Applanation tonometer

• US 20020173712A1
• Filed: 04/30/2002
• Published: 11/21/2002
• Est. Priority Date: 05/16/2001
• Status: Active Grant

• Current Assignee: Lombart Brothers, Inc. (Advancing Eyecare Holdings)
• Original Assignee: Marco Opthamalmic Incorporated
• Inventors: Teasdale, Richard Wademan, Feldon, Steven E., Netherwood, Gregory John, Burr, Bruce Allen
• Granted Patent: US 6,776,756 B2
• Time in Patent Office: Days
• US Class Current: 600/405
• CPC Class Codes: A61B 3/16 for measuring intraocular pressure, e.g. tonometers

Abstract

For calculating the intraocular pressure (IOP) of an eye, an applanation tonometer comprises an applanator formed of an optics array, a force transducer, an image sensor, and a processing circuit configured to calculate an intraocular pressure of the eye using one or more pairs of measured force and applanated area. The tonometer is provided with a disposable tip that covers the applanator, thereby providing a replaceable, sterile and transmissive interface between the tonometer'"'"'s applanator and a patient'"'"'s eye. Preferably, the applanating surface has a matte finish. The tonometer calculates the intraocular pressure using a predetermined relationship between interocular pressure and the slope of the line defined by data relating to the forces required to applanate the eye and the geometry of applanated portions of the eye. In a preferred embodiment, the data acquisition is synchronous. The tonometer may be of the type of a portable, hand-held device or a device affixed to and used in conjunction with a slit-lamp design. Also disclosed is a method and device for applying a disposable tip to the applanator.

Claims

1. An applanation tonometer for measuring an intraocular pressure of an eye, comprising:

an applanator for applanating a portion of an eye, wherein the applanator comprises a fiberoptics array;

a force sensor operatively coupled to the applanator, wherein the force transducer is adapted to measure a force applied to the eye by the applanator;

an image sensor adapted to receive an image of the applanated portion of the eye and measure therefrom a geometrical property of the applanated portion of the eye; and

a processing circuit communicatively coupled to the force transducer and the image sensor, wherein the processing circuit is adapted to calculate an intraocular pressure of the eye using a measured force from the force transducer and a corresponding measured geometrical property from the image sensor.

2. The applanation tonometer of claim 1, wherein the geometrical property comprises an area of the applanated portion of the eye.

3. The applanation tonometer of claim 1, wherein the geometrical property comprises a diameter of the applanated portion of the eye.

4. The applanation tonometer of claim 1, further comprising a light source for illuminating at least a portion of the eye.

5. The applanation tonometer of claim 1, wherein the applanator and image sensor are optically coupled with a lens system, the lens system adapted to focus an image of the applanated portion of the eye from the applanator to the image sensor.

6. The applanation tonometer of claim 1, wherein the force transducer comprises a piezoelectric element.

7. The applanation tonometer of claim 1, wherein the image sensor comprises one of a charge-coupled and CMOS device.

8. The applanation tonometer of claim 1, wherein the processing circuit is adapted to calculate an intraocular pressure of the eye using a plurality of measured forces from the force transducer and a corresponding plurality of measured geometrical properties from the image sensor.

9. The applanation tonometer of claim 1, further comprising a disposable tip adapted to cover at least part of the applanator where the applanator is designed to applanate an eye.

10. The applanation tonometer of claim 1, wherein the applanation tonometer is a portable, hand-held device.

11. The applanation tonometer of claim 1, further comprising a display for displaying the calculated intraocular pressure.

13. The applanation tonometer of claim 12, wherein the first signal relates to the area of the image of the applanated portion of the eye.

14. The applanation tonometer of claim 12, wherein the first signal relates to the diameter of the image of the applanated portion of the eye.

15. The applanation tonometer of claim 12, further comprising a light source for illuminating at least a portion of the eye.

16. The applanation tonometer of claim 12 wherein the proximal end of the fiber optic array is backlit.

17. The applanation tonometer of claim 12, wherein the proximal end of the fiberoptics array is optically coupled to the first sensor with a lens system, the lens system adapted to focus an image of the applanated portion of the eye from the proximal end of the fiberoptics array to the first sensor.

18. The applanation tonometer of claim 12, wherein the processor is adapted to calculate an intraocular pressure of the eye using a plurality of corresponding first and second signals.

