Field of the invention

[0001] The present invention concerns a contact lens for determining the eye temperature, a device comprising said contact lens and a methods related thereof. Description of related art

[0001] Contact lens are classically used to provide vision-correcting functionality, cosmetic enhancement or therapeutic effects. Each function is provided by a physical characteristic of the lens. Wearable lens may incorporate a lens assembly having an electronically adjustable focus to augment or enhance performance of the eye with a vision corrective function. A pigment incorporated into the lens can provide a cosmetic enhancement. An active agent incorporated into a lens can provide a therapeutic functionality.

[0002] More recently, contact lens have been described as medical device for assessing a physiological parameter of a patient, such as intra ocular pressure, concentration of sugar or metabolites, or for providing temperature of the ocular surface. For instance, such contact lens generally incorporate electronic sensors to detect concentrations of target particular chemicals in the tear film. [0003] Contact lens with sensor embedded in the core of the lens are used for measuring the eye temperature. However, when it comes to providing accurate and reliable measurements, the existing device does not provide satisfying data notably because the sensor sensitivity is biased by the eye temperature and/or the environment temperature. That is why, there is a need to provide an improved solution for measuring the eye temperature, in particular the temperature of the ocular surface, in an accurate manner. Brief summary of the invention

[0004] One of the aim of the invention is to provide a contact lens free from or limiting the limitations of the known contact lens.

[0005] In particular, one aim is to provide a contact lens allowing accurate determination of the eye temperature, in particular the ocular surface of the eye.

[0006] According to the invention, these aims are achieved by means of a contact lens comprising a sensor system for determining the ocular surface temperature of a patient, the contact lens comprising an eye side and an exterior side, the eye side being designed for contacting the patient eye, the exterior side being designed for contacting the exterior

environment or the lid of the patient,

The contact lens being characterized in that the sensor system comprises at least two sensors, a temperature sensor and a reference sensor, the temperature sensor being arranged for measuring the temperature of the eye side, the reference sensor being arranged for measuring the

temperature of the exterior side.

[0007] The contact lens according to the present invention comprises at least two sensors, a temperature sensor and a reference sensor. Each sensor is capable of measuring a temperature on one side of the contact lens, the eye side for the temperature sensor and the exterior side for the reference sensor.

[0008] The temperature sensor is used for measuring the temperature of the ocular surface when the eye side of the contact lens is placed onto the eye. However, the temperature measured by the temperature sensor is influenced by the exterior environment condition on the exterior side of the contact lens. There is a drift, i.e. a temperature drift, between the effective temperature of the ocular surface and the temperature of the ocular surface as measured by the temperature sensor. The environmental condition on the exterior side of the contact lens can modify the

temperature as measured by the temperature sensor on the eye side of the contact lens. For instance, a temperature drift is classically observed when the eye is opened and the contact lens is exposed to the solar radiation. A temperature drift can also be observed when the eye is open and the environmental temperature (for example 10°C) is too different from the average eye temperature (classically between 34°C to 35°C). Finally, a drift can be observed when the eyelid is closed. Thus, depending on the environmental condition, there is a need to correct the temperature measured by the temperature sensor to obtain the effective temperature of the ocular surface. That is why, the reference sensor aims at measuring the temperature of the exterior side of the lens to evaluate the influence of the exterior environment on the temperature measured by the temperature sensor on the eye side. The temperature measured by the temperature sensor is corrected by the reference temperature provided by the reference sensor to obtain the effective temperature of the ocular surface. The contact lens according to the present invention is capable of providing accurate data of the temperature of the ocular surface that takes into account the temperature of the exterior environment. [0009] The temperature sensor is used for measuring the eye

temperature. For instance, the temperature sensor measures accurately in the variation zone of the eye temperature, classically between 31 °C and 38°C. The temperature sensor can be used for continuous monitoring of the eye temperature on the eye side, for instance over 24 h, or from 1 to 7 days.

[0010] In one embodiment, the temperature or the reference sensor have about 0.5°C sensitivity, preferably 0.2°C to 0.1 °C sensitivity.

[0011] The reference sensor is used for measuring the temperature on the exterior side of the contact lens, so as to determine the variation of the environmental condition. For instance, the reference sensor measures temperature between -40°C and +60°C. The reference sensor allows tuning the temperature measured by the temperature sensor and consequently avoiding the temperature drift. The reference sensor can be used for continuous monitoring of the temperature on the exterior side of the contact lens for instance over 24 h, or from 1 to 7 days.

[0012] In one embodiment, the temperature sensor and the reference sensor are placed side by side in the contact lens.

[0013] In an embodiment, the temperature sensor and the reference sensor are diametrically opposed in the contact lens.

