DE102005030347A1 - Concentration determining method e.g. for determining blood glucose concentration in aqueous fluid and or tissue of eye, involves having optical radiation for production of RAM illumination by reciprocal effect - Google Patents

Abstract

The method involves having an optical radiation for the production of RAM illumination by reciprocal effect with a material along a path of rays (5) in a chamber (1), focused in a range of an eye (2) and along a detection ray path (8). Incident radiation is detected by detection signals, which is produced by RAM on a reciprocal effect of the radiation with the material. Detection paths within range of a cornea (11) of the eye do not overlap. A function of the detection signals is determined for the concentration of the material. An independent claim is included for a device for the determination of a concentration of a material in a chamber.

Description

The The present invention relates to a method and an apparatus for determining a concentration of at least one substance in the aqueous humor and / or in the tissue of an eye.

The Determination of a concentration of a substance or several substances in the aqueous humor and / or tissue of the eye can be used for various, in particular medical, applications of interest. For example, imagine the regular blood glucose measurement for diabetics a significant burden, as they have always been painful Blood collection, usually from a fingertip, is connected. In particular, Type I diabetics should take at least five blood glucose measurements daily carry out, to be able to adjust the insulin level exactly. Because of the painful procedure The blood collection will be on average only two to three measurements per Day performed, what creeping organic damage or a significantly reduced life expectancy can result.

Out For this reason, there is considerable effort, a reliable, non-invasive Method to find the blood sugar or glucose content in the body too measure up. A promising approach is based on the measurement of Glucose content in the aqueous humor of the eye, as this is representative of the glucose content is in the blood.

Next Contains glucose the aqueous humor but other substances such. Albumin, ascorbic acid and Salts that may be diagnostically of interest.

A possibility for the determination of the concentration of glucose in the aqueous humor of the Eye is the eye, or the aqueous humor of the eye, to illuminate with optical excitation radiation and in the aqueous humor to detect generated Raman radiation. The intensity of the glucose Raman spectrum in relation to to that of the water Raman spectrum then lets Conclusions on the Concentration of glucose in the aqueous humor too.

So is in US 5,243,983 described to use stimulated Raman spectroscopy to determine the glucose content. For this purpose, a pumping beam and a measuring beam are superimposed and blasted through the eye. After passing through the eye, the intensity of the measuring beam is detected, which is reduced according to the concentration of glucose with respect to the intensity in front of the eye. This method has the disadvantage that the stimulated Raman scattering is a non-linear optical effect, so that for detection large intensities are necessary, which could possibly affect the eye permanently.

In WO 00/02479 A1 is likewise the determination of a concentration of glucose in the aqueous humor of the eye. This is done along a Excitation beam path optical excitation radiation through an im Excitation beam path arranged beam splitter blasted onto the eye. There by Raman scattering on the glucose in the aqueous humor arising Detection radiation passes over the excitation beam path up to the beam splitter which detects the detection radiation from the excitation beam path. The detection radiation can then be detected. In this method, however, excitation radiation Generate autofluorescence in the cornea, resulting in a disruptive signal background in the detection leads, the at an unfavorable Signal-to-noise ratio to lead can.

It It can be assumed that both Procedure Laser power of at least 30 mW and typical measuring times of at least 10 seconds.

It would be, however desirable, the glucose concentration in a measuring time of less than 70 seconds with a small error and only a low radiation exposure to be able to determine.

Of the The present invention is therefore based on the object, a method and a device for determining a concentration of at least one Stoffs, in particular of glucose, in the aqueous humor and / or in the tissue of the eye, the determination of the concentration of the substance with only small radiation exposure with a low Meßfehfer allowed.

The Task is solved by a method for determining a concentration at least a substance in the aqueous humor and / or in the tissue of an eye, at the optical excitation radiation for generating Raman radiation by interaction with the at least one substance along an excitation beam path in an aqueous humor and / or tissue-containing area of the eye, along a detection beam path incident detection radiation to form detection signals is detected by Raman interaction of the excitation radiation with which at least one substance is generated, whereby excitation and detection beam path at least in the region of a cornea of Eye does not overlap significantly, and depending from the detection signals, the concentration of the at least one Stoffs is determined.

The problem is still solved by a Device for determining a concentration with at least one substance in the aqueous humor and / or in the tissue of an eye, comprising an illumination device for emitting optical excitation radiation for generating Raman radiation by interaction with the at least one substance on the eye along an excitation beam path, one in the excitation beam path arranged excitation optics for focusing the excitation radiation in a aqueous humor and / or in a tissue-containing area of the eye, a detection device for detecting incident along a detection beam path detection radiation, which is generated by Raman interaction of the excitation radiation with the at least one substance, and for delivering corresponding Detection signals, and an evaluation device for determining the concentration of the at least one substance in dependence on the detection signals of the detection device, wherein the excitation and the detection beam path at least in a region with a thickness of at least 0.5 mm, preferably at least 1 mm, do not overlap before the focus of the excitation radiation.

to Determination of the concentration of the substance in the aqueous humor and / or Tissue of the eye, the Raman effect is used, i. the excitation radiation gets from the substance under a through the properties of the molecules of the substance certain frequency or wavelength shift scattered. Basically these are any type of Raman effect, in particular the spontaneous Raman scattering, in which Stokes' scattering and anti-Stokes radiation is generated whose wavelength is opposite to the Excitation radiation corresponding to, for example, vibration properties of the molecule changed is. The excitation radiation is expedient depending on the one to be investigated Fabric chosen, so that the Raman effect can occur.

