Air pulse tonometers

Abstract

Disclosed is a tonometer (100) for measuring an intraocular pressure of an eye (102), the tonometer comprising: an air pulse generator; a corneal oscillation measurement sensor (106); a controller (108) coupled to the air pulse generator (104) and the corneal oscillation measurement sensor, wherein the controller is configured to: control the air pulse generator to generate an excitation air pulse (116) and send the excitation air pulse towards the eye at a velocity lying in a range of 15- 130 metres per second; control the corneal oscillation measurement sensor (106) to measure a signal related to corneal oscillations caused by incidence of the excitation air pulse on the eye; and determine the intraocular pressure from the measured signal.

Description

[0001] AIR. PULSE TONOMETERS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to tonometers for measuring intraocular pressure of eyes using air pulse. Moreover, the present disclosure relates to methods for measuring intraocular pressure of eyes with tonometers using air pulse.

[0004] BACKGROUND

[0005] Intraocular pressure (IOP) measurement is an essential component of ophthalmic diagnostics, playing a vital role in assessing ocular health and detecting conditions such as glaucoma. Herein, the IOP refers to a pressure exerted by vitreous fluid inside an eye chamber that retains shape of the eye, provides support to a retina of the eye, and acts as a shock absorber, thus protecting delicate structures of the eye from external forces. Herein, the IOP measurement serves as a fundamental parameter for assessing ocular health and detecting abnormalities, particularly in conditions such as glaucoma which causes damage to optic nerve leading to progressive vision impairment. Accurate and reliable IOP measurement is essential for early detection and monitoring of eye conditions like, ocular hypertension, uveitis, traumatic eye injuries, and the like, that can affect the IOP of the eye. Therefore, it is imperative to have precise, consistent, and patient-friendly methods for measuring the IOP to ensure effective diagnosis and treatment.

[0006] Conventionally, tonometers are used to measure the IOP. Examples of such tonometers are rebound tonometers, dynamic contour tonometers, Goldmann applanation tonometers, and non-contact (Air-Puff) tonometers. Typical conventional non-contact tonometers (air puff) are based on the Imbert-Fick principle that requires applanating the cornea from a reasonably large area (several millimeters in diameter). In air puff tonometer intensity of the air flow is slowly increased so that the cornea first reaches the applanation state and then it bends over the applanation state. Then the air flow intensity is decreased so that the cornea returns to its normal state. This requires relatively high pressure to displace the cornea and the procedure takes relatively long time that might both cause discomfort. Also, area of the air puff on the cornea surface is large leading to need to have large force on the air puff.

[0007] However, existing non-contact tonometers face challenges in delivering accurate and reliable IOP measurement consistently. One significant limitation of the existing non-contact tonometers is that those requires relatively high pressure air puff, which causes discomfort and irritation to the eye. These limitations result in unreliable IOP measurements, particularly in patients eye conditions.

[0008] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks.

[0009] SUMMARY

[0010] The aim of the present disclosure is to provide a tonometer and a method for measuring an intraocular pressure of an eye to enhance an accuracy and reliability of measuring the intraocular pressure by utilizing controlled excitation air pulses, while minimizing patient discomfort through non- invasive techniques. The aim of the present disclosure is achieved by a tonometer for measuring an intraocular pressure of an eye and a method for measuring an intraocular pressure of an eye with a tonometer as defined in the appended independent claims to which reference is made to. Advantageous features are set out in the appended dependent claims. Throughout the description and claims of this specification, the words "comprise" , "include", "have", and "contain" and variations of these words, for example "comprising" and "comprises" , mean "including but not limited to", and do not exclude other components, items, integers or steps not explicitly disclosed also to be present. Moreover, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0011] Present disclosure is not based on the Imbert-Fick principle and applanation state is not needed. Instead, we provide way to measure intra ocular pressure by sending a gentle air impulse to displace the cornea from its normal position. After the impulse the cornea starts to oscillate as a damped harmonic oscillator returning to the normal state. Oscillations are function of eye pressure.

[0012] Furthermore, in the present disclosure the air pulse and the oscillation measurement are targeted on the one side or point of the cornea. Thus, no surface wave or spatio-temporal information is required to determine the IOP. Instead the present disclosure measures the bulk movement of the cornea from a single location of the cornea. It has been found out that it is sufficient to obtain reliable measurement results.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1A illustrates a schematic illustration of a tonometer for measuring an intraocular pressure of an eye, FIG. IB illustrates a schematic illustration of an air pulse generator of FIG. 1A, FIG. 1C illustrates an exemplary scenario for measuring a first distance between an eye and a nozzle with reference to FIG. 1A, when the tonometer is in use, in accordance with an embodiment of the present disclosure;

[0015] FIG. 2 illustrates a graphical representation of different states of a corneal displacement during measurement of an intraocular pressure by a tonometer, in accordance with an embodiment of the present disclosure;

[0016] FIG. 3 illustrates a graphical representation of an intraocular pressure value as a function of corneal frequency, in accordance with an embodiment of the present disclosure;

[0017] FIG. 4 illustrates a graphical representation of an air velocity in respect to pressure at surface of eye (cornea);

[0018] FIG. 5 illustrates steps of a method for measuring an intraocular pressure of an eye with a tonometer, in accordance with an embodiment of the present disclosure.

[0019] DETAILED DESCRIPTION OF EMBODIMENTS

[0020] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practising the present disclosure are also possible.

[0021] In a first aspect, the present disclosure provides a tonometer for measuring an intraocular pressure of an eye, the tonometer comprising: an air pulse generator; a corneal oscillation measurement sensor; a controller coupled to the air pulse generator and the corneal oscillation measurement sensor, wherein the controller is configured to: control the air pulse generator to generate an excitation air pulse and send the excitation air pulse towards the eye at a velocity lying in a range of 15 - 130 metres per second; control the corneal oscillation measurement sensor to measure a signal related to corneal oscillations caused by incidence of the excitation air pulse on the eye; and determine the intraocular pressure from the measured signal.

[0022] In a second aspect, the present disclosure provides a method for measuring an intraocular pressure of an eye with a tonometer, the method comprising: aligning the tonometer with respect to the eye; providing an excitation air pulse towards the eye at a velocity lying in a range of 15-130 metres per second, for forming a pressure of 0.5mmHg to 35 mmHg on a surface of the eye upon incidence of the excitation air pulse on the eye; measuring a signal related to corneal oscillations caused by the incidence of the excitation air pulse on the eye; and determining the intraocular pressure of the eye from the measured signal.

