WO1994023642A1 - Tonometre - Google Patents

Tonometre Download PDF

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Publication number
WO1994023642A1
WO1994023642A1 PCT/GB1994/000836 GB9400836W WO9423642A1 WO 1994023642 A1 WO1994023642 A1 WO 1994023642A1 GB 9400836 W GB9400836 W GB 9400836W WO 9423642 A1 WO9423642 A1 WO 9423642A1
Authority
WO
WIPO (PCT)
Prior art keywords
eye
receiver
signal
tonometer
intra
Prior art date
Application number
PCT/GB1994/000836
Other languages
English (en)
Inventor
Paul Toleman
Original Assignee
Paul Toleman
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Paul Toleman filed Critical Paul Toleman
Priority to AU65112/94A priority Critical patent/AU6511294A/en
Priority to JP6522934A priority patent/JPH08508900A/ja
Priority to EP94912654A priority patent/EP0696897A1/fr
Publication of WO1994023642A1 publication Critical patent/WO1994023642A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/10—Eye inspection
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
    • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
    • A61B3/16—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for measuring intraocular pressure, e.g. tonometers
    • A61B3/165—Non-contacting tonometers

Definitions

  • This invention relates to a tonometer for measuring Intra-ocular pressure.
  • Tonometry is the common procedure for measuring the Intra-ocular pressure of the eye.
  • Many known tonometric assessments require the use of anaesthesia and contact with the eye or a short blast of high pressure air to be directed at the eye. These known methods cause a sensation in the eye resulting in discomfort to the patient. What is more contact with the eye may result in abrasion and cross infection. Repeated measurements comprising contact with the eye also have a massaging effect on the eye which may adversely affect the accuracy of subsequent measurements.
  • the present invention has been made from a consideration of this problem.
  • a tonometer for measuring the Intra-ocular pressure of an eye comprising an emitter for emitting a signal towards the eye, a receiver for receiving the signal on being reflected from the eye, and a monitoring device for monitoring the amplitude of the signal received by the receiver, wherein the emitter and/or receiver is movable relative to the eye while the monitoring device is operating, the monitoring device comprising means for taking and/or storing a measurement when the distance between the eye and the receiver is such that substantially the strongest signal is received, characterised in that the tonometer comprises means for compensating for variations in the cornea1 radius of the eye.
  • a method for monitoring the Intra-ocular pressure of an eye comprising directing a signal towards the eye, collecting the signal reflected from the eye and monitoring the amplitude of the collected signal, wherein the emitter and/or receiver is movable relative to the eye while the monitoring device is operating, the monitoring device comprising means for taking and/or storing a measurement when the distance between the eye and the receiver is such that substantially the strongest signal is received, characterised in that the method further comprises compensating for variations in the corneal radius of the eye.
  • the acoustic impedence of the incident wave is
  • the acoustic impedence of the reflected wave is
  • R 2 P 2 C 2
  • the means for compensating for the corneal radii of the eye may comprise a mathematical equation or a table, graph or the like of known values for comparison purposes.
  • the relevant information may be fed into a computer or the like such that the Intra-ocular pressure may be displayed instantaneously.
  • the tonometer comprises means for providing coherent emitted signals.
  • the signals are preferably arranged at substantially 60° to the receiver.
  • coherent ultrasound sources By arranging for coherent ultrasound sources to emit waves at about 60° to the receiver the waves interfere and superimpose creating a single wave of increased amplitude.
  • the signal preferably comprises an ultrasound wave; that is a wave having a higher frequency than those detectable by the human ear.
  • an ultrasound wave that is a wave having a higher frequency than those detectable by the human ear.
  • 40KHz waves are suitable, although other frequencies may well be appropriate.
  • the monitoring device is preferably an oscilloscope or meter such as voltmeter.
  • Fig.l is a schematic illustration of one tonometer for use in accordance with the present invention.
  • Fig.2 is a schematic illustration of the tonometer of Fig.l;
  • Fig.3 shows the tonometer of Fig.2 in use
  • Fig.4 shows a longitudinal sectional view through a tonometer in accordance with the invention
  • Fig.5 shows a graph of corneal radius and amplitude of the wavefront directed towards the eye against the Intra ⁇ ocular pressure of the eye;
  • Fig.6 shows a further tonometer in accordance with the invention
  • Fig.7 shows the principle of operation of the tonometer of Fig.6
  • Fig.8 shows a simplified analysis of the direction of the wavefronts reflected from the cornea
  • Fig.9 shows a graph of peak amplitude (mV) against radius of curvature of the cornea recorded with different angles of approach of the wavefront.
  • an electric circuit produces a stable 40 KHz ultrasound wave 11 which is used to drive an emitter 12 from an oscillating high frequency electronic signal.
