DD222203A1 - APPLANATATIONSTONOMETER - Google Patents

Abstract

The invention relates to an optical-electronic applanation tonometer which excludes subjective measurement errors, eliminates the influence of the tracheal fluid and can be used on both the patient sitting and lying down. Both the intraocular pressure at constant applanation area and the area at constant pressure can be measured. The measuring element consists essentially of optical fibers, which direct light from a light source to the applanation surface and feed the light reflected from the eye to optical sensors. Their electrical signals are further processed into a digital display. The incident next to the applanation light rays are deflected by the spherical eye side and gedaempft by the Traenenflessigkeit so that their reflections reach only with reduced intensity of light to the optical sensors and produce a weaker electrical signal. This is eliminated by a threshold, whereby the influence of the Traenenfluessigkeit on the measurement result is largely avoided. Fig. 1

Description

01276 DD / 17 3. 02. 1984

Applanation tonometer Field of application of the invention

The invention relates to a device for measuring the intraocular pressure according to the principle of applanation tonometry.

Characteristic of the known technical solutions

There are three basic principles for measuring intraocular pressure, impression tonometry, applanation tonometry, and non-contact tonometry.

Impression tonometer measures the depth of corneal bondability caused by a metal stamp loaded with a known weight. At the same weight, the fertility behaves inversely as the intraocular pressure, it is greater when the intraocular pressure is lower and vice versa. The resistance of the cornea to deformation is neglected. The main shortcoming of impression tonometry is due to the fact that the placement of the tonometer and the indentation of the metal temple increase the intraocular pressure. The pressure observed at the moment of reading corresponds to the tonometric pressure and not to the tension prevailing inside the eye before the tonometer is set up. However, the handling of the impression tonometer is quite simple, so that the measurement is also carried out by nurses and ophthalmologists can be. However, since it is not the tonometric pressure but rather the intraocular pressure that is to be measured, either an inaccuracy of the measurement must be accepted, or additional calculations are required -.

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Another disadvantage of these devices is that in the measurement of eye pressure, the transmission of the measurement result by means of moving parts, stamp, axis, lever uad pointer takes place, so that changes in the friction values of these moving mechanical parts can distort the measurement result. - ^

An impression tonometer, which manages without mechanical movable transmission elements for the display is described in the DB-OS 31 12 910 A1. This device is designed for Laogzeitmessung and has a sensor in the form of an eye-mountable on the elastic contact lens, which carries on its underside a small rounded centric elevation ·· - On the bottom of the sensor is distributed over the entire surface of an electrical conductor in the form applied to a spiral. The upper side of the contact lens is provided with an optionally perforated or spirally extending electrical conductor track. The electrical conductors on the upper and lower surfaces are interconnected and form a passive sensor resonant circuit. Furthermore, an active resonant circuit is provided with a high-frequency generator. This resonant circuit is preferably incorporated in a spectacle frame, as well as a dip-meter and a telemetry transmitter. The sensor is deformed according to the intraocular pressure, thereby changing the resonance frequency of the sensor circuit. This change can be achieved either by the so-called dip frequency, i. a breakdown in the oscillation spectrum of the active oscillation circuit or as a change in the oscillation amplitude of the active, operated with a single frequency active resonant circuit are determined and corresponding intraocular pressures are assigned.

But this device has the general, above-mentioned

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th disadvantages of impression tonometer. They are overcome when using the Applanationsprinzips, this goes ^v - from the law of Jmbert from which states that the pressure in a fluid-filled spherical container corresponding to the backpressure which flattens a specific surface of this sphere. However, this law only determines exactly if the spherical wall is very thin and the deformation sets no resistance. This is the case with the eyeball, which is why an intraocular pressure measurement on the basis of this law is possible in two different ways - is. ... "'.. ..''.'".V;''"::

1. A constant weight tonometer can be used and the flattened surface measured.

2. It can be determined the force required v., · To a known surface of constant size _; applanate.

Known is a tonometer from Perkins, which consists of a plastic cylinder whose lower, planar end is provided with a graduation. At the top there is a magnifying glass. After instillation of fluorescenzin into the conjunctival sac, the diameter of the applanated corneal surface can be determined by optical reading on the degree scale. The determination of the intraocular pressure is carried out here by means of a constant force.

Also known is a tonometer that operates on the basis of a constant surface applanierten surface. The grain is flattened with the help of the square base of a glass prism. Intraocular pressure is measured by amplifying the pressure of the prism on the eye until the flattened circular corneal area becomes kit

01276 DD / 17 3. 02. 1984

the four sides of the Prisma base is level.