[0023] The present disclosure provides the aforementioned first aspect and the aforementioned second aspect, wherein the tonometer is provided for measuring an intraocular pressure of an eye. Herein, the tonometer comprises the air pulse generator that can produce the excitation air pulse with a controlled velocity range of 15 to 130 meters per second. This velocity range enables generation of stable, undistorted corneal oscillations corresponding to a natural oscillatory mode (i.e., a natural biomechanical response) of cornea, for accurate IOP measurement. The speed of the excitation air pulse towards the eye refers in this disclosure to the speed of the excitation air pulse at surface of the eye. Depending on tonometer the speed of the air when it exists from tonometer might be slightly larger since the speed might reduce if measurement distance is large. This precise control ensures that a force applied to a cornea is sufficient to induce measurable oscillations without causing discomfort to the eye. This feature addresses the critical issue of balancing effectiveness and patient comfort. The tonometer provides the excitation air pulse that creates only a small displacement on the cornea, primarily inducing corneal oscillations in posterior-anterior direction of the cornea (which corresponds to natural resonance axis) without inducing other oscillations modes (such as torsional or transverse modes). This improves reliability of IOP measurement. Beneficially, the ability to control the air pulse generator at a velocity lying within a specific range enables the tonometer to adapt to different eye conditions and patient sensitivities. This versatility ensures that the tonometer can be used across a wide range of patients, including those with varying corneal properties. Beneficially, the air pulse generator provides the excitation air pulse that is stable. Moreover, the corneal oscillation measurement sensor accurately captures corneal response to the excitation air pulse generated by the air pulse generator. Hence, measuring the signal related to the corneal oscillations leads to more accurate IOP readings. Moreover, the incorporation of the controller that manages both the air pulse generator, and the corneal oscillation sensor streamlines the IOP measurement process. This automation reduces the need for manual adjustments of settings of the tonometer and minimizes error, leading to consistent measurements. It will be appreciated that an accurate IOP measurement supports better clinical decision-making. This reliability is essential for the early detection and ongoing monitoring of ocular diseases, hence improving patient outcomes. Furthermore, it will be appreciated that the ability of the tonometer to produce and measure responses at different air pulse velocities makes the tonometer versatile for various clinical settings, hence enhances its utility for ophthalmologists, optometrists, and the like. Indeed, when air velocity is controlled to be at the surface of the cornea 15-130m / sec it will form a pressure at the surface of the cornea of 0.5-35mmHg. This causes cornea to displace 5-500 micrometers. Nozzle diameter determines diameter of the air impulse at cornea and the diameter on the cornea is same (or approximately same) as the diameter of the nozzle. Typically, the formfactor is circular i.e diameter can be used to determine area. Since the speed of the air molecules at the surface causes a pressure on the cornea the force can be controlled by two parameters 1) the air velocity and 2) the size of the nozzle. It has been found that nozzle diameters of 0.1-3mm and given air velocities, provide good impact on the cornea to enable corneal oscillations to form in a level which is detectable. Size of the air flow at the cornea is circular having similar diameter (within few %'s) as the diameter of the nozzle. Also, it has been found that using said parameters do not cause discomfort for the patients. The term "tonometer" refers to a device that is used to measure the intraocular pressure (IOP). The term "intraocular pressure" refers to a pressure exerted by vitreous fluid inside an eye chamber that retains shape of the eye, provides support to a retina of the eye, and acts as a shock absorber, thus protecting delicate structures of the eye from external forces. Measuring the IOP is essential in determining and assessing a health condition of the eye and such measurement of the IOP is carried out by the tonometer.

[0024] Optionally, the tonometer comprises a distance sensor for measuring a first distance between the eye and the tonometer. In this regard, the term "distance sensor" refers to an electronic component integrated into the tonometer, designed to measure a distance between the tonometer and the corneal surface of the eye. Herein, the term "first distance" refers to the distance between the corneal surface of the eye and the tonometer, wherein distance to the corneal surface of the eye starts from a nozzle of the tonometer. Notably, an accurate measurement of the IOP using the tonometer requires precise positioning relative to the eye. Herein, the distance sensor ensures that the tonometer is positioned at an optimal distance for reliable readings. This enhances the accuracy and consistency of the IOP measurements, ensuring that the results are not affected by variations in the distance between the tonometer and the eye. Optionally, the distance sensor emits a signal (for example, such as infrared signal, ultrasonic signal, laser signal and the like) towards the eye. The signal then reflects back from the surface of the eye and is detected by the distance sensor. Hence, the time taken for the signal to return is used to calculate the first distance between the tonometer and the eye. In an implementation, the controller of the tonometer receives input from the distance sensor and adjusts the position of the tonometer or prompts user to reposition it if necessary. A technical effect of providing the distance sensor in the tonometer is that such provision ensures that the tonometer is positioned at a controlled and an optimal distance from the eye, which is essential for the accurate and reproducible IOP measurements.

[0025] Throughout the present disclosure, the term "air pulse generator" refers to a component of the tonometer that produces the excitation air pulse which is directed onto corneal surface of the eye during IOP measurement. It will be appreciated that the air pulse generator enables non-contact measurement of IOP, ensuring controlled corneal oscillations for the accurate IOP readings, thereby enhancing the comfort of the patient.

[0026] Optionally, the air pulse generator comprises: a pressure chamber, a nozzle, and a valve arranged between the pressure chamber and the nozzle, wherein when controlling the air pulse generator to generate the excitation air pulse, the controller is configured to perform at least one of: adjust a pressure of pressurized air held in the pressure chamber; adjust at least one of: a diameter, a shape, of an exit aperture of the nozzle; open the valve and close the valve after a first period of time elapses after opening the valve.

[0027] In this regard, the term "pressure chamber" refers to a sealed enclosure designed to store and maintain pressurized air. Notably, the pressure chamber serves as a reservoir where air is stored to a specified pressure level before being directed towards the eye through the valve and the nozzle. The pressure chamber ensures that there is a consistent and controlled supply of pressurized air, which is essential for generating the excitation air pulse used in measuring the IOP. Herein, the term "nozzle" refers to a device that controls a flow of the excitation air pulse towards the eye. Notably, the air pulse generator utilizes a pressure generation means to generate the excitation air pulse of certain pressure inside of the nozzle, wherein the nozzle then guides said excitation air pulse towards the eye. Herein, the term "valve" refers to a mechanical device located between the pressure chamber and the nozzle, which is capable of swift opening and closing. A primary function of the valve is to control a flow of pressurized air from the pressure chamber to the nozzle. Examples of the valve may include, but are not limited to a solenoid valve, a diaphragm valve, a check valve, a pressure relief valve, and a control valve. In this regard, the valve can be opened or closed by the controller according to programmed instructions to regulate a timing and a duration of the excitation air pulse. This capability enables the tonometer to precisely control when and for how long pressurized air is released towards the eye, influencing an intensity and a duration of the corneal oscillations.

