WO2009157825A1

WO2009157825A1 - A method and device for diagnosing ear conditions

Info

Publication number: WO2009157825A1
Application number: PCT/SE2008/050761
Authority: WO
Inventors: Mikael Sundberg; Anders Johansson; Åke ÖBERG; Tomas STRÖMBERG
Original assignee: Atos Medical Ab
Priority date: 2008-06-24
Filing date: 2008-06-24
Publication date: 2009-12-30

Abstract

Device for measuring physical properties of the tympanic membrane (TM), comprising an elongated probe (12) with a distal end (15) for inspection of the ear, wherein a plurality of optical fibres is arranged in said elongated probe. Said first detector means (23) is designed for measuring the intensity of light reflected from the tympanic membrane.The device also comprises means for producing a pressure provocation of the tympanic membrane and means for analysing the mobility of the tympanic membrane during provocation.

Description

A METHOD AND A DEVICE FOR DIAGNOSING EAR CONDITIONS

Technical Field

The invention relates to a device and a method for measuring physical properties in general and physical properties of human tissues in the ear. The device in accordance with the invention can be used in connection with diagnosing ear conditions such as acute otitis media (AOM).

AOM is one of the most common infectious diseases of childhood. In- cidence figures vary greatly in the current literature. This probably reflects different threshold through time for seeking medical attention for earache and different diagnostic criteria between researchers rather than a true difference in incidence. AOM can in general terms be defined as purulent inflammation in the middle ear which starts abruptly, is of short duration and can be clinically verified.

Antibiotics have for long been recommended in the treatment of AOM but indefinite diagnostic criteria, a high percentage of spontaneous healing and an increasing awareness of microbial resistance have led to revision of the therapeutic guidelines in several European countries Myringotomy with demonstration of purulent middle ear fluid, as a proof of bacterial infection, is considered the gold standard of AOM identification. In practice however, the diagnosis is often based on the combination of symptoms, such as earache, rubbing of the ear, fever, and changes of the characteristics of tympanic membrane (TM). An otoscopic assessment of the TM can be challenging even for the most experienced clinician because of overlapping findings with other conditions where antibiotics are not needed. Bulging due to the presence of middle ear fluid with decreased mobility and reddening and thickening of the TM with loss of the normal contour are signs associated with AOM but may also be seen in otitis media with effusion (OME). OME can be regarded as either a sequel of AOM or as a consequence of Eustachian tube dysfunction, and is characterised by the presence of a middle ear effusion for 3 months or more but a general absence of gross signs of infection. Redness of the TM can also be seen in virus related conditions such as common cold.

Prior Art

Several studies of the otoscopic findings in AOM have failed to identify a specific sign or symptom in making an accurate diagnosis, but bulging of the TM seems to be an important variable. Pneumatic otoscopy, otomicro- scopy, tympanometry and acoustic reflectometry are other previously sug- gested techniques for evaluating the TM as adjunctive tools in AOM diagnosis.

Different kinds of otoscopes have been used for diagnosis of otitis media, the standard device being used for a subjective assessment of tympanic membrane characteristics. A conventional pneumatic otoscope will allow subjective assessment of tympanic membrane mobility. A video otoscope can be used for a Quasi-objective assessment of tympanic membrane characteristics that allow for post-examination as the video signal can be recorded on analog/digital media.

A tympanometer is used for measurement of acoustic immittance of the ear canal and middle ear and will allow an objective assessment of tympanic membrane mobility. Acoustic immittance is a general term used to refer either to acoustic impedance or acoustic admittance measurements. At present most of the devices are based on admittance measurement. Acoustic admittance is the ease with which acoustic energy is transferred from one system to another, which is the opposite of acoustic impedance. If the air in the ear canal is easily set into a vibration, the admittance is high. If the air is difficult to set into a vibration, the admittance of the system is low. Tympanometry is the measurement of acoustic admittance as a function of ear canal pressure and the resulting graph is a tympanogram. Positive or nega- tive pressure introduced to the sealed ear canal decreases the admittance of the air in the ear canal by stiffening the tympanic membrane. The effect of air pressure on acoustic admittance measured in the ear canal is systematically altered by the middle ear disease.