These tonometers, among other disadvantages, have, above all, the fact that they strip off a too large horn hair surface and thus artificially increase the internal pressure at the moment of the molding process.

This error is avoided by a device which has a chamber provided with a nanometer whose one side consists of a thin elastic membrane. This is brought to the cornea and the pressure in the chamber increased until the membrane becomes even. At this moment, the pressure inside the chamber corresponds to the intraocular pressure.

Another well-known tonometer from Goldmann is mounted on a slit lamp. It consists of a provided with a plastic cylinder torsion balance. The front surface of the cylinder is flat. It is brought to the cornea and here exerts an increasing pressure, which is measured with the help of the torsion balance. The tonometer is mounted on a biomicroscope with a maximum gap. Through the transparent cylinder, the contact zone of the cornea can be observed. The examination takes place in violet light, after the tear fluid has been dyed with the aid of fluorescein, the periphery of the contact zone appearing as a fine, intensely green colored circle.

These two devices require a high technical effort, are expensive and can only be operated by specialists, ie ophthalmologists.

In addition, Goldmann's tonometer fulfills the condition that the applanated surface must be very small (it is 7.35 mm ² ), but it is extremely sensitive

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against, albeit slight resistance, that the cornea opposes to deformation. Also, the upper vascular tension of the tear fluid displaced to the periphery falsifies the measurement result by a pressure on the cylinder, since it is not possible to keep the contact zone between the eye and the tonometer dry.

The Tonometer by Goldmann can only be used in seated patients. In certain cases, for example, with congenital glaucoma, that is with increased intraocular pressure, it is often necessary to perform an anesthesia examination and perform the tonometry while lying down. The well-suited for this purpose tonometer from Draeger is. but constructed so that the pressure exerted by the prism with

This means that no flammable precursors can be used for anesthesia because the tonometer's engine may generate sparks. In addition, the general arterial pressure and thus the eye pressure can be reduced by anesthetics. In addition, the measurement must take place at a moment when the eye is looking straight ahead. The use of a pair of tweezers to correct the line of sight would, however, bring about a measurement error, since the eye pressure is increased. That's all. Devices with a longer duration of the measuring process of loading.

Another well-known tonometer by Mac Kay-Marg contains at the top of the measuring head a small, fixed in an elastic cuff quartz cylinder whose position shift caused by just a few microns, an electrical impulse 'is recorded. The measuring head is fed with a low-frequency, low-voltage current and the current fluctuations caused by the pressure applied to the quartz crystal are amplified. The interpretation of the Toaogramme

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but is still utastritten and the problem of calibration unresolved.

The Won-Contact tonometer (NOT) of the American Optical Comp. produces 12 ms.'last air blasts, within which the Btromges.chgeschwindigkeit increases linearly to a maximum. When such a puff of air hits the eye in the direction of the optical axis, the cornea becomes more and more flattened _; and finally dented. I'm obliquely invading covenant ©! parallel light rays are reflected as a parallel bundle when the air blast precisely applanates a central area of 3 "by 6 mm in diameter. This reflected bundle is caught by a selenium cell and thus marks the current velocity and thus the intensity of the air blast required for applanation. In experiments with this instrument, however, a measurement error width was four times greater than that of Goldmann applanation tone. V

The US-PS 39 13 390 describes an optical applanation tonometer, in which a movable piston of glass fibers is used, which is changeable by metal weight rings in its contact pressure. At the top of the glass fiber piston, a measuring scale is arranged, which is located in the focus range of a viewing optics with attached device. Durch.die glass fibers, the image of the applanation is transferred from the lower support surface exactly to the upper surface provided with the scale and can be measured there. The disadvantage of this device is that it must be read optically manually, which does not exclude subjective errors on a measuring scale.

Another optically acting applanation tonometer is described in DE-OS 26 43 879 .. In this device, the flat surface of a prism with. constant pressure against the

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Cornea surface pressed and light rays are directed at an angle alpha on this surface. Since the refractive indices of the prism and the eye are much closer to each other than the prism and air coefficients, the light rays striking the contact surface continue and are absorbed into the interior of the eye, while the light rays outside the outer edge reflect the contact surface The difference between radiated and reflected light gives a measure of "footprint." This device has two major drawbacks: Corneal opacities or white scars also reflect the light so that measurement errors can not be ruled out, or the device may even be present in certain patients not applicable ·

In addition, tear fluid, which collects in varying degrees around the support surface and is never completely avoidable, falsifies the measurement result, since it absorbs the light rays and prevents reflection in its region.

