Applanation tonometer

• US 6,776,756 B2
• Filed: 04/30/2002
• Issued: 08/17/2004
• Est. Priority Date: 05/16/2001
• Status: Expired due to Fees

• 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
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): McCrosky, David J.
• Application Number:
  US10/137,234
• Publication Number:
  US 20020173712A1
• Time in Patent Office: 840 Days
• Field of Search: 600/398, 600/399, 600/405, 600/406, 600/561, 600/587, 428/426, 428/428, 428/330, 359/599
• 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 fiber optics array for transferring an image of a contact surface of an eye from a first end to a second end of the array within the tonometer;

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

an image sensor adapted to receive from the second end of the array an image of the applanated portion of the eye from the first end of the array 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 for acquiring data at a rate of approximately 20 Hz to 60 Hz, 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 from the second end of the array and through the array 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 or 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, with an internal power supply.

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

12. The applanation tonometer of claim 1, wherein the rate is approximately 30 Hz.

13. The applanation tonometer of claim 1, further including a disposable tip on the first end of the fiber optics array for engaging a contact surface of an eye, the disposable tip serving to diffuse reflected light.

14. An applanation tonometer comprising:

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

a first sensor optically coupled to the proximal end of the fiber optics 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, a rate of approximately 20 Hz to 60 Hz, wherein the processor is adapted to calculate therefrom an intraocular pressure of the eye using the first and second signals.

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

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

17. The applanation tonometer of claim 14, further comprising a light source for illuminating through the array at least a portion of the eye.

18. The applanation tonometer of claim 14, wherein the proximal end of the fiber optic array is backlit.

19. The applanation tonometer of claim 14, wherein the proximal end of the fiber optics array is optically coupled to the firs 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 fiber optics array to the first sensor.

20. The applanation tonometer of claim 14, wherein the processor is adapted to calculate an intraocular pressure of the eye using a plurality of corresponding first and second signals.

21. The applanation tonometer of claim 14, further comprising a light-diffusing disposable tip adapted to cover at least part of the fiber optics array where the fiber optics array is designed to applanate an eye.

22. The applanation tonometer of claim 14, wherein the distal end of fiber optics array has a matte finish.

23. 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.

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

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

26. The method of claim 23, wherein the applanating step comprises using a fiber optics array to applanate the eye.

27. The method of claim 23, wherein the acquiring step is synchronous.

28. The method of claim 23, wherein the data points are acquired at the rate of approximately 20 Hz to 60 Hz.

29. 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 an optically light-diffusing 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.

30. A method as in claim 29 wherein the elastic member is an O-ring.

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

an applanator for applanating a portion of an eye, the applanator comprising a fiber optics array for transferring an image of a contact surface of an eye from a first end to a second end of the array within the tonometer;

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

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

a processing circuit communicatively coupled to the force sensor and the image sensor for acquiring data at a rate of approximately 20 Hz to 60 Hz, 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; and

a disposable tip for the distal end of the applanator comprising a small sheet of thin light-transmitting but optically light-diffusing film secured onto a distal end of the fiber optics array.

32. An applanation tonometer as in claim 31, wherein the data rate is approximately 30 Hz.

33. An applanation tonometer as in claim 31, wherein the disposable tip is secured at the distal end of the array via an elastic member.