EP1420682A1

EP1420682A1 - Non-contact tonometer

Info

Publication number: EP1420682A1
Application number: EP02754090A
Authority: EP
Inventors: Rudolf WÄLTI
Original assignee: Haag Streit AG
Current assignee: Haag Streit AG
Priority date: 2001-08-31
Filing date: 2002-08-22
Publication date: 2004-05-26
Also published as: WO2003020122A1; JP2005500889A

Abstract

A non-contact tonometer (10), provided with an optical system defining a beampath (32), comprises a connector device for the selectively releasable connection of a device (70), provided with means for emission and reception of light. The connector device is embodied such that light radiation, transmitted by a device (70) connected to the tonometer (10), is injected into the beam path (32) of the tonometer (10). The non-contact tonometer (10) is comparatively inexpensive and permits a precise determination of the pressure of the inner eye.

Description

Non-contact tonometer

Technical field

The invention relates to a tonometer for the contactless determination of the intraocular pressure (also referred to as a "non-contact tonometer"). State of the art

Non-contact tonometers of the type described in US-A-3,585,849 are widely used for periodic monitoring of intraocular pressure in patients. Such tonometers are provided with an air nozzle which is arranged centrally in front of the cornea of the eye to be examined and which generates an air pulse which causes the cornea to deform in such a way that its front surface changes from its natural convex shape to a concave shape through a planar intermediate shape (applanation) Shape is transformed. After the end of the air pulse, the cornea returns to the convex shape from the concave via the planar due to the intraocular pressure. The time required for the reshaping of the cornea is a measure of the intraocular pressure. To determine this time or the time until the cornea returns to the planar shape, the reflection of a light beam directed onto the cornea and reflected by it is detected.

The accuracy of the intraocular pressure determination carried out in this way depends, among other things, on the precise positioning and alignment of the tonometer in relation to the patient's eye. For the exact positioning of the tonometer in front of the cornea, the tonometer described in US Pat. No. 5,299,573 is provided with an optical system which defines a beam path leading through the air nozzle. With exact positioning, the portion of a light beam emitted along the beam path that is reflected back from the front of the comea has an intensity maximum.

However, the time used for the return of the cornea as a measurement for determining the intraocular pressure depends not only on the intraocular pressure, but also to a not inconsiderable extent on the thickness of the cornea. In order to be able to correct the intraocular pressure derived from the return time of the cornea with regard to the systematic measurement errors caused by different coma thicknesses, WO-A-95/20342 proposes a multifunctional ophthalmological device which functions both as a pachymeter for determining the coma thickness and also Has the function of a tonometer for determining the intraocular pressure. The intraocular pressure is measured in the manner of one of the pneumatic non-contact tono- meters, and the measurement of the corneal thickness is carried out by geometrically mapping the front and back reflections of a light beam passing through the cornea onto CCD cells. DE-A-196 47 1 14 describes a further multifunctional ophthalmological device for the simultaneous determination of the intraocular pressure and the corneal thickness, the corneal thickness being measured here in a laser interferometric manner.

The previously known ophthalmological devices for contactless determination of the intraocular pressure are either imprecise because they do not correct the measurement errors caused by different corneal thicknesses, or they have a complex construction and are accordingly bulky and expensive.

Presentation of the invention

The object of the invention is to provide an ophthalmic device for the contactless determination of the intraocular pressure, which is comparatively inexpensive and enables a precise determination of the intraocular pressure.

The solution to the problem is defined by the features of claim 1. According to the invention, a non-contact tonometer with an optical system defining an optical path has a connection device for the optionally releasable connection of a device provided with means for transmitting and receiving light, the connection device being designed such that light radiation emitted by the device connected to the tonometer, is coupled into the beam path of the tonometer.

In connection with the present description and the claims, light is not only understood to mean only the visible region of the spectrum of electromagnetic radiation, but rather all regions of the spectrum that are customary for ophthalmic applications. Thus, in addition to the visible area, the other visible range adjacent infrared and ultraviolet regions of the spectrum of electromagnetic radiation referred to as light.