The US-PS 35 64 907 (identical to the DS-OS 20 40 238) and 37 03 095 tonometer described that work completely electrically. In this case, a pressure measurement is used to generate a strong signal by means of a spring-holder-like probe which is brought into contact with the cornea of the patient. The tear-wet area in the applanation surface produces another signal that is proportional to the size of this area. Both signals are combined and displayed as intraocular ocular pressure on a simple analog meter · The device of US-PS 37 03 095, a second probe is still present, the patient must have in hand. A disadvantage of this

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Is equipment that the range of Tränenflussigkeit can also here not be eliminated and that the probes are attached to cables and separate the display device connected via the _cable} is set up "Moreover, also material-related tolerances and Alterungseracheioungen, Eg In addition, a calibration of the device is necessary before each measurement, which makes its practical handling more difficult.

The US-PS 43 05 399 describes a miniaturized device in the form of a contact lens. Here, the position of mutually displaced coils for frequency change is used, which forms a measure of the intraocular pressure. Here, too, changes in Re ibungswiderstände USSD material tolerances can lead to incorrect measurement results. ;

In DE-OS 22 21 317 a tonometer is described which contains an inner and a concentrically arranged around this tubular outer pressure-sensitive measuring element. These elements act on strain gauges, which are arranged on deformable straps. The presence of four gauges signals when the device is properly in contact with the eye, however, only gross inclinations of the tonometer are detected, while lower perpendiculars are no longer displayed when the toning pressure is applied. ...,

Another optically measuring tonometer is described in US-PS 41 92 317 * The optical measuring method consists in an array of photodiodes and photodetectors, between which there are two lines provided transparent scales, which are moved by the Tonisierungsstempel against each other. This moire strips are generated, the

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used in a known manner as a measure of the movement of the stamp. This very handy device has above all also the defect that a movable measuring device with u. U * variable friction is present. \

DE-AS 26 22 990 and US-ES 37/14819 describe 'Luftstrahlt onotaet he. Here is a powerful air jet against '' the eye is directed and deformation of the ocular surface measured. Although it can be considered an advantage that these devices operate without mechanical contact, the patient often feels the required strong airflow is even more unpleasant. The measurement accuracy is much lower than the Applantiönstonometern. ,

Overall, the known devices are either in the Meßgenaiiigkeit unsatisfactory or technically and in terms of cost very expensive. Another disadvantage is the optical adjustment process, which is time-consuming and can only be performed by experienced examiners in sufficient quality, which due to the subjective observation and measurement of the size of the applanation surface in the optical devices errors are still not be ruled out. Moreover, due to their structure, most devices are difficult to clean and disinfect and must be dismantled for this purpose.

Object of the invention

The aim of the invention is to avoid the high cost of cost and technically complicated equipment, and overcome the difficulties in Meßνorgang un cleaning.

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Explanation, the essence of the invention

The invention has for its object to provide a device for measuring the Augeηinnendrucks that can be produced without high cost, which is easy to handle and easy to use and avoids subjective errors in the measurement. In this case, the measured value is to be determined by optical-electronic means without moving mechanical transmission elements after placement of the device on the cornea without additional adjustment or adjustment procedures and be directly digitally readable. The device should largely eliminate the influence of the tear fluid on the measurement result. It should be applicable to both the patient sitting and lying, and it should be possible to determine both the area at a constant predetermined pressure and the pressure at ein.er predetermined surface. In addition, the device should be easy to clean and disinfect. ,

This object is achieved by a tonometer for measuring intraocular pressure according to the Applanationsprinzip having an axially movable measuring element, with which a force is exerted on the eye and in which this Meßel.eaient consists essentially of optical fibers, with one or more Light sources and optical sensors interact. These light guides are brought together on the flattening of the eye side to a flat applanation surface. On the opposite side, the light guides are arranged to receive light from the light source (s). This light is directed to the applanation surface where it is reflected by the eye surface when the device is attached. The reflected light is transformed from the light guides to optical seas.

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ren, ζ. As photodiodes, and converted by these into electrical signals that are processed by known electronic means to a digital display.

In a first variant of the tonometer according to the invention with optical-electronic measured value detection, photoelectronic transmitters and photoelectronic receivers are alternately arranged as light sources on the side of the movable element opposite the applanation surface on the ends of the individual fibers of the light guide. The light respectively radiated from a photoelectronic transmitter into a light-receiving fiber optic fiber is reflected at the applanation surface and is guided by an adjacent optical fiber leading to it on this arranged photoelectronic receiver. , ^; ,

, } * '

In a second variant with the same measuring principle, on the side of the movable element opposite the applanation surface on the ends of the individual fibers, the optical fibers can be arranged on each fiber over a part of the cross section of the surface optoelectronic receiver. From a light source, which is arranged above the axially movable measuring element in the housing, is irradiated by the remaining part of the cross section light in the optical fiber and returned to the reflection on the applanation in the same optical fiber to the optoelectronic receiver and converted into electrical signals.

