Background reduction apparatuses and methods of ocular surface interferometry (OSI) employing polarization for imaging, processing, and/or displaying an ocular tear film

• US 9,642,520 B2
• Filed: 04/25/2013
• Issued: 05/09/2017
• Est. Priority Date: 04/01/2009
• Status: Active Grant

• Current Assignee: TearScience Inc. (Johnson & Johnson)
• Original Assignee: TearScience Inc. (Johnson & Johnson)
• Inventors: Korb, Donald R., Weber, William L., Chinnock, Randal B., Gravely, Benjamin T., Grenon, Stephen M.
• Primary Examiner(s): PINKNEY, DAWAYNE
• Application Number:
  US13/870,214
• Publication Number:
  US 20130229624A1
• Time in Patent Office: 1,475 Days
• Field of Search: 351206, 351200, 351205, 351209, 351210, 351221-223, 351245, 351246, 351212, 351208, 351160 R, 351159, 351247
• CPC Class Codes: A61B 3/0025 characterised by electronic signal processing, e.g. eye models
• CPC Class Codes: A61B 3/0041 characterised by display arrangements
• CPC Class Codes: A61B 3/1005 for measuring distances inside the eye, e.g. thickness of the cornea A61B3/11 takes precedence
• CPC Class Codes: A61B 3/101 for examining the tear film
• CPC Class Codes: A61B 3/14 Arrangements specially adapted for eye photography apparatus or arrangements for taking photographs per se G03B
• CPC Class Codes: G06T 2207/30041 Eye; Retina; Ophthalmic
• CPC Class Codes: G06T 7/0012 Biomedical image inspection

Abstract

Background reduction apparatuses and methods of Ocular surface interferometry (OSI) employing polarization are disclosed for measuring a tear film layer thickness (TFLT) of the ocular tear film, including lipid layer thickness (LLT) and/or aqueous layer thickness (ALT) and can be used to evaluate and potentially diagnosis dry eye syndrome (DES). In certain disclosed embodiments, a multi-wavelength light source can be controlled to illuminate the ocular tear film. Light emitted from the multi-wavelength light source undergoes optical wave interference interactions in the tear film. An imaging device can be focused on the lipid layer of the tear film to capture optical wave interference interactions of specularly reflected light from the tear film combined with a background signal(s) in at least one image. The at least one image can be processed and analyzed to measure a tear film layer thickness (TFLT), including lipid layer thickness (LLT) and/or aqueous layer thickness (ALT).

Claims

1. An apparatus for imaging an ocular tear film of an eye, comprising:

an imaging device platform for mounting an imaging device along an imaging axis;

a light source attached to the imaging device platform and arranged to direct a light at an illumination angle that is off axis relative to the imaging axis to avoid projecting light directly into a pupil of an eye, the light including unpolarized light having a first intensity in an illumination path to illuminate a region of interest (ROI) of an ocular tear film, thereby producing a specularly reflected light in a first polarization plane containing optical wave interference from the ROI of the ocular tear film;

a polarizer disposed in the illumination path having a polarization axis parallel or substantially parallel to the first polarization plane of the specularly reflected light such that a background signal comprised of the unpolarized light returned from the ROI of the ocular tear film has a second intensity less than the first intensity; and

an imaging device attached to the imaging device platform and configured to capture the optical wave interference of the specularly reflected light and the background signal from the ROI of the ocular tear film.

2. The apparatus of claim 1, wherein the light source is multi-wavelength.

3. The apparatus of claim 2, wherein a control system is configured to receive at least one image containing the optical wave interference of the specularly reflected light and the background signal captured by the imaging device while illuminated by multi-wavelength light passing through the polarizer.

4. The apparatus of claim 1, wherein background subtraction is not utilized to reduce the background signal.

5. The apparatus of claim 1, wherein the polarizer attenuates the unpolarized light thereby increasing a ratio of the specularly reflected light to the background signal comprised of the unpolarized light returned from the ROI of the ocular tear film.

6. The apparatus of claim 1, wherein the background signal includes the unpolarized light from the ocular tear film comprising at least a portion of the background signal.

7. The apparatus of claim 1, wherein the polarizer decreases the first intensity of the background signal comprised of the unpolarized light returned from the ROI of the ocular tear film as compared to the first intensity of the background signal if the polarizer were not disposed in the illumination path.

8. The apparatus of claim 1, further comprising a second polarizer disposed in an imaging path of the imaging device.

9. The apparatus of claim 8, wherein the second polarizer has a polarization axis aligned parallel or substantially parallel with the specularly reflected light in the first polarization plane from the ROI of the ocular tear film.

10. The apparatus of claim 8, wherein the unpolarized light making up the background signal is reduced by at least 50 percent compared to utilization of the polarizer alone.

11. The apparatus of claim 8, wherein a ratio of specularly reflected light intensity from the ocular tear film to background signal intensity is at least 400 percent.

12. The apparatus of claim 8, wherein the second polarizer is held by a rotatable holder such that the second polarizer is selectively disposable between a first position within the imaging path of the imaging device and a second position outside the imaging path of the imaging device.

13. The apparatus of claim 12, wherein the rotatable holder is coupled to an electric motor that is usable to selectively dispose the second polarizer between the first position and the second position.

14. The apparatus of claim 1, further comprising:

the polarizer being disposed in an illumination path between a multi-wavelength light source and the ocular tear film,

wherein the polarizer has a polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film; and

a second polarizer disposed in an imaging path of the imaging device,

wherein the second polarizer has a polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film.