[0028] Herein, the controller is configured to increase or decrease the pressure of the pressurised air that is stored in the pressure chamber. This adjustment is typically achieved through mechanisms such as a pressure regulator (as described later) that is controlled by the controller. Beneficially, by adjusting the pressure of pressurized air by optionally using the pressure generating means, the controller can ensure that the excitation air pulse has optimal force when it reaches the corneal surface. This adjustment is essential for generating adequate corneal oscillations without causing discomfort or damage to the eye, thus improving accuracy of the IOP measurements. Furthermore, adjusting the pressure of pressurized air prior to release enables tuning of velocity of the excitation air pulse. Additionally, it also does not discomfort the patient when the tonometer is used for measuring the IOP. Moreover, the controller is configured to adjust the exit aperture of the nozzle either by mechanically altering the nozzle shape (for example, such as using an adjustable diaphragm) or by switching between different nozzles with varying diameters or shapes. This adjustment is made such that a diameter of the excitation air pulse incident on the surface of the eye lies in a range of 0.1 millimetres to 3.0 millimeters. The diameter of the excitation air pulse could be equal to or larger than the diameter of the exit aperture. In one instance, the diameter of the excitation air pulse is equal to the diameter of the exit aperture. In another instance, the diameter of the excitation air pulse is larger than the diameter of the exit aperture. Such instance is practical in nature, as the excitation air pulse spreads once it exits the exit aperture while travelling between the tonometer and the eye, as said excitation air pulse starts dissipating immediately. It will be appreciated that the ability to control parameters such as the pressure and configuration of the nozzle influences the spread of the excitation air pulse, ensuring that the excitation air pulse is appropriately sized and focused when it reaches the corneal surface. Such precise control contributes to the accuracy and reliability of the IOP measurements, as well as enhances patient comfort by minimizing the force exerted on the eye. Additionally, the ability to switch between different nozzles or alter the nozzle shape makes the tonometer adaptable to a variety of eye sizes and shapes of different patients. As an example the diameter can be between 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05,

[0029] 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75,

[0030] 1.8, 1.85, 1.9, 1.95, 2.0, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45,

[0031] 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, to 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95,

[0032] 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65,

[0033] 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.0, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35,

[0034] 2.4, 2.45, 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, or 3.0 millimeters (mm). In preferable embodiment the diameter is select to be less than distance between lower and upper eye lid.

[0035] Furthermore, optionally, the controller is configured to open the valve to allow the pressurized air to pass through the exit aperture of the nozzle and generate the excitation air pulse. The controller then closes the valve after the first period of time. In this regard, the "first period of time" refers to a duration during which the valve of the air pulse generator remains open. The first period of time is controlled by the controller to regulate the timing and duration of the excitation air pulse directed onto the corneal surface of the eye. It will be appreciated that controlling the duration (i.e., the first period of time) for which the valve is open, enables for precise management of duration and pressure of the excitation air pulse. This control ensures that the excitation air pulse is neither too long nor too short, hence providing just a right amount of the force to obtain the corneal oscillations for procuring accurate measurements of the IOP. Furthermore, by opening the valve only for the first period of time, there is defined an impulse time profile of the excitation air pulse, which supports corneal excitation according to a natural resonance mode of the cornea. A technical effect of configuring the controller in such a manner is that it enables precise control over the force, duration, and the diameter of the excitation air pulse. This precision ensures accurate IOP measurements while minimizing patient discomfort and reducing a risk of irritating the eye.

[0036] Optionally, wherein: the exit aperture of the nozzle is mechanically-adjustable using an actuation arrangement between diameter of 0.1 to 3.0 mm and / or the nozzle is detachably attached to the pressure chamber to change the nozzle between nozzles of different exit aperture diameters.

[0037] In this regard, the term "actuation arrangement" refers to a mechanical arrangement integrated into the tonometer that enables the adjustment of the diameter of the exit aperture. The actuation arrangement may include components, but are not limited to, adjustable diaphragms, mechanical irises, or other mechanisms capable of modifying the aperture size of the aperture size dynamically and accurately. Herein, the actuation arrangement can vary the diameter of the exit aperture of the nozzle within the range of 0.1 millimetre (mm) to 3.0 millimetres (mm), hence allowing precise control over the diameter of the excitation air pulse. For example, the diameter may range from 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05,

[0038] 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75,

[0039] 1.8, 1.85, 1.9, 1.95, 2.0, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45,

[0040] 2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, 3.0, 3.05, 3.1, 3.15,

[0041] 3.2, 3.25, 3.3, 3.35, 3.4, 3.45 up to 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45,

[0042] 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15,

[0043] 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85,

[0044] 1.9, 1.95, 2.0, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35, 2.4, 2.45, 2.5, 2.55,

[0045] 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, 3.0, 3.05, 3.1, 3.15, 3.2, 3.25,

[0046] 3.3, 3.35, 3.4, 3.45 or 3.5 millimeters (mm).This capability to customize the diameter of the excitation air pulse ensures optimal adaptation to different patient needs and eye conditions, enhancing the accuracy and comfort of the IOP measurements while maintaining consistency and reliability across diverse clinical settings. In an example, based on corneal characteristics of the eye of a patient, a smaller diameter of 1 mm can be used for patients with sensitive eyes, ensuring gentler air pulses and minimizing discomfort. Conversely, in another example, based on corneal characteristics of the eye of the patient, a larger diameter of 3 mm can be employed for patients with thicker corneal tissues to achieve adequate corneal oscillations for the accurate IOP measurements. Optionally, the nozzle can be detached and replaced with other nozzles of different exit aperture diameters. This feature enhances operational flexibility by allowing healthcare providers to easily switch between nozzles of different diameters based on patient-specific requirements or varying measurement conditions. For instance, if a patient has particularly sensitive eyes, a smaller nozzle diameter can be quickly installed to deliver a gentler air pulse, thereby minimizing discomfort during the IOP measurements. A technical effect of the aforementioned is that enabling both mechanical adjustment of the diameter of the exit aperture of the nozzle and the ability to detachably interchange nozzles, the tonometer can efficiently cater to varying patient needs and measurement conditions.

[0047] Optionally, the valve is one of: an electrostatic microvalve, a piezoelectric microvalve, a thermo-pneumatic microvalve, an electromagnetic microvalve, a microelectromechanical systems (MEMS) microvalve. In this regard, the term "electrostatic microvalve" refers to a valve that controls the flow of air through an application of electrostatic forces and it can be used to modulate the excitation air pulse directed at the eye, ensuring controlled and the accurate IOP measurements. The term "piezoelectric microvalve" refers to a valve that operates by using the piezoelectric effect, with an advantage of rapid response and precise control capabilities, facilitating accurate timing and duration of the excitation air pulse during the IOP measurements. The term "thermopneumatic microvalve" refers to a valve that operates by utilizing thermal expansion of gases or liquids to control the valve mechanism. In the tonometer, the thermo-pneumatic microvalve can offer a compact and efficient solution for regulating the airflow for the excitation air pulse. The term "electromagnetic microvalve" refers to a valve that operates based on the principle of electromagnetism. In the tonometer, it will be appreciated that the electromagnetic microvalve offers rapid response times and precise control over the airflow. The term "microelectromechanical systems microvalve" refers to a valve that is fabricated using microfabrication techniques commonly associated with microelectromechanical systems (MEMS) technology. In the tonometer, it will be appreciated that the MEMS microvalve offers precise control and compact size due to their microfabricated nature. This enables for efficient modulation of the excitation air pulse in the tonometer, enhancing accuracy and reliability in the IOP measurements. A technical effect of the aforementioned is that it offers flexibility in the tonometer design by enabling the selection of different microvalve types. This ensures optimal performance in generating and controlling the excitation air pulse hence leading to more accurate and consistent IOP measurements.

