Pressure-adjustable test eye for tonometers

Abstract

The present solution relates to a pressure-adjustable test eye for tonometers, in particular for contactless tonometers. The proposed pressure-adjustable test eye for tonometers consists of a base element with a pressure source, at the edge of which base element a film, simulating the cornea, is fastened, the resulting cavity being filled with liquid or gas. According to the invention, the film simulating the cornea has, starting from a central, mechanically excitable region, gradually varying conducting properties for mechanical waves. For simulation of the cornea, a film is used which is self-supporting and has a certain residual stiffness. The pressure-adjustable test eye is intended for tonometers, in particular contactless tonometers, in order to generate the most realistic measurement signals possible, in order to be able to carry out regular function tests and / or calibrations. However, the pressure-adjustable test eye can also be used in elastography or elastometry in order, for example, to enable a pre- and postoperative evaluation of corneas to be carried out.

Description

[0001] Pressure-adjustable test eye for tonometer

[0002] The present invention relates to a pressure-adjustable test eye for tonometers, particularly for non-contact tonometers. Test eyes are primarily used to regularly check and / or calibrate medical devices for correct function.

[0003] A tonometer is used to measure intraocular pressure (IOP). An increase above the normal value of this pressure is usually one of the most important, but not the only, risk factor for glaucoma. Lowering the IOP, for example through medication (eye drops or drug-depot implants) or surgical intervention, is the most important therapeutic measure in glaucoma treatment, which is why tonometric monitoring of the IOP is an important tool in guiding therapy. However, glaucoma can also be present when the intraocular pressure is within the above-mentioned normal range (normal-tension glaucoma), and increased intraocular pressure outside the normal range (hypertension) merely gives rise to suspicion of the disease.

[0004] Glaucoma, also known as glaucoma, refers to a series of eye diseases of various causes that result in irreversible damage to the nerve fibers of the optic nerve. In advanced stages of the disease, this becomes noticeable at the point where the optic nerve exits as increasing hollowing (expansion) or paleness and atrophy of the optic nerve head (papilla). This results in characteristic visual field defects (scotomas), which in extreme cases can lead to blindness in the affected eye.

[0005] Elevated intraocular pressure can be easily measured regularly, for which various solutions are known in the state of the art. For the sake of completeness, it should be noted that the commonly reported intraocular pressure (IOP) is the relative pressure of the eye, particularly of the aqueous humor, relative to atmospheric pressure. If this relative pressure is significantly elevated, for example, a noticeable hardening of the eye occurs, which is why, before the availability of tonometers, ophthalmologists at least performed a qualitative assessment of intraocular pressure by palpation. However, this IOP must be distinguished from absolute pressures, such as those sometimes determined by intraocularly implanted pressure sensors when these are not related to the prevailing atmospheric pressure.

[0006] Tonometers for determining intraocular pressure are important diagnostic devices in ophthalmology, particularly for the detection of ocular hypertension as a major risk factor for glaucoma and for therapy monitoring, but also in emergency medicine for the detection of high intracranial pressures that are transmitted to the eye.

[0007] Tonometers, as medical devices, should be regularly checked for proper function and / or calibrated. Unfortunately, this is a difficult task, as the pressure-dependent interaction of an eye with the respective tonometer is complex, and various pressure levels must be tested. This remains a largely unsolved problem, particularly for dynamic, non-contact tonometers, such as airpuff or rebound tonometers, or the shock wave tonometer described in

[0001] .

[0008] In the state of the art, solutions are known in which substitutes are used that, for example, simulate the reaction of an eye to be measured without contact tonometrically.

[0009] US 2014 / 0323843 A1 describes a tool for calibrating a non-contact tonometer (NCT). The tonometer calibration tool consists of an "electronic eye" that can be positioned in front of an air outlet channel of a non-contact tonometer. It includes a pressure sensor for receiving the air pulse and a transmitter for providing a pseudo-applanation event.

[0010] In particular, the electronic eye simulates the reaction of an eye being measured non-contact by mimicking a pressure-dependent deflection of a light reflex on a "cornea" dynamically deformed by an air puff. However, the light beam is not actually deflected; instead, a similar light signal is generated, dependent on the air puff, which is detected by the air-puff tonometer instead of the deflected light beam.

[0011] It is obvious that this tool cannot be used to test the full function of the tonometer, since the measuring beam of the tonometer is not actually deflected.

[0012] There is no known calibration verification for rebound tonometers from the state of the art.