The tonometer according to the invention is based on a conventional non-contact tonometer. This means that the tonometer according to the invention is a fully functional non-contact tonometer even without a connected additional device and can be used as such. Since such known tonometers are comparatively handy, widespread and correspondingly inexpensive, the tonometer according to the invention also has these advantages. In particular, it is much lighter, easier to handle and easier to use than multifunctional ophthalmic devices of the type described in WO-A-95/20342 or DE-A-196 47 1 14.

As is customary for customary non-contact tonometers, the tonometer according to the invention also has an optical system defining a beam path for the detection of a light beam reflected by the eye to be examined in order to enable precise positioning and adjustment of the tonometer in front of the eye to be examined. According to the invention, the non-contact tonometer is further provided with a connection device for the optionally detachable connection of an additional device, which is designed to emit and receive light radiation, the connection device being designed such that - when the additional device is on the tonometer is connected - the light radiation emitted by the additional device is coupled into the beam path of the tonometer. The connection device of the tonometer comprises at least optical coupling means which make it possible to couple light radiation from outside the tonometer into the beam path of the tonometer. Such optical coupling means can include, for example, windows or pinholes in the tonometer housing, which allow the passage of light radiation, and / or beam deflection means, such as beam splitters, mirrors, reflectors, lenses, prisms, etc., which guide the light radiation within the tonometer and couple it into the beam path of the tonometer , The connection device of the tonometer can further comprise mechanical coupling means, which can be an optionally detachable mechanical coupling of the additional device or enable a light transmission device (such as an optical fiber or an adapter) that can be connected to this.

An additional device that can be connected to the tonometer can be designed to determine further parameters or measurement parameters of the eye to be examined. If required - i.e. if the measurement of further eye parameters is desirable - the additional device can be connected to the tonometer according to the invention by means of the connection device, after which further eye parameters can be measured in addition to the return time of the cornea (after its e.g. pneumatic deflection). Since, in addition to the return time of the cornea, numerous other eye parameters also have an influence on tonometry, the precision of the tonometer measurement can be improved by measuring and taking them into account when determining the intraocular pressure.

Because according to the invention the light radiation, which is emitted by the additional device connected to the tonometer, is coupled into the beam path of the tonometer, no separate system is required for the adjustment of the additional device in front of the eye to be examined. Rather, the adjustment can be carried out with the aid of the corresponding adjustment system of the tonometer. If necessary, the positioning and / or the fixing of the additional device in front of the patient's eye is advantageously also carried out using the means provided for positioning and / or fixing the tonometer. No separate means or devices for the positioning, adjustment and / or fixation of the additional device in front of the eye to be examined are then required.

The connection device of a tonometer according to the invention preferably comprises a beam splitter which is arranged in the beam path of the tonometer between a light detection unit and a nozzle outlet opening of the tonometer. The light detection unit of the tonometer can comprise, for example, a photodetector and / or an eyepiece. The nozzle outlet of the tonometer must be placed in front of the eye to be examined. Air or another medium is blown out through them in order to generate the air pulse required to deflect the cornea. If an additional device by means of Connection device is connected to the tonometer, the beam splitter ensures the coupling of a light beam emitted by the additional device into the beam path of the tonometer and in the opposite beam direction for the coupling out of a light beam from the beam path of the tonometer and the transmission of the decoupled light beam to the additional device. The beam splitter can be permanently installed in the tonometer so that it remains in the beam path of the tonometer even without an additional device connected. Tonometric measurements are still possible, however, in comparison to a beam path without a beam splitter, a weakening of the light beam from the tonometer has to be accepted. As an alternative, the beam splitter can also be arranged removably in the beam path of the tonometer, so that it can be removed from the beam path of the tonometer if no additional device is connected to the tonometer.

Instead of a beam splitter, the connection device can, however, also have other suitable means for coupling the light radiation emitted by the additional device into the beam path of the tonometer, such as e.g. Mirrors, reflectors, prisms etc.