In this case, the optoelectronic receiver arranged on each fiber of the optical waveguide advantageously occupies half the cross-section of the optical waveguide fiber. It can be designed both as a circular segment surface, in particular as a semicircular surface

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be, as well as in the form of a circular ring or a preferably concentrically arranged circular area which is smaller than the cross-sectional area of the optical fiber.

The light source in the housing may be in the form of one or more light-emitting diodes or as another light source, suitably arranging a diffusion foil in front of the light sources.

As light, any electromagnetic wavelength from ultraviolet to infrared, both visible and invisible, can be used. In order to eliminate disturbances due to unavoidable secondary light, the wavelength can advantageously be in the infrared range from 0.85 to 25 μm, preferably in the order of 1.3 μm. Clocked light can also be used.

In order to eliminate incorrect measurements by the tear fluid, our reflex light of a certain intensity is detected. For this reason, a threshold value transmitter is provided in the known per se electronic Meßwertumformer circuit.

According to the inventive principle can be advantageously created an easy-to-use device for use on the patient lying.

In this case, the axially movable measuring element is arranged vertically movable in a housing and receives a constant weight with which it presses on the eyeball. The axially movable measuring element consists essentially of the optical fibers, which cooperate with one or more light sources and optical sensors in the manner described above. The electrical signals are in a known manner

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processed to a digital display. In this arrangement, the electronic means, the digital display and the batteries for power supply are arranged in the housing for handling the device.

In order to avoid any mechanical friction between the measuring device which is axially movable in relation to the housing used for handling, the coupling for the transmission of the input energy for the optoelectronic transmitters and for the transmission of the output signals of the optoelectronic receivers takes place either optically-electronically or inductively. For this purpose, optoelectronic transmitters are provided in the housing in the first case, which cooperate with corresponding receivers on the axially movable measuring element, the latter supplying the individual optical fibers arranged optoelectronic transmitter with energy. The electrical signals of the optical fibers arranged on the receiver, which form this from the reflected light are supplied to optoelectronic transmitters, which transmit them in the form of light on them in the housing arranged opto-electronic receiver.

It is as mentioned above, also possible to transmit the energy between the housing and the axially movable Meßelemeht \ smoothly inductively. For this purpose, an inductive sensor is provided in the housing, which is operatively connected to a corresponding position of the axially movable measuring element inductive receiver, which in turn is connected to the input of the arranged on the optical fiber optoelectronic transmitters. The output of the optoelectronic receivers disposed on the optical fibers is connected to an inductive sensor disposed on the axially movable metering element and operatively connected to an inductive receiver in the housing

01276 DD / 17 3 "02. 1984

is disposed at a suitable location in the same. The inductive elements can be provided both in the form of coils, as well as in the form of vapor deposited or otherwise applied by known methods structures, it is expedient to arrange coils in the housing and vapor-deposited on the axially movable measuring element or on 'otherwise. to arrange applied structures.

To ensure proper working with the tonometer on the patient lying, this must be kept exactly vertical. For this reason, at least three optocouplers, preferably reflex couplers, are distributed over the circumference on the housing, at the exit point of the axially movable measuring element. In the region of the axially movable measuring member, which faces the optocouplers during measurement, this is provided with an annular reflective coating. When the device is exactly vertical, the light beam emitted by the optical transmitter of the reflex coupler is reflected by the reflective coating on the device placed on the eye and received by the optical receiver of the reflex coupler. The generated electrical signal can be used to trigger the measurement process. If the device is mounted so that the axially movable measuring element is not vertical, so is tilted, and rests against the housing, the emanating from the transmitter of the reflex coupler light beam is deflected by the reflective coating of the measuring element up or down and does not reach the receiver. The non-existent electrical signal blocks the measurement process. Upon execution of the reflective pad in a suitable width is achieved at the same time that the device does not work in an unsupplied state. Two differently colored LEDs, which are arranged at a suitable position of the housing, indicate whether the device measures or whether the measuring

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Process is interrupted, so that the device-Γ de is informed about the state of the device and the time when ^it is kept exactly vertical,

When using the device on a seated patient; the device is expediently designed so that the axially movable measuring element with the applanation surface is fastened horizontally movable on a lever whose horizontal force can be regulated in order to be able to set a given pressure of the applanation surface on the eye.