[0048] Optionally, the air pulse generator further comprises a pressure sensor and a pressure regulator arranged in the pressure chamber, and wherein the pressure is set between range of 0.05 bars to 5 bars with the pressure regulator. In this regard, the term "pressure sensor" refers to a device arranged within the pressure chamber of the tonometer that continuously monitors pressure of a pressurized air within the pressure chamber. The term "pressure regulator" refers to a mechanical component arranged within the pressure chamber of the tonometer that adjusts the pressure of pressurized air to a predefined range. Herein, the pressure sensor continuously monitors the pressure inside the pressure chamber and sends real-time feedback and / or near-real time feedback to the controller. Based on the feedback received from the pressure sensor, the controller is configured to adjust the pressure regulator. In an instance, if the pressure lies outside the range 0.05 bars to 5 bars , the controller is configured to generate and send signals to the pressure regulator to either increase or decrease the pressure to lie within the range 0.05 bars to 5 bars The pressure regulator is configured to respond to such signals by modulating the flow of air into or out of the pressure chamber. As an example, if the pressure may be 0.01 bars, i.e., it lies lower than a lower value of the range, the pressure regulator may open to allow air into the pressure chamber. This increases the pressure within the pressure chamber. As another example, if the pressure may be 6 bars, i.e., it lies higher than a higher value of the range, it may release air to reduce the pressure inside the pressure chamber.

[0049] Subsequently, when the pressure is set between the range 0.05 bars to 5 bars, the controller is configured to generate and send another signal to the pressure regulator to maintain this pressure level, wherein the another signal comprises instructions. Herein, the pressure sensor continues to monitor and provide feedback to ensure consistent pressure throughout the measurement process. A technical effect of the aforementioned is that the precise adjustment of the pressure between range of 0.05 bars to 5 bars with the pressure regulator ensures the excitation air pulse has optimal force for accurate corneal oscillations during the IOP measurements. The pressure might be set to be between ranges of 0.05 bars, 0.1 bars, 0.2 bars, 0.3 bars, 0.4 bars, 0.5 bars, 0.6 bars, 0.7 bars, 0.8 bars, 0.9 bars, 1.0 bars, 1.5 bars, 2.0 bars, 2.5 bars, 3.0 bars, 3.5 bars, 4.0 bars, 4.5 bars up to , 0.1 bars, 0.2 bars, 0.3 bars, 0.4 bars, 0.5 bars, 0.6 bars, 0.7 bars, 0.8 bars, 0.9 bars, 1 bars, 1.0 bars, 1.5 bars, 2.0 bars, 2.5 bars, 3.0 bars, 3.5 bars, 4.0 bars, 4.5 bars, or 5.0 bars..

[0050] Throughout the present disclosure, the term "corneal oscillation measurement sensor" refers to a sensing device configured to sense and measure the corneal oscillations induced at the corneal surface by the excitation air pulse. The corneal oscillation measurement sensor is also configured to transmit information corresponding to the corneal oscillation to the controller present in the tonometer. The corneal oscillation measurement sensor is configured to measure various characteristics of corneal oscillations observed on the corneal surface after the excitation air pulse impacts on the corneal surface. Optionally, the various characteristics of the corneal oscillation used herein may refer to: an amplitude, a frequency, a damping factor, a duration, a phase, a value corresponding to pea k-to- peak amplitude, and other characteristics. The various characteristics of the corneal oscillation are dependent on the force of the excitation air pulse exerted on the corneal surface.

[0051] Optionally, the corneal oscillation measurement sensor is one of: a confocal chromatic sensor, a laser displacement sensor, a camera an optical coherence tomography (OCT)-based sensor, an ultrasonic sensor. In this regard, the confocal chromatic sensor measures the corneal oscillations by analysing chromatic dispersion of light reflected from the corneal surface. The confocal chromatic sensor provides high resolution and accuracy in detecting minute changes in corneal movement of the corneal surface by analysing variation in wavelengths of light reflected from the corneal surface. The OCT-based sensor provides detailed visualization and precise measurement of the corneal oscillations. The OCT-based sensor uses low-coherence interferometry to capture cross- sectional images of the eye, including corneal dynamics of the eye. In this regard, the OCT-based sensor directs a beam of low-coherence light into the eye, where it interferes with light reflected from various depths within a tissue. Then, by measuring the resulting interference patterns, the OCT-based sensor constructs high-resolution cross-sectional images that reveal detailed structural information, including corneal dynamics such as thickness variations and movement over time. The ultrasonic sensor uses ultrasound waves to detect corneal movements. A technical effect of the aforementioned is that the corneal oscillation measurement sensor is selected from sensors for its ability to accurately and reproducibly measure corneal changes, ensuring reliable IOP readings.

[0052] Throughout the present disclosure, the term "controller" refers to a computational device that is operable for controlling overall operation of the tonometer. The controller is configured to control the air pulse generator for adjusting the force exerted on the eye by the excitation air pulse that is directed towards the eye, for accurate measurement of the IOP. In an example, the controller may be any one of an embedded microcontroller, a microprocessor, a field-programmable gate array (FPGA), digital signal processor (DSP), an application-specific integrated circuit (ASIC), a programmable logic circuits, an on-the chip control system, and any other suitable control module configured to receive input from the corneal oscillation measurement sensor pertaining to the corneal oscillation; to process information available in the received input; and to control components of the air pulse generator such as the nozzle, the diameter of the exit aperture of the nozzle and the valve, pressure inside of the pressure chamber, duration and timing of opening the valve, thereby adjusting the force exerted on the eye by the excitation air pulse. The controller may be implemented as an internal component of the tonometer, an external component of the tonometer, or a combination thereof.

