WO2017167670A1 - Lentille de contact, système et procédé de mesure d'une caractéristique physiologique d'un œil d'un sujet - Google Patents

Lentille de contact, système et procédé de mesure d'une caractéristique physiologique d'un œil d'un sujet Download PDF

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Publication number
WO2017167670A1
WO2017167670A1 PCT/EP2017/057139 EP2017057139W WO2017167670A1 WO 2017167670 A1 WO2017167670 A1 WO 2017167670A1 EP 2017057139 W EP2017057139 W EP 2017057139W WO 2017167670 A1 WO2017167670 A1 WO 2017167670A1
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WO
WIPO (PCT)
Prior art keywords
contact lens
eye
light
force
antenna
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Application number
PCT/EP2017/057139
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English (en)
Inventor
Kiran Hamilton J. DELLIMORE
Koray Karakaya
Susanne Maaike VALSTER
Ron Martinus Laurentius Van Lieshout
Original Assignee
Koninklijke Philips N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Koninklijke Philips N.V. filed Critical Koninklijke Philips N.V.
Publication of WO2017167670A1 publication Critical patent/WO2017167670A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
    • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
    • A61B3/16—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for measuring intraocular pressure, e.g. tonometers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
    • G02B1/041—Lenses
    • G02B1/043—Contact lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C7/00—Optical parts
    • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
    • G02C7/04—Contact lenses for the eyes
    • G02C7/049—Contact lenses having special fitting or structural features achieved by special materials or material structures

Definitions

  • the invention relates to a contact lens for use in measuring a physiological characteristic of an eye of a subject and a system and a method of measuring a physiological characteristic of an eye of a subject.
  • Aqueous humor or aqueous fluid
  • IOP intraocular pressure
  • Elevated IOP is of great concern because it can lead to optic nerve damage and is the clinically established risk factor for the development of glaucoma (i.e., a condition of increased pressure within the eyeball, causing gradual loss of sight) or even to permanent vision loss.
  • Normal (i.e. healthy) IOP ranges between 10-21 mm Hg, while ocular hypertension is diagnosed if the IOP is > 21 mmHg in one or both eyes (measured on 2 or more occasions).
  • there can be a significant diurnal variation in the IOP throughout the course of a day which can make diagnosing ocular hypertension and glaucoma challenging.
  • Elevation in the pressure of the aqueous humor, leading to ocular hypertension, can occur as a result of several factors:
  • Eye trauma - Blunt or chemical injury to the eye can affect the balance of aqueous production and drainage from the eye, leading to ocular hypertension. Sometimes this can occur months or even years after the injury has occurred.
  • Eye conditions and diseases e.g., pseudoexfoliation syndrome, pigment dispersion syndrome, uveitis and corneal arcus.
  • 5.5g (55 mN) is applied to produce corneal indentation, with up to 15g (150 mN) applied in some cases.
  • This is accomplished by gently placing a disinfected prism mounted on a tonometer head against the cornea, which is then observed by the examiner using a cobalt blue filter to view two green semi circles.
  • the force applied to the tonometer head is then adjusted using a dial connected to a variable tension spring until the inner edges of the green semicircles in the viewfmder meet.
  • an area of 3.06 mm 2 has been flattened, the opposing forces of corneal rigidity and the tear film are roughly approximate and cancel each other out allowing the IOP in the eye to be determined from the force applied based on the Imbert-Fick law:
  • non-contact air puff tonometry This works by measuring the time from the generation of an air puff until the cornea is flattened or applanated, which is detected via an electro-optical system. Higher IOP is indicated by a longer time taken to flatten the eye.
  • non-contact tonometers have two drawbacks: 1) they require topical anaesthesia administration, and 2) they are not considered to be an accurate way to measure IOP but instead a fast and simple way to screen for high IOP.
  • non-contact tonometers have been shown to correlate well with Goldmann tonometry measurements and are particularly useful for measuring IOP in children and other non-compliant patient groups.
  • a variation of the non-contact air puff tonometer is the ocular response analyzer which does not require topical anaesthesia and provides additional information on the biomechanical properties of the cornea. It uses an air pulse to deform the cornea into a slight concavity. The difference between the pressures at which the cornea flattens inward and outward is measured by the machine.
  • a contact lens for use in measuring a physiological characteristic of an eye of a subject; the contact lens comprising a first material, wherein the first material is such that a property of the first material changes in response to incident light, and wherein the first material is arranged such that, when the contact lens is worn on the eye and light is incident on the first material, the contact lens applies a force to the eye.
  • the contact lens enables a force to be applied to the eye of the subject in a relatively unobtrusive manner, since the contact lens, which is already generally unobtrusive for the wearer, can be actuated to generate the force through the use of light.
  • the property of the first material changes in response to incident light having a particular wavelength or wavelengths. This has the advantage that the application of the force by the contact lens will only be triggered by light of the particular wavelength or wavelengths.
  • the property of the first material that changes in response to incident light is the shape and/or size of the first material.