In this embodiment, several variants are possible. The device may in principle be designed in the same way as that for "lying on the patient, except that the axially movable measuring element is fastened to said lever, which is guided through a slot of the housing and ^: again optically or inductively to the housing is coupled, which contains the power supply and the electronic means, including the display

But it can also be carried out integrally on the lever and thus axially movable so that an embodiment in the form of a fixed housing and a relatively movable to this measuring element unnecessary. In this embodiment for seated patients, the applanation surface is located at the front end of the axially horizontally movable lever end, and the power supply, electronic means and digital display can be located anywhere on the device, easily visible to the examiner.

Tear liquid measurements taken by displacement of applanation surface and by capillary action collecting around the applanation surface are avoided by providing only specular reflection light

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Intensity is detected, generated by weak reflection light signals from optoelectronic receivers are by t. filtered out a threshold. . >

The electronic evaluation circuit and the digital display:

may be carried out by known means such that one; ,;

Display of the minimum, middle and maximum value of the eye! '

pressure, due to the dependence on the pulsation pressure I

of the blood is possible. This can be done by saving the three i; Values and queries seen on only one digital display

or by three separate digital displays. It is also possible to: with the variation of the value with the current display possible,

which may be stopped at any value. ^;

The tonometer according to the invention knows the known ones;

Devices have the following "advantages: .. · ·"'}

- Low technical equipment effort. ί

- low cost ·

- easy handling ^; Usability for non-specially trained persons

- Optoelectronic data acquisition and display, thereby

free of subjective errors j

- no mechanical friction in the measuring system, which may vary due to external circumstances and lead to measurement errors i

- small size

- easy to clean and disinfect

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- Extensive elimination of the influence of the flow of tears'. ''''''';' /:. \: ^v .

- high resolution. : /

Ausführunssbeispiel

The invention will be explained in more detail below with reference to exemplary embodiments. In the accompanying drawings:

1 shows a schematic representation of the course of the light rays in the area of the applanation surface in the case of a tonometer whose measuring element consists essentially of optical fibers; .

Fig. 2: a first variant of both the axially movable measuring element alternately contains optical-electronic transmitter and receiver on the individual fibers of the light guide;

3 shows a second variant in which a part of the cross-section of each individual optical fiber is equipped with an optical-electronic sensor;

4 shows a variant of the tonometer according to the invention for use on a lying patient with an axially movable measuring element with optoelectronic coupling to the housing serving for handling, shown schematically, in section;

5i a second variant of the tonometer according to the invention zur.Verwendung the lying patient with an axially movable measuring element with inductive

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Coupling to the handling housing, shown schematically in FIG. Cut;

Fig. 6

to 8: schematic representation of device variants for use in sedentary patients.

Fig. 1 shows a schematic representation of the operation of the optically-electronically measuring Applanationstonometers invention. The consisting essentially of a plurality of optical fibers 2 axially movable measuring element 1 we are placed with a flat ground and polished surface with a pressure P on the eyeball 3, whereby a flattened Fiäch'e F arises on the eyeball. Laterally from this surface, the displaced and attracted by the capillary tear liquid 4 collects. This leads to measurement errors in the electrical surface measurements and can also be the cause of a subjective optical measurement error. In the tonometer according to the invention, light L is now radiated into the light guides. In the area of applant surface F, the light is reflected uninterrupted and travels through the same or an adjacent light guide as reflex light R. In the region of the tear fluid, the light also first appears on the eyeball 3 reflected and although at an angle. When reflected light transposes this light into a light guide as refracted reflected light, its luminous intensity is less pronounced by the absorption in the tear fluid and the luminance reduced by the oblique impingement on the light guide than the intensity of the reflected light R. This reduced light intensity enters the optical sensor, a weaker electrical signal, which is then eliminated in the connected per se known electronic Ausertungsschaltung by a threshold. So it will be

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only the reflex light R is measured and thus the influence of the tear fluid is largely eliminated.

In the variant of the Appiantionstonometers shown in i'igur 2 with opto-electronic Meßvierterfassung the axially movable measuring element 1 is also just polished and polished on the serving for flattening of the eye 3 side. On the side opposite the applanation surface F of the axially movable measuring element 1, the light guides 2 are alternately arranged as light sources photoelectronic transmitters 6 and photoelectronic receivers 7 on the ends of the individual fibers 2 '. The light L which is irradiated by a respective photoelectronic transmitter 6 into a light-receiving optical fiber 2.1 is reflected at the applanation surface F and is reflected by an adjacent reflected light _; R leading optical fiber 2.2 is guided to the arranged on this photoelectric receiver 7.