There the scattered Raman radiation typically has a low intensity and so that the detected Raman radiation has an unfavorable signal-to-noise ratio, on the one hand, the excitation radiation in the area selected for examination focused on the eye to get there a high intensity. In addition, according to the invention provided that the excitation beam path and the detection beam path at least in The area of the cornea of the eye does not overlap, i. the excitation beam path and the detection beam path in the area spatially separated are so through that Interaction of the excitation radiation with the cornea Radiation as possible is not coupled into the detection beam path. In the device is it provided for that purpose the excitation beam path and the detection beam path in one do not overlap given area before the focus of excitation radiation, i.e. spatially in this area are separated from each other. This area has at least one thickness of 0.5 mm, preferably at least 1 mm. Indicated that the area Before the focus is, in particular also understood that this adjacent to the focus area or the area in the direction of the Focus bounding area from this maximum of 30 mm, preferably at most 10 mm away.

The Detection radiation can then in a known manner by the Detection device detected to form the detection signals become. The detection signals are then the evaluation device supplied from which determines the concentration of the substance, preferably the intensity the excitation radiation either absolutely or by a corresponding Calibration is assumed to be known.

By this training of the beam paths can the signal-to-noise ratio be increased significantly, so that at a very short measuring time the concentration of the substance, at least for example typical for glucose Concentrations in aqueous humor, in a short time, preferably in less than 10 seconds, preferably with a better accuracy can be measured as 10%.

Basically in the method uses any optical excitation radiation in Raman scattering through interaction with the substance occurs. However, it is preferred that as the optical excitation radiation Radiation with one wavelength in the wavelength range between 320 nm and 700 nm, preferably between 370 nm and 420 nm, is used. In the device, it is preferable that the illumination device as optical excitation radiation radiation with a wavelength in the wavelength range between 320 nm and 700 nm, preferably between 370 nm and 420 nm, gives off. This choice of the wavelength of the excitation radiation or the lighting device has the advantage that with decreasing Wavelength the Raman intensity increases, so that through this choice the measurement time can be further reduced.

When Excitation radiation is preferably optical radiation with a low spectral bandwidth of preferably less than 5 nm used to be an impairment the detection of Raman radiation by fluorescence radiation by the excitation radiation is generated, or elastically scattered excitation radiation to avoid.

As a lighting device can basically serve any lighting device, the excitation radiation in the desired Wel gives off lenlängenbereich. However, the illumination device preferably comprises at least one light emitting diode, a laser, a laser diode or a superluminescent diode. The use of a laser, a laser diode or a superluminescent diode has the advantage that in this way high-intensity optical excitation radiation can be generated, which moreover is easy to focus, so that the detection radiation can also have a relatively high intensity.

Basically, it is sufficient that the lighting device Emits excitation radiation in only a narrow wavelength range. It is however, it is preferred that the Lighting device with respect to the mean wavelength of the Excitation radiation is tunable. This has the advantage that with the Lighting device, for example, the excitation wavelength the substance to be tested can be matched, so that an in relationship to the excitation radiation as possible strong detection radiation is generated.

Preferably In the method, the area of the eye is focused in which the excitation radiation is illuminated in the manner of a dark field illumination. In the device For this purpose, preferably the excitation and detection beam path designed so that the Focus area of the excitation radiation in the manner of a dark field illumination is illuminated. This means that preferably the detection beam path across from the excitation beam path inclined at least in the area in front of the focus extends and no excitation radiation directly from the excitation beam path can be coupled into the detection beam path, i. yourself propagates along the detection beam path. This has the advantage that the Detection device solely on the detection of Raman radiation can be designed and thus have a higher sensitivity can.

There in the method and apparatus no imaging of the examined Range is necessary, in addition to the arrangement of the detection beam path No special requirements relative to the excitation beam path be placed on the detection beam path. Preferably in the detection beam path, however, a detection optics for focusing provided the detection radiation.

Basically, the Detection optics and the excitation optics are separated from each other, i. have different optical components. In the device However, preferably a focusing optic forms the excitation optics and at least part of a detection optics for focusing the detection radiation. This has the advantage that the device only a few different components need to have and beyond also an orientation of excitation and detection beam path can be performed much easier on each other.

Basically it is possible that yourself Excitation beam path and detection beam path in the focusing Overlap optics. Preferably overlap However, excitation beam and detection beam path also not in the focusing optics. This means that even there the excitation and the detection beam path spatially from each other are separated. This training offers the advantage that by Fluorescence or scattering in the focusing optics from the excitation radiation emerging radiation is not coupled into the detection beam path and interferes with the detection of Raman radiation. This measure also increases the signal-to-noise ratio.

In principle, excitation and detection beam path except for the aforementioned limitations run arbitrarily. According to a preferred embodiment surrounds in the method, however, in the area of the eye of the detection beam path the excitation beam path at least partially, preferably completely. at encloses the device the detection beam path in at least one section in the area the eye at least partially, preferably completely, the excitation beam path. Here, the indication in the area of the eye means a shift around the eye surface with a thickness of the distance between cornea and excitation optics or at least 1 mm. This training has the advantage that the excitation radiation simply for example by means of a mirror in the enclosed by the detection beam path Area can be mirrored, the mirror along the Excitation beam from the focus of the outgoing radiation on the Path to the detection device blocked. Preferably run Detection and excitation beam path at least in the range between the excitation optics and the focus in this form. Very cheap, there easy to obtain is the cross section of the detection beam path in the section annular and the excitation beam path runs there in the interior of the detection beam path. Particularly preferred is the annular cross-section as a circular ring shaped.

