the system samples of said pulses of laser light being delivered to the cornea of the patient;

comparing an output signal from the photo detector to a reference value derived from the treatment sequence and at least one previously measured photo detector output signal value for a pulse directed to the photodetector from the last optical element in the system; and

providing an indication of the performance of the laser system in response to said comparison.

2. The method of claim 1, wherein the directing of portions of the energy of the pulses being delivered to the cornea of the patient is performed by transmitting the pulses through a beam splitter that is the last optical element in an optical path leading to the cornea of the patient.

3. The system of claim 1, wherein laser light pulses for ablating the cornea and detected by the photo detector are 193 nm UV light pulses.

4. The method of claim 1, wherein the pulses of laser light are controlled so that selected portions of the cornea are ablated by controlling the spatial dimensions of broad beam laser light pulses.

5. The method of claim 4, wherein the broad beam pulses have a spot diameter of from ½

to 8 mm on the cornea of the patient.

6. The method of claim 1,

wherein the pulses of laser light are produced by a laser triggered by a triggering signal from a treatment computer;

wherein the pulses of a laser light are spatially modulated responsive to signals from the treatment computer; and

wherein the treatment computer employs a treatment algorithm appropriate for the patient to determine the spatial modulation of the pulse.

7. The method of claim 6, wherein a second, monitoring computer separately runs the treatment algorithm and provides the reference value responsive to separately inputted treatment parameters and the at least one previously measured photo detector output signal value.

8. The method of claim 6, wherein the comparison is initiated by the monitoring computer responsive to the laser triggering signal.

9. The method of claim 6, wherein the indication of performance is an alarm signal produced when the output signals from the photo detector for a predetermined number of pulses deviate a predetermined amount from the corresponding reference values.

10. The method of claim 6, further comprising the step of shutting down the laser system in response to an indication of performance failure.

11. A system for producing a predetermined treatment pattern of laser pulses for selectively ablating the cornea of a patient and for detecting a pattern of pulses as the pulses are being delivered to the patient comprising:

a laser for producing laser light pulses;

means for controlling pulses of laser light from the laser so that selected portions of the cornea of the patient are ablated in accordance with the predetermined treatment pattern including a first, treatment computer which runs a treatment algorithm based on inputted treatment parameters to produce the predetermined treatment pattern;

a detector for producing signals during treatment indicative of the laser pulses being delivered to the patient over a selected time interval;

a beam splitter for splitting the pulsed laser beam and directing to the detector samples of the pulses as they are delivered to the cornea; and

a second, fail-safe computer for separately running the treatment algorithm to provide reference values for sampled pulses responsive to separately inputted treatment parameters, for comparing signals from the detector with the reference values and for providing an indication of performance of the system in response to the comparison.

12. The system of claim 11, further comprising means for producing a display of the spatial energy distribution of the laser pulses being delivered to the patient.

13. The system of claim 11 further comprising memory for storing energy distribution information derived from the signals produced by the detector.

14. The system of claim 11, wherein the system is a broad beam system using pulses having a spot diameter of from ½

to 8 mm on the cornea of the patient.

15. The system of claim 11, wherein the photo detector is an electronic camera and wherein the laser pulses are focused to produce images of the laser pulse spots.

16. The system of claim 11, further comprising means for controlling the system in response to the signals produced by the detector.

17. The system of claim 16, wherein the control of the system includes shutting down the system upon detection of an improper spatial energy distribution.

18. The system of claim 11, wherein the controlling means scans the laser pulses across an area of the cornea to be ablated.

19. The system of claim 18, wherein the system is a slit scanning laser system.

20. The system of claim 18, wherein the system is a flying spot scanner.

21. The system of claim 20, wherein the system uses laser spots having a diameter between 1 and 2 mm and a pulse rate between 50 and 200 Hz.