A tonometer arrangement according to the invention comprises a non-contact tonometer with an optical system defining a beam path and a connection device for the optionally releasable connection of a device provided with means for transmitting and receiving light, the connection device being designed such that light radiation which is transmitted from the device connected to the tonometer, is coupled into the beam path of the tonometer. The tonometer arrangement further comprises a device provided with means for transmitting and receiving light, which is designed such that it can be connected to the tonometer by means of the connection device of the tonometer in such a way that light radiation emitted by the device connected to the tonometer is in the beam path of the tonometer is coupled. Thus, a tonometer arrangement according to the invention comprises a device set consisting of at least one tonometer and a further device which can optionally be detachably connected to this tonometer. The device of the tonometer arrangement that can be connected to the tonometer is preferably designed such that after the device is connected to the tonometer, the tonometer arrangement for measuring the corneal thickness and / or the comea curvature and / or corneal topography and / or the tear film thickness and / or the comeal epithelium thickness and / or the thickness of a comal flap of an eye to be examined, whereby a comea flap is to be understood as a flap of the cornea which is partially cut away from the cornea in connection with a surgical operation and can be folded forward by it. All of these eye parameters mentioned have an influence on tonometry. The precision of the tonometer measurement can be improved by measuring them and taking them into account when determining the intraocular pressure. For example, in the case of a pachymeter suitable for measuring the corneal thickness - if, for example, there is a suspicion that the corneal thickness of the eye to be examined deviates considerably from an average value of the corneal thickness - the pachymeter can be connected to the tonometer according to the invention by means of the connecting device, whereupon In addition to the return time of the cornea (after its pneumatic deflection, for example), the corneal thickness can also be measured and the two measured values can be used to precisely determine the intraocular pressure.

In addition to devices for measuring eye parameters relevant to tonometry, according to the invention basically other devices suitable for ophthalmological applications can also be connected to the tonometer which are designed to emit light radiation, e.g. Devices for laser surgical treatment of the eye.

According to a preferred embodiment of the invention, the device which can be connected to the tonometer comprises an interferometer which is designed for interferometric measurements based on light radiation emitted by the interferometer, coupled into the beam path of the tonometer via the connection device of the tonometer and at least partially through the beam path of the tonometer and the connection device is reflected back to the interferometer. In contrast to interferometers previously used for ophthalmic applications, it is not necessary that Interferometer of the tonometer arrangement according to this embodiment of the invention is provided with its own means for positioning, aligning, adjusting and / or fixing the interferometer in front of the eye to be examined. The positioning, alignment, adjustment and / or fixation of the interferometer is rather advantageously carried out with the aid of the corresponding systems of the tonometer.

The interferometer used as part of the tonometer arrangement according to the invention can be an interferometer based on the interferometric measuring principle of optical short coherence reflectometry (English "optical low coherence reflectrometry" or OLCR). Such interferometers are known from the publications WO-A-01/19303 and WO-A-01/38820. They are suitable for measuring the corneal thickness and the tear film thickness.

The interferometer used as part of the tonometer arrangement according to the invention can also be an interferometer based on the interferometric measuring principle of optical short coherence tomography (OCT). Such interferometers are known from WO-A-99/22198 and WO-A-01/19303. They are suitable for measuring coma curvature and corneal topography.

In addition to the interferometer types mentioned above, the device that can be connected to the tonometer can in principle also include other interferometers suitable for ophthalmic applications.

According to a further preferred embodiment of the invention, the tonometer arrangement additionally comprises an adapter unit which has at least one lens. The adapter unit is used to optically adapt the device that can be connected to the tonometer to the tonometer. The adapter unit makes it possible to connect a large number of different devices designed to emit light radiation with different optical properties of the emitted light radiation to the tonometer. It is designed such that it can be arranged between the device that can be connected to the tonometer and the tonometer in such a way that a light beam emitted by the device passes through the lens and is then coupled into the beam path of the tonometer. The adapter unit can be designed as a separate unit that can be detached from the tonometer and from the device that can be connected to it, and can be arranged at any suitable point in the light transmission path between the tonometer and the device. As an alternative to this, however, it can also be designed as part of the connection device of the tonometer or as part of the device that can be connected to the tonometer.