An acoustic reflectometer can be used for an objective assessment of tympanic membrane mobility and a spectroscopic otoscope provides an ob- jective assessment of tympanic membrane color.

Fluorescence spectroscopy has been utilized by Sorrel et al Bacteria identification of otitis media with fluorescence spectroscopy, Lasers in surgery and medicine 1994;14:155-163, and Spector et al, Noninvasive fluorescent identification of bacteria causing acute otitis media in a chinchilla model. The Laryngoscope 2000;110:1119-1123, for the identification of pathogens causing AOM in vitro and in vivo.

US Patent US 7,058,441 discloses a device capable of obtaining a spectrum of reflected light from an ear of a subject and a processing unit in connection with said device, which is capable of translating the obtained spectrum of reflected light to one or more output values related to the condition of the ear. There is further disclosed a method for detecting and diagnosing ear related conditions comprising the steps of illuminating inside the ear; inserting a device to the ear canal capable of conveying at least one spectrum of reflected light from said ear to a processing unit; and activating said processing unit thereby translating at least one spectrum of reflected light provided at the time of activating to one or more output values related to the condition of the ear.

Summary of the Invention

It is assumed that the optical properties of the TM are similar to those of human skin since the TM is covered by epidermis lined by simple cuboidal epithelium. Consequently, the reflectance spectra of the healthy and the erythematous TM ought to differ in the same way as the spectra of healthy and erythematous human skin. An object of the invention is to provide a device that will improve the possibilities to perform diagnosis of acute otitis media. In accordance with the invention the device is provided with means for applying diffuse reflectance spectroscopy in combination with a pressure provocation of the tym- panic membrane. The invention combines the subjective assessment of tympanic membrane appearance and the objective measures of tympanic membrane mobility and effusion characterization.

The device in accordance with the invention comprises an elongated probe, a first end of which being operatively connected to a housing and a second end of which is designed to be inserted in the external auditory canal to a position close to the TM.

In one embodiment of the present invention the spectral analytical instrument includes at least one amplitude- or frequency-modulated light source in form of a light emitting diode (LED) or a laser diode (LD) and at least one photodetector (e.g., a photo diode, photo transistor, CCD or CMOS detector) where the detector is sensitive to electromagnetic radiation in the range 200-2000 nm.

In the housing there is provided light generating means and at least one detector means. The light generating means are operatively connected to a plurality of optical fibers that extend through the probe to a position in the vicinity of the second end of the probe. There is further provided means for producing air pressure variations allowing quantification of physiological properties of the tympanic membrane. In one embodiment in accordance with the invention there is provided also a pressure transducer for measuring pressure variations in the external auditory canal caused either by a manually controlled pneumatic bulb or by a pneumatic control unit.

The optical fibers can be divided into at least two sets of fibers. A first set of the optical fibers is used to convey light from the light sources to the TM. A second set of fibres is used to convey light reflected from the TM and the ear to a photodetector arranged in the housing. Said second set of fibres can be divided further into subsets if different detectors are used. It is also possible to use the same set of fibers for conveying light in both directions, for instance by using so called fiber couplers.

The light from the light sources is directed towards the tissue in front of the probe and is used for diffuse reflectance spectroscopy. A minor por- tion of the light is specularly reflected from the surface and will have basically the same properties as the generated light. A major part of the light will penetrate into the tissue and interact with different objects such as red blood cells. The light reflected will be diffuse and due to different properties of the objects also properties of the light will change. The diffuse reflected light will have different intensities at different wavelengths.