  • the change in the size and/or shape of the first material is any of an increase in the size/length of the first material when light is incident on the first material, a decrease in the size/length of the first material when light is incident on the first material, an increase in the volume of the first material when light is incident on the first material, or a decrease in the volume of the first material when light is incident on the first material.
  • the first material is a light-responsive polymer.
  • the light-responsive polymer is a nano-composite film, a liquid-crystalline elastomer, a polymer with liquid crystals, an azobenzene- or spiropyran- or Triphenylmethane-based system, salicylideneaniline, or a polypeptide-based system, or any combination thereof.
  • the property of the first material that changes in response to incident light is the wettability of the first material.
  • the first material is a light-responsive polymer.
  • the light-responsive polymer is a polymer comprising or containing spiropyran moieties grafted onto membrane surfaces.
  • the contact lens is formed entirely from the first material. This can make the contact lens easier to manufacture.
  • the contact lens comprises one or more regions or layers of the first material. These regions or layers can be arranged to provide a required force by the contact lens in response to incident light.
  • the contact lens further comprises one or more regions of a hydrophilic material.
  • the one or more regions of the hydrophilic material are located on a side of the contact lens that is arranged to contact the eye. This has the advantage that the one or more regions of the contact lens will grip the liquid on the eye and improve the transfer of the force to the eye.
  • the contact lens further comprises one or more regions of a hydrophobic material. These one or more regions, in combination with the one or more regions of the hydrophilic material, can also improve the transfer of the force to the eye.
  • the contact lens further comprises two or more visible markings, and wherein the visible markings are arranged so that the spacing therebetween changes when the contact lens is being used to apply the force to the eye.
  • the contact lens further comprises a radio frequency
  • RF, antenna have the advantage that an indication of the response of the eye to the applied force can be communicated from the RF antenna to an external reader device.
  • the RF antenna is arranged such that a characteristic of the RF antenna changes when the contact lens is being used to apply the force to the eye.
  • the RF antenna is used to sense the response of the eye to the applied force, and no separate sensor for sensing the response of the eye is required.
  • a system for measuring a physiological characteristic of an eye of a subject comprising a contact lens as described above; a light source; a measurement device for measuring the response of the eye to the applied force; and a control unit for analyzing the measured response of the eye to determine a measurement of the physiological characteristic.
  • the measurement device is an imaging device that is configured to obtain one or more images of the eye and the contact lens.
  • control unit is configured to analyze the one or more images of the eye and the contact lens to determine a change in specular reflection from the surface of the contact lens when the force is applied to the eye by the contact lens.
  • the contact lens further comprises two or more visible markings, and wherein the visible markings are arranged so that the spacing therebetween changes when the contact lens is applying the force to the eye, and wherein the control unit is configured to analyze the one or more images of the eye and the contact lens to determine a change in the spacing between the visible markings when the force is applied to the eye by the contact lens.
  • control unit is configured to analyze the one or more images of the eye and the contact lens to determine a change in an interference pattern for the contact lens due to differences in light reflection from the front and back of the contact lens when the force is applied to the eye by the contact lens.
  • the contact lens further comprises a radio frequency, RF, antenna;
  • the measurement device is a reader unit that is configured to receive a signal from the contact lens; and the control unit is configured to analyze the received signal to determine the measurement of the physiological characteristic.
  • a method of measuring a physiological characteristic of an eye of a subject comprising illuminating a contact lens worn on the eye of the subject with light, wherein the contact lens comprises a first material and the first material is such that a property of the first material changes in response to the light, and wherein the first material is arranged such that the contact lens applies a force to the eye in response to the light; measuring a response of the eye of the subject to the applied force; and determining a measurement of the physiological characteristic using the measured response.
  • the method enables a force to be applied to the eye of the subject in a relatively unobtrusive manner through the use of light to actuate the contact lens, and a physiological characteristic of the eye can be measured from the response of the eye to the applied force.
  • the step of measuring comprises obtaining one or more images of the eye and the contact lens.
  • the step of determining the measurement of the physiological characteristic comprises analyzing the one or more images of the eye and the contact lens to determine a change in specular reflection from the surface of the contact lens when the force is applied to the eye by the contact lens.
  • the contact lens further comprises two or more visible markings, and wherein the visible markings are arranged so that the spacing therebetween changes when the contact lens is applying the force to the eye, and wherein the step of determining the measurement of the physiological characteristic comprises analyzing the one or more images of the eye and the contact lens to determine a change in the spacing between the visible markings when the force is applied to the eye by the contact lens.
  • the step of determining the measurement of the physiological characteristic comprises analyzing the one or more images of the eye and the contact lens to determine a change in an interference pattern for the contact lens due to differences in light reflection from the front and back of the contact lens when the force is applied to the eye by the contact lens.
  • the contact lens further comprises a radio frequency, RF, antenna; the step of measuring comprises receiving a signal from the contact lens; and the step of determining the measurement of the physiological characteristic comprises analyzing the received signal to determine the measurement of the physiological characteristic.
  • the contact lens can be as described in any of the embodiments of the first aspect described above.