According to a particularly preferred embodiment, in the method in the region of the eye, the excitation beam path encloses the detection beam path at least partially, preferably completely. In the device, the excitation beam path at least partially, preferably completely, encloses the detection beam path in at least one section in the region of the eye. Here, the indication in the range of As in the previous paragraph, a layer around the ocular surface with a cornea-excitation optical path thickness of at least 1 mm. Preferably, detection and excitation beam paths extend at least in the region between the excitation optics and the focus in this form. This embodiment has the advantage that the excitation radiation is less likely to reach the central retinal area, which is particularly sensitive to radiation damage. Preferably, the cross section of the excitation beam path is annular and the detection beam path runs there in the interior of the excitation beam path. In the device, the illumination device is preferably designed to emit an excitation beam or excitation beam having an annular cross-section and the detection beam path extends at least in the region between the excitation optics and the focus in the interior of the excitation beam path. For the formation of the excitation beam, the illumination device can have, for example, a radiation source whose radiation exit surface is annular. However, the illumination device preferably comprises a source of optical excitation radiation and a coupling device which couples the excitation radiation with an annular cross-section into the excitation optics. The coupling device may in particular be a fiber optic coupler. In addition, either the detection radiation can be reflected out of the interior of the volume enclosed by the excitation beam path or the excitation radiation can be coupled in through an annular mirror through which the detection beam path passes. In particular, the use of mirrors allows a particularly simple construction of the device.

Basically the optical excitation radiation emitted with constant intensity become. Preferably, however, in the method, the excitation radiation pulsed delivered. The lighting device of the device is Accordingly, preferably for the delivery of pulsed excitation radiation educated. This embodiment allows advantageously a better dissipation of the excitation radiation generated heat in the aqueous humor or in the tissue of the eye, so that an impairment of the eye can be avoided even more safely.

at another embodiment of the method, the excitation radiation with a predetermined timed pulse or modulated delivered and the detection signals become dependent formed and / or processed by the time course. In the Device according to the invention is the lighting device to with a predetermined temporal course formed pulsed or modulated emission of excitation radiation and the detection device and / or the evaluation device are trained to be dependent from the time course to form the detection signals and / or to process. This embodiment has the advantage that the Signal-to-noise ratio can be lowered further, so that the determination of the concentration with greater accuracy can be done. In particular, a per se known lock-in measuring method be used. The time course can be, for example by a corresponding device in the lighting device or the evaluation be predetermined. In this case is the detection device and / or the evaluation device with the Illuminating device connected to the time course reproducing Receive signals. However, it is also possible that the evaluation and / or the detection device emits corresponding signals to the illumination device.

As already mentioned, enough it basically, that of the area of the eye in which the focus of the excitation radiation lies, outgoing detection radiation reaches the detection device. To be as possible largely to prevent further Radiated from other areas of the eye or even the environment in the detection beam path can be coupled, the detection radiation is in the process from the area in which the excitation radiation is focused, in focused a fine pinhole and then detected. In the device is in the detection beam path in front of the detection device a arranged fine pinhole and at least a portion of a detection optics forms the focus of the excitation optics on the pinhole. In order to In particular, a confocal detection of the Raman radiation can be achieved which has the advantage that essentially only radiation the focus area of the excitation radiation focused on the aperture becomes, passes through them and is then focused. Other radiation against it falls next to the hole of the aperture on the aperture itself and passes not to the detection device, so that in turn the signal-to-noise ratio is increased.

The excitation radiation entering the focus area of the eye experiences not only Raman scattering but also an elastic scattering in which the wavelength is not changed. It is therefore preferred in the method that the detection radiation is filtered for the at least partial suppression of elastically scattered excitation radiation. In the device, a notch filter is arranged in the detection beam path, which at least partially suppresses elastically scattered excitation radiation in the detection beam path, which by interaction of the excitation radiation with the at least one substance generated Raman radiation, however, lets through. As a result, the Raman radiation can be detected more accurately in an advantageous manner. In particular, when a spectrometer is used in the detection device, a clear and quantitatively very good separation of the Raman bands from the band of the elastically scattered excitation radiation can take place. The scattered excitation radiation may in particular be Rayleigh radiation.

Further it is preferred in the method that the detection radiation for suppression is filtered by fluorescent radiation caused by the excitation radiation is produced. The device according to the invention has preferably via a bandpass filter, the for the generated Raman radiation is permeable. Preferably the transmitted band is so narrow that only the Raman radiation and optionally Radiation with wavelengths in the range between the wavelengths the Raman radiation can be transmitted, other wavelength ranges however, at least partially suppressed. Also by this can be avoided that interference to a detector in the detection device that falls as background a precise recording of the intensity of the made Raman radiation obstructed.

Additionally or Alternatively, the detection radiation of a polarization-dependent filtering be subjected, so that only Detection radiation of a predetermined polarization state detected becomes. In the device is to the detection beam path and / or a polarization filter is arranged in the detection device, the radiation of a given state of polarization passes. When Polarizing filters can Linear or circular polarizers are used. If so the Raman radiation and the fluorescence or Rayleigh radiation With respect to the polarization can then with the polarizing filter a better signal-to-noise ratio be achieved.