In the variant with the same measuring principle, which is shown in Figure, on the opposite side of the Applanationsflache F of the axially movable member 1 on the ends of the individual fibers 2 ^1, the optical fiber 2 on each fiber 2 ¹ each over a portion of the cross section of Surface optoelectronic receiver 7 may be arranged. From an external light source (not shown), light L is irradiated into the optical fiber 2 'by the remaining part of the cross section and, after the reflection at the applanation surface F, is returned to the optoelectronic receiver 7 in the same optical fiber and converted into electrical signals. In this case, the optoelectronic receiver 7 arranged on each fiber '2' of the optical waveguide advantageously occupies half the cross section of the optical waveguide fiber 2 ¹ . It can be embodied both as a circle segment surface, in particular as a semicircular surface, and in the form of a circle

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Annular ring or a preferably concentrically arranged circular area, which is smaller than the cross-sectional area of the optical fiber 2 *.

The light source, which is arranged in the stationary part of the housing, may be formed by one or more light-emitting diodes, which is arranged in the axial direction with respect to the axial element 1 behind a scattering film / are.

To exclude measurement errors by scattered secondary light can in. Tonometers for measuring except visible light also ITV or IR radiation can be used. A particularly advantageous wavelength is on the order of 1.3 / um. You can also use clocked light.

10 are supplied with electrical energy and the output signals of the photoelectric transmitters are also via optocouplers

11 transmitted from the movable measuring element 1 to the located in the housing 5 electrical means 9 of the evaluation circuit, which processes these signals to a digital display 12, which can be made visible at any point.

As shown in Fig. 5, the. Coupling between the housing 5 and the axially movable measuring element 1 also made inductively. For this purpose, an inductive sensor is provided on the input side of the energy in the housing 5, which is connected to the energy source. Opposite him is located on the axially movable measuring element 1, an inductive receiver 14 which is connected to the input of the photoelectric receiver. From the output of the photoelectric transmitter, the output signals are passed to an inductive sensor 16, which is arranged on the axially movable measuring element 1 with respect to an inductive receiver 16. The latter sends his signals to an electronic

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evaluation circuit that converts it to an ad. '. ... ^y \: \

To control that the device is held exactly vertical or to ensure that the device measures only in exactly vertical position and thus friction by grinding on the walls of the housing 5 or erroneous measurements by oblique placement are avoided, is on all devices for use provided on the patient lying a monitoring device. This consists of at least three optocouplers, preferably reflex couplers 17 .with adjacent transmitters and receivers. These reflex couplers 17 are distributed uniformly over the circumference at the location of the housing 5, at which point the axially movable measuring element 1 exits from the housing 5. At the location of the axially movable measuring element 1, which during measurement, d. H. when placed on the eye 3 measuring elements 1 the reflex couplers 17 is opposite, a reflective coating 18 is annularly applied. ί

When exactly vertical device from the optical transmitter of the reflex coupler 17, z. B. a photodiode emitted light beam when placed on the eye device from the reflective coating 18 and reflected by the optical receiver, for. B. a photodiode or a phototransistor received. The generated electrical signal can be used to trigger the measurement process. If the axially movable measuring element 1 and the housing 5 are not perpendicular to the axis, the light beam emitted by the photodiode of the reflex coupler 17 is deflected upwards or downwards by the reflective coating 18 of the measuring element 1 and does not reach the receiver. The non-existent electrical signal blocks the measuring process ·

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When running the pad in a suitable width is achieved at the same time that the device does not work when not mounted.

Two differently colored LED'19 and 20, which are arranged at a suitable location of the housing, indicate whether the device measures or whether the measurement process is interrupted. This means that the person working with the device is always informed about the period in which the device is working or even that it is not set up.

In all of the above-mentioned variants for use on a patient lying in the housing required for handling 5 and the electronic means 9 for further processing of the electrical signals of the optical sensors to a digital display, this display itself and the required battery for power supply housed. This makes the device completely independent and easy to handle. Since only the applanationsflache F of the axially movable measuring element 1 protruding relatively far out of the housing comes into contact with the eye 3 and this is easy to clean either as ground, polished glass surface or provided with a smooth coating 21 of a suitable material, is also a hygienic application secured. It is also understood that the axially movable measuring elements are secured against falling out of the housing.

The possible embodiments shown in FIGS. 6, 7 and 8 are suitable for use of the tonometer according to the invention on a sitting patient. This form is mainly used in devices for clinical examinations * why a higher technical equipment effort and

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a not so easy handling as in the variants explained above can be accepted ·

In the embodiment of Fig. 6, the axially movable fyleßelement, which in this example consists essentially of optical fibers 2, formed as an integral part of a first arm 22 of a lever 23, at the zvei- tera. Poor. 24, a variable, preferably displaceable weight 25 is provided for the regulation of the horizontal pressure P, with which the applanation patch F presses on the eyeball The change in pressure can, of course, also be effected in another way Cable 26, expediently led out at the pivot point 27 of the lever to an evaluation and display device 28 which contains the power supply, the light source or light sources, the photoelectronic elements, the electronic evaluation circuit and the digital display 12.