  • Figure 1 is an illustration of a contact lens according to the invention
  • Figure 2 is an illustration of the use of a contact lens according to the invention to apply force
  • Figure 3 is an illustration of a contact lens according to a first specific embodiment
  • Figure 4 is an illustration of a contact lens according to a second specific embodiment
  • Figure 5 is an illustration of a contact lens according to a second specific embodiment
  • Figure 6 is a flow chart illustrating a method of measuring a physiological characteristic of an eye of a subject according to the invention
  • Figure 7 is an illustration of a first exemplary system for measuring a physiological characteristic of an eye of a subject
  • Figure 8 is an illustration of a second exemplary system for measuring a physiological characteristic of an eye of a subject
  • Figure 9 is an illustration of a contact lens comprising an antenna according to an exemplary embodiment.
  • Figure 10 is a flow chart illustrating a method of measuring a physiological characteristic of an eye of a subject according to an embodiment.
  • measuring intraocular pressure remains a generally obtrusive process for the subject.
  • IOP intraocular pressure
  • the invention provides a contact lens that can be used to apply a force to an eye of a subject for the purposes of measuring IOP, or for measuring any other physiological characteristic of the eye in which a force is to be applied to the eye to make the measurement.
  • a contact lens or a pair of contact lenses
  • the contact lens according to the invention is configured so that a force can be selectively applied by the contact lens when an IOP (or other physiological characteristic) measurement is to be made. Since the force required to make the IOP measurement is relatively small, the IOP measurement can be made almost or completely unobtrusively for the subject.
  • Figure 1 illustrates a contact lens 2 according to a general embodiment of the invention.
  • Figure 1(a) shows a front view of the contact lens 2
  • Figure 1(b) shows a side view of the contact lens 2.
  • the term "contact lens” should be understood to refer to any device that is suitable for wearing in or on the eye for an extended period of time. It should be appreciated that contact lenses according to embodiments of the invention are preferably, but need not be, transparent.
  • the contact lens 2 is generally circular with a concave curvature configured to contact a corneal surface of an eye.
  • the contact lens 2 comprises a material 4 that is responsive to light.
  • the material 4 which is also referred to herein as a 'first' material, is responsive to light in the sense that a property of the material 4 changes when light is incident on the contact lens 2.
  • the property of the material 4 that changes should be a property that can lead to a force or strain being generated by the contact lens 2.
  • the first material 4 can be responsive to a particular wavelength or wavelengths of light (so the property of the material 4 only changes when light of a particular wavelength or wavelengths illuminates the material 4).
  • the material 4 is responsive to light with a wavelength between 400-475 nm, e.g. in the blue/violet part of the visible spectrum.
  • the material 4 is responsive to light with a wavelength corresponding to the green and/or red (or infra-red) parts of the spectrum. It will be appreciated that the wavelength or wavelengths of light that the material 4 is responsive to can depend on the specific nature/type and/or configuration of the material 4.
  • the property of the material 4 that changes in response to incident light can be the shape and/or size of the material 4. Therefore, illuminating the contact lens 2 (and in particular the first material 4 in the contact lens 2) with light (or light of a particular wavelength or wavelengths) can cause the shape and/or size of the material 4 to change in response to light, which can apply a force to the eye of the subject.
  • the change in the size and/or shape of the material 4 can be any of an increase in the size/length of the material 4 when light is incident on the first material 4, a decrease in the size/length of the material 4 when light is incident on the first material 4, an increase in the volume of the material 4 when light is incident on the first material 4, or a decrease in the volume of the material 4 when light is incident on the first material 4.
  • Figure 2 is an illustration of the use of a contact lens 2 according to the invention to apply force.
  • the contact lens 2 is in a 'relaxed' state, i.e. the contact lens 2, when worn by a subject, does not apply any force, or any appreciable force, to the eye of the subject.
  • this state light of the particular wavelength or wavelengths is not incident on the contact lens 2 (or light at the particular wavelength or wavelengths is incident on the contact lens 2 but below an intensity level required to actuate the first material 4).
  • the shape and/or size of the first material 4 changes so that the shape of the contact lens 2 moves into a 'force' state in which the contact lens 2 applies a force F to the eye.
  • the change in the shape and/or size of the first material 4 results in a contraction in the diameter of the contact lens 2 and the eye being squeezed by the contact lens 2.
  • the effect of the change in size and/or shape of the first material 4 on the shape of the contact lens 2 can depend on the arrangement or configuration of the first material 4 in the contact lens and the nature of the change in size and/or shape of the first material 4 in response to the incident light.
  • the change in size and/or shape from the state shown in Figure 2(a) to the state shown in Figure 2(b) can be relatively instantaneous, or take up to a few seconds, depending on the nature/type and/or configuration of the first material 4.
  • the first material 4 can be a light-responsive polymer, i.e. a polymer that is responsive to light.
  • the light-responsive polymer can be a nano-composite film, a liquid-crystalline elastomer, another form of polymer with liquid crystals, an azobenzene- or spiropyran- or Triphenylmethane-based system,
  • salicylideneaniline or a polypeptide-based system, or any combination thereof.