The adapter unit can be provided with a beam deflection system for controllably deflecting the light beam emitted by the device. This makes it possible to guide the light beam emitted by the device connected to the tonometer laterally over the cornea of the eye to be examined, so that measurements can be carried out successively at different lateral locations on the cornea. The beam deflection system comes e.g. one or more movable mirrors, one or more transversely displaceable lenses, and other known beam deflection systems in question. The integration of the beam deflection system into the adapter unit has the advantage that only a single beam deflection and adapter functional unit, which can be used for a large number of different devices, is required to connect and adapt various devices working with deflectable beams to the tonometer. In principle, however, it is also possible to arrange a beam deflection system at any suitable point in the light transmission path between the tonometer and the device, regardless of an adapter unit which may or may not be present.

According to a further variant of the invention, in addition to the tonometer and the device which can be connected to it, the tonometer arrangement further comprises a fiber connection unit which has at least one light-conducting fiber and is designed such that it can be arranged between the device which can be connected to the tonometer and the tonometer in such a way that that the light radiation emitted by the device is coupled into the beam path of the tonometer after passing through the fiber. A flexible single-mode fiber is preferably used as the light-conducting fiber. Such fibers only result in a slight weakening of the light radiation and ensure due to their flexibility that the tonometer can be moved almost freely with respect to the connected device, the light guide connection (ie the coupling of the light radiation emitted by the connected device into the tonometer) is retained even during relative movements between the tonometer and the connected device. The fiber connection unit makes it possible to install the device that can be connected to the tonometer at a fixed location and only to arrange the tonometer on a mechanically movable adjustment and positioning unit (which includes, for example, a cross slide), which provides the positioning, alignment and adjustment of the tonometer required for eye examination with respect to the eye to be examined.

If the connection device of the tonometer or an adapter unit arranged in front of it is designed for light radiation, which is emitted by the connected device in the form of a free-space beam, the fiber connection unit can be provided on the tonometer side with an in / out coupler, which couples the light radiation out of the fiber and into it converts a free space beam. In the opposite direction, the free-space beam coming from the tonometer or from the adapter unit is coupled into the fiber of the fiber connection unit through this coupling-in / coupling-out. Otherwise, ie if no adapter unit is provided and the connection device of the tonometer is designed for light radiation, which is emitted by the connected device in a light guide, the fiber connection unit can be provided on the tonometer side with a fiber connector which transmits light between the light fiber of the fiber connection unit and an optical fiber the connection device of the tonometer. Similarly, the fiber connection unit can also be provided on the side of the device to be connected to the tonometer with an in / out coupler or a fiber connector, depending on whether this device is designed to emit / receive open space light radiation or light radiation guided in an optical fiber.

The fiber connection unit can be designed as a separate unit that can be detached from the tonometer and from the device that can be connected to it, and can be arranged at any suitable point in the light transmission path between the tonometer and the device. As an AI Alternatively, however, it can also be designed as part of the connection device of the tonometer or as part of the device that can be connected to the tonometer.

From the following detailed description and the entirety of the claims, further advantageous embodiments and combinations of features of the invention result.

Brief description of the drawings

The drawings used to explain the exemplary embodiment show:

Fig. 1 shows a tonometer arrangement according to a preferred embodiment of the

Invention in a simplified schematic representation;

FIG. 2 shows a simplified schematic illustration of a fiber connection unit for the tonometer arrangement from FIG. 1.

In principle, the same parts are provided with the same reference symbols in the figures.

Ways of Carrying Out the Invention

The tonometer arrangement shown in FIG. 1 comprises a non-contact tonometer 10, a measuring device 70 that can be connected to the tonometer 10, a fiber connection unit 60 and an adapter unit 50.

