Air pulse tonometer for measuring intraocular pressure of an eye

Abstract

Disclosed is tonometer (100) for measuring intraocular pressure of eye (102), tonometer comprising: air pulse generator (104); displacement sensor (106); controller (108) coupled to air pulse generator and displacement sensor, wherein controller is configured to: control air pulse generator to generate excitation air pulse (110) and send excitation air pulse towards eye in first time period lying in range of 1 millisecond -15 milliseconds; control displacement sensor to measure signal related to deformation of cornea produced by excitation air pulse during first time period to form corneal displacement profile; determine, from the corneal displacement profile, the intraocular pressure of the eye.

Description

[0001] AIR. PULSE TONOMETER FOR MEASURING INTRAOCULAR PRESSURE OF

[0002] AN EYE

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to tonometers for measuring intraocular pressures of eyes. Moreover, the present disclosure relates to methods for measuring intraocular pressures of eyes with tonometers.

[0005] BACKGROUND

[0006] In the domain of ophthalmic diagnostics, precise measurement of an intraocular pressure (IOP) plays a vital role in identifying and managing conditions such as glaucoma. Accurate IOP readings are essential for timely intervention and treatment decisions to prevent vision loss. Typically, traditional methods for measuring the IOP often involve both contact-based and non-contact-based approaches, such as applanation tonometry and air-puff tonometry. The traditional methods, while effective in accuracy, can be uncomfortable for patients and may introduce variability in measurements due to factors like corneal biomechanics and operator technique.

[0007] Conventionally, applanation tonometry is widely accepted method, which involved flattening a small area of cornea to measure force required and calculate the IOP. However, this method is accepted for its accuracy but requires a direct contact with an eye and can be invasive and uncomfortable for patients. Conventional non-contact tonometers (using for example an air puff) are based on the Imbert-Fick principle that requires applanating the cornea from a reasonably large area (several millimeters in diameter). While improving patient comfort, these methods can still be susceptible to variations in measurement due to factors like air puffforce calibration and corneal response dynamics. However, existing methods in tonometry continues to face significant limitations. Firstly, contact-based methods can lead to patient discomfort and require precise calibration for accurate measurements. Secondly, non-contact-based methods, while minimizing discomfort may not consistently provide reliable IOP measurements across all patients, particularly those with irregular corneal surfaces or variations in corneal biomechanics. These challenges highlight the ongoing need for innovations that enhance the accuracy, reliability, and patientfriendliness for measuring the accurate IOP hence provides advancements in ophthalmic care towards more effective diagnostic tools.

[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 achieve precise, reliable, and non-invasive measurements of an intraocular pressure. 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.

[0011] 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.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1A illustrates a schematic illustration of a tonometer for measuring an intraocular pressure of an eye, and FIG. IB illustrates a schematic illustration of an air pulse generator of FIG. 1A, in accordance with an embodiment of the present disclosure;

[0014] FIG. 2A illustrates a graphical representation of a corneal deformation, and FIGs. 2B and 2C illustrate graphical representations of an excitation air pulse as a function of time, in accordance with an embodiment of the present disclosure; and

[0015] FIG. 3 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.

[0016] DETAILED DESCRIPTION OF EMBODIMENTS

[0017] 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.

[0018] 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 displacement sensor; a controller coupled to the air pulse generator and the displacement sensor, wherein the controller is configured to: control the air pulse generator to generate an excitation air pulse and control the air pulse generator to send the excitation air pulse towards the eye in a first time period lying in a range of 1 millisecond - 15 milliseconds; control the displacement sensor to measure a signal related to deformation of cornea produced by the excitation air pulse during the first time period to form a corneal displacement profile; and determine, from the corneal displacement profile, the intraocular pressure of the eye.

[0019] 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 during a first time period lying in a range of 1 millisecond -15 milliseconds; measuring a signal related to a deformation of cornea produced by the excitation air pulse during the first time period to form a corneal displacement profile; and determining the intraocular pressure of the eye from the corneal displacement profile.