The light from the light sources will also penetrate the TM and be reflected from the middle ear and through the TM back to the light detector means. Light reflected from the middle ear will indicate existence of purulent middle ear fluid, as a proof of bacterial infection. The detecting means is arranged to receive the reflected light and to detect intensities at different wavelengths, preferably within an interval of 200-2000 nm. In a first embodiment the detecting means comprises separate sensors for detecting different wavelengths. In a second embodiment reflected light is received in a single detector and then analyzed with regard to intensity at different wavelengths. It is possible also to use a combination of the detector embodiments.

The mobility of the TM can be assessed by measuring the intensity of the reflected light as a function of the pressure variations caused by the associated means. It is further possible to assess the presence of fluid in the middle ear by arranging the detector means for measuring reflected light at wavelengths in the interval 800-2000 nm.

Normally, the detector means will be arranged for measuring presence and/or concentration of various chromophores by specifically analyzing the reflected light in the wavelength interval 200-2000 nm. By specifically ar- ranging the detector means for analyzing the reflected light in the interval 450-900 nm the oxygen saturation of the blood in the inspected area can be measured. The diffuse reflectance spectroscopy arrangement in accordance with the invention also will allow identification of a purulent effusion as opposed to a serous effusion. A combination of two or more analyzing steps described above will highly improve the diagnosis of acute otitis media. The pressure provocation of the tympanic membrane is performed through an air channel that can be included in the probe and extend along the fibers. A pressure transducer for measuring pressure variations during pressure provocation can be included in the air channel or be arranged elsewhere in air contact with the TM. In accordance with the invention detected backscattered light from the tympanic membrane during pressure provocation, either via a manual bulb or via an automatic pneumatic control system, allow for quantification of tympanic membrane mobility.

The present invention will allow an objective quantification of physio- logical properties of the tympanic membrane and the middle ear related to acute otitis media, myringitis and otitis media with effusion.

It is preferred that the ear speculum is replaceable, making it possible to fit the speculum to the size of the external auditory canal of the individuals). The light sources could be of various wavelengths, where the different wavelengths are chosen to allow for separable detection and quantification of the mentioned chromophores.

The different light sources could be modulated in frequency or amplitude to allow for parallel detection from all light sources. In another embodi- ment, the light sources are activated in sequence, allowing for time-gated detection of the backscattered light.

In yet another embodiment, a broad spectrum light source is chosen, and the chromophore quantification is made possible by introducing wavelength separating devices on the detector side (e.g., filters, gratings, spec- trometers etc.) The invention can be equipped with a starting trigger allowing the operator to decide when a measurement is to be recorded. In another embodiment, the instrument records the signals continuously.

Brief description of the drawings

Fig. 1 is a schematic side elevational view of a first embodiment of a device in accordance with the invention including a control apparatus and a probe,

Fig. 2 is a schematic view showing components of the control apparatus of Fig. 1 ,

Fig. 3 is a cross sectional view from ///-/// in Fig. 1 of a first configuration of optical fibres in the tip of the probe, Fig. 4 is a cross sectional view from ///-/// in Fig. 1 of a second configuration of optical fibres in the tip of the probe,

Fig. 5 is a schematic block diagram of the device in accordance with the invention,

Fig. 6 is a schematic side elevational view of a second embodi- ment of a device in accordance with the invention including a probe and a manually operated bladder, and

Fig. 7 is a schematic block diagram showing components of a pneumatic means.

Detailed description

In the embodiment shown in Fig. 1 a device in accordance with the invention comprises an instrument 10 designed as a modified sinuscope suitable for visual inspection of narrow body cavities, such as the auditory canal. The instrument 10 is T-shaped with a vertical grip section 11 supporting a probe 12 and an eyepiece 13 extending in opposite directions. In Fig. 1 the probe is inserted in the external auditory canal 14. A tip 15 of the probe 12 is positioned 5-10 mm from the tympanic membrane 16.

The instrument 10 is operatively connected to a control apparatus 17 through a cable 18. The cable 18 holds a plurality of optical fibres as will be described below. The optical fibres extend from a lower section of the vertical grip section to the probe 12. In the probe the optical fibres extend together with an ocular channel (c.f. Fig. 3 and Fig. 4) that connects to the eyepiece 13.