The light irradiated by the photoelectric transmitters 6 in the interior of the evaluation and display device 28 into the optical fibers is directed to the applanation surface F, reflected by the apple 3 and returned to the photoelectric receiver also arranged in the evaluation and display device 28. The generated electrical signals are further processed to a digital display, as already mentioned several times above. In the embodiment of Fig. 7, the possible inaccuracies are eliminated by mechanical repercussions of the optical fiber cable on the lever forces by the transition from the movable to the fixed part of the device takes place on optical Weese. It is therefore a fixed housing 5 is provided in which the attached to the lever arm 22 axially movable measuring element 1 moves smoothly. The embodiments of the measuring element 1 and the housing

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are arbitrarily analogous to those of the embodiments for use on the patient lying down. . ^

In Fig. 7, the measuring element is designed analogously to Fig * 3 and the light source is arranged on the rear wall of the housing. But there are, as already mentioned, other forms possible. ' The. Fiber optic cable 26 extends here from the stationary housing 5 to the evaluation and display device 28..

In a variant of FIG. 8, the entire evaluation and display elements with the measuring element in a. Piece, to be executed without relative mobility. Then, the housing 5 is fixedly arranged on the lever arm 22 and has a, the diameter of the measuring element of the other variants corresponding projection 29, on the front surface of the applanation surface, F is provided in the manner already described. The electronic means (not shown) and the digital display 12 are then housed in the housing 5 pivotable and movable with the lever arm 22. Again, the power supply can be done by means of an external power source, \ then the supply line 'is expediently introduced at the pivot point of the lever to the repercussions .auf. to keep the torque low. But it can also aucb. a battery may be provided in the housing.

Again, the front surface. 31 be provided with a suitable smooth "cover 21 to facilitate cleaning and disinfection.

- 25 -

Claims (14)