[0013] This applies to both the Tono-Vera rebound tonometer from Reichert and the I-Care from Revenio. Therefore, no calibration or test eyes are known that can simulate realistic, intraocular pressure-dependent behavior, which could be used to verify intraocular pressure-dependent measurements.

[0014] In [1], experiments for shock wave and rebound tonometry were described, using a phantom eye consisting of a film stretched over a cylinder. It is stated there that various film materials and thicknesses were tested, and that ultimately a 50 μm thick TPU film provided the most useful results. This phantom eye was also subjected to a pressure adjustable via a manometer in the range of 10 ... 70 mmHg. A comparison of the signal curves shown in this publication for this eye phantom and a pig eye model, however, shows that the signals in the phantom eye exhibit a significantly different structure from the signals in the biological sample (many oscillations and lower damping behavior).

[0015] In this regard, reference is made to the article [1], which compares, among other things, the signal curves of shock wave tonometric measurements on a cylindrical phantom eye with a screw-on ring and on a pig's eye.

[0016] The state of the art also describes solutions for “test eyes” for non-tonometric applications.

[0017] According to [2], artificial anterior chambers are known that can be used for surgical manipulation of corneas or for training purposes.

[0018] The chamber is a special device that allows the anatomical positioning of a donor's corneoscleral tissue cap with the epithelial side facing up. The chamber is used to support the donor tissue and maintain sufficient pressure while performing a lamellar dissection or full-thickness trephination on the donor tissue.

[0019] However, our own experiments with such an artificial anterior chamber using corneal substitute materials have shown that the tonometric signals obtained were not sufficiently usable. This led to the suspicion that the unnatural nature of the corneal substitute material's retention (local pressing) and the associated abrupt transition to the hard chamber material were the cause of the problem. For further experiments, a test eye (artificial eye) that was anatomically correct in certain aspects and is particularly used for surgical training was used. Although this test eye exhibited realistic corneal thicknesses of 0.5 mm (central) to 0.8 mm (peripheral) and an 8 mm "dilated" pupil, it also produced unsatisfactory results even after modification for pressure application.

[0020] Literature:

[0021] [1] https: / / doi.Org / 10.1371 / journal, pone.0227488

[0022] [2] https: / / bpic.com / products / barron-artificial-anterior-chamber /

[0023] [3] https: / / d0i.0rg / l 0.1371 / journal, pone.0227488

[0024] [4] https: / / www.innoform-coaching.de / blog / 2021 / 06 / 07 / was-sind-eigentlich- pe-ld-pe-hd-pe-lld-und-ldpe-qenau / )

[0025] The present invention is based on the object of providing a test eye to enable intraocular pressure-dependent measurements, particularly for dynamic, non-contact tonometry methods. In particular, the test eye should generate measurement signals that are as realistic as possible in order to enable regular functional tests and / or calibrations.

[0026] This object is achieved with the proposed pressure-adjustable test eye for tonometers, particularly for contactless tonometers, consisting of a base element with a pressure source, to the edge of which a cornea-mimulating film is attached, the resulting cavity being filled with liquid or gas. The cornea-mimulating film has gradually varying conduction properties for mechanical waves, emanating from a central, mechanically excitable region. Preferred developments and advantageous embodiments are the subject of the dependent claims and essentially relate to the cornea-mimulating film attached to the edge of the base element.

[0027] According to a first embodiment, the cornea-imitating film has a flat or curved surface, the central, mechanically excitable area of ​​which has an area between 500 and 8000 mm 2 has.

[0028] According to a second advantageous embodiment, the film simulating the cornea has a homogeneous, isotropic structure and is transparent and elastic.

[0029] According to a third advantageous embodiment, the inner and outer sides of the film are smooth and contain no mechanical disturbances, so that a low optical and acoustic scattering effect is achieved.

[0030] According to a fourth advantageous embodiment, the film simulating the cornea consists of PVC, TPU or PE, in particular PE-LD.

[0031] Further preferred developments relate to the design of the gradually varying conduction properties of the film for mechanical waves through property modification. In particular, the property modification includes a variation in the curvature and / or a variation in the thickness and / or a variation in the elasticity of the cornea-simulating film.

[0032] According to a final preferred development, a damping element is provided directly beneath the cornea-simulating film, which damping element is designed and arranged such that the central, mechanically excitable region has a minimum distance from the damping element of 10 to 2000 μm, in particular 500 to 800 μm. Particularly preferably, the film and the damping element located directly beneath it gradually approach each other, with the proximity particularly preferably decreasing from the inside to the outside.