The control apparatus 17 comprises a power supply 27 that is con- nected to other devices and components of the control apparatus in a conventional manner. A light source 20 is operatively connected to a light source control 28 that will turn on and turn of the light source 20 in line with a control sequence.

A detector unit 29 comprises at least two detectors, one for optical measurements and one for pressure measurements. A signal processing means 30 receives detected signals from the detector unit 29 and analyzes the signals on the basis of different criteria. The result of the analyze is presented on a presentation panel, or display unit, 34.

The pressure provocation of the TM is caused by pneumatic means 36. In a simple embodiment, c.f. Fig. 6, the pneumatic means comprises a manually operated bladder or bulb 37. In a more developed system the pneumatic means 36 comprises a pump, a control processor, a motor and a sensor or transducer.

The basic units of the control apparatus 17 related to the optical com- ponents are shown in Fig. 2. In this embodiment all units are enclosed in a cover 19. In other embodiments some or all units can be arranged as separate units or be provided in a computer and software implementation. A first light source 20 generates white light that is used for illuminating the TM. The light source serves both the visual inspection via the otoscope and as light for the diffuse reflectance spectroscopy as will be described below. The first light source can be similar to an Avantes HL-2000-LL, 7 W output, VIS-NIR spectral range, Eerbeek, Netherlands). Light from the first light source is directed into a first set of optical fibres 21 that is embedded in said cable 18 and extends to the end of the probe 12. The fibres in said first set of optical fibres are distributed in the end of the probe to provide an appropriate inten- sity level and a suitable distribution of light over the TM.

The light from the first set of optical fibres 21 is reflected from the TM and received in a second set of optical fibres 22 that extends also from the tip of the probe to the control apparatus 17. The fibres in the second set of optical fibres 22 are connected to a first detector means 23 that can be con- figured basically in different ways.

In a first embodiment the first detector means 23 is a single detector that is connected to a signal processor 24 in the control apparatus 17. The single detector produces data corresponding to the intensity of the diffuse reflected light. The signal processor 24 in this embodiment is configured to apply an erythema detection algorithm on the acquired data. A novel algorithm utilizes the fact that the photon absorption in the Q-band of various blood chromophores is different in erythymatous and in normal tissue.

A quantity, derived from the spectra, to be used for separating the states "erythematous tissue" and "normal tissue" that is independent of the geometrical distance between the probe head and site of measurement was desirable. For this reason the quotient

^650

was used.

R₆₅₀ and R_λ are the reflectivity at 650 nm and λ nm, respectively. Normalization was performed by dividing every sample in each spectrum with its reflectivity at 650 nm. A variety of λ:s were tested. λ:s were selected in the absorption peak of bilirubin and the Q-band of oxyhemoglobin (HbO₂) (460 nm, 542 nm and 576 nm). In addition, λ-values were chosen based on measurements of Qλ in normal and erythematous TM, .in order to maximize discrimination. It was observed that Qx discriminated well at λ:s near 490 nm and 576 nm.

In accordance with the invention based on a two-wavelength or four- wavelength system the first detector means can include discrete detectors for each specific frequency. Each detector can be combined with a narrow filter, to achieve the desired frequency characteristics. Appropriate centre wavelengths are 460 nm, 490 nm, 542 nm, 576 nm and 650 nm. The detectors are connected to the signal processor 24 in the control apparatus 17. In such an embodiment the signal processor 24 can have a less complicated design.

In the embodiment shown in Fig. 2 a second light source 25 is also included. The second light source emits light that is directed towards the target tissue as a visual reference when the probe is positioned in the external auditory canal. A separate optical fibre, or a set of fibres, 26 is provided for conveying the light to the end of the probe. In one embodiment the second light source 25 is a laser diode that emits light at the wavelength 632 nm.