Especially can advantageously circularly polarized excitation radiation can be used, and the resulting Raman radiation detected polarization-dependent become. In the device to the lighting device designed to deliver circularly polarized excitation radiation and / or it is a circular polarizer in the excitation beam path intended. This development has the advantage that it with circularly polarized excitation radiation is basically also possible, chiral, this means, optically active, molecules, which include glucose and lactate, by examination by means of To identify Raman radiation. This effect is also called Raman optical activity (ROA) (see L. Barren, L. Hecht, H. Bell, Science Progress, 1998, 81 (1), 17-34). Investigations based on this effect are particularly suitable for the Examination of tissue in the eye.

Out the intensity of the at least one substance corresponding Raman spectrum in relationship to that of the water Raman spectrum or in relation to the intensity of the excitation radiation or at known intensity The excitation radiation by calibration can be determined by known methods the concentration of the substance can be determined.

The Method can be designed for different types of Raman scattering be, in particular spontaneously emitted Raman scattering and non-linear Raman scattering (CARS). In the device are the lighting device to excite the corresponding Raman radiation in the examined Substance and the detection device for the detection of the excited Raman radiation and optionally existing filters for transmission the Raman radiation formed.

Basically it is possible to use any detection device by means of which the Raman radiation detectable separately from other radiation components is. Could do this For example, a simple photodetector with a time in its passband changing, narrow-band Filter are used whose signals are detected time-dependent and thus wavelength-dependent. Preferably, however, a spectrally resolving detection device is used with a dispersing element and one in the beam path downstream, spatially resolution Detector used. Under a dispersing element is thereby an optical functional element understood, the optical radiation spectrally in space decomposed differently spreading spectral components. For example it may be a dispersion prism and / or a diffraction grating and / or a Etalon or a wedge include. The then preferably spatially resolving detector may comprise, for example, a CCD array or a CMOS field by means of the spatially separated by the dispersing element Spectral components of the detection radiation detected separately can be. In particular, you can Prism or grating spectrometer are used.

In order to reproducibly enable a good alignment between excitation beam path, eye and detection beam path, the device preferably has a positioning aid for positioning the eye relative to the device. In particular, can serve as a positioning aid means with a contact surface for the head or parts thereof, which is shaped so that the head relative to the device assumes a fixed position in which the eye in the excitation and detection beam path lies. For a more precise alignment between the illumination beam path and the eye, the device preferably has a fixation light source which is arranged such that, when the fixation light emitted by the fixation light source is viewed with the eye, the eyeball assumes a favorable position for carrying out the method.

Especially preferred in the device is at least one for at least for radiation in the wavelength range the Raman radiation intransparent eyecup so around excitation and detection beam path arranged around that at Applying the eyecup in the area of the eye the incidence of environmental radiation is avoided on the eye and / or in the detection beam path. In particular, you can the area between the eye and head and an opening in a housing the device through which the excitation radiation off and the detection radiation enters, optically separated from each other. This has the advantage that possible interference radiation repressed can be. About that In addition, the eyecup can be used to achieve a good fit is preferably flexible to the head, serve as a positioning aid.

The Device may be incorporated in an ophthalmological device, in particular then when to measure the concentration of substances in the aqueous humor or tissue of the eye to serve other than glucose. Preferably however, if it is a tabletop device, particularly preferred as a handheld device, trained so that a Diabetics simply and noninvasively the glucose content in the aqueous humor of the eye or, for example, this glucose content Can determine blood sugar value. In a version as a handheld, this has preferably over a subject for a battery or a battery to power the lighting, Detection and evaluation device.

The Invention can not only for Glucose be used as the substance to be detected. Rather, it is it prefers that the Detection radiation in the range of Raman radiation of at least one of the substances selected from the group lactate, glucose, proteins, amino acids, urea, ascorbic acid, drugs and / or diagnostic markers detected in the aqueous humor or eye tissue becomes. In the case of the device, the detection device is for this purpose designed that detection radiation in the field of Raman radiation at least one of the substances selected from the group of lactate, Glucose, proteins, amino acids, Urea, ascorbic acid, Medicaments and / or diagnostic markers in the aqueous humor or eye tissue is detectable. You can do this If appropriate, also filters arranged in the beam path can be selected accordingly.

The noninvasive method according to the invention In particular, it can also be used continuously or at short intervals become. The invention is therefore also a method of control a delivery of a feed substance into the body, in which by the method according to the invention the concentration of at least one substance in the aqueous humor of the eye and / or the eye tissue, and the delivery of the feed dependent on is determined by the concentration determined. For this purpose, the inventive device have a corresponding output interface for concentration signals, which reflect the concentration of the measured substance.

Another The invention relates to methods for determining a concentration at least one substance in the aqueous humor and / or in the tissue of the eye by means of Raman scattering of optical excitation radiation through the substance, in which as optical Excitation radiation Radiation with a wavelength in the wavelength range between 320 nm and 700 nm, preferably between 370 nm and 420 nm, is used, and an apparatus for carrying out the method, which is a Illumination device for emitting optical excitation radiation with one wavelength in the wavelength range between 320 nm and 700 nm, preferably between 370 nm and 420 nm. This choice of wavelength the excitation radiation or the illumination device has for otherwise any method of measuring the concentration of a substance in the Eye using Raman radiation the advantage that with decreasing wavelength the Raman intensity increases, so that by this choice the signal-to-noise ratio can be increased.

The Invention will be described in more detail by way of example with reference to the Drawings explained. Show it:

1 1 a schematic representation of a device according to a first preferred embodiment of the invention in front of an eye,

2 a cross section through the beam path in a focusing optics of the device in 1 .