[0020] The present disclosure provides the aforementioned first aspect and the aforementioned second aspect, for measuring an intraocular pressure (IOP) of an eye. Herein, the use of the displacement sensor enables for precise measurement of corneal deformation, which is essential for accurately determining the IOP. Beneficially, the excitation air pulse lying in a range of 1 millisecond - 15 milliseconds ensure an expeditious measurement process, reducing discomfort for a patient and minimizing overall procedure time. This precise control over the excitation air pulse duration enhances consistency of measurements and enables for accurate assessment of corneal displacement. Herein, the aforementioned method emphasizes aligning the tonometer with the eye, which ensures that the excitation air pulse is accurately directed towards the cornea. It will be appreciated that non-contact nature of the excitation air pulse method is less invasive and more comfortable for patients compared to contact-based methods hence reducing the risk of infection and corneal abrasion. Furthermore, the non-contact nature of the excitation air pulse method minimizes mechanical stress on cornea, preserving the integrity of corneal tissue and avoiding potential complications associated with the contact-based methods. This present disclosure differs from the Imbert-Fick principle as an applanation state is not needed. According to present disclosure the intraocular pressure is defined from the displacement / velocity profile of the cornea that is measured during excitation air pulse.

[0021] The term "tonometer" refers to a device that is used to measure the intralocular 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.

[0022] Throughout the present disclosure, the term "air pulse generator" refers to a component of the tonometer for producing 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 movement for an accurate IOP readings, thereby enhancing patient's safety.

[0023] 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 within the pressure chamber to regulate a force of the excitation air pulse emitted from the nozzle; regulate a duration of the excitation air pulse by controlling opening and closing of the valve; and adjust a velocity of air through the nozzle to achieve the peak value of corneal displacement.

[0024] 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 nozzle. In an embodiment the air pulse generator comprises an air pump which is used to fill the pressure chamber with air. Further alternatively the air pump can be used to generate air pump directly. The pressure chamber ensures that there is 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. Notably, the air pulse generator utilizes a pressure generation means to generate the excitation air pulse of certain pressure inside of the nozzle. 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 is 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. Herein, the pressure within the pressure chamber is controlled to modulate the force of the excitation air pulse. By increasing or decreasing the pressure, the tonometer can generate the excitation air pulse that is strong enough to deform the cornea to a measurable extent but not so strong as to cause discomfort or damage. In this regard, the tonometer may be precisely controlled to customize the force and shape of the excitation air pulse for individual patients. It will be appreciated that the pressure chamber's consistent and controlled supply of pressurized air ensures reliable IOP measurements, enhancing an accuracy and reliability of the tonometer. In one optional embodiment pressure chamber can be implemented or considered to be part of the air pump.

[0025] Moreover, the valve controls the duration of the excitation air pulse by opening and closing at specific intervals. This ensures that the excitation air pulse is delivered for an optimal length of time to achieve desired corneal deformation. It will be appreciated that the precise control over the timing and duration of the excitation air pulse, facilitated by the valve, enables for adjusted air pulses that can accommodate different patient sensitivities and corneal conditions hence reducing discomfort and increasing patient compliance.

[0026] Additionally, the velocity of the air through the nozzle is adjusted to ensure that the excitation air pulse achieves the peak value of corneal displacement. It will be appreciated that by adjusting the velocity of air through the nozzle, the tonometer can fine-tune the force applied to the cornea, ensuring that the corneal deformation is optimal for the accurate IOP readings without causing unnecessary stress or damage to the eye. Herein, the velocity is essential for determining the force applied to the cornea and its subsequent deformation. Notably, the velocity of air is different from the velocity of the corneal deformation. The velocity of air defines the force which is applied to the cornea.

[0027] A technical effect of configuring the controller in such a manner is that it enables precise control over at least one of: the pressure, the duration, and the velocity of the air, which ensures accurate IOP measurements while minimizing the patient discomfort and reducing a risk of irritating the eye.

[0028] Optionally, the air pulse generator further comprises: a pressure sensor; and a pressure regulator arranged in the pressure chamber; wherein the controller is configured to adjust the pressure within the pressure chamber to maintain the pressure within a range of 0.05 to 5 bars to achieve the peak value of corneal displacement.

[0029] 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. Herein, the pressure sensor continues to monitor and provide feedback to ensure consistent pressure throughout the measurement process to achieve the peak value of corneal displacement. 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 order to achieve the peak value of the corneal displacement. Herein, the pressure inside the pressure chamber may, for example, lie in a range from 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10,

[0030] 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70,

[0031] 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30,

[0032] 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, 2.65, 2.70, 2.75, 2.80, 2.85, 2.90,