The non-contact tonometer 10 has a piston 1 which is displaceably guided in a cylinder 12. By suddenly moving the piston 14, a pulsating air flow can be blown out through a cylinder opening 16. The air flows through a connecting line 18 into an air chamber 20 and is ejected from there in the form of air pulses through an air nozzle 22 which is arranged centrally in front of the cornea of an eye 2 to be examined. The rear wall of the air chamber 20 opposite the air nozzle 22 is provided with a translucent window 24. This window 24 is part of an optical system for. exact alignment and adjustment of the tonometer 10 in front of the eye 2 to be examined and for determining the applanation of the cornea of the eye 2 caused by the air pulses. The optical system of the tonometer 10 further comprises an objective lens 26, a collimator lens 28 and a first photodetector 30 which are arranged in a straight line behind the window 24. A first beam splitter 34 is arranged between the objective lens 26 and the collimator lens 28 and reflects the light radiation emitted by a light source 36 of the tonometer 10 through the objective lens 26, the window 24 and the air nozzle 22, the light radiation between the light source 36 and the first beam splitter 34 passes through a condenser lens 38. A second beam splitter 40 is arranged between the collimator lens 28 and the first photodetector 30, which reflects part of the light beam to a second photodetector 42, while another part of the light beam passes through the second beam splitter 40 to the first photodetector 30.

Overall, a beam path 32 is defined by the optical system of the tonometer 10 such that light, which is emitted continuously by the light source 36, passes along the beam path 32 through the condenser lens 38, is reflected by the first beam splitter 34 and by the objective lens 26, the Window 24 and the air nozzle 22 fall through onto the cornea of eye 2. From this, the light radiation is partially reflected back along the beam path 32 through the air nozzle 22, the window 24, the objective lens 26, the first beam splitter 34 and the collimator lens 28 to the second beam splitter 40. Part of this light radiation is reflected by the second beam splitter 40 to the second photodetector 42, another part of the light radiation passes through the second beam splitter 40 and a third beam splitter 44 to the first photodetector 30.

With the first photodetector 30, a temporal radiation maximum is detected, from which the time is determined which the cornea needs after a deflection by an air pulse until it returns to a planar shape. This time is used to calculate the intraocular pressure. The second photodetector is used to determine a Radiation maximum, which indicates within the scope of the alignment of the tonometer 10 that the light beam emerging through the air nozzle 22 is aligned perpendicular to the corneal surface of the eye 2.

The third beam splitter 44 is arranged between the second beam splitter 40 and the first photo detector 30 in the beam path 32 of the tonometer 10. This third beam splitter 44 is part of a connection device for optionally detachable connection of the measuring device 70 which can be connected to the tonometer 10. In addition to the third beam splitter 44, the connection device of the tonometer 10 further comprises a coupling piece (not shown) attached to the tonometer 10, which is part of a first coupling device (not shown), which further has a counterpart (not shown) corresponding to the coupling piece attached to the tonometer, which is attached to the adapter unit 50. The first coupling device is used for optionally releasably coupling the adapter unit 50 to the tonometer 10 in such a way that in the coupled state, light radiation in the form of a free-space beam can be transmitted from the adapter unit 50 to the tonometer 10 and in the opposite direction. For the purpose of the optionally releasable coupling of the adapter unit 50 to the tonometer 10, any of those which are common in technical optics, e.g. screwable or only pluggable coupling device can be used.

The adapter unit 50 serves to optically adapt the measuring device 70 to the optical system of the tonometer 10 and has two adapter lenses 52, 54 for this purpose. On the side of the adapter unit 50 remote from the tonometer, a coupling piece (not shown) is attached to the adapter unit 50, which is part of a second coupling device, which further comprises an on / off coupler 62, which is attached to the end of the fiber connection unit 60 on the tonometer side. The in / out coupler 62 can optionally be releasably coupled to the coupling piece attached to the adapter unit 50 such that, in the coupled state, light radiation in the form of a free space beam can be transmitted from the in / out coupler 62 to the adapter unit 50 and in the opposite direction. The in / out coupler 62 can, for example, only consist of one fiber connector and one with a perforated end piece, which is used only to hold the fiber and let the jet emerge.