  • the property of the material 4 that changes in response to incident light is the wettability of the material 4. Therefore, illuminating the contact lens 2 (and in particular the first material 4 in the contact lens 2) with light (or light of a particular wavelength or wavelengths) can cause the wettability of the material 4 to change in response to light, which can apply a force to the eye of the subject. Good wettability is important for force transfer between the contact lens 2 and the eye.
  • the material 4 can be such that the incident light changes the surface of the contact lens 2 such that it switches between hydrophilic and hydrophobic states, and the switching between these two states will enable a stable, reproducible contact between the eye and the contact lens 2.
  • the first material 4 can be a light-responsive polymer, for example a polymer comprising or containing spiropyran moieties grafted onto membrane surfaces, which exhibit reversible wettability- switching and protein adhesion.
  • the first material 4 can have a known response to incident light, and therefore the force applied by the contact lens 2 to the eye can be controlled through the selective illumination of the contact lens 2 with light.
  • a contact lens 2 according to the invention shown in Figures 1 and 2 can be used to apply a force of the order of 5-200 milliNewtons (mN) to the eye. This amount of force is sufficient to measure IOP, since in Goldmann tonometry forces in the region of 55mN and 150mN are used.
  • mN milliNewtons
  • the first material 4 may be such that on removal of the incident light, the property of the first material 4 reverts to an original value or state (e.g. an original size and/or shape or wettability).
  • the first material 4 may be such that the property of the first material 4 reverts to an original value or state (e.g. an original size and/or shape or wettability) on application of light of a different wavelength, or white light.
  • the contact lens 2 can be formed entirely from the first material 4, but in other embodiments the contact lens 2 can be formed partly from the first material 4, and partly from one or more other materials. These other materials can be materials that are conventionally used to construct and form contact lenses.
  • the other materials can include a silicone hydrogel.
  • the contact lens 2 is partly formed from the first material 4, the contact lens 2 can comprise one or more regions of first material 4, and/or the contact lens 2 can comprise one or more layers of first material 4 within the structure of the contact lens 2.
  • Figure 3 illustrates a contact lens 2 according to a first specific embodiment of the invention.
  • the contact lens 2 comprises a plurality of regions 8 made from the first material 4.
  • the rest of the contact lens 2 is formed from a second material (e.g. a conventional material used in contact lenses).
  • the contact lens 2 comprises eight regions 8 of the first material 4 spaced generally evenly around the contact lens 2.
  • the first material 4 when light is incident on the first material 4, the first material 4 reduces in size and results in the diameter of the contact lens 2 being reduced, as indicated by arrows 10. This reduction in size squeezes the eye behind/underneath the contact lens 2 (i.e. applies a force to the eye).
  • the arrangement shown in Figure 3 is merely exemplary, and other arrangements and
  • configurations of the first material 4 can be used.
  • the contact lens 2 can comprise one or more regions of a hydrophilic material.
  • the one or more regions of hydrophilic material can be located at least on the side of the contact lens 2 that is in contact with the eye during use. As the surface of the eye is covered with a liquid (the tear film), the hydrophilic material will therefore grip the liquid and thus the eye more than a hydrophobic material (which would repel the liquid).
  • the hydrophilic material and the first material 4 can be located in different parts of the contact lens 2 or in different layers of the contact lens 2.
  • the first material 4 can be a hydrophilic material.
  • FIG. 4 An exemplary embodiment of a contact lens 2 comprising a hydrophilic material is shown in Figure 4.
  • the contact lens 2 comprises a first material 4 as described above, and a region 12 of hydrophilic material arranged around the periphery of the contact lens 2.
  • Region 12 is shown as an annulus in Figure 4, but it will be appreciated that region 12 can take other shapes, and/or multiple regions 12 can be provided.
  • the annulus 12 of hydrophilic material improves the grip of the contact lens 2 to the eye, and thereby improves the application of the force to the eye.
  • the contact lens 2 can also include one or more regions
  • the region 14 is located in the center of the contact lens 2, but it will be appreciated that the region 14 can take different shapes and/or locations as desired.
  • FIG. 5 Another exemplary embodiment of a contact lens 2 comprising a hydrophilic material is shown in Figure 5.
  • the contact lens 2 comprises a plurality of regions 16 of hydrophilic material that are interspersed with a plurality of regions 18 of hydrophobic material.
  • Figure 6 illustrates a method of measuring a physiological characteristic of an eye of a subject according to an embodiment of the invention. This method measures a physiological characteristic of the eye using any of the contact lenses 2 described above. In preferred embodiments, the physiological characteristic is the IOP of the eye.
  • the physiological characteristic is a property of the tear film on the eye, for example the stability of the tear film, a volume of the tear film, a thickness of the tear film, a change in the thickness of the tear film, a thickness or relative thickness of one or more particular layers of the tear film (e.g. lipid layer, intermediate layer or mucin layer), a change in the thickness or relative thickness of one or more particular layers of the tear film, the recovery of the tear film following the application of a force, a rheological property of the tear film, the viscosity of the tear film, or the break-up of the tear film.