[0014] In one embodiment, the temperature sensor is coated with a first insulator stack comprising at least one gas layer and one polymer layer between the temperature sensor and the exterior side. The first insulator stack allows isolating the temperature sensor from the exterior

environment to minimize the influence of the exterior environment on the temperature sensor. The first insulator stack comprises at several gas layers and several polymer layers. The first insulator stack can comprise alternate layers of gas and polymer.

[0015] In an embodiment, the reference sensor is coated with a second insulator stack comprising at least one gas layer between the eye side and the reference sensor. The second insulator stack allows isolating the reference sensor from the eye to limit the influence of the eye on the reference sensor. The second insulator stack can also comprise at least one gas layers and one polymer layer. The second insulator stack can comprise alternate layers of gas and polymer.

[0016] In an embodiment, the first insulator stack and the second insulator stack are identical. [0017] In particular, the gas layer can be made of a mixture of gas. For instance, the gas layer can be an air layer, i.e. an air gap. Air gaps are known to be very efficient for thermal insulation. The gas can also be made of oxygen, argon, nitrogen or mixture related thereof. [0018] The polymer layer is preferably made of polymer or mixture of polymer with a low heat transfer coefficient, below 0.4 W.m ^"1 .K. For instance, the polymer layer can comprise polyethersulfone (PES),

polyvinylidene fluoride (PVDF), polyimide (PI), resin or mixture related thereof.

[0019] In an embodiment, the temperature sensor and/or the reference sensor is coated with a solar radiation cover. The solar radiation cover allows limiting the temperature drift induced by solar radiation. In particular, the cover comprises low emissivity material, for instance aluminium, brass, copper, gold, nickel.

[0020] In one embodiment, the temperature sensor and/or the reference sensor is coated with a watertight film. Watertight film is used for preventing water ingress in the sensor system, in particular in the reference sensor or the temperature sensor. In particular, the first insulator stack coating the temperature sensor and/or the second insulator stack coating the reference sensor is coated with a watertight film

[0021] In particular, the solar radiation cover can cover the watertight film, said watertight film coating the first insulator stack or the second insulator stack. [0022] In an embodiment, the lens further comprises an aperture opposite the temperature sensor. The aperture enables a direct contact between the tear film of the eye and the temperature sensor to improve the sensitivity of the temperature sensor. The direct contact between the tear film and the sensor will increase the sensitivity of the sensor system due to the removal of the contact lens material barrier. The aperture also allows increasing the transmission speed of the temperature data between the ocular surface and the temperature sensor.

[0023] In one embodiment, the sensor system further comprises at least two antennas, each sensor being connected to an antenna. [0024] In one embodiment, the contact lens comprises a battery connected to the sensor system for supplying energy to the sensor system.

[0025] In an embodiment, the lens further comprises an equilibrium system. The equilibrium system is used for balancing the displacement of the center of gravity due to the implementation of elements in the contact lens, such as the elements of the sensor system. In particular, the

equilibrium depends on the position of the sensor system, in particular the position of the temperature sensor and the reference sensor in the contact lens. Technics used to improve the contact lens stability include for instance prism ballasting stabilizing geometry or balanced vertical thickness profile.

[0026] In one embodiment, the contact lens comprises a lower part on the eye side covered by an upper part on the exterior side, said lower part comprising a housing for receiving the sensor system. The contact lens can be produced by cast moulding technology. In cast moulding, in a first step, the lower part of the contact lens with a 360° housing is moulded for receiving the sensor system. The temperature sensor and the reference sensor are seated above the corneal or limbal or scleral part of the eye. Once all the elements of the sensor system are placed, the lower part is overmoulded to create the upper part of the contact lens and complete the assembly.

[0027] The contact lens total diameter can vary between 14.5 to 20 mm and the central thickness can vary between 100um to 1000um. The contact lens material can be hydrogel, silicone hydrogel or silicone elastomer optically clear or a mixture of these materials. The contact lens can have a free central optic zone diameter of -7-8 mm where no elements, notably of the sensor system, crosses inside.

[0028] Advantageously, the contact lens according to the present invention can be used for monitoring of the eye temperature, for instance for 24 h, or over several days, for instance over 7 days. [0029] The contact lens according to the present invention can also be used for diagnosing an eye disease by determining the eye temperature.