3 a schematic representation of a device according to a third preferred embodiment of the invention in front of an eye, and

4 a schematic representation of an apparatus according to a fourth preferred embodiment of the invention in front of an eye.

In 1 comprises a device for determining a concentration of a substance in the chamber water 1 in the anterior chamber and / or in the tissue of an eye 2 , According to a first preferred embodiment of the invention in a housing 3 a lighting device 4 for the delivery of optical excitation radiation to the eye 2 along an excitation beam path illustrated by vertical hatching 5 for generating Raman radiation by interaction with the substance, one in the excitation beam path 5 arranged, serving as an excitation optical focusing optics 6 for focusing the excitation radiation, a detection device 7 for detecting along a detection beam path 8th incident detection radiation, which is generated by Raman interaction of the excitation radiation with the substance, and for outputting corresponding detection signals, and an evaluation device 9 for determining the concentration of the substance as a function of the detection signals of the detection device 7 , wherein the excitation and the detection beam path 5 respectively. 8th at least in a region with a thickness of at least 0.5 mm, preferably at least 1 mm, before the focus 10 the excitation radiation, ie in particular in the area of the cornea 11 of the eye, do not overlap or are spatially separated.

Im in the figures by horizontal hatching marked detection beam path 8th are successively a detection optics 12 that the focusing optics 6 and a confocal look 13 includes, as well as a notch filter 14 , a fluorescence filter 15 and a polarizing filter 16 arranged.

The lighting device 4 has a radiation source for emitting optical excitation radiation having a wavelength in the wavelength range between 320 nm and 700 nm, preferably only between 370 nm and 420 nm whose spectral width is less than 5 nm, so that the excitation radiation is in a wavelength range of 5 nm width , The radiation source used in this example is a corresponding laser diode which emits optical radiation in the region of 405 nm.

The emitted excitation radiation is transmitted via a light guide 17 and an annular coupling element 18 the illumination device collimates into the focusing optics 6 coupled, so that the cross section of the incoming illumination beam is circular. The lighting device 4 is therefore designed to emit an excitation beam having an annular cross-section. More specifically, the excitation beam path has a cylindrical portion and a conical portion. The conical section is preferably formed by at least one annular lens and / or at least one annular mirror in the front region of the focusing optics 6 generated.

The focusing optics 6 in the form of a lens is partially in an opening 19 in the case 3 arranges and focuses the collimated or parallel excitation radiation in the focus 10 into the chamber the eye 2 ,

The interaction of the excitation radiation with the substance in the aqueous humor 1 resulting Raman radiation occurs as detection radiation at least partially in the detection optics 12 one that has the focusing optics 6 includes. The focusing optics 6 first collapses the detection radiation, which then in the confocal optics 13 entry.

The in the detection beam path 8th in front of the detection device 7 arranged confocal optics 13 comprises two identical converging lenses 20 and 20 ' at a distance of twice the focal length of the converging lenses. In the middle between these collecting lenses 20 and 20 ' is a fine pinhole or pinhole aperture 21 arranged. Therefore, form the focusing optics 6 and the condenser lens 20 the focus 10 the excitation radiation on the opening of the pinhole 21 off, so that essentially only out of focus 10 the focusing optics 6 and thus the excitation optics coming radiation the pinhole 21 pass substantially unattenuated and to the detection device 7 can get.

The circular inlet cross-section or field stop of the confocal optics 13 is slightly smaller than or as large as the opening of the cross section of the excitation beam at its entry into the focusing optics and coaxially selected therewith so that only the eye 2 coming rays of the detection radiation in the confocal optics 13 may occur within the detection beam path, but not along the excitation beam path 5 have spread. As a result, the detection beam path runs 8th in the area between the focus 10 and the exit from the focusing optics 6 or the excitation optics in the interior of the excitation beam path concentric with this. In other words, the detection beam path is at least partially, in the example complete, in the area of the eye in front of the focus 10 and in focusing optics 6 enclosed by the excitation beam path. This is 2 illustrating a cross section through the beam paths orthogonal to the optical axis of the focusing optics 6 in the area of the same shows.

This overlaps the excitation beam path 5 and the detection beam path 8th in a range between the entry of the excitation radiation into the focusing optics 6 and a disk or cup around the focus 10 at a distance of 0.5 mm from the focus 10 Not. The area has a thickness of more than 20 mm. By using the focusing optics 6 as an incentive and at the same time as part of the detection optics 12 This makes the construction of a confocal system much easier. Due to the spatial separation of excitation and detection beam path in the focusing optics 6 can not continue by interaction of the excitation radiation with the focusing optics 6 resulting fluorescence radiation or otherwise elastically scattered radiation are coupled into the detection beam path, ie propagate along the detection beam path, resulting in an increased signal-to-noise ratio.

Of the Excitation and detection beam path are therefore designed to that the Focus area of the excitation radiation in the manner of a dark field illumination is illuminated, i. that excitation radiation not directly, but only after scattering in the detection beam path and thus affect the measurement of the concentration of the substance can.

The one in the detection beam path of the detection optics 12 following notch filters 14 , Also called notch filter, is used to suppress elastic, ie without wavelength change, for example by Rayleigh scattering, scattered excitation radiation that passes through the scattering in the detection beam path. It therefore has a very low transmission in the region of the wavelength of the excitation radiation, but a high transmission of other radiation, in particular in the region of the Raman radiation generated by the interaction of the excitation radiation with the substance.

