Noncontact type tonometer

• US 4,944,303 A
• Filed: 12/24/1987
• Issued: 07/31/1990
• Est. Priority Date: 12/27/1986
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Topcon 1-GO 75-Ban Hasunuma-Cho Itabashi-Ku Tokyo-To
• Original Assignee: Topcon Corporation
• Inventors: Katsuragi, Kenjiro
• Primary Examiner(s): Hindenburg, Max
• Assistant Examiner(s): Lacyk, John P.
• Application Number:
  US07/137,611
• Time in Patent Office: 950 Days
• Field of Search: 128/645, 128/648
• US Class Current: 600/401
• CPC Class Codes: A61B 3/165 Non-contacting tonometers

Abstract

A noncontact type tonometer, in which an axial line extending in the direction of air pulse projected by an air pulse projecting nozzle towards a cornea of an eye to be tested is coaxial with an optical axis of an alignment optical system for verifying an alignment with respect to a vertex of the cornea, includes an anterior portion observing system capable of optically observing an anterior portion of the eye and having an optical axis coaxial at least with a part of the optical axis of the alignment optical system.

Claims

1. A noncontact type tonometer having an orifice tube for discharging a fluid to deform a cornea of an eye under test and an alignment optical system for aligning an axis of the orifice tube with the cornea and viewing the anterior portion of the eye under test, said alignment optical system comprising:

an orifice tube disposed along an axis;

projection means for projecting an alignment target mark onto the cornea of the eye under test, the alignment target mark including light of a first range of wavelengths;

illumination means for illuminating an anterior portion of the eye under test with light of a second range of wavelengths different from said first range of wavelengths;

first imaging optical means, having a first optical axis coaxial with the axis of the orifice tube, for forming an image of the alignment target mark on a plane and for passing light of the first range of wavelengths;

second imaging optical means for forming an image of the anterior portion of the eye on the plane and for passing light of the second range of wavelengths; and

reticle means for providing a reticle image on the plane, the relative positions between the reticle image and at least one of (i) the image of the alignment target and (ii) the image of the anterior portion of the eye formed on the plane being indicative of the relative positions of the axis of the orifice tube and the cornea.

2. A non-contact tonometer as claimed in claim 1, wherein the reticle is an image of a reticle plate projected onto the plane.

3. A non-contact tonometer as claimed in claim 1, wherein the reticle formed on the plane is co-axial with the first optical axis.

4. A non-contact tonometer as claimed in claim 1, wherein said first range of wavelengths is in the infrared range.

5. A non-contact tonometer as claimed in claim 4, wherein said second range of wavelengths is in the visible range.

6. A non-contact tonometer as claimed in claim 1, wherein said second imaging optical means includes a first dichroic mirror disposed along said first optical axis for passing light in said first range of wavelengths and reflecting light in said second range of wavelengths along a second optical path, a second dichroic mirror for passing light in said first range of wavelengths and reflecting light in said second range of wavelengths along said first optical axis, and at least one mirror for reflecting light in said second range of wavelengths emanating from said first dichroic mirror to said second dichroic mirror.

7. A non-contact tonometer as claimed in claim 6, further including a reduction projecting system lens group disposed between said first and second dichroic mirrors for forming a reduced image of the anterior portion of the eye on the plane.

8. A non-contact tonometer as claimed in claim 7, wherein the first imaging optical means includes an objective lens for collimating light reflected from the cornea and a telephoto lens for forming the image of light rays reflected from the cornea onto the plane disposed along the first optical axis, the first dichroic mirror being disposed between the objective lens and the telephoto lens.

9. A non-contact tonometer as claimed in claim 8, wherein said first range of wavelengths is in the infrared range.

10. A non-contact tonometer as claimed in claim 9, wherein said second range of wavelengths is in the visible range.

11. A non-contact tonometer as claimed in claim 1 wherein said second imaging optical means includes an annular lens disposed along the first optical axis for forming a reduced image of the anterior portion of the eye on the plane and an annular filter disposed between the cornea of the eye under test and the annular lens for passing only light in said second range of wavelengths to the annular lens.

12. A non-contact tonometer as claimed in claim 11, wherein the first imaging optical means includes an objective lens for collimating light reflected from the cornea and a telephoto lens for forming the image of light rays reflected from the cornea on the plane disposed along the first optical axis, the annular lens being disposed about the objective lens.