  • the stability of the tear film for example the stability of the tear film, a volume of the tear film, a thickness of the tear film, a change in the thickness of the tear film, a thickness or relative thickness of one or more particular layers of the tear film (e.g. lipid layer, intermediate layer or mucin layer), a change in the thickness or relative thickness of one or more particular layers of the tear film, the recovery of the tear film following
  • a contact lens 2 worn on the eye of the subject is illuminated with light.
  • the contact lens 2 comprises a first material 4 and the first material 4 is such that a property of the first material 4 changes in response to the light.
  • the light may be of a particular wavelength or a wavelength selected from a range of particular wavelengths, and causes the contact lens 2 to apply a force to the eye.
  • a response of the eye to the applied force is measured (step 103).
  • a measurement device is provided that is able to measure the response of the eye to the applied force.
  • the measurement device comprises an imaging device that can be used to obtain images of the eye and contact lens 2, and the images are processed to identify changes in specular reflection and/or an interference pattern indicative of the response of the eye to the applied force.
  • the contact lens 2 can comprise a radio frequency (RF) antenna that is arranged in the contact lens 2 such that the strain in the antenna wire is changed by the shape of the eye, and a signal from the RF antenna can be measured by the measurement device and processed to determine the response of the eye to the applied force.
  • RF radio frequency
  • a measurement of the physiological characteristic e.g. IOP
  • IOP physiological characteristic
  • FIG 7 is an illustration of a first exemplary system for measuring a physiological characteristic of an eye of a subject in which the method of Figure 6 can be implemented.
  • the system comprises a contact lens 2 as described above that is to be worn on the eye 20 of a subject (it will be appreciated that the contact lens 2 is shown as spaced from the eye 20 in Figure 7 simply for ease of illustration), a light source 22 that is for emitting light towards the contact lens 2 in order to change the property of the first material 4 in the contact lens 2 and thereby apply a force to the eye 20.
  • the light source 22 can be configured to emit light at any required wavelength, and where the first material 4 is responsive to a particular wavelength or wavelengths of light, the light source 22 can be configured to emit light at one of those particular wavelengths.
  • the light source 22 can be any suitable type of light source, including one or more lasers or light emitting diodes, LEDs.
  • the light source 22 can be configured to be used in the vicinity of (i.e. near) the contact lens 2, e.g. within 10cm of the contact lens 2 or less. In other embodiments, the light source 22 can be configured to be used some distance from the contact lens, e.g. more than 10cm from the contact lens 2.
  • the light from the light source 22 can be coupled to the contact lens 2, or to a relevant part of the contact lens 2, using an optical waveguide, e.g. an optical fiber.
  • an optical waveguide e.g. an optical fiber.
  • a 'grating' can be provided that can couple the light to the contact lens 2.
  • the system also comprises a measurement device in the form of an imaging device 24 that is for obtaining one or more images of the eye and contact lens 2.
  • the imaging device 24 can obtain images before, during and after the force has been applied to the eye 20 by the contact lens 2.
  • the imaging device 24 can be a camera, or any other type of light sensitive apparatus.
  • the system also comprises a control unit that is connected to the imaging device 24 and that analyses the image or images obtained by the imaging device 20 to determine the physiological characteristic.
  • the control unit may also control the light source 22 to emit light in order to initiate the measurement of the
  • control unit may be provided in the same device as the imaging device 24, or it may be provided in a separate component of the system.
  • the control unit can be implemented in numerous ways, with software and/or hardware, to perform the required function(s).
  • the control unit may comprise one or more microprocessors that may be programmed using software to perform the required functions.
  • the control unit may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field- programmable gate arrays (FPGAs).
  • ASICs application specific integrated circuits
  • FPGAs field- programmable gate arrays
  • the control unit analyses the images to identify changes in specular reflection from the surface of the contact lens 2, i.e. changes in the reflection of light from the smooth surface of the contact lens 2.
  • the control unit determines a measure of the specular reflection from the contact lens 2 before the force is applied and a measure of the specular reflection from the contact lens 2 while the force is being applied.
  • the amount of change in the specular reflection from the relaxed state to the force-applying state provides an indication of the physiological characteristic to be measured. For example, where the physiological characteristic is IOP, the amount of change in the specular reflection from the relaxed state to the force-applying state provides an indication of the IOP. Higher IOP will lead to a smaller change in specular reflection (i.e.
  • the determined change in the specular reflection from the relaxed to the force-applying state can be compared to one or more threshold values to determine whether the determined change corresponds to a high, low, or healthy value of the IOP.
  • the threshold values can be specific to the subject, or based on averages of a population of healthy/unhealthy subjects.
  • specular reflection can be detected using slit-lamp photography or biomicroscopy of the ocular surface (which is sometimes used in clinical practice for assessing corneal damage, etc.).
  • the contact lens 2 can be provided with two or more visible lines or other markings thereon and the control unit can analyze the images of the contact lens 2 to determine the distance/spacing between the lines or other markings.