Since high sensitivity and specificity are desired it is appropriate not to rely on one single diagnostic parameter. Therefore, information about the mobility of the TM obtained as described above can be combined with other diagnostic parameters characterizing AOM, such as information about the geometry of the tympanic membrane as described below, still with reference to Fig. 2 and information about presence and/or concentration of various chromophores. By specifically arranging the detector means for analyzing the reflected light in the interval 450-900 nm information about the oxygen saturation of the blood in the inspected area can be measured. The diffuse reflectance spectroscopy arrangement in accordance with the invention also will allow identification of a purulent effusion as opposed to a serous effusion.

The control apparatus 17 also comprises a control unit 31 operatively connected to other units of the control apparatus, such as the signal processor 24 and a memory unit 46. The light sources are driven by a driver unit 32, which is operated by the control unit. Data, such as operating commands, can be fed in by an input device 33, such as a keyboard or other appropriate means. In a simple embodiment the input device comprises a single trigger that will operate the control apparatus 17 when set into different positions. The trigger or any other suitable input device can be arranged on the instrument 10, for instance on the vertical grip section 11.

Data produced by the signal processor 24 and the imaging system can be displayed on a display unit 34, which also may include or consist of other audiovisual means, such as light diodes and loudspeakers. The data can also be transferred to further computing, analyzing and monitoring means (not shown). In one embodiment the display unit 34 is arranged to display an indication of the physical status of the TM. In a further developed system in accordance with the invention the display indicates the medical status of the TM. As stated above several units of the control apparatus 17, such as the control unit 31 , the input device 33 and the display unit 34, can be part of a conventional personal computer or an application specific computer. The tip 15 of the probe is covered by a protective and optically neutral cap 38, c.f. Fig. 7. Preferably the cap 38 is disposable.

In the embodiments shown in Fig. 3 and Fig. 4 the tip 15 of the probe comprises a plurality of optical fibres and an ocular channel 35. The fibres are gathered in a semicircular section in the embodiment shown in Fig. 3. The number of individual fibres is chosen so as to supply each of the detectors in the first detector means 23 with a sufficient amount of reflected light. Normally, at least five individual fibres are used for each detector and each detector frequency. A pressure sensor 54 is provided in the ocular channel in this embodiment, c.f. Fig. 7.

In Fig. 4 an embodiment comprising an annular configuration of the fibre carrying part of the probe head is shown. A circular outer section of the probe head is used for the first set of optical fibres 21 and the second set of optical fibres 22. A central part of the probe head forms the ocular channel 35. A plurality of channels are formed in the probe head and in each channel a plurality of fibres are arranged. Every second channel holds elements of the first set of optical fibres 21 and every second channel holds elements of the second set of optical fibres 22. These fibres and the corre- sponding detector means are operated in correspondence with the description with reference to Fig. 3 and Fig. 4. All sets of fibres are arranged along a semicircular line outside the ocular channel 35. A pressure sensor 54 is provided in the ocular channel in this embodiment, c.f. Fig. 7.

Two separate optical fibres, or set of fibres, 26' arranged opposite each other are provided for facilitating the positioning of the probe head in the ear of a patient. In this embodiment the second light source 25 produces a collimated light that will be directed from the optical fibres 26' in two intersecting beams. After intersecting the light beams will hit the tympanic membrane in two separate and distinctive positions. By adjusting the distance between the probe and the tympanic membrane until target areas of the light beams are located at opposite side edges of the tympanic membrane it is possible position the probe at an appropriate distance from the tympanic membrane.

A basic block diagram illustrating the function of the device in accor- dance with the invention is shown in Fig. 5. A light source section 39 comprises first light source 20 and in some embodiments also second light source 25. Light from the light source section 39 is directed through a waveguide section 40 comprising a plurality of fibers or similar light guiding means. The pneumatic means 36 generates the air pressure variations used for the pressure provocation of the TM.