19. The applanation tonometer of claim 12, further comprising a disposable tip adapted to cover at least part of the fiberoptics array where the fiberoptics array is designed to applanate an eye.

20. The applanation tonometer of claim 12, wherein the distal end of the fiberoptics array has a matte finish.

12. An applanation tonometer comprising:

a fiberoptics array adapted to applanate a portion of an eye at a distal end of the fiberoptics array, whereby an image of the applanated portion of the eye is transmitted to a proximal end of the fiberoptics array;

a first sensor optically coupled to the proximal end of the fiberoptics array, the first sensor adapted to produce a first signal relating to the image of the applanated portion of the eye;

a second sensor adapted to produce a second signal relating to a force applied to the eye by the tonometer; and

a processor communicatively coupled to the first and second sensors for receiving first and second signals, respectively, therefrom, wherein the processor is adapted to calculate an intraocular pressure of the eye using the first and second signals.

21. A method of determining an intraocular pressure of an eye comprising:

applanating a portion of an eye, varying the applanation of the eye over a period of time;

acquiring a plurality of data points at distinct times, each data point comprising a first datum and a second datum, wherein the first datum relates to a force required to applanate the eye, and the second datum relates to a geometrical property of the applanated portion of the eye;

determining a slope of a line defined by the plurality of data points; and

calculating the intraocular pressure using the slope and a predetermined relationship between said slope and intraocular pressure.

22. The method of claim 21, wherein the second datum relates to the area of the applanated portion of the eye.

23. The method of claim 21, wherein the second datum relates to the diameter of the applanated portion of the eye.

24. The method of claim 21, wherein the applanating step comprises using a fiberoptics array to applanate the eye.

25. The method of claim 21, wherein the acquiring step is synchronous.

27. The disposable tip of claim 26, wherein the second surface has a matte finish.

28. The disposable tip of claim 26, wherein the tip is formed at least in part of polyethylene fibers infused into a sheet.

29. The disposable tip of claim 26, wherein the tip is formed of semi-transparent ethyl vinyl acetate.

30. The disposable tip of claim 29, wherein the tip is contained within a sterile package.

31. The disposable tip of claim 26, wherein the attachment mechanism comprises a key fitting.

26. A disposable tip for use with an applanation tonometer, the tip comprising:

a light-transmitting applanating region adapted to fit over an applanator of a tonometer, the applanating region having a first surface adapted to optically couple with an applanator and a second surface adapted to contact an eye; and

an attachment mechanism for detachably attaching the tip to a tonometer.

32. A disposable tip for use with an applanation tonometer wherein the applanation tonometer includes an applanator having a polished smooth surface, the tip comprising

a light-transmitting applanating region adapted to fit over the applanator of the tonometer, the applanating region having a first smooth interior surface adapted to optically couple with the outer surface of the applanator, and having a second surface adapted to contact an eye, the second surface having a matte finish.

33. A disposable tip for use with an applanation tonometer as in claim 32, wherein the outer surface of the applanator and the inner contacting surface of the tip are flat.

36. The applanation tonometry system of claim 35, wherein the applanation tonometer and disposable tip are formed to attach using a key fitting mechanism.

38. A method as in claim 37 wherein the elastic member is an O-ring.

40. A disposable tip as in claim 39 wherein the elastic member is an O-ring.

41. A disposable tip as in claim 39 wherein the film is semi-transparent ethyl vinyl acetate having a matte surface on the side thereof distal from the tip of the applanator.

34. A disposable tip for use with an applanation tonometer further comprising an attachment mechanism for detachably attaching the tip to a tonometer.

35. An applanation tonometry system comprising:

an applanation tonometer having a smooth applanating surface adapted to applanate a portion of an eye; and

a disposable tip detachably attachable to the applanating surface of the tonometer, wherein the disposable tip comprises an optically smooth proximal surface for contacting the applanating surface of the tonometer and a distal surface having a matte finish.

37. A method of forming a disposable tip on a distal end of an applanator of a tonometer comprising the steps of

disposing an elastic ring in an intermediate cavity of an assembly tool,

disposing a film in an upper cavity of the assembly tool, and

moving a distal end of the applanator of the tonometer axially into the assembly tool and down into a lower cavity to cause the film to wrap around the distal tip of the applanator and the elastic member to secure the ring thereto.

39. A disposable tip for a distal end of an applanator of a tonometer comprising a small sheet of thin film secured onto a distal end of an applanator via an elastic member.