The fluorescence filter following in the detection beam path 15 is a bandpass filter that transmits only the desired spectral range of the Raman radiation generated by the substance. For example, it may have a bandwidth of 200 nm, with one edge of the band being at the wavelength or middle wavelength of the excitation radiation. In the example, a sharp-edged interference filter is used as the fluorescence filter, which at the same time also serves for improved suppression of components of the excitation radiation that are scattered elastically into the detection beam path.

Between the fluorescence filter 15 and the detection device 7 is the optional polarization filter 16 , In the example, a circular polarizer which transmits substantially only radiation or radiation components with a predetermined state of polarization. If Raman radiation, fluorescence radiation and / or elastically scattered excitation radiation differ in terms of their polarization for a substance, a better signal-to-noise ratio can be achieved with the polarization filter.

The detection radiation then enters the detection device 7 a, which detects the detection radiation spectrally resolved, so it can be interpreted as a spectrometer. It includes a first lens 22 , a dispersing functional element 23 for the spectral decomposition of the detection radiation, in the example a dispersively acting prism, and a second lens 22 ' for focusing the detection radiation onto an at least one-dimensional arrangement of photodetection elements, in the example a CCD line scan camera 24 ,

The dispersive prism 23 deflects different spectral components of the detection radiation at different angles, so that different spectral components assigned to them different photodetection elements of the CCD line scan camera 24 fall. The detection signals formed by the photodetection elements reproduce the spectrum of the detection radiation due to the known position of the photodetection elements. The dispersing functional element and the arrangement of photodetection elements are selected such that the Raman lines or bands known for the given substance at the excitation wavelength of the excitation radiation can be separated spectrally and separated from one another and from elastically scattered detection radiation.

The detection device 7 , more precisely, the CCD line scan camera 24 , is with the evaluation device 9 connected to the detection signals of the detection device 7 receives.

The evaluation device 9 serves to determine the concentration of the substance from the detection signals of the detection device 7 and in addition has an interface for the connection to the detection device 7 via a processor and a memory in which data and an evaluation program to be executed by the processor for the evaluation of the detection signals are stored. The evaluation device 9 It also has an output device, in the example a display, in other examples a device for voice output, via which a concentration value for the substance determined from the detection signals can be output to a user.

In this example, the evaluation device is used 9 at the same time as a control device for the lighting device 4 , It controls the illumination device in such a way that it outputs the excitation radiation modulated with a predetermined time profile. The evaluation device 9 is formed by appropriate choice of the program to process as a function of the time course, the detection signals. In particular, the measured data with a lock-in method he which is known to those skilled in the electronic measuring technology and leads to an improvement of the signal-to-noise ratio in the measurement.

In the memory of the evaluation device 9 Reference data are stored that represent the expected, for the given substance at the selected wavelength of the excitation radiation specific Raman spectrum. The intensity of the excitation radiation in the focus area and the extent of the focus 10 as well as the losses of the excitation radiation and the detection radiation through the optical elements of the device are known, for example from calibration measurements, and corresponding data are in the memory of the evaluation device 9 saved.

The program for the evaluation device includes instructions for the execution of the following operations. The evaluation device determines the intensity of the Raman radiation generated on the basis of the detection signals and the data about the spectral position of the Raman radiation. This is proportional to the concentration of the substance in focus 10 , By means of a, for example, also determined by Kalibriermessungen, proportionality factor, the processor calculates the concentration of the substance from the determined intensity and outputs the value via the output device.

The lighting device 4 and the evaluation device 9 be about a battery 25 in a battery compartment in the housing 3 energized. The device is therefore very compact and designed as a handheld device.

Around the opening 19 of the housing 3 through which the focusing optics 6 sticks out, around is a non-transparent, flexible eyecup 26 arranged, which, when attached to the skin surface 30 around the area of the eye 2 is pressed, the area between the eye and device visually separates from the environment. The eyecup 26 also serves as a positioning aid to the eye 2 and align the device with each other.

The concentration of the substance in the aqueous humor is determined by the illumination device 4 generated optical excitation radiation for generating Raman radiation by interaction with the substance along the excitation beam path 5 into the aqueous humor 1 contained chamber of the eye 2 focused. The wavelength of the excitation radiation is selected specifically for the substance so that well-detectable Raman radiation is generated by the interaction of the excitation radiation with the substance.

Especially in the field of focus 10 Raman scattering of the excitation radiation therefore occurs by interaction with the substance in the aqueous humor 1 , The generated Raman radiation forms the detection radiation along the detection beam path 8th runs. Excitation beam path 5 and detection beam path 8th overlap in the area of the eye in front of the focus 10 not, ie are spatially separated, so that in particular by fluorescence of the excitation radiation to the cornea 11 resulting radiation does not propagate substantially along the detection beam path.

The out of focus 10 scattered, coupled into the detection beam path detection radiation is focused on the fine pinhole and then collimated again, so that essentially only parts of the focus 10 to the detection device 7 can reach.

The detection radiation then passes through the notch filter after filtering 14 , the fluorescence filter 15 and optionally the polarizing filter 16 into the detection device 7 in which it is first spectrally decomposed and then spectrally resolved to form detection signals is detected. By using the polarizing filter 16 Therefore, only detection radiation of a predetermined by this filter polarization state is detected.

As a function of the detection signals, the evaluation device then determines 9 as previously described, the concentration of the substance and outputs this.