The light source section 39 can comprise a plurality of light emitting elements operating at different wavelengths. The elements can be frequency or amplitude modulated to allow a parallel detection from all elements. They can also be activated in sequence, so as to obtain a time-gated detection of the backscattered light. A plurality of detectors is included in a detector section 41. The detector section 41 comprises light detectors and preferably a pressure detector. The device can have an appearance similar to a conventional otoscope or endoscope 42. Signals detected by the different detectors are transferred to the signal processing means 30 capable of analyzing pressure signals and light signals. Data indicative of the status of the TM is presented at a presentation unit 43.

The light sources used in different embodiments can be either light emitting diodes, laser diodes or other suitable light sources. The detectors can be photodiodes, phototransistors, CCD-detectors, CMOS-detectors, a spectrometer or other suitable light detecting devices.

The light source(s) can be provided at or in the vicinity of the distal end of the device. Such device could also be fitted using optical fibers for conveying light from the device to the tympanic membrane and vice versa. It is preferred that the ear speculum is replaceable, making it possible to fit the speculum to the size of the external auditory canal of the individuals).

The light sources could be of various wavelengths, where the different wavelengths are chosen to allow for separable detection and quantification of the mentioned chromophores.

The different light sources could be modulated in frequency or amplitude to allow for parallel detection from all light sources. In another embodiment, the light sources are activated in sequence, allowing for time-gated detection of the backscattered light. In yet another embodiment, a broad spectrum light source is chosen, and the chromophore quantification is made possible by introducing wavelength separating devices on the detector side (e.g., filters, gratings, spectrometers etc.)

The invention could be equipped with a starting trigger allowing the operator to decide when a measurement is to be recorded. In another embodiment, the instrument records the signals continuously. An illustrative example of a basic embodiment of the invention is shown in Fig. 6. The appearance is similar to a conventional otoscope with a handle 44, an otoscope head 45, an ear speculum 47 and a lens 48. A striking difference as compared to a conventional otoscope is bladder or bulb 37 used for generating air pressure pulses during the provocation of the TM. An optical fiber cord 49 extends from the handle 44 to the control apparatus.

The pneumatic means 36 shown in Fig. 7 comprises a pump 50 driven by a motor 51. A pressure control unit 52 generates control signals for the pump and the motor, so as to provide the required air pressure pulses. A sensor unit 53 is provided for obtaining a signal indicative of the generated air pressure variations. The sensor unit 53 can comprise a pressure sensor 54 which can be provided in the ocular channel as shown in Fig. 3 and Fig. 4. The pressure sensor also can be provided in the otoscope head 45 or in any other location where a relevant air pressure signal can be obtained. In further alternative embodiment the sensor unit 53 can comprise a positional sensor or similar device capable of obtaining a signal indicative of the position of a valve that is opened when the air pulse is transferred to the TM. The sensor unit 53 also can be implemented as a an output of the pressure control unit 52 indicative of the generation and transfer of an air pulse.

Claims

1. A device for measuring physical properties of the tympanic membrane (TM), comprising an elongated probe (12) with a distal end (15) for inspec- tion of the ear, wherein a plurality of optical fibres is arranged in said elongated probe and the plurality of fibres including either a first set of fibres (21 ) for conveying light from a light source to said distal end of said probe and a second set of fibres (22) for conveying light reflected from the tympanic membrane in front of said distal end to a first detector means or a set of fi- bres both for conveying light from a light source to said distal end of said probe and for conveying light reflected from the tympanic membrane in front of said distal end to a first detector means (23), and wherein said first detector means (23) is designed for a spectroscopy based measurement, c h a r a c t e r i s e d by an air pressure generating means, an air channel conveying air from said air pressure generating means to the distal end of the probe (12), a second detector means for detecting the mobility of the tympanic membrane during pressure provocation caused by said air pressure generating means.

2. A device in accordance with claim 1 , wherein said first detector means (23) is a single detector for detecting the light intensity at selected wavelengths or at a spectrum of wavelengths, that is connected to a signal proc- essor (24) provided in a control apparatus (17), said signal processor (24) being configured to apply an erythema detection algorithm on data acquired from said first detector means (23).

3. A device in accordance with claim 1 , wherein said air pressure generating means comprises an air pump operatively connected to a pressure control unit.