22. A system for producing a predetermined treatment sequence of laser light pulses of varying dimension for ablating the cornea of a patient and for continuously monitoring the predetermined treatment sequence being delivered to the patient comprising:

a laser for producing laser light pulses;

a spatial modulator for varying the dimensions of spots projected on the cornea by the laser light pulses;

treatment electronic means for controlling the laser and spatial modulator in accordance with entered data indicative of the predetermined treatment sequence for the patient;

a beam splitter for reflecting a portion of the electromagnetic energy of the laser light pulses delivered to the cornea of the patient and transmitting a portion of the electromagnetic energy of the same laser light pulses, the beam splitter being the last optical element in an optical path leading from the laser to the cornea of the patient;

a laser pulse detector optically coupled to the beam splitter and receiving said portion of electromagnetic energy transmitted through the beam splitter for producing monitoring signals indicative of the laser light pulses delivered to the patient; and

means for comparing the monitoring signals with reference values for the predetermined sequence of laser light pulses.

23. The system of claim 22, wherein the treatment electronic means triggers the laser to produce a light pulse and triggers a comparison of the monitoring signal with a corresponding reference value.

24. The system of claim 22, wherein the laser is a pulsed excimer laser and the spatial modulator includes an iris and slit of varying size, whose size is electronically controlled by the treatment electronic means.

25. The system of claim 22, further comprising a beam homogenizer between said laser and said spatial modulator.

26. The system of claim 22, wherein the laser pulse detector is an electro-optic detector which converts a split portion of electromagnetic energy of the laser pulse from the beam splitter to fluorescent light which is then used to produce an electronic signal.

27. The system of claim 22, further comprising an optical baffle between the beam splitter and the detector for absorbing light scattered by foreign material on the beam splitter.

28. The system of claim 22, wherein the laser pulse detector is an electro-optic detector for producing electronic monitoring signals in response to 193 nm UV light pulses.

29. The system of claim 22, wherein said comparing means comprises:

monitoring electronic means for producing reference values indicative of the expected energy of laser pulses to be delivered to the cornea of the patient, said reference values being calculated in accordance with the data indicative of the predetermined treatment sequence of pulses for the patient; and

electronic means for comparing the monitoring signals with the corresponding reference values calculated by the monitoring electronic means.

30. The system of claim 29, wherein the treatment and monitoring electronic means are separately programmed digital computing devices.

31. The system of claim 30, wherein at least one of said computing devices stores a record of the pulses delivered during the treatment.

32. A system for producing a predetermined treatment sequence of laser pulses for selectively ablating the cornea of a patient and for monitoring the predetermined treatment sequences of pulses as the pulses are being delivered to the patient comprising:

a laser for producing laser light pulses;

means for controlling the size and energy of laser light pulses delivered to the cornea of a patient so that selected portions of the cornea of the patient are ablated in accordance with the predetermined treatment sequence;

a laser pulse detector for producing monitoring signals during treatment indicative of the energy of the laser pulses delivered to the patient; and

a beam splitter optically coupled to the laser pulse detector onto which the controlled laser light pulses are directed prior to reaching the cornea of the patient, the beam splitter having a front surface mirror for reflecting a portion of the energy of the controlled laser light pulses to deliver said portion to the cornea of the patient and for transmitting to the laser pulse detector samples of the delivered pulses, wherein the front surface of the front surface mirror is the last optical surface in an optical path leading from the laser to the cornea of the patient.

33. The system of claim 32, wherein the laser pulse detector produces monitoring signals related in value to the total energy of each of the pulses of light delivered to the cornea of the patient.

34. The system of claim 32, wherein the laser pulse detector comprises an area photo sensor for producing monitoring signals indicative of the spatial energy distribution of pulses of light delivered to the cornea of the patient.

35. The system of claim 32, wherein the controlling means controls the size of broad beam laser spots projected on the cornea of the patient.

36. The system of claim 35, wherein the pulses have a spot diameter of from ½

to 8 mm on the cornea of the patient and a repetition rate of 10 to 50 Hz.