WO1997013448A2

WO1997013448A2 - Device for determining blood glucose level

Info

Publication number: WO1997013448A2
Application number: PCT/DE1996/001971
Authority: WO
Inventors: Gerhard Müller
Original assignee: Laser- Und Medizin-Technologie Gmbh Berlin
Priority date: 1995-10-14
Filing date: 1996-10-14
Publication date: 1997-04-17
Also published as: WO1997013448A3; DE19538372A1; DE29623431U1

Abstract

The proposed device for determining blood glucose level comprises the following elements: a light source (3) for producing a measurement radiation used to illuminate a part (2) of the body using a wavelength for which the optical properties of the body part (2) depend on the concentration of the blood component in question; a light detector (10) for detecting the measurement radiation which has been attenuated in the body part (2) to a degree dependent on the said concentration; and an evaluation unit (12) for determining the concentration of the blood component as a function of the radiation detected. The illuminated body part is an eye (2) and the light detector (10) for measuring the reflected light is set up in the path of the radiation reflected or back scattered in the anterior chamber (1) of the eye. A focusing system (6) is mounted between the light source (3) and the illuminated eye (2) to prevent damage to the retina by the measurement radiation. The focusing system focuses the measurement radiation in the anterior chamber (1) of the eye in such a way that the radiation nearer to the retina is substantially blocked by the iris (7), and/or the selected wavelength of the measurement radiation lies within the absorption range of the aqueous humour in order to prevent damage to the retina.

Description

Device for determining blood glucose

description

The invention relates to a device for the non-invasive determination of the concentration of a blood component, in particular for the determination of blood glucose, according to the preamble of claim 1.

Devices for determining the blood glucose concentration are known which are based on the influence of the blood glucose concentration on the absorption properties of the human body tissue. The known devices therefore have a light source which shines transcutaneously through a part of the body of the person to be examined, for example the earlobe, the fingertip or the inner lip, at glucose-specific wavelengths in the near infrared or medium infrared, the measuring radiation depending on the blood glucose concentration is weakened. A light detector is therefore arranged on the opposite side of the irradiated body part, which detects the transmitted measuring radiation and feeds a corresponding signal to an evaluation unit which uses it to calculate the blood glucose concentration.

However, the problem here is that the blood glucose-specific signal is extremely small compared to underground signals due to water and tissue absorption. In particular, the high value of the water absorption changes depending on the temperature, so that practically no meaningful measurement signal can be obtained. Another disadvantage of these devices is that both the so-called tissue glucose concentration and the blood glucose concentration are measured simultaneously and there is practically no possibility of differentiating the two signals. Beyond that Such measurements are falsified in that the light propagation in the tissue is not adequately taken into account as a multiple scattering process.

Furthermore, devices for determining blood glucose are known which are based on the determination of the optical activity, that is to say the change in the direction of polarization by the right-handed glucose, of the irradiated tissue. These devices also have the disadvantage that the propagation of light in the tissue is not adequately taken into account. In addition, the optical activity of the irradiated tissue depends not only on the blood glucose concentration, but is also influenced by the concentration of other optically active blood or tissue components. A further disadvantage of these devices is the extreme dependence of the measurement result on the irradiated layer thickness, which must therefore also be determined, which is not possible or is only possible with increased technical effort.

The invention is therefore based on the object of creating a device for non-invasive blood glucose determination which enables simple and accurate measurement of the blood glucose concentration and avoids the above-mentioned disadvantages of the known devices.

Starting from a device according to the preamble of claim 1, the object is achieved by the characterizing features of claim 1.

The invention includes the technical teaching of introducing measuring radiation into the anterior chamber of an eye of the test person by means of a light source in order to determine the concentration of a blood component and the intensity of the reflected or backscattered measurement radiation to be detected by a light detector in order to determine the blood concentration of the respective blood component from the concentration-dependent intensity of the reflected or backscattered measurement radiation.