4. A device in accordance with claim 1 , wherein said air pressure generating means comprises a manually operated bladder.

5. A device in accordance with claim 1 , wherein said said first detector means (23) is a detector for detecting the light intensity at selected wavelengths or at a spectrum of wavelengths in a wavelength interval of 800-2000 nm, that is connected to a signal processor (24) provided in a control apparatus (17), said signal processor (24) being configured to apply a fluid pres- ence detection algorithm on data acquired from said first detector means (23).

6. A device in accordance with claim 1 , wherein said said first detector means (23) is a detector for detecting the light intensity at selected wave- lengths or at a spectrum of wavelengths in a wavelength interval of 200-2000 nm, that is connected to a signal processor (24) provided in a control apparatus (17), said signal processor (24) being configured to apply a chromo- phore presence detection algorithm on data acquired from said first detector means (23).

7. A device in accordance with claim 1 , wherein said said first detector means (23) is a detector for detecting the light intensity at selected wavelengths or at a spectrum of wavelengths in a wavelength interval of 450-900 nm, that is connected to a signal processor (24) provided in a control appa- ratus (17), said signal processor (24) being configured to apply an oxygen saturation detection algorithm on data acquired from said first detector means (23).

8. A device in accordance with claim 1 , wherein said light source comprises a plurality of light emitting elements modulated in frequency to allow parallel detection of signals received from different light emitting elements.

9. A device in accordance with claim 1 , wherein said light source comprises a plurality of light emitting elements modulated in amplitud to allow parallel detection of signals received from different light emitting elements.

10. A device in accordance with claim 1 , wherein said light source comprises a plurality of light emitting elements that are activated in sequence for the detection of signals received from different light emitting elements.

11. A device in accordance with claim 2, wherein said erythema detection algorithm utilizes the fact that the photon absorption in the vicinity of the Soret band and the Q band of various blood chromophores is different in erythematous and in normal tissue.

12. A device in accordance with claim 1 , wherein said first detector means (23) comprises at least two separate detectors, a first detector having a peak sensitivity at 650 nm and a second detector having a peak sensitivity at 576 nm.

13. A device in accordance with claim 1 , wherein said first detector means (23) comprises at five separate detectors, a first detector having a peak sensitivity around 650 nm, a second detector having a peak sensitivity around 460 nm, a third detector having a peak sensitivity around 490 nm, a fourth detector having a peak sensitivity around 542 nm, and a fifth detector having a peak sensitivity around 576 nm.

14. A device in accordance with claim 1 , wherein said first set of fibres (21 ) for conveying light from a light source to said distal end of said probe and said second set of fibres (22) for conveying light reflected from the tympanic membrane in front of said distal end to a first detector means (23) are ar- ranged along a circular line and wherein an ocular channel (35) is arranged radially within said circular line.

15. A device in accordance with claim 14, wherein a separate optical fibre, or set of fibres, (26') is arranged on either side of said ocular channel (35) diametrically opposed to each other for directing light towards the tympanic membrane and for producing visual reference points on the tympanic membrane.

16. A device in accordance with claim 14, wherein a separate optical fibre, or set of fibres, (26, 26') is operatively connected to a second light source (25) for conveying light that is directed towards target tissue as a visual reference.

17. A device in accordance with claim 1 , wherein said probe (12) extends from a vertical grip section (11 ) and an eyepiece (13) is optically connected to an ocular channel extending through said probe (12).

18. A method for measuring physical properties of the tympanic membrane (TM), including the following steps:

a) illuminating the tympanic membrane with light from a light source,

b) detecting light reflected from the tympanic membrane,

c) analysing the intensity at selected wavelengths or a spectrum of wavelengths, d) generating air pressure pulses directed against the tympanic membrane, and e) analysing the reflected light to obtain a signal indicative of the mobility of the tympanic membrane.

19. A method in accordance with claim 18, also including the steps of obtaining information indicative of the air pressure pulses directed