15. The apparatus of claim 14, wherein randomly polarized light making up the background signal is reduced by at least 50 percent compared to utilization of the polarizer alone.

16. The apparatus of claim 14, wherein a ratio of specularly reflected light intensity from the ocular tear film to background signal intensity is at least 400 percent.

17. The apparatus of claim 1, wherein the background signal includes at least one of stray light and ambient light.

18. The apparatus of claim 1, wherein a multi-wavelength light source is comprised of a multi-wavelength Lambertian light source configured to uniformly or substantially uniformly illuminate the ROI of the ocular tear film.

19. The apparatus of claim 1, wherein the polarizer is a circular polarizer.

20. The apparatus of claim 3, wherein the control system is further configured to display the at least one image on a visual display.

21. A method of imaging an ocular tear film of an eye, comprising:

directing multi-wavelength light including unpolarized light having a first intensity in an illumination path to illuminate a region of interest (ROI) of an ocular tear film thereby producing a specularly reflected light in a first polarization plane containing optical wave interference from the ROI of the ocular tear film while avoiding projecting the multi-wavelength light directly into a pupil of an eye;

polarizing the unpolarized light such that a background signal comprised of the unpolarized light returned from the ROI of the ocular tear film to have a second intensity less than the first intensity;

capturing at least one image of the optical wave interference of the specularly reflected light and the background signal from the ROI of the ocular tear film; and

receiving the at least one image containing the optical wave interference of the specularly reflected light and the background signal.

22. An apparatus for imaging an ocular tear film of an eye, comprising:

an imaging device platform for mounting an imaging device along an imaging axis;

a multi-wavelength light source attached to the imaging device platform and arranged to direct a multi-wavelength light at an illumination angle that is off axis relative to the imaging axis to avoid projecting light directly into a pupil of an eye, the light including unpolarized light having a first intensity in an illumination path to illuminate a region of interest (ROI) of an ocular tear film, thereby producing a specularly reflected light in a first polarization plane containing optical wave interference from the ROI of the ocular tear film;

a polarizer disposed in the illumination path having a polarization axis parallel or substantially parallel to the first polarization plane of the specularly reflected light such that a background signal comprised of the unpolarized light returned from the ROI of the ocular tear film has a second intensity less than the first intensity;

an imaging device attached to the imaging device platform and configured to capture the optical wave interference of the specularly reflected light and the background signal from the ROI of the ocular tear film; and

a control system configured to receive at least one image containing the optical wave interference of the specularly reflected light and the background signal captured by the imaging device while illuminated by the multi-wavelength light passing through the polarizer.

23. The apparatus of claim 22, wherein background subtraction is not utilized to reduce the background signal.

24. The apparatus of claim 22, wherein the polarizer attenuates the unpolarized light thereby increasing a ratio of the specularly reflected light to the background signal comprised of the unpolarized light returned from the ROI of the ocular tear film.

25. The apparatus of claim 22, wherein the background signal includes the unpolarized light from the ocular tear film comprising at least a portion of the background signal.

26. The apparatus of claim 22, wherein the polarizer decreases the first intensity of the background signal comprised of the unpolarized light returned from the ROI of the ocular tear film as compared to the first intensity of the background signal if the polarizer were not disposed in the illumination path.

27. The apparatus of claim 22, further comprising a second polarizer disposed in an imaging path of the imaging device.

28. The apparatus of claim 27, wherein the second polarizer has a polarization axis aligned parallel or substantially parallel with the specularly reflected light in the first polarization plane from the ROI of the ocular tear film.

29. The apparatus of claim 27, wherein the unpolarized light making up the background signal is reduced by at least 50 percent compared to utilization of the polarizer alone.

30. The apparatus of claim 27, wherein a ratio of specularly reflected light intensity from the ocular tear film to background signal intensity is at least 400 percent.

31. The apparatus of claim 27, wherein the second polarizer is held by a rotatable holder such that the second polarizer is selectively disposable between a first position within the imaging path of the imaging device and a second position outside the imaging path of the imaging device.

32. The apparatus of claim 31, wherein the rotatable holder is coupled to an electric motor that is usable to selectively dispose the second polarizer between the first position and the second position.

33. The apparatus of claim 22, further comprising:

the polarizer being disposed in an illumination path between the multi-wavelength light source and the ocular tear film,

wherein the polarizer has a polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film; and

a second polarizer disposed in an imaging path of the imaging device,

wherein the second polarizer has a polarization axis that is parallel or substantially parallel to the first polarization plane of the specularly reflected light from the ROI of the ocular tear film.

34. The apparatus of claim 33, wherein randomly polarized light making up the background signal is reduced by at least 50 percent compared to utilization of the polarizer alone.

35. The apparatus of claim 33, wherein a ratio of specularly reflected light intensity from the ocular tear film to background signal intensity is at least 400 percent.

36. The apparatus of claim 22, wherein the background signal includes at least one of stray light and ambient light.

37. The apparatus of claim 22, wherein the multi-wavelength light source is comprised of a multi-wavelength Lambertian light source configured to uniformly or substantially uniformly illuminate the ROI of the ocular tear film.

38. The apparatus of claim 22, wherein the polarizer is a circular polarizer.

39. The apparatus of claim 22, wherein the control system is further configured to display the at least one image on a visual display.