Limbal-based eye tracking

• US 7,682,023 B2
• Filed: 12/31/2004
• Issued: 03/23/2010
• Est. Priority Date: 01/09/2004
• Status: Expired due to Fees

• Current Assignee: Customvis, PLC
• Original Assignee: Customvis, PLC
• Inventors: Van Saarloos, Paul
• Primary Examiner(s): Stultz; Jessica T
• Application Number:
  US10/585,129
• Publication Number:
  US 20080252849A1
• Time in Patent Office: 1,908 Days
• Field of Search: 351/209
• US Class Current: 351/209
• CPC Class Codes: A61B 3/113 for determining or recording eye movement
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

A method of determining and/or tracking the position of an eye, includes utilizing at least two wavelength components of a plural wavelength zone that traverses the limbus of the eye to obtain a profile of whiteness and/or redness across the zone, and identifying from the profile at least one predetermined reference position that indicates the position of the eye. Apparatus for carrying out the method is also disclosed.

Claims

1. A method of determining and/or tracking the position of an eye, including:

utilizing at least two wavelength components of a plural wavelength image of a zone that traverses the limbus of the eye to obtain a profile of whiteness and/or redness across the zone; and

identifying from the profile at least one predetermined reference position that indicates the position of the eye.

2. A method according to claim 1 wherein said zone is a linear zone.

3. A method according to claim 1 wherein said profile is obtained by analyzing the relative intensities of the two wavelength components across said zone.

4. A method according to claim 3 wherein said zone extends substantially radially across the limbus.

5. A method according to claim 1, wherein said at least one predetermined reference position is identified as the centre point of a segment of said zone in which said whiteness and/or redness profile has the greatest gradient.

6. A method according to claim 1, including recording said plural wavelength image prior to carrying out said utilizing and identifying steps.

7. A method according to claim 1, wherein said two wavelength components are in the visible light range of the electromagnetic spectrum.

8. A method according to claim 1, wherein said image is a digitally recorded image.

9. A method according to claim 8 wherein said image is a digital video record or like image of the zone.

10. A method according to claim 1 wherein said profile of whiteness is obtained.

11. A method according to claim 1 wherein said profile of whiteness is obtained from at least two of three wavelength components that mix to characterize the colors of the image.

12. A method according to claim 11 wherein substantially equal intensities of the wavelength components indicates the sclera, while a high intensity of one or two of the wavelength components relative to the other (s) indicates the iris.

13. A method according to claim 11 wherein said three wavelength components comprise red, green and blue (RGB) in a color video system.

14. A method according to claim 1 wherein said image includes the whole or substantially the whole limbus.

15. A method according to claim 1 further including locating the position of the centre of the eye by determining data points comprising multiple said reference positions at spaced intervals about the limbus and then analyzing these data points to locate the centre of the limbus and thereby characterized the position of the eye.

16. A method according to claim 1 incorporated in a method of treating an eye by laser ablation and utilized to determine track the position of the eye for the purpose of properly positioning each laser pulse.

30. A method according to claim 2 wherein said zone extends substantially radially across the limbus.

31. A method according to claim 4, including recording said plural wavelength image prior to carrying out said utilizing and identifying steps.

34. A method according to claim 4 wherein said image includes the whole or substantially the whole limbus.

35. A method according to claim 2 incorporated in a method of treating an eye by laser ablation and utilized to determine track the position of the eye for the purpose of properly positioning each laser pulse.

36. A method according to claim 4 incorporated in a method of treating an eye by laser ablation and utilized to determine track the position of the eye for the purpose of properly positioning each laser pulse.

17. Ophthalmic laser ablation apparatus including:

means to deliver a pulsed laser beam for performing a laser ablation procedure on an eye of a patient;

means positionable to view and record a plural wavelength component digital image of at least a zone of the eye of the patient that traverses the limbus of the eye; and

analysis means connected to receive said digital image and programmed to;

(i) utilize at least two wavelength components of a plural wavelength image of a zone that traverses the limbus of the eye to obtain a profile of whiteness and/or redness across the zone; and

(ii) identifying from the profile at least one predetermined reference position that indicates the position of the eye.

18. Apparatus according to claim 17 wherein said zone is a linear zone.

19. Apparatus according to claim 17 wherein said profile is obtained by analyzing the relative intensities of the two wavelength components across said zone.

20. An apparatus according to claim 19 wherein said means positionable to view and record a plural wavelength component digital image of at least a zone of the eye is arranged so that said zone extends substantially radially across the limbus.

21. Apparatus according to claim 17 wherein said at least one predetermined reference position is identified as the centre point of a segment of said zone in which said whiteness profile has the greatest gradient.

22. Apparatus according to claim 17 wherein said two wavelength components are in the visible light range of the electromagnetic spectrum.

23. Apparatus according to claim 17 wherein said image is a digitally recorded image.

24. Apparatus according to claim 23 wherein said image is a digital video record or the like image of the zone.

25. Apparatus according to claim 17 wherein said analysis means is programmed to obtain said profile of whiteness.

26. Apparatus according to claim 17 wherein said profile of whiteness is obtained from at least two of three wavelength components that mix to characterized the colors of the image.

27. Apparatus according to claim 26 wherein substantially equal intensities of the wavelength components indicates the sclera, while a high intensity of one or two of the wavelength components relative to the other (s) indicates the iris.

28. Apparatus according to claim 26 wherein said three wavelength components comprise red, green and blue (kGB) in a color video system.

29. Apparatus according to claim 17 wherein said image includes the whole or substantially the whole limbus.

38. An apparatus according to claim 18 wherein said means positionable to view and record a plural wavelength component digital image of at least a zone of the eye is arranged so that said zone extends substantially radially across the limbus.

39. Apparatus according to claim 20 wherein said profile of whiteness is obtained from at least two of three wavelength components that mix to characterized the colors of the image.

40. Apparatus according to claim 39 wherein substantially equal intensities of the wavelength components indicates the sclera, while a high intensity of one or two of the wavelength components relative to the other (s) indicates the iris.

41. Apparatus according to claim 20 wherein said image includes the whole or substantially the whole limbus.

32. A method according to 4 wherein said profile of whiteness is obtained from at least two of three wavelength components that mix to characterize the colors of the image.

33. A method according to claim 32 wherein substantially equal intensities of the wavelength components indicates the sclera, while a high intensity of one or two of the wavelength components relative to the other (s) indicates the iris.

37. A method according to claim 32 incorporated in a method of treating an eye by laser ablation and utilized to determine track the position of the eye for the purpose of properly positioning each laser pulse.