IMPLANT FOR DETERMINING INTRAOCULAR PRESSURE

Abstract

An implant for determining intraocular pressure includes at least one electrical pressure sensor for measuring the intraocular pressure, at least one microchip that is connected to the pressure sensor, and at least one antenna that is connected to the microchip, the microchip generating digitally encoded data from the electrical signals of the pressure sensor, which data can be transmitted by an antenna, using electromagnetic waves, to a receiver located outside the eye, and components being accommodated in a small housing, the outer dimensions of which are limited such that the implant can be positioned between the sclera and the choroid of the eye, is improved in that the pressure sensor is accommodated on an outer housing side of the implant, which outer housing side is brought into contact with the choroid in the eye is disclosed.

Claims

1. A method for determining intraocular pressure, comprising the steps of: providing an implant (1), the implant comprising at least one electrical pressure sensor (6) for measuring the intraocular pressure, at least one microchip (7) that is connected to the pressure sensor (6), and at least one antenna (8) that is connected to the microchip (7), wherein the microchip (7) generates digitally encoded data from the electrical signals of the pressure sensor (6), wherein the data is transmitted by the antenna (8), using electromagnetic waves, to a receiver located outside an eye (2), and wherein the components of the pressure sensor (6), the microchip (7) and the antenna (8) are accommodated in a small housing (11), wherein the pressure sensor (6) is accommodated on an outer housing side (16) of the implant (1); positioning the implant (1) between the sclera (3) and the choroid (4) of the eye (2), and introducing the implant (1) into a pocket (5) formed between the sclera (3) and the choroid (4); positioning the pressure sensor (6) between the sclera (3) and the choroid (4); bringing the pressure sensor (6) into contact with the choroid (4) of the eye (2); and positioning the outer housing side (16) to face the sclera (3).

2. The method according to claim 1, wherein the outer housing side (16) provided with the pressure sensor (6) comprises a flexible membrane (18) in the region of the pressure sensor (6) as a protective layer against ingress of liquid, the intraocular pressure acting on the pressure sensor (6) via the choroid (4) and the membrane (18).

3. The method according to claim 1, wherein the housing (11) thereof is flat and elongate in the shape of an ellipsoid or cuboid having rounded corners and edges.

4. The method according to claim 3, wherein the length (12) of the housing (11) is less than 7 mm, its width (13) is less than 3.5 mm and its thickness (14) is less than 2 mm.

5. The method according to claim 1, wherein the housing (11) is moulded from plastics material.

6. The method according to claim 1, wherein the implant (1) is provided with an electronic temperature sensor (19) that is connected to the microchip (7) and measures the temperature of the eye, and in that the microchip (7) generates data from the electrical signals of the temperature sensor (19), which data is transmitted by the antenna (8), using electromagnetic waves, to the receiver located outside the eye (2).

7. Implant according to claim 1, wherein the antenna (8) consists of an electrical coil that surrounds the microchip (7) provided with the pressure sensor (6).

8. Implant according to claim 1, wherein the implant (1) is coated with a pharmacologically active substance, wherein the pharmacologically active substance includes one of heparin or mytocin C, in order to prevent reactions of the eye such as inflammation, coagulation, tissue formation or encapsulation that would be detrimental either to the eye or to the pressure measurement.

9. Implant according to claim 1, wherein, operating as an active RFID tag, the implant (1) is provided with a data store in order to carry out measurements autonomously and to save the measurement data in the data store until the data are retrieved, by means of a radio link, by a reader located outside the eye (2).

10. Implant according to claim 1, wherein the housing (11) comprises nubs on the outer housing side (16).

11. Implant according to claim 1, wherein the housing (11) is concave on the outer housing side (16) thereof facing the choroid (4)

12. A method of measuring intraocular pressure comprising the steps of: providing a pressure measurement arrangement comprising an implant (1) according to claim 1; and providing a reader arranged outside the eye (2) for receiving measurement data that are transmitted by the implant (1) via a radio link to a receiver of the reader, wherein the reader is provided with a timer, an air pressure sensor and a data store, and provides the air pressure data of the air pressure sensor with a time stamp and saves the data in the data store in order to temporally assign the saved air pressure data to the intraocular pressure measurement data delivered by the implant (1) and to correct the air pressure data, with respect to air pressure influences, to the intraocular pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Embodiments of the invention are explained in more detail below with reference to the figures, in which, in detail:

[0027] FIG. 1 is a cross section of an eye comprising an inserted implant;

[0028] FIG. 2 is a detail A from FIG. 1 comprising the implant inserted in a pocket between the sclera and choroid;

[0029] FIG. 3 is a greatly enlarged plan view of an implant according to the invention;

[0030] FIG. 4 is a side view of the implant from FIG. 3;

[0031] FIG. 5 is a side view of a second embodiment of the implant having concave and convex lateral faces.

[0032] An implant 1 according to the invention is shown in all figures and is intended to be implanted in an animal or human eye 2. The outer wall of the eye 2 is formed by the sclera 3, the inner side of which is adjacent to the choroid 4 that lies beneath it. As can be seen best in FIG. 2, the implant 1 lies in a cavity 5 that is shaped like a pocket and is formed in the suprachoroidal region between the sclera 3 and the choroid 4.

