GB2374925A

GB2374925A - Pressure detectors

Info

Publication number: GB2374925A
Application number: GB0110045A
Authority: GB
Inventors: Anant Sharma
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-04-24
Filing date: 2001-04-24
Publication date: 2002-10-30
Also published as: GB0110045D0

Abstract

An intraocular pressure sensor comprises a transducer 1 surgically inserted in an eye 2 of a patient. The transducer 1 is powered by a battery or a solar cell located within the eye 2. The transducer 1, either continuously or intermittently, emits radiation which varies in amplitude or wavelength in accordance with intraocular pressure. An external detector 4 senses the emitted radiation and generates an output calibrated to give a pressure reading. Alternatively, the transducer is passive with no power supply. The transducer responds to an external source of radiation by producing a return beam of radiation which varies in accordance with intraocular pressure. The transducer may deform and reflect or refract the incident beam of radiation, in which case the direction of the return beam determines the pressure measurement. Alternatively, the transducer comprises a chemical which fluoresces in dependence on intraocular pressure.

Description

PRESSURE SENSORS The present invention relates to pressure sensors, and more particularly to pressure sensors which can be located within the body to measure the intracorporal pressure. In particular, the present invention relates to pressure sensors which can be inserted into an eye of a patient in order to measure the intraocular pressure.

It is desirable to measure the intraocular pressure of patients suffering from glaucoma, and indeed also patients considered at risk from such a condition, such as relatives of those suffering from glaucoma.

With conventional intraocular pressure sensors, the intraocular pressure is sensed externally to the eye, such as by applying a stream of gas under pressure to the outer surface of the eye and measuring either the resultant instantaneous deformation of the surface or the time taken for the surface of the eye to regain its previous configuration.

However, such a measurement of intraocular pressure is necessarily indirect. Furthermore, such a sensor is capable of measuring only the instantaneous pressure at any given time and cannot easily measure pressure variations.

It would therefore be desirable to provide a sensor which can sense intraocular pressure more directly than has hitherto been possible.

In accordance with a first aspect of the present invention there is provided a sensor for measuring an intracorporal pressure-dependent parameter comprising means, located in use within a region of the body, and responsive to the intracorporal pressure in said region, for generating an output in the form of electromagnetic radiation which can be sensed from a position external to the body.

The sensor is preferably arranged for measuring an intraocular pressure-dependent parameter, the pressure-responsive means being located in use within the eye so as to be responsive to the intraocular pressure.

Such an intraocular pressure sensor can be inserted or sutured into the eye as a separate unit or can form a part of an intraocular lens implanted into the eye routinely, such as after cataract surgery, or it can form part of any other intraocular implant.

The electromagnetic radiation of the output may be within the radio-frequency range or, in the case of an intraocular pressure sensor, may alternatively comprise visible radiation.

The sensor preferably comprises a body which deforms by an amount in dependence on the pressure and which is arranged to generate the output which varies in dependence on the degree of deformation.

In accordance with a second aspect of the present invention there is provided a sensor for measuring an intracorporal pressure-dependent parameter comprising means, located in use within a region of the body, and responsive to the intracorporal pressure in said region for affecting a beam of incident radiation by an amount in dependence on the pressure, the arrangement being such that the intracorporal pressure-dependent parameter can be measured by irradiating the said region of the body and measuring a property of the affected radiation emerging from the said region.

The sensor preferably comprises means, such as a chemical substance, which fluoresces in response to the incident radiation by an amount dependent on the intracorporal pressure.

The sensor may alternatively comprise means arranged either to refract or to reflect the incident radiation by an amount dependent on the intracorporal pressure.

The sensor is preferably sensitive to pressures within the range 10 mmHg below atmospheric pressure to 80 mmHg above atmospheric pressure and may be sensitive to pressures up to 200 mmHg above atmospheric pressure.

The pressure-dependent parameter may be : the relative value of the absolute intracorporal pressure and a predetermined pressure value, such as pressure above atmospheric pressure ; the gradient of the intracorporal pressure, or indeed any higher derivative ; a change of pressure with respect to time ; a time-averaged value of the intracorporal pressure ; or the maximum or minimum value of the intracorporal pressure within a predetermined measurement period.

The sensor may be arranged to generate an output only when the intracorporal pressure is greater than a predetermined value.

Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein : Figure 1 illustrates schematically in cross-section a first embodiment of the present invention ; and Figure 2 illustrates schematically in cross-section a second embodiment of the present invention.

With reference to Figure 1, an intraocular pressure sensor in accordance with a first embodiment is in the form of a pressure transducer I which has been surgically inserted in an eye 2 of a patient. The transducer 1 is powered by an electrical power supply in the form of a battery 3 located within the eye 2, which is able to supply power to the transducer 1 for in excess of twenty years.

The shape of the transducer 1 is cubic, having a side length of approximately 3 mm, although the transducer could alternatively be spherical with a diameter of approximately 3 mm.

The battery 3 enables the transducer 1 to emit radiation which varies in accordance with the instantaneous value of the intraocular pressure. The variation may be in amplitude or wavelength or indeed any other parameter which can be sensed. A suitable detector 4 placed externally to the eye at the time of measurement senses the radiation emitted from

the transducer 2 and generates an output signal which is calibrated to give a reading in terms of intraocular pressure. The radiation may be emitted from the transducer 1 either continuously or intennittently.