[0033] To avoid asymmetric deformations caused by gravity for all of the above-mentioned configurations, the test eye is positioned for measurements with the base element horizontally aligned and the cornea-simulating film facing up or down. However, it is also possible to modify the properties of the cornea-simulating film in such a way that the test eye is not unacceptably deformed by gravity under measurement conditions.

[0034] The proposed pressure-adjustable test eye is intended for tonometers, especially for non-contact tonometers, in order to generate measurement signals as close to reality as possible in order to perform regular functional tests and / or calibrations.

[0035] However, the proposed pressure-adjustable test eye is applicable not only for tonometry, but also for elastography or elastometry, for example, to enable the pre- and postoperative evaluation of corneas.

[0036] The invention is described in more detail below using exemplary embodiments. These show:

[0037] Figure 1 : a pressure-adjustable test eye with a flat foil,

[0038] Figure 2: a pressure-adjustable test eye with a curved foil,

[0039] Figure 3: a pressure-adjustable test eye with a foil with varied

[0040] Curvature, Figure 4: a pressure-adjustable test eye with a foil of varied thickness,

[0041] Figure 5: a pressure-adjustable test eye with a damping element arranged under the foil and

[0042] Figure 6: a pressure-adjustable test eye with a foil of varying curvature, varying thickness and a damping element.

[0043] The proposed pressure-adjustable test eye for tonometers, in particular for contactless tonometers, consists of a base element with a pressure source, to the edge of which a foil simulating the cornea is attached, the resulting cavity being filled with liquid or gas.

[0044] Since it is in principle possible for the base element and the cornea-simulating film to be manufactured in one piece, this variant will also be included in the following description.

[0045] According to the invention, the cornea-replicating film, emanating from a central, mechanically excitable region, has gradually varying conduction properties for mechanical waves. According to the invention, a film is used to replicate the cornea that is self-supporting and has a certain residual rigidity.

[0046] The central, mechanically excitable area is the area of ​​the foil that is to be stimulated by a tonometer to be tested, for example by an air blast, in order to generate measurement signals that are as realistic as possible.

[0047] Water, silicone oil, or similar fluids can be used for the cavity. It is also possible to partially or completely fill the test eye with gas, for example, to simulate the measurement conditions in a partially gas-filled patient eye. Gas fillings, such as the very dense but nontoxic sulfur hexafluoride, are used, among other things, in the treatment of retinal detachments. Because sulfur hexafluoride is chemically inert, it can also be used in a test eye.

[0048] For the sake of simplicity, the film simulating the cornea will be referred to simply as the film in the following.

[0049] According to the invention, the base element holding the film is plate- or cylindrical-shaped, with its diameter being greater than its height. Preferably, the base element additionally has at least one pressure sensor to detect the pressure setting of the test eye. The pressure sensor is advantageously designed such that it can perform a pressure measurement relative to the ambient atmospheric pressure, for example, using a can-type or membrane barometer that is measurably deformed by the pressure difference between the test eye fluid and the ambient pressure. Alternatively, an absolute pressure sensor (for example, a temperature-compensated, miniaturized MEMS or piezoresistive sensor) can be used in the test eye; however, this would then require a second pressure sensor to determine the ambient atmospheric pressure as a reference value.Another variant is the pairing of these two sensors in a pressure sensor module that emits a differential electrical measurement signal for the relative pressure in the test eye.

[0050] Figure 1 shows a first pressure-adjustable test eye consisting of a cylindrical base element 1.1 with a pressure source 2, to whose edge a flat film 3.1 is attached. The resulting cavity 4 is filled with liquid or gas, as indicated by the hatching. Pressure sensors are not shown for clarity. In contrast, Figure 2 shows a second pressure-adjustable test eye consisting of a flat base element 1.2 with a pressure source 2, to whose edge a curved film 3.2 is attached. The resulting cavity 4 is filled with liquid or gas, as indicated by the hatching.

[0051] Preferred further developments and advantageous embodiments essentially relate to the film attached to the edge of the base element.

[0052] According to a first embodiment, the cornea-simulating film has a flat or curved surface. This can, for example, be in the shape of a sphere or an ellipsoid. Particularly preferably, the central, mechanically excitable region of the film has an area between 500 and 8000 mm. 2 on.

[0053] According to a second advantageous embodiment, the cornea-replicating film has a homogeneous, isotropic structure, which is preferably transparent and elastic. It is particularly advantageous if the film is also optically reflective, with a reflectance between 0.1 and 10%. This average reflectivity should be related to perpendicularly incident, non-polarized light. Changes in reflectivity can be achieved through suitable surface coatings. Alternatively, reductions in film backside reflections can also be achieved by incorporating dyes that absorb the measurement radiation on its way to the back of the film and back.