According to the invention, this is based on the new and surprising finding that the fluid in the anterior chamber of the human eye is to be regarded as the ultrafiltrate of the blood plasma and therefore has a strict correlation with a glucose content which corresponds to that of the blood plasma.

However, the invention is not limited to determining the blood glucose concentration, but rather can be used to measure the concentration of all blood components in which the concentration in the eye fluid has a predetermined dependence on the blood concentration. The invention is also not limited to humans as a measurement object, but can also be used with animals.

According to the invention, provision is therefore made for a measurement light to be introduced into the anterior chamber by means of a first light source, the wavelength of the measurement radiation for exciting glucose-specific Raman bands preferably being in the near infrared range. In this case, emission wavelengths in the range from 650 nm to 2.5 μm have proven to be advantageous.

Furthermore, according to the invention, a light detector is provided, which is arranged in front of the irradiated eye for measuring the measurement radiation reflected or backscattered in the eye fluid. The concentration of the respective blood component is then determined by an evaluation unit which is connected on the input side to the light detector. The evaluation unit preferably subjects the reflected or backscattered measurement radiation to Fourier transform infrared Raman spectroscopy in order to be able to subsequently calculate the blood concentration sought from the spectral intensity distribution.

In a variant of the invention, provision is also made to prevent damage to the retina by the measuring radiation by largely preventing direct exposure of the retina to the measuring radiation. For this purpose, focusing optics are provided which focus the measuring radiation generated by the first light source in the anterior chamber in such a way that the measuring radiation essentially hits the iris diaphragm on the retina side, thereby preventing damage to the retina even at high intensities of the measuring radiation .

This focusing optics preferably has a high-aperture, short focal length dark field objective, as is known, for example, from light microscopy. The dark field lens is arranged in front of the subject's eye, the excitation radiation being focused radially symmetrically into the anterior chamber of the eye. The light-filled double cone is focused in such a way that it is already so divergent in the retinal focus area that it does not fall through the pupil onto the retina, but is stopped by the iris diaphragm.

In another variant of the invention, on the other hand, provision is made to use a wavelength in the range of strong absorption of water to prevent retina damage by the measuring radiation. This is for protection No separate optics are required for the retina before the measuring radiation, since the measuring radiation is sufficiently attenuated until the retina is reached due to absorption by the eye fluid in order to prevent damage to the retina. Wavelengths above 1.5 μm have proven to be advantageous. The detection of the reflected or backscattered measurement radiation is then carried out - as already described above - by a light detector and a downstream evaluation unit, preferably using the technologies of the so-called Fourier transform infrared Raman spectroscopy.

A further variant of the invention provides for the examined eye to be fixed during the measurement. This is particularly advantageous if, as already described above, a focus is used to prevent the retina from being damaged by the measuring radiation ¬ rungsoptik is provided, which generates a strongly divergent beam on the retina side, since the effectiveness of such focusing optics is only fully available with a certain spatial position of the eye and decreases when the viewing direction changes. In this variant of the invention, the eye is fixed in that a fixation mark is faded into the field of vision, which is fixed by the test subject and causes the eyes to be immobilized in a defined position. The fixation mark is generated by a second light source with an emission wavelength in the visible wavelength range, the light exit opening of which is arranged spatially fixed in the field of view of the subject. An optical waveguide, one end of which is connected to the second light source, is particularly advantageous for this purpose, while the light outlet opening is arranged in the field of view of the examined eye.

In a further variant of the invention, an optical filter is provided between the light detector and the examined eye in the beam path of the reflected measuring radiation, which suppresses light in those wavelength ranges in which the intensity of the backscattered or reflected measuring radiation is only slight Depends on the concentration of the blood component to be determined. As a result, the proportion of measuring radiation that reaches the light detector has a significantly greater dependence on the concentration to be determined, which simplifies the measurement and increases the accuracy.