[0030] The invention also concerns a device for determining the ocular surface temperature of a patient, the device comprising: - At least a contact lens according to the invention;

- A computing module connected to the sensor system for processing the temperature data providing a computed temperature

[0031] The computed module is in charge of processing the temperature data, i.e. temperatures measured by the temperature sensor and

temperatures measured by the reference sensor. The algorithm will analyse and treat the data to provide a computed temperature corresponding to the effective temperature of the ocular surface. The computed module, in particular the algorithm of the computed module, implements a correction coefficient to the measured temperature (by the temperature sensor) based on the reference temperature (from the reference sensor) to compute an effective temperature corresponding to the temperature of the ocular surface. Thus, the computed module allows the conversion between the measured temperature and the effective temperature to overcome the temperature drift. For instance, the correction coefficient can be based on theoretical formula, calculated with FEM analysis and verified by empirical measurements or experimental measurements.

[0032] The computed module can be controlled by a user to provide the computed temperature on demand, whenever the user is in need of the information. Alternatively, the computed module can also be programmed to perform the processing automatically, i.e. self-monitoring, on a regular basis, for instance every 15 minutes or every hour.

[0033] In an embodiment, the device further comprises a reader for displaying the computed temperature. The reader is connected to the computing module for displaying the computed temperature. The reader can further display the measured temperature from the reference sensor or the measured temperature from the temperature sensor. Temperature readings can be made on demand by a user. Alternatively, the reader can be programmed to update the computed temperature displayed on the reader on a regular basis, for instance every 15 minutes or every hour.

[0034] The reader can also be synchronized with the computed module so as to display the most recent computed temperature processed by the computed module or alternatively several recent computed temperatures to display the change of the eye temperature over time. [0035] In one embodiment, the device further comprises a storage unit connected to the computed module for storing temperatures data and the computed temperature.

[0036] In an embodiment, the device further comprises an energy supply module, for instance a battery, for supplying energy to the contact lens via the antennas. In particular, the energy supply module is connected to the antenna via a wireless connection.

[0037] The connection between the elements of the device (computing contact lens, computing module, reader, storage unit, energy supply module) is either made with wire or wireless. In particular, the connection between the contact lens and the computing module is wireless.

[0038] The invention further relates to a method for determining the ocular surface temperature of a patient, the method comprising the successive steps of: a) Placing at least a contact lens according to the invention onto the eye of a patient; b) Providing at least one measured temperature with the

temperature sensor and one reference temperature with the reference sensor; c) Providing a computed temperature by processing said measured temperature and said reference temperature with an algorithm based method, said computed temperature corresponding to the effective temperature of the ocular surface of the eye of the patient. [0039] In one embodiment, the method further comprises repeating steps a) to c) for monitoring the eye temperature of the patient over at least 24 hours.

[0040] In many eye pathologies, it is necessary to gather temperature data over a long duration to diagnose a pathology, typically from 1 hour to 24 hours or even several days. The present invention aims at helping diagnosing pathologies (for instance glaucoma or vascular diseases) by providing accurate eye temperature over long duration.

[0041] The present invention also concerns a method for determining the interocular surface temperature of a patient, the method comprising the successive steps of: a) Placing one contact lens according to the present invention onto each eye of a patient; b) Providing at least two measured temperatures with the temperature sensor and one reference temperature with the reference sensor; c) Providing computed temperatures by processing said measured temperatures and said reference temperatures with an algorithm based method, said computed temperatures corresponding to the effective temperature of the interocular surface of the eye of the patient.

[0042] It is known that a temperature difference between the eyes, in particular between the ocular surface of the eyes, i.e. a difference between the temperature of the right eye and the temperature of the left eye, of about 0.5°C (in absolute value) might be used to diagnose pathologies (for instance glaucoma or vascular diseases). The method according to the present invention allows controlling the temperature of both eyes to help diagnosing eye pathologies. [0043] In one embodiment, the method comprises repeating steps a) to c) for monitoring the interocular temperature of the patient over at least 24 hours.

[0044] In the present invention, the terms "exterior environment" refer to the environment contacting the exterior side of the contact lens when the lens is placed onto the eye of the patient. The exterior side of the lens can be in contact with the exterior environment and with the lid of the patient. In such case, the reference temperature measured by the reference sensor can also be influenced by the lid when the lid contacts the exterior side of the contact lens. [0045] The embodiments described for the contact lens also apply to the device according to the present invention, and to the method according to the present invention, mutatis mutandis.

Brief Description of the Drawings

[0046] The invention will be better understood with the aid of the description of an embodiment given by way of example and illustrated by the figures, in which:

Figure 1 shows an overview of a contact lens according to a first embodiment, the lens being placed onto a model of a human eye globe; Figure 2 represents an overview of the contact lens according to the first embodiment; Figure 3 represents an overview of a lower part of the contact lens according to the first embodiment;

Figure 4 represents a cross-section view of a contact lens according to the first embodiment; Figure 5 represents an enlarged cross section view of a temperature sensor of the contact lens according to the first embodiment;

Figure 6 represents an enlarged cross section view of a reference sensor of the contact lens according to the first embodiment; Detailed Description of possible embodiments of the Invention

[0047] Contact lens:

[0048] Figures 1 to 6 represent a first embodiment of a contact lens according to the present invention. However, the present invention is not limited to this embodiment. [0049] The contact lens 1 is designed for being placed onto the eye globe of a patient, as illustrated schematically in figure 1.