The fiber connection unit 60 shown in a detailed view in FIG. 2 serves to create a flexible, light-conducting connection between the measuring device 70 and the tonometer 10 or the adapter unit 50 coupled to the tonometer 10. In addition to the in / out coupler 62, the fiber connection unit 60 includes Furthermore, a flexible, light-guiding monomode fiber 66 and a fiber connector 64. The in / out coupler 62 is attached to the monomode fiber 66 at the end of the tonometer. It couples the light radiation emitted by the measuring device 70 out of the fiber 66 and converts it into a free-space beam, which is introduced into the adapter unit 50. In the opposite direction, the input / output coupler 62 couples a free-space beam coming from the adapter unit 50 into the single-mode fiber 66. The fiber connector 64 is attached to the end of the single-mode fiber 66 on the measuring device side. It can optionally be releasably connected to a connector counterpart 72 corresponding to the fiber connector 64, which is attached to an optical fiber 74 of the measuring device 70, the optical fiber 74 in turn being a momomode fiber 74. In the connected state, the fiber connector 64 and the connector counterpart 72 create a light-transmitting, fiber-optic connection between the optical fiber 74 of the measuring device 70 and the single-mode fiber 66 of the fiber connection unit 60.

The measuring device 70 shown in FIG. 1 comprises a fiber-optic interferometer based on the interferometric measuring principle of optical short-coherent tomography, as described in the publication WO-A-01/19303. The optical fiber 74 provided with the connector counterpart 72 is part of the measuring arm of this interferometer.

If the measuring device 70 is connected to the tonometer 10 via the fiber connection unit 60 and the adapter unit 50, the measuring device 70 emits light by feeding light radiation into the optical fiber 74. This light radiation is conducted via the connector counterpart 72, the fiber connector 64 and the single-mode fiber 66 to the in / out coupler 62, which couples it out of the single-mode fiber 66 and as a free-space beam passed through the adapter lenses 52, 54 to the third beam splitter 44. From this the light beam is reflected in the direction of the beam path 32 of the tonometer 10 and thereby coupled into this beam path 32. It passes from the third beam splitter 44 through the second beam splitter 40, the collimator lens 28, the first beam splitter 34, the objective lens 26, the window 24 and the air nozzle 22 and falls on the cornea of the eye 2. The light beam becomes part of this reflected back along the beam path 32 through the air nozzle 22, the window 24, the objective lens 26, the first beam splitter 34, the collimator lens 28 and the second beam splitter 40 to the third beam splitter 44, coupled out of the beam path 32 by this and through the adapter lens sen 54, 52 reflected to the in / out coupler 62. The in / out coupler 62 couples the free-space beam coming from the adapter unit into the single-mode fiber 66, through which the light radiation reflected back by the eye 2 to the fiber connector 64, the connector counterpart 72 and finally into the light fiber 74 and thus into the measuring arm of the fiber-optic interferometer Meter 70 is passed. The light radiation back-reflected by the eye 2 is evaluated interferometrically in the measuring device 70 in order to determine the thickness of the cornea of the eye 2. The measured value for the corneal thickness determined in this way is then used together with the return time of the cornea measured by the tonometer 10 in order to determine the internal pressure of the eye 2.

Instead of the arrangement between the second beam splitter 40 and the first photodetector 30, in other variants of the invention the third beam splitter 44 can also be arranged at other suitable locations in the beam path 32 of the tonometer 10, e.g. between the second beam splitter 40 and the second photodetector 42 or between the first beam splitter 34 and the condenser lens 38 or between the condenser lens 38 and the light source 36.