In a first variation of the first embodiment, the power supply comprises a solar cell located either within the eye or externally.

In a second variation of the first embodiment, the power supply comprises a battery located within the eye and arranged to be recharged by a solar cell located either within theeye or externally.

With reference to Figure 2, an intraocular pressure sensor in accordance with a second embodiment is also in the form of a pressure transducer 5 which has been surgically inserted in an eye 6 of a patient and having the same over-all shape and size as the first embodiment. However, the transducer 5 is passive, in that no power supply is required.

During measurement, an incident beam of radiation of a suitable wavelength is applied to the transducer 5 from a radiation source 7 located externally to the eye 6, and the transducer 5 responds to the incident beam of radiation by producing a return beam of radiation which varies in accordance with the instantaneous value of the intraocular pressure, and the return beam of radiation is sensed by a detector 8. The transducer 5 may respond to intraocular pressure by deformation and may therefore simply reflect or refract the incident beam of radiation, in which case the direction of the return beam is determined in order to provide a measurement of the intraocular pressure. Alternatively, the transducer 5 may comprise a chemical substance which fluoresces by an amount dependent on the intraocular pressure, and the intensity and/or the wavelength of the return beam is determined in order to provide the required measurement.

In both of the above-described embodiments, the sensors are capable of measuring intraocular pressure within the range of 10 mmHg below atmospheric pressure to 80 mmHg above atmospheric pressure, this range being the normal range of pressure encountered in the human eye.

Although the present invention has been described with reference to two specific embodiments, it will be apparent that numerous variations are contemplated and that the scope of the invention is to be determined in accordance with the claims appended hereto. Thus, for example, the present invention is not limited to sensors for measuring intraocular pressure-dependent parameters, but extends to sensors for measuring any intracorporal pressure-dependent parameters, such as blood pressure.

Claims

CLAIMS: 1. A sensor for measuring an intracorporal pressure-dependent parameter comprising means, located in use within a region of the body, and responsive to the intracorporal pressure in said region, for generating an output in the form of electromagnetic radiation which can be sensed from a position external to the body.
2. A sensor as claimed in claim 1 and arranged for measuring an intraocular pressure- dependent parameter, the pressure-responsive means being located in use within the eye so as to be responsive to the intraocular pressure.
3. A sensor as claimed in claim 1 or claim 2, wherein the electromagnetic radiation of the output is within the radio-frequency range.
4. A sensor as claimed in claim 2, wherein the electromagnetic radiation of the output comprises visible radiation.
5. A sensor as claimed in an preceding claim, comprising a body which deforms by an amount in dependence on the pressure and which is arranged to generate the output which varies in dependence on the degree of deformation.
6. A sensor for measuring an intracorporal pressure-dependent parameter comprising means, located in use within a region of the body, and responsive to the intracorporal pressure in said region for affecting a beam of incident radiation by an amount in dependence on the pressure, the arrangement being such that the intracorporal pressure-dependent parameter can be measured by irradiating the said region of the body and measuring a property of the affected radiation emerging from the said region.
7. A sensor as claimed in claim 6 and arranged for measuring an intraocular pressure- dependent parameter, the pressure-responsive means being located in use within the eye so as to be responsive to the intraocular pressure.

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8. A sensor as claimed in claim 6 or claim 7, wherein the sensor comprises means which fluoresces in response to the incident radiation by an amount dependent on the intracorporal pressure.
9. A sensor as claimed in claim 6 or claim 7, wherein the sensor comprises means which is arranged to refract the incident radiation by an amount dependent on the intracorporal pressure.
10. A sensor as claimed in claim 6 or claim 7, wherein the sensor comprises means which is arranged to reflect the incident radiation by an amount dependent on the intracorporal pressure.
11. A sensor as claimed in any preceding claim and arranged to be sensitive to pressures within the range 10 mmHg below atmospheric pressure to 80 mmHg above atmospheric pressure.
12. A sensor as claimed in any preceding claim and arranged to be sensitive to pressures within the range 10 mmHg below atmospheric pressure to 200 mmHg above atmospheric pressure.
13. A sensor as claimed in any preceding claim, wherein the pressure-dependent parameter comprises the relative value of the absolute intracorporal pressure and a predetermined pressure value.
14. A sensor as claimed in any one of claims 1 to 12, wherein the pressure-dependent parameter comprises the gradient of the intracorporal pressure.
15. A sensor as claimed in any one of claim 1 to 12, wherein the pressure-dependent parameter comprises a time-averaged value of the intracorporal pressure.
16. A sensor as claimed in any one of claim 1 to 12, wherein the pressure-dependent

I parameter comprises the maximum or minimum value of the intracorporal pressure within a predetermined measurement period.

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17. A sensor as claimed in any one of claims 1 to 12, and arranged to generate an output only when the intracorporal pressure is less than a predetermined value.
18. A sensor as claimed in any one of claims 1 to 12, and arranged to generate an output only when the intracorporal pressure is greater than a predetermined value.
19. A sensor substantially as hereinbefore described with reference to the accompanying drawings.