  • the ultrasound waves are directed at the eye 13 from the emitter 12.
  • the ultrasound waves are subsequently reflected from the corneal surface of the eye 13 and are then collected by a receiver 14.
  • the receiver 14 is connected to a monitoring apparatus 15 such as an oscilloscope or after appropriate amplification and rectification the returning signal can be assessed.
  • the amplitude of the soundwaves arriving at the receiver may be analysed by way of monitoring apparatus.
  • the reflected signal is at its strongest and thus record and store the potential difference measured when the receiver is in that location.
  • the signal Prior to storage the signal is reflected and amplified in order to facilitate calibration and accurate measurement of the Intra-ocular pressure.
  • the measured signal on the monitoring apparatus 15 is related to the rigidity of the eye and in turn to the Intra ⁇ ocular pressure of the eye.
  • the tonometer head 20 comprises concentrically arranged inner and outer tubes 21,22.
  • the transmitter 23 and receiver 24 are mounted in the inner tube 21.
  • Concentric apertures 25,26 are provided at the right end of the tubes as illustrated.
  • the inner receiver tube 21 extends beyond the outer transmitter tube 22.
  • the transmitter 23 transmits a wave which passes between the inner and outer tubes and is reflected by the eye into the inner receiver tubes 21 and receiver 24 located therein.
  • the measurement taken on the monitoring apparatus can be used to give the Intra-ocular pressure of the eye.
  • the reading given by the monitoring apparatus should be compensated to allow for variations in the corneal radius of the eye.
  • This may be taken into account in a calibration graph which can be used to derive the Intra-ocular pressure of the eye from the reading given on the monitoring apparatus.
  • This information in the calibration graph can be fed into a computer or like apparatus so that the Intra-ocular pressure can be instantaneously displaced.
  • the calibration graph used to derive the Intra-ocular pressure is shown in Fig.5.
  • the graph allows for variations in the radius of curvature of the eye so as to eliminate these variations from the measured reading.
  • the amplitude of the received wavefront is measured over a range of radii of curvature and Intra-ocular pressure. It is noted that Fig.5 is shown by way of illustration only and is not intended to represent any specific results.
  • the amplitude is recorded and the corneal radius is measured.
  • the Intra-ocular pressure can then be derived from the graph shown in Fig.5. For example, with a known corneal radius of 7.5mm and an amplitude of "X" volts the Intra-ocular pressure is observed to be 30mmHg.
  • Intra-ocular pressure can be calculated mathematically, and instantaneously displayed, the mathematics taking account of the variations in the corneal radius.
  • the tonometer head 20 comprises concentrically arranged inner and outer tubes 21,22.
  • the transmitter 23 and receiver 24 are mounted in the inner tube 21.
  • Concentric apertures 25,26 are provided at the right end of the tubes as illustrated.
  • the inner receiver tube 21 extends beyond the outer transmitter tube 22.
  • a tonometer 30 comprises a transmitter 31 and a receiver 32.
  • a wave absorbent cone 33 is provided between the transmitter 31 and receiver 32.
  • the trans itter 31 emits two coherent wave signals "A" and "B" out of the tonometer via exits 34,35.
  • the wave signals A,B are arranged at an angle * Q' to the longitudinal axis of the tonometer where - ⁇ - is 60°.
  • the signals are directed towards the eye and are subsequently reflected from the corneal surface of the eye. They are then collected by the receiver 32.
  • the receiver 32 is connected to a monitoring apparatus such as an oscilloscope and after appropriate amplification and rectification the returning signal can be assessed.
  • the amplitude of the soundwaves arriving at the receiver may be analysed by way of the monitoring apparatus.
  • the measured signal on the monitoring apparatus 35 bears a direct relationship to the rigidity of the eye and in turn to the Intra-ocular pressure of the eye.
  • Figs. 8 and 9 show the theory behind the operation of the tonometer of Figs. 6 and 7.
  • Fig.8 shows a simplified geo etrical analysis of the path of the wavefronts (in 2 dimensions) considering angles "Q of 30° and 60° as reflected from a flat and a convex surface.
  • Figure 9 illustrates the difference in peak amplitude recorded with differing values of " ⁇ " on two spherical surfaces with radii of curvature 7.00mm and 8.4mm. This indicates that as increases the influence of the radius reduces and appears to be minimised as ⁇ approaches 60°.
  • the design of the tonometer head can be used to minimise the influence of the radius of curvature of the cornea.

Landscapes

  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Ophthalmology & Optometry (AREA)
  • Biophysics (AREA)
  • Veterinary Medicine (AREA)
  • Public Health (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Medical Informatics (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • Radiology & Medical Imaging (AREA)
  • Pathology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Eye Examination Apparatus (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)