13. A non-contact tonometer as claimed in claim -2, wherein said first range of wavelengths is in the infrared range.

14. A non-contact tonometer as claimed in claim 13, wherein said second range of wavelengths is in the visible range.

15. A non-contact tonometer as claimed in claim 4, further including TV camera means having sensitivity in the infrared range for converting an infrared image of the alignment target mark into an electronic signal, the electronic signal being capable of being converted into a visible image by a TV monitor.

16. A non-contact tonometer as claimed in claim 9, further including TV camera means having sensitivity in the infrared range for converting an infrared image of the alignment target mark into an electronic signal, the electronic signal being capable of being converted into a visible image by a TV monitor.

17. A non-contact tonometer as claimed in claim 13, further including TV camera means having sensitivity in the infrared range or converting an infrared image of the alignment target mark into an electronic signal, the electronic signal being capable of being converted into a visible image by a TV monitor.

18. A non-contact type tonometer having an orifice tube for discharging a fluid to deform a cornea of an eye under test and alignment optical system for aligning an axis of the orifice tube with the cornea and viewing the anterior portion of the eye under test, said alignment optical system comprising:

an orifice tube disposed along an axis;

projection means, having an optical axis, at least a part of which is coaxial with the axis of the orifice tube, for projecting an alignment target mark onto a cornea of the eye under test, the alignment target mark including light of a first range of wavelengths;

illumination means illuminating an anterior portion of the eye under test with light of a second range of wavelengths different from said first range of wavelengths;

first imaging optical means, having a first optical axis coaxial with the axis of the orifice tube, for forming an image of the alignment target mark on a plane and for passing light of the first range of wavelengths;

second imaging optical means, having an optical axis at least a part of which is coaxial with the axis of the orifice tube, for forming an image of the anterior portion of the eye on the plane and for passing light of the second range of wavelengths; and

reticle means for providing a reticle image on the plane, the relative positions between the reticle image and at least one of (i) the image of the alignment target and (ii) the image of the anterior portion of the eye formed on the plane being indicative of the relative positions of the axis of the orifice tube and cornea.

19. A non-contact type tonometer as claimed in claim 18, wherein said first imaging optical means includes an objective lens for collimating light reflected from the cornea and a telephoto lens for forming the image of light rays reflected from the cornea onto the plane disposed along the first optical axis, wherein said second imaging optical means includes:

a first dichroic mirror disposed between said objective lens and said telephoto lens for passing light in said first range of wavelengths and reflecting light in said second range of wavelengths along a second optical path;

a second dichroic mirror disposed along said first optical

axis for passing light in said first range of wavelengths and reflecting light in said second range of wavelengths along said first optical axis;

at least one mirror for reflecting light in said second range of wavelengths emanating from said first dichroic mirror to said second dichroic mirror; and

a reduction projecting system lens group disposed between said first and second dichroic mirrors for forming a reduced image of the anterior portion of the eye on the plane.

20. A non-contact type tonometer as claimed in claim 19, wherein said first range of wavelengths is in the infrared range and said second range of wavelengths is in the visible range.

21. A non-contact type tonometer as claimed in claim 20, further including TV camera means having sensitivity in the infrared range for converting an infrared image of the alignment target mark into an electronic signal, the electronic signal being capable of being converted into a visible image by a TV monitor.

22. A non-contact type tonometer as claimed in claim 18, wherein said first imaging optical means includes an objective lens for collimating light reflected from the cornea and a telephoto lens for forming the image of light rays reflected from the cornea onto the plane disposed along the first optical axis, wherein said second imaging optical means includes;

an annular lens disposed about said object lens of said first imaging optical means; and

an annular filter disposed between the cornea of the eye under test and said annular lens for passing only light in said second range of wavelengths to said annular lens.

23. A non-contact type tonometer as claimed in claim 22, where said first range of wavelengths is in the infrared range and said second range of wavelengths being in the visible range.

24. A non-contact type tonometer as claimed in claim 23, further including TV camera means having sensitivity in the infrared range for converting an infrared image of the alignment target mark into an electronic signal, the electronic signal being capable of being converted into a visible image by a TV monitor.