According to further variants of the invention, instead of the measuring device 70 shown in FIG. 1, any other device suitable for ophthalmological applications, which is provided with means for transmitting and receiving light, can optionally be detachably connected to the tonometer 10 again. This can be, for example trade any of the devices described in WO-A-01/38820, WO-A-99/22198 and WO-A-01/19303. If such a device does not emit or receive the light as shown in FIG. 1 via an optical fiber 74, but via a free-space beam, a further adapter device 50, which is similar to the adapter device 50 shown in FIG. 1, can be located between the device and a fiber connection unit, which essentially corresponds to the fiber connection unit 60 shown in FIG. 1.

In summary, it should be noted that the invention specifies an ophthalmic device for the contactless determination of the intraocular pressure, which is comparatively inexpensive and enables a precise determination of the intraocular pressure.

Claims

claims

1. Tonometer (10) for the contactless determination of the intraocular pressure, with an optical system defining a beam path (32), characterized in that the tonometer (10) is a connection device for optionally detachable connection of a device provided with means for transmitting and receiving light (70), the connection device being designed such that light radiation which is emitted by the device (70) connected to the tonometer (10) is coupled into the beam path (32) of the tonometer (10).

2. Tonometer (10) according to claim 1, characterized in that the connection device comprises a beam splitter (44) in the beam path (32) of the tonometer

(10) is arranged between a light detection unit (30) and a nozzle outlet opening (22) of the tonometer (10) to be arranged in front of the eye (2) to be examined.

3. Tonometer arrangement with a tonometer (10) according to claim 1 or 2, characterized in that it further comprises a device provided with means for transmitting and receiving light (70), which is designed such that it by means of the connection device of the tonometer ( 10) can be connected to the tonometer (10) such that light radiation emitted by the device (70) connected to the tonometer (10) is coupled into the beam path (32) of the tonometer (10).

4. Tonometer arrangement according to claim 3, characterized by a design of the to the tonometer (10) connectable device (70) such that after connecting the device (70) to the tonometer (10), the tonometer arrangement for measuring the corneal thickness and / or the Comea curvature and / or coma topography and / or the tear film thickness and / or the comeal epithelium thickness and / or the thickness of a comal flap of an eye (2) to be examined is suitable.

5. Tonometer arrangement according to claim 3 or 4, characterized in that the device (70) which can be connected to the tonometer (10) comprises an interferometer which is designed for interferometric measurements on the basis of light radiation emitted by the interferometer via the connection device of the Tonometer (10) is coupled into the beam path (32) of the tonometer (10) and is at least partially reflected back through the beam path (32) of the tonometer (10) and the connection device to the interferometer.

6. Tonometer arrangement according to claim 5, characterized in that the interferometer is an interferometer based on the interferometric measuring principle of optical short-coherent reflectometry (English "optical low coherence reflectrometry" or OLCR).

7. Tonometer arrangement according to claim 5, characterized in that the interferometer is based on the interferometric measuring principle of the optical short coherents

Tomography (English "optical low coherence tomography" or OCT) based interferometer is.

8. Tonometer arrangement according to one of claims 1 to 7, characterized in that it further comprises an at least one lens (52, 54) having adapter unit (50) which is designed such that it can be connected between the device connected to the tonometer (10) (70) and the tonometer (10) can be arranged such that a light beam emitted by the device (70) after passing through the lens (52, 54) is coupled into the beam path (32) of the tonometer (10).

9. Tonometer arrangement according to claim 8, characterized in that the adapter unit (50) is further provided with a beam deflection system for controllably deflecting the light beam emitted by the device (70).

10. Tonometer arrangement according to one of claims 3 to 9, characterized in that it further comprises a fiber connection unit (60) having at least one light-conducting fiber (66), which is designed such that it can be connected between the device (10) that can be connected to the tonometer (10). 70) and the tonometer (10) can be arranged such that the light radiation emitted by the device (70) after passing through the fiber (66) is coupled into the beam path (32) of the tonometer (10).