[0054] According to a third advantageous embodiment, the inner and outer sides of the film are smooth and contain no mechanical disturbances, so that a low optical and acoustic scattering effect is achieved.

[0055] According to a fourth advantageous embodiment, the cornea-simulating film is made of PVC, TPU, or PE, in particular PE-LD. These materials have proven particularly suitable for generating measurement signals that are as realistic as possible.

[0056] In principle, other types of PE film can also be used, such as PE-VLD, PE-LD, PE-MD, and PE-HD (from "very low density," through "low density," "medium density," "linear low density," and up to "high density"). For information on PE film types, please refer to article [4].

[0057] Further preferred developments relate to the design of the gradually varying conduction properties of the film for mechanical waves through property modification. In particular, the property modification includes a variation in the curvature and / or a variation in the thickness and / or a variation in the elasticity of the cornea-simulating film. Property modification of the film is understood here, for example, to mean deep-drawing the film during the manufacturing process, whereby the curvature is somewhat flattened in the center.

[0058] Figure 3 shows a third pressure-adjustable test eye consisting of a flat base element 1.2 with a pressure source 2, to whose edge a curved foil 3.3 is attached. The resulting cavity 4 is also filled with liquid or gas, which is indicated by the hatching. In particular, the gradually varying conduction properties for mechanical waves were generated by varying the curvature of the curved foil 3.3.

[0059] Figure 4 shows a fourth pressure-adjustable test eye consisting of a flat base element 1.2 with a pressure source 2, to whose edge a curved foil 3.4 is attached. The resulting cavity 4 is also filled with liquid or gas, which is again indicated by the hatching. In particular, the gradually varying conduction properties for mechanical waves in this variant were generated by varying the thickness of the curved foil 3.4. The foil preferably has a thickness in the range between 10 and 1000 μm.

[0060] Another possibility for creating gradually varying conduction properties for mechanical waves is to vary the elasticity of the film, for example, through local stretching, thermal or chemical treatment, or coating. According to the invention, the film has a modulus of elasticity in the range of 0.2 to 1000 MPa, in particular in the range below 10 MPa.

[0061] According to a final preferred development, a damping element is provided directly beneath the corneal-simulating film, which is designed and arranged such that the central, mechanically excitable region has a minimum distance from the damping element of 10 to 2000 μm, in particular 500 to 800 μm. Furthermore, a pressure equalization facility can be provided in the damping element.

[0062] Figure 5 shows a fifth pressure-adjustable test eye consisting of a flat base element 1.2 with a pressure source 2, to whose edge a curved foil 3.5 is attached. The resulting cavity 4 is also filled with liquid or gas, as indicated by the hatching. In particular, a damping element 5 with a pressure compensation element in the form of an opening 5.1 is arranged beneath the curved foil 3.5.

[0063] Particularly preferably, the film and the damping element located immediately below it gradually approach each other, with the approach particularly preferably decreasing from the inside to the outside.

[0064] Figure 6 shows a sixth pressure-adjustable test eye consisting of a flat base element 1.2 with a pressure source 2, to whose edge a curved foil 3.6 is attached. The resulting cavity 4 is again filled with liquid or gas, as indicated by the hatching. A damping element 5 is also arranged beneath the curved foil 3.6. In particular, the gradually varying conduction properties for mechanical waves in this variant were generated by varying the thickness and curvature of the curved foil 3.6 and the varying distance of the damping element.

[0065] According to the invention, a sufficiently slow, gradual approach between the foil and the damping element in the peripheral direction is required, whereby a defined distance must be maintained in order to avoid signal interference.

[0066] The damping element can also be designed in such a way that the film and the damping element touch or are connected outside the central, mechanically excitable area.

[0067] According to the invention, the film and the damping element preferably have different mechanical properties.

[0068] According to a further embodiment, the damping element arranged directly beneath the corneal-simulating film can be integrated into the base element.

[0069] The foil is positioned at a defined distance from the attenuation element or gradually approaches it peripherally until contact occurs. This creates a gradual coupling between the foil and the attenuation element, resulting in more realistic signal attenuation of the signals generated during contactless tonometry.

[0070] In order to reduce the gravity-induced stresses for all the above-mentioned configurations

[0071] To avoid deformation, the test eye is positioned for measurements so that the base element is horizontal and the cornea-replicating film faces up or down. It is also possible to modify the properties of the cornea-replicating film in such a way that the test eye is not unacceptably deformed by gravity under measurement conditions.