[0033] 2.95, 3.00, 3.05, 3.10, 3.15, 3.20, 3.25, 3.30, 3.35, 3.40, 3.45, 3.50,

[0034] 3.55, 3.60, 3.65, 3.70, 3.75, 3.80, 3.85, 3.90, 3.95, 4.00, 4.05, 4.10,

[0035] 4.15, 4.20, 4.25, 4.30, 4.35, 4.40, 4.45, 4.50, 4.55, 4.60, 4.65, 4.70,

[0036] 4.75, 4.80, 4.85, 4.90, 4.95 up to 0.10, 0.15, 0.20, 0.25, 0.30, 0.35,

[0037] 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95,

[0038] 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55,

[0039] 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15,

[0040] 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, 2.65, 2.70, 2.75,

[0041] 2.80, 2.85, 2.90, 2.95, 3.00, 3.05, 3.10, 3.15, 3.20, 3.25, 3.30, 3.35,

[0042] 3.40, 3.45, 3.50, 3.55, 3.60, 3.65, 3.70, 3.75, 3.80, 3.85, 3.90, 3.95,

[0043] 4.00, 4.05, 4.10, 4.15, 4.20, 4.25, 4.30, 4.35, 4.40, 4.45, 4.50, 4.55,

[0044] 4.60, 4.65, 4.70, 4.75, 4.80, 4.85, 4.90, 4.95, 5.00 bars It will be appreciated that maintaining the pressure within the pressure chamber within said range ensures that the excitation air pulse is delivered to the cornea in a consistent and a controlled manner. Such manner of delivering the pressure is essential for achieving peak value of corneal displacement accurately, which directly impacts the reliability of the IOP measurement. Alternatively, if the pressure lies outside the range 0.05 to 5 bars, the controller is configured to generate and send a control signal to the pressure regulator to either increase or decrease the pressure to lie within said range. The pressure regulator is configured to respond to such control signals by modulating the flow of air into or out of the pressure chamber.

[0045] As an example, if the pressure may be 0.04 bars, i.e., the pressure 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. Conversely, if the pressure may be 5.2 bars, i.e., the pressure lies higher than a higher value of the range, the pressure regulator may release air to reduce the pressure inside the pressure chamber. Subsequently, when the pressure is set between the range 0.05 to 5 bars, the controller is configured to maintain this pressure within the pressure chamber. A technical effect of the aforementioned feature is that the excitation air pulse always hits the cornea of the eye in a gentle manner and still achieve the peak value of displacement for subsequent measurements. Further benefit of controlling the air velocity at the surface of the cornea or the air pressure (function of velocity of the air) at the surface of the cornea is that the corneal deformation / movement can be controlled precisely to measure, for example, the corneal deformation amplitude or velocity of deformation changes. Limiting the pressure or velocity enhances comfort for the patient.

[0046] Optionally, the nozzle is detachably attached to the pressure chamber to change the nozzle between nozzles of different exit aperture diameters. In this regard, the nozzle can be easily removed and replaced with different nozzles that have varying exit aperture diameters. The diameter of the exit aperture of the nozzle directly influences a parameter of the excited air pulse that is sent towards the eye, wherein the parameters comprise at least one of: an air velocity, an air pulse diameter, focusing the air flow (i.e controlling diameter of the air pulse), an air pulse duration, and pressure inside the nozzle. The parameter is used to control at least one of: the force with which the excitation air pulse is emitted from the nozzle, an area of contact of the excitation air pulse at the cornea, during the measurement process. This influences the peak value and the area of the corneal displacement, which in turn affects the accuracy and reliability of the IOP measurements. Additionally, it will be appreciated that having different exit aperture diameters of the nozzle enables customizing the tonometer based on user requirement. It will be appreciated that, medical professionals can select a nozzle of a particular exit aperture diameter based on factors like patient comfort, corneal characteristics, desired measurement sensitivity, and so forth, which ensures reliable and adaptable IOP readings.

[0047] A technical effect of the aforementioned feature is that the nozzle of the tonometer can be customized based on eye condition of the patient, so that the excitation air pulse that is incident on the cornea is gentle and does provide discomfort to the patient.

[0048] Throughout the present disclosure, the term "displacement sensor" refers to a sensor specifically designed to measure minute changes in a position, or a movement of the cornea caused by the excitation air pulse during the IOP measurement. Notably, the displacement sensor detects and quantifies the corneal deformation, including the peak value of the corneal displacement, oscillation frequency, and related parameters which are essential for accurate determination of the IOP using noncontact air pulse tonometry methods.