[0033] The implant 1 can be positioned ab interno transversely through the anterior chamber of the eye 2 by means of a surgical approach through the iridocorneal angle to the implantation site. Alternatively, the implant can be positioned through the sclera 3 by making the smallest incision possible, in practice approximately 5 mm long, through the sclera 3. In this way, the incision can either extend directly perpendicularly, which may require subsequent wound closure, or it can be a lamellar incision and therefore self-closing. The incision is made in the region of or behind the pars plana, for example in parallel with the ora serrata. Subsequently, a cavity or pocket 5 is formed in the suprachoroidal space between the sclera 3 and the choroid 4, using a viscoelastics material such as hyaluronic acid which is injected using an atraumatic cannula. The implant 1 can now be introduced into the pocket 5 using forceps or the insertion tool 20 described below. If required, the implant 1 is rotated inside the pocket 5 in the direction of rotation 32 by 90° about its vertical axis, which is possible due to the fact that the different layers of the eyeball merely lie on top of one another but are not stuck together.

[0034] The stability of the eye's shape is due to the intraocular pressure. Rotating the implant has the advantage of allowing the telemetry coil 8 contained in the implant to be brought into an advantageous position, as far forward as possible and directly behind the pars plana, the long side being in parallel therewith. The implant 1 is thus either in parallel with the viewing direction 9 and therefore aligned with the optical axis of the eye 2, or it is rotated by 90° relative to the viewing direction 9 and therefore oriented in parallel with the pars plana. The aim is to position the implant as far forward as possible so that it can be reached as easily as possible by the telemetry.

[0035] The surgically produced sclera aperture does not necessarily have to be closed after the implant 1 has been positioned. Normally, the sclera will grow back of its own accord without further intervention. If required, however, it can be closed by means of a suture, biological adhesive, or the like.

[0036] As can be seen best in FIGS. 3 and 4, the implant 1 has an electrical pressure sensor 6 for measuring the intraocular pressure, a microchip 7 on which the pressure sensor 6 is attached and connected to the microchip 7, and an antenna 8 in the form of an electrical coil that is made of insulating gold wire and supported by spacers 10. The gold wire is wound around the microchip 7 in a plurality of turns. The housing 11 of the implant 1 is moulded from synthetic resin or formed of silicone rubber, the above-mentioned components being enclosed therein. In particular, the implant could, for example, be embedded in a plurality of layers of silicone rubber having varying degrees of hardness in order to achieve greater stability. In this case, a sensor-side layer is made of softer material and a back layer is made of harder material. The housing 11 is flat and elongate and is in the shape of a cuboid having rounded corners and edges, and nubs on one housing side. The length 12 of the housing 11 is approximately 6 mm, its width 13 is approximately 3 mm and its thickness 14 is approximately 1.5 mm. The housing 11 is provided with three nubs 17 on an outer housing side 15 that faces the sclera 3 of the eye 2 in the implanted state, the nubs being arranged in the manner of the corners of a triangle. As a result, the same implant 1 can be used for eyes 2 of varying sizes, the sclera 3 of which is concavely curved to varying degrees on its inner side without the degree of curvature having a significant influence on the mechanical tension to which the implant 1 is exposed in the eye 2. As a result, the accuracy of the pressure measurement is improved.

[0037] The pressure sensor 6 is arranged on the other outer housing side 16 of the housing 11 that faces the choroid 4 in the implanted state. A flexible membrane 18 is located between the pressure sensor 6 and the choroid 4 as a protective layer against ingress of liquid. The membrane 18 presses against the pressure-sensitive surface of the pressure sensor 6 and, on the other side, against the choroid 4. The pressure sensor 6 is thus in full-surface contact with the choroid 4 via the membrane 18.

[0038] The implant 1 lies in the eye 2 in a tension-free manner between the sclera 3 and the choroid 4. Due to physiological ocular pressure and force relationships, the intraocular pressure also fixes the implant 1 in place by means of the choroid 4. The choroid 4 lies on the membrane 18 of the planarly extended pressure sensor 6 as a thin, soft choroid coat. As a result, the coupling between the pressure sensor 6 and the aqueous humour of the vitreous body of the eye 2 is not, or is only insignificantly, affected. The implant 1 therefore does not measure the pressure in the suprachoroidal space, but rather in the inner eye.

[0039] Furthermore, the implant 1 is provided with a temperature sensor 19 that is attached to the microchip 7. The temperature sensor 19 is used for measuring the temperature of the eye in the suprachoroidal space. Just like the electrical signals of the pressure sensor 6, the electrical signals of the temperature sensor 19 are registered by the microchip 7 and digital data are generated in which the temperature values and pressure values are encoded. The digital data are transmitted by the antenna 8, using electromagnetic waves, to a receiver located outside the eye 2. The pressure and temperature data can be saved in and analysed by the receiver. Analysis of the temporal progression of the pressure or temperature is thus also possible.

[0040] In a variant, as shown in FIG. 5, the outer housing side 16 of the housing 11 of the implant 1 that faces the choroid can be concave. The outer housing side 15 of the housing 11 opposite the sclera 3 is convex in the embodiment shown. The design can take one form or the other, depending on the requirements. Thus, the convex and concave sides can also be arranged vice versa, or both sides can be convex or both sides can be concave.

LIST OF REFERENCE NUMERALS

[0041] 1 Implant [0042] 2 Eye [0043] 3 Sclera [0044] 4 Choroid [0045] 5 Pocket/cavity [0046] 6 Pressure sensor [0047] 7 Microchip [0048] 8 Antenna/coil [0049] 9 Viewing direction [0050] 10 Spacer [0051] 11 Housing [0052] 12 Length [0053] 13 Width [0054] 14 Thickness [0055] 15 Outer housing side [0056] 16 Outer housing side [0057] 17 Nubs [0058] 18 Membrane [0059] 19 Temperature sensor