[0053] Throughout the present disclosure, the controller is configured to generate the excitation air pulse by sending control signals that adjusts parameters such as pressure, duration, and timing. When the controller receives a signal from the corneal oscillation measurement sensor, the controller uses this feedback to refine these parameters for an optimal excitation. For instance, based on the received signal, the controller adjusts components of the air pulse generator (such as the valve, the pressure chamber, the pressure regulator etc.) to precisely control the intensity and timing of the excitation air pulse. As an example of timing is to time the measurement to take place after the tonometer is in correct measurement distance or angle i.e aligned to correct position in respect to the eye. Further parameter to timing is that the IOP measurements may be repeated, for example, to obtain a best result the final IOP reading may be an average of 3-6 measurements. Thus, the timing can also be used to time these repeated measured so that the oscillation of the previous measurement has ended before the next measurement begins. These adjustments ensure that the excitation air pulse effectively induces measurable corneal oscillations, facilitating the accurate measurement of the IOP. Herein, the controller is configured to send the signal to the air pulse generator to generate the excitation air pulse with a velocity lying in a range of 15 to 130 meters per second (m / s). For example, the velocity may range from 15, 30, 45, 60, 75, 90, 105, 120, 135 meters per second up to 30, 45, 60, 75, 90, 105, 120, 135, or 150 meters per second. When the excitation air pulse having the velocity lying in this range is incident on the eye, there is formed a pressure of the excitation air pulse at a surface of the eye, said pressure lying in a range of 0.5mmHg to 35mmHg. This means that the controller can control the air pulse generator to increase or decrease the velocity of the excitation air pulse, thereby ensuring a corresponding precise corneal oscillation. In an example, based on corneal characteristics of the eye of a patient, the controller may be required to send the excitation air pulse towards the eye at a velocity of 120 meters per second to produce the corneal oscillations to measure the IOP effectively. Herein, the controller may be configured to increase the pressure in the pressure chamber accordingly to achieve this velocity. In another example, for patients where a lower velocity is sufficient, the controller may be required to send the excitation air pulse towards the eye at a velocity of 50 meters per second to produce the corneal oscillations to measure the IOP effectively. Herein, the controller may be configured to decrease the pressure in the pressure chamber accordingly to achieve this velocity. It will be appreciated that controlling the air pulse generator in such a manner ensures consistent and precise corneal oscillations. This control optimizes the IOP measurements by maintaining resonance conditions of the corneal oscillations, thereby improving diagnostic accuracy and reliability in ophthalmic evaluations. In deed pressure on the surface of the eye could be in range of from 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 mmHg up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35 mmHg. This pressure range allows the cornea to deform elastically and predictably, improving accuracy and preserving measurement linearity across a range of lOPs.

[0054] It will be appreciated that the velocity of the excitation air pulse at the surface of eye is 15-130 m / s, so that a natural resonance oscillation mode of the cornea is enabled when the excitation air pulse is incident on the cornea. This velocity range ensures a minimal requisite corneal deformation and avoidance of applanation (since applanation introduces nonlinearities and errors in measurement), for enabling accurate IOP measurement. Therefore, this velocity range allows for high patient comfort and safety, whilst also ensuring that the IOP determination is accurate. Notably, low velocities (such as velocities less than 15 m / s) could lead to inadequate excitation, resulting in low signal to noise ratio of the signal related to the corneal oscillations for patients with high IOP. Conversely, high velocities (such as velocities greater than 130 m / s) could trigger nonlinear corneal deformation, leading to signal artifacts or irregular damping. Furthermore, this velocity range produces stable, reliable, and interpretable signals related to corneal oscillations, which also enable accurate IOP measurement across a wide IOP spectrum.

[0055] The velocity for the air pulse at the surface of eye is 15-130 m / s as discussed. These velocities cause a pressure on the surface of the eye that is less than approximately 35mmHg. This is a lower pressure than the conventional air-puff (applanation based tonometer) tonometer induces to the eye being approximately half of the maximum pressure value used in the air-puff tonometer. The cornea is highly sensitive to the pressure. Therefore, using a lower pressure reduces the discomfort for the patient. This is enabled by the novel technology where intraocular pressure (IOP) is detected by measuring the oscillation frequency of the cornea after the air impulse and calculating IOP from the frequency. The corneal deformation caused by the air pulse is between 5-500 pm (micro meter) that is also lower than the deformation caused by the conventional air-puff tonometer. The area of the nozzle / air pulse relates to the force exerted on the cornea. In addition, importantly the diameter also influences on how well the air pulse stays focused during the flow from the nozzle to the cornea. The wider diameter can help to maintain the air flow more focused. Thus, the nozzle diameter could be 0.1-3mm in diameter. In general correlation between the pressure on the eye can be calculated from the speed of the air (which corresponds to force or impact of the air) and diameter of the air pulse at the surface of the eye (which corresponds to area). Pressure is force / area. Since in the present disclosure distance between nozzle exit aperture and the eye is in range of 4-20mm the size of the air pulse on the surface of the eye is approximately (slightly larger in practice) same as the diameter of the nozzle aperture. Deformation caused using said parameters is less than 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490 or 500 pm (micro meters).

[0056] Throughout the present disclosure, the term "signal" as used herein contains information related to various characteristics of the corneal oscillations corresponding to the excitation air pulse. After initiating the excitation air pulse through the air pulse generator, the controller is configured to activate the corneal oscillation measurement sensor. The corneal oscillation measurement sensor begins capturing data immediately upon exposure to the corneal surface where the excitation air pulse has impacted. Notably, data collected using the corneal oscillation measurement sensor, may include changes in reflected light (for the OCT-based sensor) or changes in acoustic signals (for the ultrasonic sensor), which is then processed by the controller. The controller is configured to analyze the signal to determine an amplitude, a frequency, and other characteristics of the corneal oscillations, that are required for measuring the IOP accurately. Based on established calibration data specific to a design of the tonometer, the controller is configured to correlate the corneal characteristics of the corneal oscillations with the IOP. Using the measured signal parameters, the controller is configured to calculate the IOP. For example, the controller may adjust parameters such as air pulse velocity or intensity based on real-time feedback from the corneal oscillation measurement sensor to optimize the accuracy of the IOP measurements. The IOP value is then displayed or recorded for clinical assessment and decision-making.

[0057] Optionally, when determining the intraocular pressure from the measured signal, the controller is configured to: determine a frequency of the corneal oscillations, from the measured signal; and calculate the intraocular pressure, based on the frequency.

[0058] In this regard, the corneal oscillation measurement sensor captures data comprising the vibrations of the corneal surface induced by the excitation air pulse. Herein, determination of the frequency involves identifying a dominant oscillatory pattern within the measured signal, typically expressed in Hertz (Hz), which corresponds to the rate of the corneal movement in anterior-posterior direction (i.e., in natural oscillatory mode of cornea). This mode-selective stimulation improves signal-to-noise ratio of the measured signal and allows the frequency to be more accurately extracted. This oscillatory effect is evaluated based on corneal displacement and shape of the oscillation signal. Notably, a calibration of the tonometer includes establishing a relationship between the frequency of the corneal oscillations and known IOP values. Then, the controller is configured to apply this calibration to convert the measured frequency into the IOP value, utilizing algorithms that account for factors like corneal thickness and biomechanical properties. For example, if the measured frequency of the corneal oscillations may be 350 Hz, and calibration curve of the tonometer indicates that this frequency may correspond to an IOP of 18 mmHg, the controller uses this information to display the IOP reading. Similarly, if the frequency may be 500 Hz, and the calibration curve may indicate an IOP of 32 mmHg, the controller uses this information to display the IOP reading. It will be appreciated that determining the frequency of the corneal oscillations that has been produced by the excitation air pulse offers a non-invasive method to indirectly assess the IOP. This approach reduces patient discomfort compared to traditional tonometry methods involving direct contact with the cornea. Additionally, the IOP measurements based on the frequency provides continuous monitoring capabilities, enables to track changes in ocular biomechanics over time and adjust treatment plans accordingly. A technical effect of the aforementioned is that it enables the tonometer to leverage the frequency of the corneal oscillations as a reliable indicator of the IOP, enhancing the accuracy and non-invasiveness of the IOP measurements.