[0049] Optionally, the displacement sensor is a confocal chromatic sensor (CCS). In this regard, the confocal chromatic sensor measures the corneal displacement induced by the excitation air pulse. The CCS can detect minute changes in the distance between the sensor and the cornea, ensuring precise determination of the peak value of corneal displacement during the excitation air pulse. CCS operates by analyzing the wavelengths of the light reflected from the measured surface. The wavelength that focus on the surface of the measured objects relates to the distance of the object. This method provides accurate measurements without physical contact, aligning with non-invasively and precisely assessing the IOP based on the corneal deformation. Notably, the CCS 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. Alternatively, optionally, the displacement sensor is one of: an ultrasound sensor, a laser displacement sensor. It will be appreciated that utilizing light interference patterns instead of physical contact, the CCS reduces the risk of the patient discomfort and minimizes potential for corneal abrasion or infection, ensuring a safer measurement process. It will be appreciated that the CCS is also capable of measuring corneal thickness in real time during the IOP measurement process, similar to a pachymeter. Additionally, it will be appreciated that implementing the displacement sensor as the CCS provides an opportunity to use the tonometer as a combined tonometer-pachymeter, allowing the pachymetric results to be used to correct the IOP measurements. This integration enhances the accuracy of the IOP measurements by considering corneal thickness, thereby providing a more comprehensive assessment of ocular health.

[0050] A technical effect of using the displacement sensor as the CCS is that it enables precise and real-time measurement of the corneal displacement during the excitation air pulse. Moreover, leveraging the displacement sensor as the CCS provides an automatic pachymetry-based adjustment of the IOP measurement, based on the measured corneal thickness, thereby improving accuracy. This eliminates the clinical need for a separate pachymeter device and manual pachymeter data transfer, thereby reducing cost, patient discomfort, and workflow complexity. It may be appreciated that the tonometer's controller is configured to automatically determine whether the measured corneal thickness lies within a predefined normal range and apply a correction factor when it deviates in real-time. Said automation removes operator subjectivity and minimizes human error in manually inputting pachymetry data. Moreover, by correcting the intraocular pressure values automatically in real-time, the disclosed tonometer reduces the clinical workflow to one measurement step and enhances patient-specific accuracy that is not achievable with conventional tonometers. Thus, said synergistic integration leads to a patient-specific IOP assessment, ensuring higher diagnostic accuracy compared to conventional systems (tonometers and pachymeters) that operate on optical or applanation-only measurement, population averages, or uncorrected corneal profiles. This aforementioned feature of employing a single optical displacement sensor to perform both roles simultaneously, especially in a time-critical IOP measurement cycle, makes the disclosed tonometer novel and non- obvious in view of the conventional systems.

[0051] 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 displacement sensor pertaining to the deformation of the cornea caused by the excitation air pulse; to process information available in the received input; and to control components of the air pulse generator to adjust 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.

[0052] Throughout the present disclosure, the term "first time period" refers to a specific duration during which the excitation air pulse is generated and directed towards the eye by the tonometer. The first time period may, for example, lie in a range from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 milliseconds up to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 milliseconds. Herein, the controller is configured to initiate by generating and sending instructions to the air pulse generator, to generate a short burst of pressurized air. These instructions activate mechanisms within the air pulse generator, to release a controlled amount of air from the pressure chamber. Throughout this process, the controller maintains precise control over the duration, and optionally the intensity of the excitation air pulse. Such precise control facilitates consistent corneal deformation, which directly correlates with accurate measurements of the IOP. Furthermore, it will be appreciated that limiting the duration of the excitation air pulse to 1-15 milliseconds provides a bounded, short excitation window for measurement that is more patient friendly. In other words, with the aforementioned short excitation window for measurement, the tonometer reduces discomfort for the patient, as the cornea is exposed to the excitation air pulse briefly. This brief exposure enhances overall patient comfort and compliance. Furthermore, it will be appreciated that controlled timing of the excitation air pulse streamlines the measurement process, allowing for quicker assessments without compromising accuracy, namely, high-speed, patient-comfortable IOP measurement, not achievable with conventional tonometers that employ traditional applanation or long-pulse air tonometry. This efficiency supports enhanced workflow in clinical environments, improving throughput and patient care delivery. Furthermore, limiting the duration of the excitation air pulse to 1-15 milliseconds reduces variability by limiting corneal viscoelastic recovery interference. Additionally, limiting the duration of the excitation air pulse to 1-15 milliseconds enables higher temporal resolution of displacement capture.

[0053] Optionally, the controller is configured to: control the valve to remain open during the first time period; and control the valve to be closed after the first time period.

