Eye tracking and positioning system for a refractive laser system

• US 6,280,436 B1
• Filed: 08/10/1999
• Issued: 08/28/2001
• Est. Priority Date: 08/10/1999
• Status: Expired due to Fees

• Current Assignee: Memphis Eye & Cataract Associates Ambulatory Surgery Center
• Original Assignee: Memphis Eye & Cataract Associates Ambulatory Surgery Center
• Inventors: Williams, Roy E., Freeman, Jerre M., Freeman, James F.
• Primary Examiner(s): Dvorak, Linda C. M.
• Assistant Examiner(s): FARAH, AHMED M
• Application Number:
  US09/371,195
• Time in Patent Office: 749 Days
• Field of Search: 606/4-6, 606/10, 606/11, 606/12, 606/13, 606/17, 606/41, 351/200, 351/237, 128/898
• US Class Current: 606/5
• CPC Class Codes: A61F 2009/00846 Eyetracking
• 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 eye tracking and positioning system for use with a refractive laser system includes a camera interface, a computer, and a system for moving the patient relative to the laser beam. The computer includes a video frame grabber which extracts images of the eye from the camera, and is programmed to perform an eye tracking algorithm. The eye tracking algorithm calculates the exact center of the eye pupil, and compares the center with the desired location of the laser beam, as determined by a surgeon, with an image processing algorithm. If the relative location of the eye center and the laser beam fall outside a predetermined value, the patient chair, and thereby the patient, is repositioned relative to the laser beam, as opposed to the laser beam being repositioned relative to the patient. The repositioning counters the movement of the eye.

Claims

1. An eye tracking and positioning system for use with a refractive laser system which produces a laser beam for performing surgery on an eye of a patient, the refractive laser system having a video-out port, said eye tracking and positioning system comprising:

a) a computer system including,

i) a means for receiving an image of the eye from the video-out port,

ii) a means for processing the image, and

iii) a means determining from the processed image whether the eye is properly positioned relative to the laser beam; and

b) adjustment means for adjustably moving the patient relative to the laser beam based on input to said adjustment means from said computer system.

2. An eye tracking and positioning system according to claim 1, wherein:

said adjustment means is adapted to move the patient in X and Y directions, such that when said computer system determines that the eye is mispositioned relative to the laser beam, said adjustment means moves the patient to result in proper relative positioning of the eye of the patient and the laser beam.

3. An eye tracking and positioning system according to claim 1, wherein:

said image is a digital image.

4. An eye tracking and positioning system according to claim 3, wherein:

said means for receiving an image from the video-out port is a digital frame grabber.

5. An eye tracking and positioning system according to claim 1, wherein:

said means for processing the image includes a processor means for,

A) processing the image for eye pupil recognition,

B) determining a center of the eye pupil, and

C) calculating an offset of the center of the eye pupil from a laser beam reference location.

6. An eye tracking and positioning system according to claim 5, wherein:

said processor means is further for determining whether the offset is greater than a predetermined value.

7. An eye tracking and positioning system according to claim 6, wherein:

said computer system includes means for sending a signal, wherein when said offset is greater than said predetermined value, means for sending a signal sends a signal to said adjustment means.

8. An eye tracking and positioning system according to claim 5, wherein:

said processor means determines the center of the eye pupil by increasing the contrast between the pupil and an iris surrounding the pupil in said image.

9. An eye tracking and positioning system according to claim 8, wherein:

said image is a digital image including a plurality of intensity values, and the contrast is increased by said processor means applying a transfer function to the intensity values in the digital image to produce a bimodal histogram of the intensity values.

10. An eye tracking and positioning system according to claim 9, wherein:

said processor means determines the center of the eye pupil by further applying a threshold function to the bimodal histogram to create a binary representation of the image.

11. An eye tracking and positioning system according to claim 10, wherein:

said processor means processes said binary representation to ensure that the pupil is a circular object.

12. An eye tracking and positioning system according to claim 10, wherein:

said processor means searches said binary representation for objects having a size approximately the size of a human pupil.

13. An eye tracking and positioning system according to claim 5, wherein:

said processor means is further for determining the laser beam reference location.

14. An eye tracking and positioning system according to claim 13, wherein:

said processor means assigns the center of the pupil as the laser beam reference location.

15. An eye tracking and positioning system according to claim 13, wherein:

said processor means sets a laser beam reference location in alignment with an alignment marker.

16. An eye tracking and positioning system according to claim 1, wherein:

said adjustment means is one of a motorized surgical chair and a motorized surgical bed.

17. An eye tracking and positioning system according to claim 1, wherein:

said adjustment means is a motorized patient headrest.

18. An eye tracking and positioning system according to claim 1, further comprising:

c) a switch which activates said means for receiving a digital image of the eye from the video-out port.

19. An eye tracking and positioning system according to claim 1, further comprising:

c) a laser system which produces a laser beam for performing surgery on the eye of the patient.

20. An eye tracking and positioning system according to claim 19, further comprising:

d) a microscope which provides a magnified image of the eye and has means for supplying a video signal to the video-out port.

21. A method for positioning an eye of a patient relative to a laser beam produced by a refractive laser system for performing eye surgery on the eye, the method including:

a) obtaining an image of the eye;

b) processing the image;

c) determining from the processed image whether the eye is properly positioned relative to the laser beam; and

then

d) if the eye is not properly positioned relative to the laser beam, moving the patient relative to the laser beam to properly position the eye relative to the laser beam.