01276 DD / 17 -25 -. '3fc 02 »1984 i .. A pplanat; tonometer for measuring the intraocular pressure according to the applanation principle, which has an axially movable Meßelemenfr with which a force is applied to the eye _? for flattening part of the surface of the eye and containing cooperating means for detecting the size of the flattened surface at a given pressure, or for detecting the applied pressure for a given size of the flattened surface, characterized in that the axially movable measuring element (1) in essentially consisting of optical fibers (2) and the means cooperating therewith one or more photoelectric transmitters (6) and photoelectric receivers (7), the optical fibers (2) being ground flat on the one side serving for flattening the eye (3) and polished and disposed on the other opposite side so as to receive light (L) from the photoelectric transmitter (s) (6) and, when the flattening of the eye (3) is resting on the eye (3), from the eye (3) reflected light (R) to the photoelectric transmitters (7). 2. Applanation Tonosneter according to item 1, characterized in that the light guides (2) on the one for Abfia- .. ·. surface of the movable element (1) on the ends of the individual fibers (2 ¹ ) of the light guides (2) are alternately used as light sources photoelectronic transmitters (3). 6) and photoelectronic receivers (7) are arranged such that the. Of each a photoelectric sensor ^; the (6) sent into an optical fiber (2 ^f ) - 26 - 01276 DD / 17 - 26 - 3 · 02. 1984 Light after reflection at the Appianationsflache (F) through the adjacent fiber optic fiber (2 ') on the arranged on its photoelectric receiver (7) « 3 · applanation tonometer according to item 1, characterized in that the light guides (2) on the flattening of the eye 3 serving side of the movable element (1) just ground and polished, and that on the Appianationsflache (F) opposite side of the movable Element (1) on the ends of the individual fibers (2 x) of the light guides on each fiber (2 ¹ ) is arranged over a part of the cross section of the surface of an optoelectronic receiver (7), such that the one of the stationary Part of the housing arranged light source by the remaining part of the, cross-section into the optical fiber (2 ·) and radiated from the Appianationsflache (F) reflected light from this receiver (7) can be received and converted into electrical signals, 4. Applanation tonometer according to item 3 », characterized in that the optoelectronic receiver (7) arranged on each fiber (2 ¹ ) of the optical waveguide (2) covers half the cross section of the optical waveguide fiber (2 '). 5. Applanation tonometer according to point 3 », characterized in that on each fiber (2 ^f ) of the light guide (2) arranged opto-electronic receiver (7) is designed as a circular segment area or semicircular surface. 6. Applanation tonometer according to item 3 », characterized in that the fiber on each fiber (2 ¹ ) of the light guide 01276 DD / 17 - 27 - 3 * 02 * 1984 (2) arranged opto-electronic receiver (7) as ^; Annulus is aerated. , ^v 7 «Applanatiönstonometer according to item 3, characterized _s that disposed of on each fiber (2 ¹⁾ of the light guide (2) optoelectronic PJmpfänger (7) is arranged as a central circular area which is smaller than the cross-sectional area of the optical fiber. . 8. The Applanatiöntonometer according to item 3, characterized in that the light source in the fixed part, the housing by one or more with respect to the movable member 1 arranged photoelectric transmitter ge 'is formed and is arranged behind a scattering film. "SU Applanatiöntonometer according to item 1, characterized in that, as light, each electromagnetic wavelength from ultraviolet to infrared, sro is visible in the visible as  ,> is also invisible in the invisible area. · DA iCU Applanatiönstonometer according to item 1 in,) "by, .that the wavelength of light in the infrared be rich: j; 0.85 to 25 / um is located. 11 β Applanatiöntonometer according to item 1, characterized in that the wavelength is on the order of ^r 1.3 / um. _a ' 12. Applanatiöntonometer according to item 1, characterized da-. by that the light is clocked. '' Applanatiöntonometer according to item 1, characterized in that a threshold transmitter for blurring the 01276 DD / 17 - 28 - electrical signals are provided, which are generated by light below a predetermined light intensity of the photoelek.trischen receivers (7). 14. applanation tonometer naoh point 1, characterized in that the axially movable measuring element (1) is arranged in a housing (5) against which'es performs a relative movement, 'that it has a predetermined weight and that in the arranged in the photoelectric transmitter and receivers (6 and 7) are smoothly engaged with the housing (5). 15. The applanation tonometer according to item 14, characterized in that the housing (5) serving for handling »the batteries (8) serving for the power supply, the coupling means · for smooth energy transfer to and from the axially movable measuring element (1) the entire electronic evaluation circuit ( 9) and the display (12) , contains. 16. applanation tonometer according to item 14, characterized in that the means for the smooth coupling of the axially movable measuring element with the housing (5) via optocouplers (10). 17. Applanation tonometer according to item 16, characterized in that the optocouplers consist of light emitting diodes and photodiodes or phototransistors. 18. Applanation tonometer according to item 16, characterized in that the axially movable measuring element (1) is designed prismatic and that with the photoelectric , Transmitters and receivers (6 and 7) are connected to the surface of the prism-shaped axially opposite surface of the applanation surface (F) (6 and 7). 01276 DD / 17 - 29 - ^: 3. 02. 1984  movable measuring element (1) are arranged. 19 · applanation tonometer according to item 16, 'characterized in that the housing-provided optocoupler elements (10) relative to the upper surface of the prism-shaped axially movable measuring element (1) are arranged in the housing. -. . /. ; , 20.'Applanationstonoaieter according to item 14, ^'r characterized in that the smooth coupling of the axial be -.-'"-wegbaren measuring element (1) with the housing (5) takes place inductively · .. -..... ' ^! 21. Applanation tonometer according to item 20, characterized in that for the transmission of energy from the housing (5.) to the opto-electrical transmitters (6) on the axially bewegba-. Ren'Meßelement (1) in the housing 5 an inductive transmitter (13) is arranged and, on the axially movable measuring element (1) each have an inductive receiver (14) which is connected to the phot © electrical transmitters (6) and that. The photoelectric receiver (7) for energy transfer -. on the housing (5) with one each on the axially loaded. wegbaren measuring element (1) arranged inductive sensor (.15) are connected, which in each case with an inductive receiver (16) in the housing (5) in operative relationship. - '. , 22. Applanation tonometer according to item 20, characterized da-, by that the inductive elements are listed as coils: are. . ' /. '. ^: ' , '. 23. Applanation tonometer according to item 20, characterized:. by, that the inductive elements are designed as' ^1- evaporated or applied by other known methods structures. · 01276 DD / 17 - 30 - 3. 02. 1984 24 «applanation tonometer according to claim 14, characterized in that at the location of the housing (5)» at the axially movable measuring element (i) emerges, on the inner wall of the housing (5) at least three optocouplers are distributed over the circumference and that at the location of the axially movable measuring element (1) which is opposite to the optocouplers when the device is placed on the eye, a reflective coating (18) is applied annularly.  25. Application tonometer according to item 24, characterized in that the optocouplers are reflex couplers (17). 26. Applanation tonometer according to items 24 and 25, characterized in that the receiver de Seflexkoppler (17) are connected to a monitoring circuit. 27 Applanation tonometer according to item 1, characterized in that the applanation surface (F) has a smooth coating. For this Ό pages drawings