[0059] Optionally, the controller is configured to open the valve when the first distance is within a predetermined distance, and wherein the first period of time is 1 msec to 15 msec. As an example the first period of time can be from 1 msec, 2 msec, 3 msec, 4 msec, 5 msec, 6 msec, 7 msec, 8 msec, 9 msec, 10 msec, 11 msec, 12 msec, 13 msec, 14 msec up to 2 msec, 3 msec, 4 msec, 5 msec, 6 msec, 7 msec, 8 msec, 9 msec, 10 msec, 11 msec, 12 msec, 13 msec, 14 msec, or up to 15 msec. This range of the first period of time ensures that the generated excited air pulse is long enough to induce clean and measurable corneal oscillations having high signal fidelity, while also being short enough to avoid excessive corneal deformation or applanation (which cause patient discomfort and measurement errors). Furthermore, this range of the first period of time allows calibration of corneal displacement within a range that is well below applanation threshold, thereby enabling repeatable subapplanation displacement. In this regard, the term "predetermined distance" refers to a specific range of distance between the tonometer and the corneal surface of the eye, established based on empirical data or theoretical calculations to ensure optimal positioning of the tonometer for the accurate IOP measurement. Notably, the range of the predetermined distance is pre-defined and programmed into the controller of the tonometer. Herein, the precise control over the opening of the valve based on the first distance is essential for ensuring the accurate IOP measurements. Notably, the first distance is measured by the distance sensor, as described in detail earlier. The first distance ensures that the tonometer is optimally positioned relative to the eye, which affects the accuracy of the excitation air pulse and consequently the IOP reading. Notably, the duration for which the valve remains open which is the first period of time is also essential as it determines the duration and intensity of the excitation air pulse. The range of the first period of time also directly shapes air pressure waveform of the excitation air pulse incident on the cornea. An impulse duration in the aforesaid range (1-15 msec, or more optionally, in sub-ranges such as 1-5 msec, 1-8 msec, 3-8 msec, or similar), matches a natural response time of the corneal oscillations and ensures that corneal excitation occurs as a transient impulse. This allows for consistent corneal oscillations, minimal damping or distortions, and accurate frequency estimation, for enabling accurate IOP derivation. Furthermore, the range of the first period of time, in combination with the range of the velocity of the excitation air pulse, enables individualized tuning of the excitation air pulse for diverse clinical populations. For example, a shorter first period of time (ranging between l-5msec) may be employed for sensitive patients such as children or glaucoma suspects, to provide gentler stimulation.

[0060] When the controller detects that the first distance is within the predetermined distance, the controller opens the valve to release the excitation air pulse. However, if the first distance is outside the predetermined distance, the controller keeps the valve closed, preventing inaccurate pulse generation. Then, the valve remains open for the first period of time that ensures effective delivery of the excitation air pulse. A technical effect of the aforementioned is that it ensures the excitation air pulse is generated only when the tonometer is optimally positioned, enhancing the accuracy of the IOP measurements and improving patient comfort by delivering consistent and precise air pulses.

[0061] Optionally, a pressure of the excitation air pulse at a surface of the eye produces a corneal displacement less than an applanation point used in the conventional air-puff tonometer and Goldmann applanation tonometer. In practical terms for example displacement would range from 5 micrometers to 500 micrometers (in respect to normal non moved level of cornea). According to one example of "less displacement than an applanation point" could be that corneal surface maintains, during the impact of the air, convex form factor. In this regard, the term " pressure" refers to a pressure exerted by the excitation air pulse when it contacts the corneal surface of the eye. Notably, the pressure is essential for obtaining measurable corneal responses while avoiding excessive deformation. The term "corneal displacement" refers to a movement (namely a deformation) of the cornea in response to the excitation air pulse generated by the tonometer. The term "applanation point" refers to a specific point at which the pressure from the excitation air pulse causes the cornea to flatten. Herein, the applanation point represents a threshold beyond which the corneal shape changes significantly, potentially impacting the accuracy of the IOP measurements. Herein, the controller of the tonometer is configured to regulate the pressure of the excitation air pulse, ensuring that it is sufficient to induce the corneal oscillations without flattening of the cornea. As an example, without flattening a relatively large area (e.g. at least 3mm in diameter) of the cornea. This can be achieved through precise control mechanisms such as the pressure sensor, adjustable nozzles, and feedback from the corneal oscillation measurement sensor. The controller then dynamically adjusts the pressure and duration of the excitation air pulse based on real-time measurements to maintain the corneal displacement less than the applanation point used in conventional air-puff tonometer or Goldmann applanation tonometer. A technical effect of ensuring that the pressure of the excitation air pulse produces the corneal displacement less than the applanation point is that it enhances the accuracy of the IOP measurements. By avoiding over-applanation (of a relatively large area), the tonometer minimizes the risk of excessive corneal flattening, leading to more reliable and precise readings. This careful control of the corneal displacement also improves patient comfort during the measurement process. Since required corneal movement is less than applanation point the provided tonometer (and related method) is more safe arrangement than contactless (and contact) tonometers which are based on measuring at applanation (such as conventional air puff tonometer or Goldmann applanation tonometer). Indeed it has been surprising to find out that displacement less than applanation point caused by air pulse provides sufficient corneal oscillations to determine intra ocular pressure. Also smaller area of air impulse at the corneal surface than used in applanation based techniques is sufficient.

[0062] Optionally, the controller is further configured to use the first distance to control the velocity at which the excitation air pulse is sent towards the eye. In this regard, the controller is configured to receive the first distance from the distance sensor. Based on the first distance, the controller adjusts the velocity of the excitation air pulse to obtain the target air velocity 15-130 m / s at the surface of the eye. The controller may use algorithms to determine the velocity of the excitation air pulse for the given distance. Herein, if the tonometer is closer to the eye, the velocity may be reduced to avoid excessive force. Conversely, if the tonometer is farther from the eye, the velocity may be increased to ensure the excitation air pulse can still generate necessary corneal oscillations. It will be appreciated that adjusting the velocity of the excitation air pulse based on the first distance between the tonometer and the eye ensures optimal force application, enhancing measurement accuracy and reducing patient discomfort. By dynamically adapting the velocity, the tonometer can maintain necessary conditions for precise corneal oscillation without causing excessive pressure or understimulation. Distance-resilient excitation of the cornea, at the velocity range of 15-130 m / s, contributes to clinical robustness, and safe, real- world usability of the tonometer, especially for untrained users. In an example, when the tonometer is positioned at 2 centimetres (cm) from the eye, the controller may reduce the velocity of the excitation air pulse to 70 meters per second (when leaving the nozzle towards the eye) to avoid excessive force on the cornea, preventing discomfort and potential damage. Conversely, in another example, when the tonometer is positioned 4 cm from the eye, the controller may be configured to increase the velocity of the excitation air pulse to 120 meters per second (when leaving the nozzle towards the eye) to ensure that the excitation air pulse reaches the cornea with sufficient force to generate accurate corneal oscillations necessary for the accurate IOP measurements. A technical effect of the aforementioned is that it enables the tonometer to adaptively control the velocity of the excitation air pulse based on the first distance to the eye, ensuring optimal force application for the accurate IOP measurements while minimizing patient discomfort and avoiding potential corneal damage.