  • the change in the spacing from the relaxed state to the force- applying state (which is generally a decrease in the spacing if the contact lens 2 contracts to apply the force) provides an indication of the physiological characteristic to be measured.
  • the change in the spacing between the lines can be monitored as a function of the applied force. In the case of IOP, as noted above high or higher IOP results in less deformation of the eye 20 for a given applied force compared to lower IOP, which leads to a smaller decrease in spacing between the lines when the force is applied.
  • an absolute value for IOP by applying two different amounts of force to the eye of the subject and measuring the response of the eye (e.g. the change in the specular reflection or the change in line spacing) for each force.
  • the difference in the responses for each force can be correlated to an absolute value of IOP.
  • determining the change in shape of the contact lens 2 from the reflection measured from the lens surface or change in line spacing can be used to determine an absolute value of IOP.
  • light interference can be used to determine the measurement of the physiological characteristic.
  • changes of the interference (or wave propagation) pattern on the eye 20 and/or the contact lens 2 as a result of strain induced by the applied force can be determined by analyzing the images obtained by the imaging device 24.
  • This approach is based on the principle that leads to colors being visible on the surface of a soap bubble. For example colors are visible on a soap bubble as they arise from interference of light reflecting off the front and back surfaces of the thin soap film.
  • an interference pattern can be visible or otherwise measurable on a contact lens 2 due to differences in light reflection from the front and back of the lens 2 under the strain induced by the applied force.
  • applied strain results in changes in thickness of the contact lens 2 (where the changes are proportional to the Poisson's Ratio of the material). This change is measurable from an interference pattern, and conversely the interference pattern can be used for calculating the stress acting on the contact lens 2, and hence calculate the IOP.
  • FIG 8 is an illustration of a second exemplary system for measuring a physiological characteristic of an eye of a subject in which the method of Figure 6 can be implemented.
  • the system comprises a contact lens 2 as described above that is to be worn on the eye 20 of a subject (it will be appreciated that the contact lens 2 is shown as spaced from the eye 20 in Figure 8 simply for ease of illustration), a light source 22 that is for emitting light towards the contact lens 2 in order to change the property of the first material 4 in the contact lens 2 and thereby apply a force to the eye 20.
  • the light source 22 can be configured to emit light at any required wavelength, and where the first material 4 is responsive to a particular wavelength or wavelengths of light, the light source 22 can be configured to emit light at one of those particular wavelengths.
  • Embodiments of the light source 22 can be as described above with reference to Figure 7.
  • the system also comprises a measurement device in the form of a reader unit 26 that is for obtaining measurements of the strain in the contact lens 2.
  • the reader unit 26 can obtain measurements of the strain before, during and after the force has been applied to the eye 20 by the contact lens 2.
  • the reader unit 26 can be any type of device that has a radio frequency (RF) antenna for receiving a signal transmitted from the contact lens 2.
  • the reader unit 26 can also comprise a transmitter for transmitting an interrogation signal to the contact lens 2 to cause the contact lens 2 to transmit a signal to the reader unit 26.
  • the system also comprises a control unit that analyses the received signal to determine the strain and thus determine the physiological characteristic.
  • the control unit might be part of the reader unit 26 or it might be a separate component of the system.
  • the control unit may also control the light source 22 to emit light in order to initiate the measurement of the physiological characteristic.
  • the control unit may be provided in the same device as the reader unit 26, or it may be provided in a separate component of the system.
  • the control unit can be implemented in numerous ways, with software and/or hardware, to perform the required function(s).
  • the control unit may comprise one or more microprocessors that may be programmed using software to perform the required functions.
  • the control unit may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field- programmable gate arrays (FPGAs).
  • ASICs application specific integrated circuits
  • FPGAs field- programmable gate arrays
  • the reader unit 26 is arranged to be worn on a body part of the subject. In some such embodiments the reader unit 26 comprises, or is attachable to, a pair of spectacles. In some embodiments the reader unit 26 comprises, or is attachable to, an item of wearable head gear, such as a head band, headphones, a hat, etc. In some
  • the reader unit 26 comprises, or is attachable to, an item of gear arranged to be worn on a body part other than the head, such as a wrist band, watch, arm band, neck brace, necklace, etc.
  • the reader unit 26 is a hand-held device.
  • the reader unit 26 can be incorporated into a portable electronic device such as a smartphone or tablet computer.
  • the contact lens further comprises an RF antenna.
  • An exemplary contact lens 56 having a lens body 60 and an RF antenna 62 according to this embodiment is shown in Figure 9.
  • the contact lens 56 comprises a first material 4 that can be used to apply a force to the eye 20 in response to incident light as described above.
  • the configuration of the RF antenna 62 (and thus the properties of a signal transmitted by the RF antenna 62) depend on the strain in the contact lens 56, and thus the signal from the RF antenna 62 relates to the IOP in the eye 20.
  • the RF antenna 62 can be in the form of a wire embedded in or fixedly mounted on the lens body 60. In such embodiments a change in the shape of the contact lens 56 to apply the force to the eye 20 causes an alteration of the strain experienced by the antenna wire.