[0050] The contact lens 1 comprises an eye side 2 and an exterior side 3 as illustrated in figure 2. The eye side 2 is located on the side of the contact lens 1 designed for contacting the eye globe, in particular the tear film covering the eye globe. The exterior side 3 is on the opposite side of the contact lens 1. The exterior side 3 is the part of the contact lens designed for contacting the exterior environment. In other words, the exterior side 3 is the part of the lens that is not in contact with the eye globe.

[0051] The contact lens 1 comprises a lower part 4, said lower part 4 comprising a housing 5 formed in a recess 6 of the lower part 4 as illustrated in figure 3. The recess 6 is formed at 360° on the lower part, meaning that the housing 4 extends all around the lower part 4 of the contact lens 1. The recess 6 is formed during the cast moulding

manufacturing of the contact lens 1.

[0052] The housing is designed for receiving a sensors system 7 as illustrated in figure 4. The contact lens further comprises an upper part 8 created by overmoulding the lower part 4 with the sensor system 7 received herein.

[0053] The sensor system 7 comprises the elements required for determining the temperature of the ocular surface of the eye. The sensor system 7 comprises a temperature sensor 9 connected to a first antenna 10 (temperature sensor antenna), a reference sensor 1 1 connected to a second antenna 12 (reference sensor antenna). In the embodiment represented in figures 1 to 6, the temperature sensor 9 and the reference sensor 1 1 are diametrically opposed on the contact lens 1 , as illustrated in figures 2 and 4. However, the temperature sensor 9 and the reference sensor 1 1 can be side by side, for instance embedded in one element (not represented in figures 1 -6).

[0054] The temperature sensor 9 is coated with a first insulator stack 13 (temperature sensor insulator stack). The first insulator stack 13 comprises alternate layers of gas and polymer. The temperature sensor 9 is glued to the housing 5 and subsequently coated with the first insulator stack 13 comprising two polymer layers 14 of between 25 and 50 mu thick and two air gap 15 of 50 mu thick in an alternate manner. Then, a watertight layer 16 of 1 to 10 mu thick of parylene, silicon oxide (Si0 ₂ ) and silicon derivative is deposed around the insulator stack 14.

[0055] The temperature sensor 8 is located in the lower part 4 opposite to an aperture 17, for instance rectangular or circular shaped,

manufactured in the thickness of the lower part 4 of the contact lens as illustrated in figure 3. The aperture 17 allows the fluid connection between the tears film covering the eye globe and the temperature sensor 9 to enhance the sensitivity of the temperature sensor 9. [0056] The housing 5 is covered by a solar radiation cover 18 that creates a top air gap 19 above the watertight thin film 16. In the present

embodiment, the solar radiation cover 18 is made of a 300 to 600 nm thick of gold, brass, copper or nickel layer. The reference sensor 1 1 is glued to the solar radiation cover 18, providing one air gap on each side of the reference sensors, as illustrated in figure 5. In the embodiment represented in figures 1 to 6, the reference sensor 9 is insulated from the eye side with an air gap and the lower part 4 of the contact lens (corresponding to the second insulator stack 20). In other embodiment (not represented in figures 1 -6), the second insulator stack can also comprises at least one polymer layer and at least one gas layer.

[0057] Device for determining the ocular surface temperature

[0058] The contact lens as represented in figures 1 to 6 in a first embodiment, is combined with a computing module (not represented in figures 1 to 6) to provide a device for determining the ocular temperature of a patient. The temperatures provided by the sensor system of the contact lens are analysed and treated by the computed module with an algorithm based method. For instance, if the measured eye temperature is 31 °C (measured by the temperature sensor), the reference temperature is 5°C (measured by the reference sensor), then the computed module will select the corrective coefficient that correspond to the reference

temperature, and correct the measured temperature to provide the effective temperature of the ocular surface. For instance, the corrective coefficient could be +0.5 °C so that in this example, the effective

temperature would be 31.5°C.

Numeros de reference employes sur les figures

Contact lens

Eye side

Exterior side

Lower part

Housing

Recess

Sensor system

Upper part

Temperature sensor

First antenna

Reference sensor

Second antenna

First insulator stack

Polymer layer

Air gap

Water tight layer

Aperture

Solar radiation cover

Top air gap

Second insulator stack