[0072] For this purpose, the film could be locally stiffened or pre-shaped in such a way that the desired shape of the test eye is still guaranteed in the end, despite the additional deformation caused by gravity under measurement conditions.

[0073] The present invention provides a test eye that enables intraocular pressure-dependent measurements, particularly for dynamic, non-contact tonometry methods. In particular, the test eye generates realistic measurement signals to enable regular functional tests and / or calibrations.

[0074] The described test eye closely resembles the behavior of the human eye, particularly in the anterior chamber (cornea, iris, and limbus), in terms of mechanical excitation and vibration behavior. The interaction of the foil and the damping element allows the minimal reflection of surface waves at the edge of the cornea of ​​the real eye to be simulated.

[0075] The proposed pressure-adjustable test eye is intended for tonometers, especially for non-contact tonometers, but can also be used for elastography or elastometry.

Claims

Patent claims 1 . Pressure-adjustable test eye for tonometers, in particular for contact-free tonometers, consisting of a base element with a pressure source, to the edge of which a film simulating the cornea is attached, the resulting cavity being filled with liquid or gas, characterized in that the film simulating the cornea, starting from a central, mechanically excitable region, has gradually varying conduction properties for mechanical waves and that a damping element is provided directly below the film simulating the cornea.

2. Pressure-adjustable test eye according to claim 1, characterized in that the base element is plate-shaped or cylindrical, wherein its diameter is greater than its height.

3. Pressure-adjustable test eye according to claim 1, characterized in that the central, mechanically excitable area of ​​the cornea-imitating film has an area between 500 and 8000mm 2 has.

4. Pressure-adjustable test eye according to claim 1, characterized in that the film simulating the cornea has a homogeneous, isotropic structure.

5. Pressure-adjustable test eye according to claim 1, characterized in that the film simulating the cornea is transparent and elastic.

6. Pressure-adjustable test eye according to claim 1, characterized in that the film simulating the cornea has an optically reflective effect, with a reflectance between 0.1 and 10%.

7. Pressure-adjustable test eye according to claim 1, characterized in that the film simulating the cornea consists of PVC, TPU or PE, in particular PE-LD.

8. Pressure-adjustable test eye according to claim 1, characterized in that the gradually varying conduction properties for mechanical waves were achieved by modifying the properties of the film simulating the cornea.

9. Pressure-adjustable test eye according to claim 8, characterized in that the property modification of the film simulating the cornea includes a variation of its curvature and / or a variation of its thickness and / or a variation of its elasticity.

10. Pressure-adjustable test eye according to claim 8, characterized in that the film simulating the cornea has a thickness in the range between 10 and 1000 pm.

11. Pressure-adjustable test eye according to claim 8, characterized in that the elasticity of the film simulating the cornea has a modulus of elasticity in the range of 0.2 to 1000 MPa, in particular in the range below 10 MPa.

12. Pressure-adjustable test eye according to claim 1, characterized in that the damping element is designed and arranged such that the central, mechanically excitable region has a minimum distance from the damping element of 10 to 2000 pm, in particular 500 to 800 pm.

13. Pressure-adjustable test eye according to claim 12, characterized in that the film simulating the cornea and the damping element located immediately below it gradually approach each other.

14. Pressure-adjustable test eye according to claim 12, characterized in that the minimum distance between the central, mechanically excitable region of the cornea-imitating film and the damping element decreases from the inside to the outside.

15. Pressure-adjustable test eye according to claim 12, characterized in that the corneal-simulating film and the damping element can touch or be connected outside the central, mechanically excitable region.

16. Pressure-adjustable test eye according to claim 12, characterized in that a possibility for pressure equalization is provided in the damping element located directly beneath the film simulating the cornea.

17. Pressure-adjustable test eye according to claim 12, characterized in that the film simulating the cornea and the damping element arranged underneath have different mechanical properties.

18. Pressure-adjustable test eye according to claim 12, characterized in that the damping element arranged directly below the film simulating the cornea is integrated into the base element.

19. Pressure-adjustable test eye according to claim 1, characterized in that the test eye is arranged for measurements so that the base element is aligned horizontally and the membrane simulating the cornea points upwards or downwards, so that asymmetric deformations caused by gravity are avoided.

0. Pressure-adjustable test eye according to claim 8, characterized in that the property modification of the film simulating the cornea was carried out in such a way that the test eye is not unacceptably deformed by gravity under measurement conditions.

Images