  • the RF antenna 62 comprises a slotted patch antenna embedded in or fixedly mounted on the lens body 60. In such embodiments both the strain in the antenna material and the size of the slot are altered by a change in the shape of the contact lens 56.
  • the resistance of a conductor (such as an antenna wire) varies in dependence on the strain experienced by that conductor.
  • the strain depends on the degree of stretching or bending being experienced by the conductor.
  • the resistance of the antenna wire varies in dependence on whether the contact lens 56 is in the relaxed state or the force-applying state, and also on the extent to which the contact lens 56 deforms the eye 20 when the force is being applied.
  • the resistance of the antenna wire depends on the IOP since higher IOP will lead to a smaller change in shape of the RF antenna 62 (i.e. due to less deformation of the eye 20 when the force is applied caused by high IOP).
  • Changing the resistance of an antenna wire causes changes in the antenna transfer functions (e.g. the resonance frequency of the antenna, the quality factor (QF), etc.). This effect can be amplified by utilizing an antenna configuration which experiences a relatively high amount of stretching in response to a given change in shape of the contact lens 56.
  • Changes to the antenna transfer functions can be detected in the control unit from the signal received from the RF antenna 62 by the reader unit 26, without requiring contact between the receiver and the RF antenna 62.
  • the resistance change which caused the observed change in the antenna transfer function.
  • the resistance change will be related to the underlying shape change of the contact lens 56 by a correlation function, the exact form of which will depend on specific factors such as the form of the antenna wire, the form of the contact lens 56, and the relative arrangement of the antenna wire and the contact lens 56.
  • a calibration graph or look-up table relating antenna wire resistance to contact lens deformation is created in respect of each particular design of the contact lens 56, to enable the shape change of the contact lens 56 to be determined from a calculated resistance change.
  • the control unit is arranged to determine a correlation function relating resistance change to shape change, and to apply this to the calculated resistance values.
  • the shape of the contact lens 56 will be related to the underlying IOP by a correlation function, the exact form of which will depend on specific factors such as the nature and/or arrangement of the contact lens 56.
  • the control unit is arranged to determine a correlation function relating shape change to IOP value, and to apply this to the calculated shape change values.
  • the contact lens 56 comprises a strain gauge and a separate RF antenna 62. It will be appreciated that in some embodiments the output of the contact lens 56 can be based on the detection of a property other than strain. For instance, in some embodiments conductive plates are disposed in or on the contact lens 56 such that the distance between the plates is altered by a change in shape of the contact lens 56. The dielectric constant of the material of the contact lens between the plates will also be altered by a change in shape of the contact lens 56. The plates thus form a variable capacitor, the capacitance of which depends on the shape of the contact lens 56. In some embodiments the contact lens 56 comprises particles of a conductive material (e.g.
  • the contact lens 56 can comprise a sensor that directly measures IOP or other parameter indicative of IOP and provides the measurement signal to the RF antenna.
  • the RF antenna 62 is part of a passive antenna circuit, which means that no power supply is required for the contact lens 56.
  • the RF antenna 62 is tuned to a predefined frequency for a given strain state (i.e. a given shape of the contact lens 56).
  • the RF antenna 62 and associated circuitry is formed from a transparent conductive material, e.g. indium tin oxide (ITO), so as not to impair the sight of the subject.
  • ITO indium tin oxide
  • the RF antenna 62 and associated circuitry is arranged around the perimeter of the contact lens 56 so as not to impair the sight of the subject.
  • the reader unit 26 comprises an RF transceiver for transmitting RF energy to and receiving RF energy from the contact lens 56.
  • the RF transceiver comprises an RF signal generator, an antenna 93 and a tuning circuit.
  • the transceiver is arranged to transmit RF energy in a frequency including frequencies up to a few tens of MHz.
  • the transceiver is arranged to transmit RF energy in a range away from commonly used communication bands, and also below the energy absorption range of tissue.
  • the transceiver is able to be tuned to receive a wide range of RF frequencies (e.g. because the resonance frequency of the contact lens antenna 62 may change in accordance with changes in the IOP.
  • the control unit is arranged to determine a value of the IOP based on RF energy received from the contact lens 56.
  • the control unit is arranged to measure a transfer function of the antenna 62 at a first time and at a second, later, time.
  • the first time can be a time before a force is applied to the eye 20 and the second time can be a time during which the force is being applied to the eye 20.
  • the measured transfer function can comprise any of: a quality factor (QF), a resonance frequency, harmonics of a resonance frequency, time constants of an RLC circuit of the RF antenna 62.
  • control unit is arranged to determine a resistance of the RF antenna 62 based on the measured transfer function. In some embodiments the control unit is arranged to determine a change in shape of the contact lens 56 based on a determined resistance of the contact lens RF antenna 62, e.g. by comparing a determined resistance value to a calibration graph or look-up table relating antenna wire resistance to shape of the contact lens 56. In some embodiments the control unit is arranged to determine a value of IOP based on a determined shape of the contact lens 56, e.g. by comparing a determined shape of the contact lens 56 to a calibration graph or look-up table relating the shape of the contact lens 56 to IOP value.