Other advantageous developments of the invention are characterized in the subclaims or are shown below together with the description of the preferred embodiment of the invention with reference to the figures. It shows:

FIG. 1 shows, as a preferred embodiment of the invention, a device for determining the blood glucose concentration with an illustration of the beam paths,

Figure 2 shows the arrangement of the device of Figure 1 during the measurement and

Figure 3 shows an alternative embodiment of the device according to the invention.

The device shown in Figure 1 enables a non-invasive determination of the blood glucose concentration by Introducing measuring radiation into the front chamber 1 of an eye 2 and measuring the backscattered or reflected portion.

This is based on the knowledge that the glucose concentration in the anterior chamber 1 of the eyes 2 reflects the glucose concentration in the blood very precisely, so that it is sufficient to determine the blood glucose concentration by measuring the glucose concentration in an anterior chamber 1 and from this the blood glucose concentration to calculate.

The measuring radiation is generated by a light source 3 and brought to the required beam cross-section by an expansion optics 4. The measuring radiation is then directed with a ring-shaped mirror 5 onto a dark field illumination objective 6, which focuses the measuring radiation in the front chamber 1 of the eye 2 in such a way that after passing through the focal point it falls on the iris diaphragm 7 and thus the sensitive retina behind the Eye lens 8 not at risk. The differently strong Raman radiation which arises in the front chamber 1, depending on the glucose concentration, is bundled by the high-aperture lens 9 and, before it reaches the light detector 10, sent through a filter 11 which suppresses the interfering radiation components.

The actual calculation of the blood glucose concentration is then carried out by the evaluation unit 12, which first subjects the output signal of the light detector 10 to Fourier transform infrared Raman spectroscopy and calculates the blood glucose concentration from the spectral intensity distribution using a computing unit. In addition, the device shown enables the eye 2 to be fixed and the iris 7 to be narrowed in order to prevent damage to the sensitive retina by the measurement radiation. For this purpose, a fixation mark is faded into the field of vision, which is fixed by the test subject, which on the one hand leads to a fixation of the eye 2 and, on the other hand, to a narrowing of the iris diaphragm 7 due to the brightness of the fixation mark, since the eye 2 independently adjusts to the lighting conditions adjusts. The fixing mark is generated by a second light source designed as a fixing mark projector and is faded into the field of view via a light waveguide 13. The light exit opening of the optical waveguide 13 is arranged in front of the high-aperture lens 9 in such a way that the fixation mark only fully reaches the retina when the eye 2 is in the most favorable measuring position.

FIG. 2 shows, on the one hand, the arrangement of the device shown only schematically above in a binocular viewing device 14 and, on the other hand, the use of the binocular viewing device 14 by the person 15 to be examined.

The device described above is arranged in the tube 16.1 of the binocular viewing device 14, which is placed on the right eye of the subject 15 with an eyepiece 17.1. The other tube 16.2, on the other hand, contains a display 18 which is arranged at the transition point to the associated eyepiece 17.2. This display 18 is controlled by the evaluation unit and shows the measured blood glucose concentration, so that the person 15 to be examined only has to look into the binocular vision device 14 and the blood glucose concentration is immediately displayed. The device according to the invention is thus easy to handle that a diabetic can determine the blood glucose value in a self-test.

FIG. 3 finally shows an alternative embodiment of the device according to the invention for determining the blood glucose concentration, measuring radiation being introduced into the front chamber 1 of an eye 2 as in the exemplary embodiment shown in FIG. 1, and the proportion of the reflected or backscattered measuring radiation is measured.

The measuring radiation is generated here by a light source 19, the emission wavelength of which is above 1.5 μm, so that the measuring radiation is strongly absorbed by the eye fluid, which essentially consists of water. This advantageously prevents damage to the sensitive retina from the measuring radiation, since the measuring radiation is sufficiently attenuated after it has passed through the interior of the eye until the eye fluid reaches the retina to prevent damage to the retina. In contrast to the embodiment shown in FIG. 1, the embodiment shown therefore does not require separate focusing optics in order to prevent direct exposure of the retina.