[0063] The present disclosure also relates to the second aspect as described above. Various embodiments and variants disclosed above, with respect to the aforementioned first aspect, apply mutatis mutandis to the second aspect.

[0064] Optionally, when providing the excitation air pulse, the method comprises performing at least one of: adjusting a pressure of pressurized air held in a pressure chamber of the tonometer; adjusting at least one of: a diameter, a shape, of an exit aperture of a nozzle of the tonometer, for obtaining a diameter of the excitation air pulse at the surface of the eye lies in a range of 0.1 - 3.0 millimeters; opening a valve and closing the valve after a first period of time elapses after opening the valve, the valve being arranged between the pressure chamber and the nozzle.

[0065] Optionally, a method further comprising measuring a first distance between the eye and the tonometer and optionally using the first distance for controlling the velocity at which the excitation air pulse is sent to towards the eye.

[0066] Optionally, the step of determining the intraocular pressure from the measured signal comprises: determining a frequency of the corneal oscillations, from the measured signal; and calculating the intraocular pressure, based on the frequency.

[0067] DETAILED DESCRIPTION OF THE DRAWINGS

[0068] Referring to FIG. 1A, illustrated is a schematic illustration of a tonometer 100 for measuring an intraocular pressure of an eye 102, referring to FIG. IB, illustrated is a schematic illustration of an air pulse generator 104 of FIG. 1A, and referring to FIG. 1C, illustrated is an exemplary scenario for measuring a first distance 120 between the eye 102 and the nozzle 112 with reference to FIG. 1A, when the tonometer 100 is in use, in accordance with an embodiment of the present disclosure. With reference to FIG. 1A, the tonometer 100 comprises an air pulse generator 104, a corneal oscillation measurement sensor 106, a controller 108. Herein, the controller 108 is coupled to the air pulse generator 104 and the corneal oscillation measurement sensor 106, wherein the controller 108 is configured to: control the air pulse generator 104 to generate an excitation air pulse 116 and send the excitation air pulse 116 towards the eye 102 at a velocity lying in a range of 15-130 metres per second; control the corneal oscillation measurement sensor 106 to measure a signal related to corneal oscillations caused by incidence of the excitation air pulse 116 on the eye 102; and determine the intraocular pressure from the measured signal.

[0069] Optionally, the air pulse generator 104 comprises a pressure chamber 110, a nozzle 112, and a valve 114. Optionally, the tonometer 100 further comprises a distance sensor 118 for measuring a first distance 120 between the eye 102 and the tonometer 100. As shown in FIG. 1A, since the excitation air pulse 116 has just exited the nozzle 112 and has not reached the eye 102 yet, a diameter of the excitation air pulse 116 is equal or more to a diameter of an exit aperture 122 of the nozzle 112. I.e. air impulse tends to spread as a function of distance from the exit aperture 122. As an example, if the distance is not more than 2-5 times the diameter the diameter in the surface of the eye is approximately (a bit higher) same as the diameter of the exit aperture. Optionally, the controller 108 is further configured to use the first distance 120 to control the velocity at which the excitation air pulse 116 is sent to towards the eye 102. With reference to FIG. IB, the valve 114 is arranged between the pressure chamber 110 and the nozzle 112, wherein when controlling the air pulse generator 104 to generate an excitation air pulse 116 (shown in FIG. 1A), the controller 108 (shown in FIG. 1A) is configured to perform at least one of: adjust a pressure of pressurized air held in the pressure chamber 110; adjust at least one of: a diameter, a shape, of an exit aperture 122 of the nozzle 112; open and close the valve 114 after a first period of time elapses after opening the valve 114. Optionally, the air pulse generator 104 further comprises a pressure sensor 124 and a pressure regulator 126 arranged in the pressure chamber 110, and wherein the pressure is set between range of 0.05- 5bars with the pressure regulator 126. Optionally, the exit aperture 122 of the nozzle 112 is mechanically-adjustable using an actuation arrangement 128 between diameter of 0.1 to 3 mm and / or the nozzle 112 is detachably attached to the pressure chamber 110 to change the nozzle 112 with nozzles of different exit aperture diameters. Optionally, as an example, the actuation arrangement 128 can be inside or outside the nozzle 112.

[0070] With reference to FIG. 1C, the exit aperture 122 and the first distance 120 both influence a diameter 130 of the excitation air pulse 116. As shown, the excitation air pulse 116 that had exited from the nozzle 122 in FIG. 1A has reached the eye 102 in FIG. 1C, wherein the excitation air pulse 116 spreads while travelling between the tonometer 100 and the eye 102. Specifically, a larger exit aperture 122 results in a larger diameter 130 of the excitation air pulse 116, and similarly a greater first distance 120 also results in a larger diameter 130. Optionally, the controller 108 (shown in FIG. 1A) is configured to open the valve 114 (shown in FIG. 1A and FIG. IB) when the first distance 120 is within a predetermined distance, and wherein a first period of time is 1 msec to 15 msec. This precise control ensures that the excitation air pulse 116 has an appropriate force and coverage necessary for an accurate intraocular pressure (IOP) measurement.

[0071] FIGs. 1A-1C are merely examples, which should not unduly limit the scope of the claims herein. A person skilled in the art will recognize many variations, alternatives, and modifications of embodiments of the present disclosure.

[0072] Referring to FIG. 2 illustrated is a graphical representation of a corneal displacement 202a of an applanation state and a corneal displacement 202b of an over-applanation state of an eye. As shown, different lines indicate different states of the cornea and there are represented three states, namely, a normal state 204, an applanation state with respect to an applanation line 206, and an over-applanation state 208. Herein, the applanation line 206 characterizes an applanation point. As shown, in the normal state 204, a surface of the eye maintains its natural curvature and there is no corneal displacement. When applanation tonometer is used the applanation state is achieved when the cornea deforms to the applanation line 206. Herein, the over-applanation state 208 occurs when excessive force flattens the surface of the eye beyond the applanation line 206. Optionally, a pressure of the excitation air pulse at the surface of the eye produces the corneal displacement 202 less than the applanation line 206 used in conventional air puff tonometer or Goldmann applanation tonometer. It will be appreciated that this approach ensures consistent measurement of the IOP by maintaining the corneal displacement 202 within a specific range, to avoid the overapplanation state 208.