Abstract

Tonomètre permettant de mesurer la pression intraoculaire comprenant: un émetteur (12) destiné à émettre un signal en direction de l'÷il, un récepteur (14) destiné à recevoir le signal réfléchi par l'÷il et un dispositif de contrôle (15) destiné à contrôler l'amplitude du signal reçu par le récepteur. L'émetteur (12) et le récepteur (14) peuvent être déplacés par rapport à l'÷il. Le dispositif de contrôle (15) effectue la mesure, lorsque la distance entre l'÷il et le récepteur est telle que le signal reçu est le plus fort. Le tonomètre permet de compenser les variations de rayon de la cornée.
PCT/GB1994/000836 1993-04-22 1994-04-20 Tonometre WO1994023642A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
AU65112/94A AU6511294A (en) 1993-04-22 1994-04-20 Tonometer
JP6522934A JPH08508900A (ja) 1993-04-22 1994-04-20 トノメータ
EP94912654A EP0696897A1 (fr) 1993-04-22 1994-04-20 Tonometre

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB939308286A GB9308286D0 (en) 1993-04-22 1993-04-22 Tonometer
GB9308286.5 1993-04-22

Publications (1)

Publication Number Publication Date
WO1994023642A1 true WO1994023642A1 (fr) 1994-10-27

Family

ID=10734249

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1994/000836 WO1994023642A1 (fr) 1993-04-22 1994-04-20 Tonometre

Country Status (5)

Country Link
EP (1) EP0696897A1 (fr)
JP (1) JPH08508900A (fr)
AU (1) AU6511294A (fr)
GB (1) GB9308286D0 (fr)
WO (1) WO1994023642A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08280631A (ja) * 1995-04-17 1996-10-29 Topcon Corp 非接触式眼圧計
ES2116944A1 (es) * 1996-12-26 1998-07-16 Carreras Egana Fcp Javier Tonometro ocular mediante interferometria laser y ultrasonidos.
DE10039825A1 (de) * 2000-08-16 2002-03-21 Highyag Lasertechnologie Gmbh Übertragungseinrichtung zur Einkopplung von Laserstrahlung aus einer ersten Lichtleitfaser in eine zweite Lichtleitfaser
US7419470B2 (en) 2001-03-30 2008-09-02 Waseda University Method and device for measuring intraocular tension
EP2236075A1 (fr) * 2009-03-31 2010-10-06 Nidek Co., Ltd. Kontaktfreies Ultraschalltonometer
EP2266454A1 (fr) * 2009-06-22 2010-12-29 Nidek Co., Ltd Tonomètre ultrasonique sans contact

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5469381B2 (ja) * 2009-06-09 2014-04-16 株式会社ニデック 非接触式超音波測定装置
JP5465946B2 (ja) * 2009-07-31 2014-04-09 株式会社ニデック 非接触式超音波眼圧計

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3948248A (en) * 1974-09-05 1976-04-06 Zuckerman Joel L Method of measuring ocular pulse
EP0371590A1 (fr) * 1988-09-28 1990-06-06 The Ohio State University Tonomètre à ultrasons sans contact
US5148807A (en) * 1990-08-28 1992-09-22 Ohio State University Non-contact tonometer
EP0536574A1 (fr) * 1991-10-10 1993-04-14 Massie Research Laboratories, Inc. Tonomètre sans contact
WO1993013705A1 (fr) * 1992-01-11 1993-07-22 Paul Toleman Tonometre

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3948248A (en) * 1974-09-05 1976-04-06 Zuckerman Joel L Method of measuring ocular pulse
EP0371590A1 (fr) * 1988-09-28 1990-06-06 The Ohio State University Tonomètre à ultrasons sans contact
US5148807A (en) * 1990-08-28 1992-09-22 Ohio State University Non-contact tonometer
EP0536574A1 (fr) * 1991-10-10 1993-04-14 Massie Research Laboratories, Inc. Tonomètre sans contact
WO1993013705A1 (fr) * 1992-01-11 1993-07-22 Paul Toleman Tonometre

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH08280631A (ja) * 1995-04-17 1996-10-29 Topcon Corp 非接触式眼圧計
ES2116944A1 (es) * 1996-12-26 1998-07-16 Carreras Egana Fcp Javier Tonometro ocular mediante interferometria laser y ultrasonidos.
DE10039825A1 (de) * 2000-08-16 2002-03-21 Highyag Lasertechnologie Gmbh Übertragungseinrichtung zur Einkopplung von Laserstrahlung aus einer ersten Lichtleitfaser in eine zweite Lichtleitfaser
US7419470B2 (en) 2001-03-30 2008-09-02 Waseda University Method and device for measuring intraocular tension
EP2236075A1 (fr) * 2009-03-31 2010-10-06 Nidek Co., Ltd. Kontaktfreies Ultraschalltonometer
CN101862207A (zh) * 2009-03-31 2010-10-20 株式会社尼德克 非接触超声波眼压计
US8500638B2 (en) 2009-03-31 2013-08-06 Nidek Co., Ltd. Non-contact ultrasonic tonometer
EP2266454A1 (fr) * 2009-06-22 2010-12-29 Nidek Co., Ltd Tonomètre ultrasonique sans contact

Also Published As

Publication number Publication date
JPH08508900A (ja) 1996-09-24
EP0696897A1 (fr) 1996-02-21
AU6511294A (en) 1994-11-08
GB9308286D0 (en) 1993-06-09

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