  • the control unit uses the transmitter and receiver in the reader unit 26, measures an antenna transfer function at a first time, to determine an initial value for that antenna transfer function.
  • the reader unit 26 is positioned such that the distance between the reader unit 26 and the contact lens 56 is less than a maximum read range of the reader unit 26.
  • the measuring comprises the control unit transmitting (using the antenna) RF energy in the direction of the contact lens 56.
  • the frequency of the transmitted RF energy is in the range 13-14 MHz.
  • the transmitted RF energy comprises a pulse having a duration and a variable frequency over the duration. In some embodiments the transmitted RF energy is varied between at least two different frequencies. In some embodiments the transmitted RF energy is varied between three different frequencies. In some embodiments the transmitted RF energy is varied over a continuous range of frequencies.
  • the measuring further comprises the RF antenna 62 of the contact lens 56 receiving the RF energy transmitted by the reader unit 26.
  • the RF energy received by the contact lens RF antenna 62 induces an RF voltage in the contact lens RF antenna 62, which causes the RF antenna 62 to emit RF energy.
  • the RF energy emitted by the RF antenna 62 is then received by a receiver (antenna) in the reader unit 26.
  • the RF voltage in the RF antenna 62 is linked to the RF voltage in the reader unit antenna, such that the two antennas are coupled in a manner similar to weakly coupled transformer coils.
  • a characteristic relating to the RF signal received by the reader unit antenna is detected and recorded by the control unit.
  • the characteristic comprises the amplitude of the received RF signal.
  • the characteristic comprises the voltage in the reader unit antenna.
  • the characteristic is continuously detected and recorded for at least the duration over which the RF energy was transmitted by the reader unit 26.
  • the control unit generates a time-series of values of the characteristic.
  • the measuring further comprises calculating a value of the transfer function based on the characteristic relating to the received RF signal. In some embodiments the calculating is performed by the control unit.
  • the calculating is performed as follows.
  • the QF describes the width of the frequency spectrum of an antenna at 3dB below the peak.
  • a suitable calculation process comprises determining the maximum amplitude of the received signal and a corresponding frequency, fo, of the transmitted signal; determining a first frequency, fi , of the transmitted signal corresponding to an amplitude 3dB less than the maximum amplitude; determining a second frequency, f 2 , of the transmitted signal corresponding to an amplitude 3dB less than the maximum amplitude; and calculating a QF value using:
  • the calculating process is slightly different.
  • the maximum voltage is determined and this value is multiplied by 0.707 in order to obtain the equivalent - 3dB value.
  • the frequencies corresponding to the maximum voltage and the -3dB equivalent voltage are then determined and input into equation 2.
  • the method moves to block 502 in which the force is applied to the eye 20 by contact lens 56 in response to incident light. Applying the force to the eye 20 will increase the strain in the contact lens 56 and thus there will be a change in the strain/resistance of the RF antenna wire.
  • the control unit measures the antenna transfer function at a second time, to determine a final value for that antenna transfer function (the term "final” is used merely to distinguish this value from the initial value, and is not intended imply that no further values of the antenna transfer function are determined).
  • the determination of the final antenna transfer function value is performed in the same manner as the determination of the initial antenna transfer function value.
  • the second time is immediately after the first time, i.e. such that the control unit is continuously determining an updated antenna transfer function value, i.e. before, during and after the application of a force to the eye.
  • the control unit determines the IOP from the change in the strain between the first time and the second time using the initial antenna transfer function value and the final antenna transfer function value.
  • the determining comprises calculating a resistance change which caused the observed change in the antenna transfer function; calculating a change in the strain experienced by the contact lens antenna 62 based on the initial and final antenna transfer function values; or determining a change in shape of the contact lens 56, e.g. using a calibration graph or look-up table relating antenna wire resistance to shape change, or relating antenna wire strain to shape change.
  • the initial antenna transfer function and the final antenna transfer function used in step 508 do not have to be consecutive measurements of the antenna transfer function value.

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  • Physics & Mathematics (AREA)
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Abstract

L'invention concerne une lentille de contact destinée à être utilisée dans la mesure d'une caractéristique physiologique d'un œil d'un sujet ; la lentille de contact comprenant un premier matériau, le premier matériau étant tel qu'une propriété du premier matériau change en réponse à une lumière incidente, et le premier matériau étant agencé de sorte que, lorsque la lentille de contact est portée sur l'œil et que la lumière est incidente sur le premier matériau, la lentille de contact exerce une force sur l'œil.
PCT/EP2017/057139 2016-03-31 2017-03-27 Lentille de contact, système et procédé de mesure d'une caractéristique physiologique d'un œil d'un sujet WO2017167670A1 (fr)

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WO2021086924A1 (fr) * 2019-10-28 2021-05-06 University Of Southern California Système et procédé pour induire des modifications épigénétiques dans les cellules et le tissu oculaires et orbitaires

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