[0073] FIG. 2 is merely an example, which should not unduly limit the scope of the claims herein. A person skilled in the art will recognize many variations, alternatives, and modifications of embodiments of the present disclosure. Referring to FIG. 3, illustrated is a graphical representation of an intraocular pressure value as a function of corneal frequency, in accordance with an embodiment of the present disclosure. As shown, the intraocular pressure values are plotted on the X-axis against the corneal frequency on the Y-axis. As shown, with an increase in the corneal frequency, the intraocular pressure values also increase.

[0074] FIG. 3 is merely an example, which should not unduly limit the scope of the claims herein. A person skilled in the art will recognize many variations, alternatives, and modifications of embodiments of the present disclosure.

[0075] FIG. 4 is an illustration of velocity of air at the surface of the cornea to resulting pressure (mmHg) in corneal surface on the area which is covered by the air pulse. The area covered by the excitation air pulse can be understood to be an effective contact area of the excitation air pulse, on the corneal surface. In practice implementation, the area covered by the air pulse corresponds to area (defined by diameter, in case of circular nozzle) of nozzle which is providing the air impulse. It has been found out that if higher velocities than 130 m / sec are used it will cause discomfort to eye. I.e. when resulting pressure is higher than 35mmHg. Further if the velocity is reduced too low then amplitude of resulting corneal oscillations is too low for measuring. Practical limit has been found to be 15m / sec for air impulse.

[0076] FIG. 4 is merely an example, which should not unduly limit the scope of the claims herein. A person skilled in the art will recognize many variations, alternatives, and modifications of embodiments of the present disclosure.

[0077] Referring to FIG. 5, illustrated are steps of a method for measuring an intraocular pressure of an eye with a tonometer, in accordance with an embodiment of the present disclosure. At step 502, the tonometer is aligned with respect to the eye. At step 504, an excitation air pulse is provided towards the eye at a velocity lying in a range of 15-130 metres per second, for forming a pressure of 0.5mmHg to 35 mmHg on a surface of the eye upon incidence of the excitation air pulse on the eye. At step 506, a signal related to corneal oscillations caused by the incidence of the excitation air pulse on the eye is measured. At step 508, the intraocular pressure of the eye is determined from the measured signal.

[0078] The aforementioned steps are only illustrative and other alternatives can also be provided where one or more steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein.

Claims

CLAIMS1. A tonometer (100) for measuring an intraocular pressure of an eye (102), the tonometer comprising: an air pulse generator (104); a corneal oscillation measurement sensor (106); a controller (108) coupled to the air pulse generator and the corneal oscillation measurement sensor, wherein the controller is configured to: control the air pulse generator to generate an excitation air pulse (116) and send the excitation air pulse towards the eye at a velocity lying in a range of 15 - 130 metres per second control the corneal oscillation measurement sensor to measure a signal related to corneal oscillations caused by incidence of the excitation air pulse on the eye; and determine the intraocular pressure from the measured signal.

2. A tonometer (100) according to claim 1, wherein the air pulse generator (104) comprises: a pressure chamber (110), a nozzle (112), and a valve (114) arranged between the pressure chamber and the nozzle, wherein when controlling the air pulse generator to generate the excitation air pulse, the controller (108) is configured to perform at least one of: adjust a pressure of pressurized air held in the pressure chamber; adjust at least one of: a diameter, a shape, of an exit aperture (122) of the nozzle; open the valve and close the valve after a first period of time elapses after opening the valve.

3. A tonometer (100) according to claim 2, wherein the air pulse generator (104) further comprises a pressure sensor (124) and apressure regulator (126) arranged in the pressure chamber, and wherein the pressure is set between range of 0.05 bars to 5 bars with the pressure regulator.

4. A tonometer (100) according to any of the preceding claims, wherein the tonometer comprises a distance sensor (118) for measuring a first distance (120) between the eye (102) and the tonometer.

5. A tonometer (100) according to claim 4, wherein the controller (108) is configured to open the valve (114) when the first distance (120) is within a predetermined distance, and wherein the first period of time is 1 msec to 15 msec.

6. A tonometer (100) according to any of claims 2-5, wherein the exit aperture (122) of the nozzle (112) is mechanically- adjustable using an actuation arrangement (128) between diameter (130) of 0.1 to 3.0 mm and / or the nozzle is detachably attached to the pressure chamber (110) to change the nozzle between nozzles of different exit aperture diameters.

7. A tonometer (100) according to any of claims 2-6, wherein the valve (114) is one of: an electrostatic microvalve, a piezoelectric microvalve, a thermo-pneumatic microvalve, an electromagnetic microvalve, a microelectromechanical systems (MEMS) microvalve.

8. A tonometer (100) according to any of the preceding claims, wherein a pressure of the excitation air pulse (116) at a surface of the eye (102) produces a corneal displacement (202) less than an applanation point (206).

9. A tonometer (100) according to any of the claims 4-8, wherein the controller (108) is further configured to use the first distance (120) tocontrol the velocity at which the excitation air pulse (116) is sent to towards the eye (102).

10. A tonometer (100) according to any of the preceding claims, the corneal oscillation measurement sensor (106) is one of: a confocal chromatic sensor, a laser displacement sensor, a camera, an optical coherence tomography (OCT)-based sensor, an ultrasonic sensor.

11. A tonometer (100) according to any of the preceding claims, wherein when determining the intraocular pressure from the measured signal, the controller (108) is configured to: determine a frequency of the corneal oscillations, from the measured signal; and calculate the intraocular pressure, based on the frequency.

12. A method for measuring an intraocular pressure of an eye (102) with a tonometer (100), the method comprising: aligning the tonometer with respect to the eye; providing an excitation air pulse (116) towards the eye at a velocity lying in a range of 15-130 metres per second, for forming a pressure of 0.5mmHg to 35 mmHg on a surface of the eye upon incidence of the excitation air pulse on the eye; measuring a signal related to corneal oscillations caused by the incidence of the excitation air pulse on the eye; and determining the intraocular pressure of the eye from the measured signal.

13. A method according to claim 12, wherein when providing the excitation air pulse, the method comprises performing at least one of: adjusting a pressure of pressurized air held in a pressure chamber (110) of the tonometer (100);adjusting at least one of: a diameter, a shape, of an exit aperture (122) of a nozzle (112) of the tonometer, for obtaining a diameter (130) of the excitation air pulse (116) at the surface of the eye (102) lies in a range of 0.1 to 3.0 millimeters; opening a valve (114) and closing the valve after a first period of time elapses after opening the valve, the valve being arranged between the pressure chamber and the nozzle.

14. A method according to any of claim 12 or 13, further comprising measuring a first distance (120) between the eye (102) and the tonometer (100) and optionally using the first distance for controlling the velocity at which the excitation air pulse (116) is sent to towards the eye.

15. A method according to any of claims 12-14, wherein the step of determining the intraocular pressure from the measured signal comprises: determining a frequency of the corneal oscillations, from the measured signal; and calculating the intraocular pressure, based on the frequency.

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