The Excitation radiation is doing with a given temporal History modulated delivered and the detection signals are in dependence processed by the time course, so that noise effects are better suppressed.

The Method can by appropriate choice of the wavelength of the Excitation radiation and the filter for various substances in the aqueous humor or used in the tissue of the eye. For example, it may be the substance is a substance selected from the lactate group, Glucose, proteins, amino acids, Urea, ascorbic acid, Medicaments and / or diagnostic markers in the aqueous humor or eye tissue act. In particular, in the detection of glucose on the Base of a known dependency between the glucose content of the aqueous humor and the glucose content of the Blood instead of the glucose concentration in the aqueous humor of this corresponding blood glucose value can be output.

In a second preferred embodiment of the invention, the polarization filter is absent, so that Detection radiation arbitrary polarization state can be detected. This increases the detectable intensity of the Raman radiation entering the detection device, which results in a higher signal-to-noise ratio and thus greater measurement accuracy, in particular if polarization effects can not be used for detection.

With This device and method can reduce the concentration of Glucose in aqueous humor with an accuracy better than 10% be determined in less than 10 s.

An in 3 illustrated device according to a third preferred embodiment of the invention differs from the device of the first embodiment in the coupling of the excitation radiation in the focusing optics 6 , For unchanged parts, the same reference numerals are used as in the first embodiment and the explanations apply accordingly. In addition, the confocal optics 13 , the following filters and the detection device in 3 illustrated for simplicity only by a box K.

The lighting device 4 ' has a source 27 for collimated, ie parallel excitation radiation, in the example at an angle of 90 ° to the detection beam path 8th is delivered. The corresponding excitation beam initially has a circular cross-section whose diameter corresponds to that of the focusing optics.

In the excitation beam path 5 ' is a circular aperture 28 arranged whose center lies on the central beam of the excitation beam and whose diameter is the diameter of the cross section of the detection beam path 8th equivalent. The excitation beam path after the aperture 28 therefore has a circular cross-section.

For coupling is in the excitation beam path 5 ' a 45 ° inclined circular mirror 29 arranged, whose inner diameter is selected so that the detection beam path can pass through the opening in the mirror unhindered. The outer diameter is chosen so that the excitation beam path with annular cross section completely into the focusing optics 6 is coupled.

Overall, this results in a detection beam path also in this embodiment 8th In the area of focusing optics 6 to the focus 10 in the eye of the excitation beam at least partially, here completely, is enclosed and does not overlap with this.

The housing 3 ' is opposite the case 3 changed according to the arrangement of the lighting device.

A schematic in 4 A device according to a fourth preferred embodiment of the invention differs from that of the third embodiment in that the illumination device and the filters are interchanged with the detection device. In 4 the detection beam path are characterized by a vertical and the excitation beam path by a horizontal hatching.

This results in a detection beam path in at least one section from the exit from the focusing optics 6 up to the focus 10 at least partially surrounds the excitation beam path. In particular, it has an annular cross-section, in whose opening the excitation beam path 5 '' within the detection beam path 8th'' runs.

In other exemplary embodiments, a radiation source which can be tuned in relation to the mean wavelength of the excitation radiation, for example a tunable laser, can be used as the radiation source of the illumination device. As a radiation source, a superluminescent diode or a light-emitting diode can be used, which is followed by a preferably suitable narrow-band spectral filter in the beam path. Preferably, this has a spectral width of less than 5 nm. In particular, a light emitting diode emitting optical radiation having a wavelength λ _max = 380 nm may be used in conjunction with a bandpass filter having a spectral width of 5 nm.

The Lighting devices of a device according to the invention are preferably designed and adjusted so that the mean radiation power, which is blasted into the eye, less than 10 mW, preferably is less than 2 mW.

Farther may be used as a dispersing element instead of the prism, for example also a grid can be used.

The described methods can preferably be used for regulating a delivery of a feed substance into the body. For this purpose, the concentration of the substance in the aqueous humor of the eye and / or the eye tissue is determined by one of the methods, and regulated the delivery of the feed as a function of the determined concentration. For example, in intensive care units, the blood sugar of a patient could be detected non-invasively and, depending on the blood sugar value determined as a supply substance, insulin could be automatically absorbed by the body be supplied to the patient. However, it is also possible to determine the concentration of other substances and to use other medicines as supplements.

Claims (23)