The measuring radiation generated by the light source 19 is faded into the field of view of the eye 2 via the colimation lens 20 and the partially transparent mirror 21 and is focused by the focusing lens 22 in the front chamber 1 of the eye 2. The Raman radiation, which is dependent on the glucose concentration, is collected by the high-aperture focusing lens 22 and penetrates the partially transparent mirror 21, which has a high degree of transparency for the spectral intensity distribution of the Raman radiation. Then reached the reflected measuring radiation the light detector 23, which is connected on the output side to the evaluation unit 24. The measurement radiation is first subjected to a Fourier transform Raman spectroscopy by the evaluation unit 24, in order then to be able to calculate the blood glucose concentration as a function of the determined spectrum of the Raman radiation.

The embodiment of the invention is not limited to the preferred exemplary embodiments specified above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types.

* * * * *

Claims

Expectations

1. Device for the non-invasive determination of the concentration of a blood component, in particular for determining blood glucose, with a first light source (3, 19) for generating measuring radiation for irradiation onto a body part (2) with a wavelength at which the optical properties of the irradiated body part (2) depend on the concentration of the blood component to be determined in the irradiated body part (2), a light detector (10, 23) for detecting the measurement radiation attenuated in a concentration-dependent manner in the irradiated body part (2) and an evaluation unit (12, 24) connected on the input side to the light detector (10, 23) for determining the concentration of the blood component as a function of the measurement radiation detected by the light detector (10, 23), characterized in that the irradiated body part is a Is eye (2), the light detector (10, 23) for reflection measurement in the beam path that in the front of the eye arranged (1) reflected or back-scattered measuring radiation that between the first light source (3, 19) and the irradiated eye (2) to avoid retina damage by the measuring radiation, a focusing optics (6) is arranged, which the measuring radiation focused in the anterior chamber (1) in such a way that the measuring radiation on the retinal side is essentially stopped by the iris (7) and / or that the wavelength of the measuring radiation for preventing re-damage by the measuring radiation lies in the absorption area of the eye fluid.

2. Device according to claim 1, characterized in that the focusing optics is a high aperture and short focal length dark field illumination lens (6).

3. Device according to claim 1 or 2, characterized gekenn¬ characterized in that the first light source (3) with its light exit direction is arranged transversely to the optical axis of the dark field illumination lens (6) and for deflecting the from the first light source (3) generated measuring radiation on the dark field illumination objective (6) a partially transparent or ring-shaped mirror (5) is provided.

4. Device according to one of the preceding claims, characterized in that for fixing the eye (2) and for constricting the iris (7) a second light source with an emissi¬ on wavelength in the visible spectral range is provided, which with its Licht¬ exit opening spatially fixed in front of the irradiated eye (2) is arranged such that its radiation reaches the retina of the eye (2) as a fixation mark.

5. The device according to claim 4, characterized in that for fading in the fixing mark in the field of view of the irradiated eye (2) an optical waveguide (13) is provided, the verbun¬ the input side with the second light source and the output side with its light exit opening the irradiated eye (2) and this is arranged facing.

6. Device according to one of the preceding claims, characterized in that the wavelength of the measuring radiation for exciting Raman bands in the spectral range is substantially between 650 nm and 2.5 µm.

7. Device according to one of the preceding claims, characterized in that the wavelength of the measuring radiation to prevent retinal damage by absorption of the measuring radiation on the eye fluid is substantially greater than 1.5 µm.

8. Device according to one of the preceding claims, characterized in that an optical filter (11) is arranged between the light detector (10) and the eye (2), which suppresses light in those wavelength ranges in which the intensity of the reflected or backscattered measuring radiation has only a slight dependence on the concentration to be determined.

9. Device according to one of the preceding claims, characterized by the arrangement in a binocular view device (14), wherein in the one tube (16.1) of the binocular view device (14) at least the first light source (3, 19) and the light detector ( 10, 23) and in the other tube

(16.2) of the binocular viewer (14) has an optical input connected to the evaluation unit (12, 24) on the input side. Pointing device (18) is arranged for outputting the measured concentration.