Method for determining a concentration of at least one substance in the aqueous humor and / or in the tissue of an eye ( 2 ), wherein the optical excitation radiation for generating Raman radiation by interaction with the at least one substance along an excitation beam path ( 5 ; 5 ; 5 '' ) in an aqueous humor ( 1 ) and / or in a tissue-containing area of the eye ( 2 ) is focused along a detection beam path ( 8th ; 8th '; 8th'' ) incident detection radiation is formed to form detection signals, which is generated by Raman interaction of the excitation radiation with the at least one substance, wherein excitation and detection beam path ( 5 ; 5 '; 5 '; 8th ; 8th '; 8th'' ) at least in the area of a cornea ( 11 ) of the eye ( 2 ), and the concentration of the at least one substance is determined as a function of the detection signals. The method of claim 1, wherein as the optical excitation radiation Radiation with one wavelength in the wavelength range between 320 nm and 700 nm, preferably between 370 nm and 420 nm, is used. Method according to claim 1 or claim 2, wherein the area of the eye ( 2 ), in which the excitation radiation is focused, is illuminated in the manner of a dark field illumination. Method according to one of the preceding claims, in which in the region of the eye ( 2 ) the detection beam path ( 8th'' ) at least partially the excitation beam path ( 5 '' ) encloses. Method according to one of claims 1 to 3, wherein in the area of the eye ( 2 ) the excitation beam path ( 5 ; 5 ' ) at least partially the detection beam path ( 8th ; 8th'; 8th'' ) encloses. Method according to one of the preceding claims, in the excitation radiation with a predetermined time course Pulsed or modulated is emitted and the detection signals in dependence be formed and / or processed by the time course. Method according to one of the preceding claims, in which the detection radiation from the region in which the excitation radiation is focused, into a fine pinhole ( 21 ) and then detected. Method according to one of the preceding claims, in the detection radiation of a polarization-dependent filtering is subjected, so that only Detection radiation of a predetermined polarization state detected becomes. Method according to one of the preceding claims, wherein the detection radiation in the range of Raman radiation of at least one of the substances selected from the group lactate, glucose, proteins, amino acids, urea, ascorbic acid, medicaments and / or diagnostic markers in the aqueous humor ( 1 ) or eye tissue is detected. Device for determining a concentration of at least one substance in the aqueous humor ( 1 ) and / or in the tissue of an eye ( 2 ), comprising a lighting device ( 4 ; 4 ' ) for emitting optical excitation radiation for generating Raman radiation by interaction with the at least one substance on the eye ( 2 ) along an excitation beam path ( 5 ; 5 '; 5 '' ), one in the excitation beam path ( 5 ; 5 '; 5 '' ) arranged excitation optics ( 6 ) for focusing the excitation radiation in a aqueous humor ( 1 ) and / or in a tissue-containing area of the eye ( 2 ), a detection device ( 7 ) for detecting along a detection beam path ( 8th ; 8th '; 8th'' ) incident detection radiation, which is generated by Raman interaction of the excitation radiation with the at least one substance, and for outputting corresponding detection signals, and an evaluation device ( 9 ) for determining the concentration of the at least one substance as a function of the detection signals of the detection device ( 7 ), wherein the excitation and the detection beam path ( 5 ; 5 '; 5 ''; 8th ; 8th '; 8th'' ) at least in a region having a thickness of at least 0.5 mm, preferably at least 1 mm, in front of the focus ( 10 ) do not overlap the excitation radiation. Device according to claim 10 in which the lighting device ( 4 ; 4 ' ) emits radiation with a wavelength in the wavelength range between 320 nm and 700 nm, preferably between 370 nm and 420 nm, as the optical excitation radiation. Device according to one of claims 10 or 11, in which the illumination device ( 4 ; 4 ' ) is tunable with respect to the mean wavelength of the excitation radiation. Device according to one of Claims 10 to 12, in which the excitation and detection beam path ( 5 ; 5 '; 5 ''; 8th ; 8th'; 8th'' ) is designed so that the focus area of the excitation radiation is illuminated in the manner of a dark field illumination. Device according to one of claims 10 to 13, in which a focusing optics ( 6 ) the excitation optics ( 6 ) and at least part of a detection optics ( 12 ) for focusing the detection radiation. Apparatus according to claim 14, wherein the excitation beam path ( 5 ; 5 '; 5 '' ) and detection beam path ( 8th ; 8th'; 8th'' ) also in focusing optics ( 6 ) do not overlap. Device according to one of claims 10 to 15, in which in the area of the eye ( 2 ) the detection beam path ( 8th'' ) in at least one section at least partially the excitation beam path ( 5 '' ) encloses. Device according to one of Claims 10 to 15, in which in the region of the eye ( 2 ) the excitation beam path ( 5 ; 5 ' ) in at least one section at least partially the detection beam path ( 8th ; 8th' ) encloses. Device according to one of Claims 10 to 17, in which the illumination device ( 4 ; 4 ' ) is designed for the pulsed or modulated emission of excitation radiation with a predetermined time profile, and the detection device ( 7 ) and / or the evaluation device ( 9 ) are designed to form and / or process the detection signals as a function of the time profile. Device according to one of Claims 10 to 18, in which in the detection beam path ( 8th ; 8th'; 8th'' ) in front of the detection device ( 7 ) a fine pinhole ( 21 ) and at least a portion of a detection optics focus ( 10 ) of the excitation optics ( 6 ) on the pinhole ( 21 ) maps. Device according to one of claims 10 to 19, in which in the detection beam path ( 8th ; 8th'; 8th'' ) and / or in the detection device ( 7 ) a polarizing filter ( 16 ), which transmits radiation of a predetermined polarization state. Device according to one of claims 10 to 20, wherein an at least for radiation in the wavelength range of the Raman radiation opaque eyecup ( 26 ) is arranged so that when applying the eyecup ( 21 ) in the area of the eye ( 2 ) the incidence of environmental radiation on the eye ( 2 ) and / or in the detection beam path ( 8th ; 8th ; 8th'' ) is avoided. Method for regulating a delivery of a feed substance into the body, in which by means of a method according to one of claims 1 to 9 the concentration of at least one substance in the aqueous humor ( 1 ) of the eye ( 2 ) and / or the eye tissue is determined, and the delivery of the feed substance is regulated as a function of the determined concentration. Method for determining a concentration of at least one substance in the aqueous humor ( 1 ) and / or in the tissue of the eye ( 2 ) by means of Raman scattering of optical excitation radiation through the substance, in which radiation having a wavelength in the wavelength range between 320 nm and 700 nm, preferably between 370 nm and 420 nm, is used as optical excitation radiation.