[0054] In this regard, a purpose of controlling the valve is to manage airflow from the pressure chamber to the nozzle, thereby controlling the excitation air pulse directed towards the eye. Herein, the controller is configured to generate and send instructions to the valve to remain open for the first time period. This action enables the pressurized air to flow continuously from the pressure chamber through the nozzle, generating the excitation air pulse. When the first time period has elapsed, the controller is configured to generate and send instructions to the valve for closing. This closure stops the flow of the pressurized air, thereby terminating the excitation air pulse directed towards the eye.

[0055] It will be appreciated that by controlling the valve to remain open during the first time period, the tonometer ensures precise and consistent delivery of the excitation air pulse. This consistency is essential for obtaining reliable measurements of corneal response, which directly correlates with the accurate IOP readings. Furthermore, by promptly closing the valve after the first time period, the tonometer minimizes unnecessary exposure of the eye to the excitation air pulse, thus enhancing patient comfort and safety during the measurement process. A technical effect of the aforementioned feature is that it facilitates a controlled and accurately timed excitation air pulse, leading to accurate IOP measurements.

[0056] Throughout the present disclosure, the term "signal" refers to an output generated by the displacement sensor that represents the deformation of the cornea in response to the excitation air pulse. This signal is typically a series of electronic data points that quantify extent of the corneal displacement over time, capturing dynamic response of the cornea during and immediately after application of the excitation air pulse. The term "corneal displacement profile" refers to a comprehensive record of the deformation of the cornea over the first time period, as captured by the displacement sensor. Notably, the corneal displacement profile includes at least one of: the peak value of the corneal displacement, the time taken to reach this peak, the acceleration and deceleration phases of the corneal deformation. The corneal displacement profile is used to analyze corneal biomechanics and to accurately determine the IOP based on response of the cornea to the excitation air pulse. In this regard, the corneal displacement profile provides biomechanical insight into corneal stiffness / response. This way the corneal displacement profile increases diagnostic reliability of the present system in comparison to the conventional single applanation-point methods.

[0057] Herein, the controller is configured to activate the displacement sensor during the first time period when the excitation air pulse is applied to the eye. The displacement sensor is configured to measure the deformation of the cornea and sends these measurements to the controller. The controller then configured to process these measurements to form the corneal displacement profile. It will be appreciated that the precise and real-time measurement of the corneal deformation within the first time period ensures an accurate corneal displacement profile. This accurate corneal displacement profile is essential for reliably determining the IOP and significantly improving the overall accuracy of the tonometer.

[0058] Optionally, the corneal displacement profile is determined as a function of time during the first time period. In this regard, the air pulse generator is triggered to emit a controlled excitation air pulse in a precise manner towards the cornea of the eye. This excitation air pulse deforms the cornea of the eye temporarily, causing the cornea to displace. Simultaneously, as the excitation air pulse is generated, the controller is configured to activate the displacement sensor to start measuring the corneal displacement. In this regard, the displacement sensor captures the extent of the corneal deformation throughout the first time period. These measurements are typically recorded at a high frequency (for example, a high frequency of 1000 samples per millisecond) to accurately capture the dynamic response of the cornea. Herein, high frequency sampling during the first time period enables a detailed and high resolution of the corneal displacement profile. The captured data points are then transmitted to the controller, which processes the information to determine the corneal displacement profile. It will be appreciated that by capturing the corneal displacement profile as a function of time, the tonometer can accurately determine the dynamics of the corneal deformation. Additionally, it will be appreciated that by determining the corneal displacement profile over time, the tonometer can adapt to different patient-specific characteristics, such as varying corneal thickness or rigidity.

[0059] A technical effect of the aforementioned feature is that it enables the tonometer to account for complete deformation and recovery phases of the cornea, leading to a more accurate assessment of corneal biomechanics.

[0060] Optionally, a pressure of the excitation air pulse at a surface of the eye produces the deformation of the cornea, wherein said deformation lies in a range of 1 micrometre to 300 micrometres. Herein, the controller is configured to regulate the partial pressure of the excitation air pulse to ensure that the deformation of the cornea lies within the range of 1 micrometre to 300 micrometres. The deformation may, for example, lie in a range from 1, 2, 5, 8, 15, 20, 30, 40, 80, 140, 210, or 295 micrometres up to 10, 50, 90, 130, 170, 200, 230, 260, 280, 290, or 300 micrometres. This deformation is achieved by adjusting at least one of: velocity of the excitation air pulse, the duration of the excitation air pulse, the intensity of the excitation air pulse, the configuration of the nozzle, thus ensuring that the force applied to the cornea is sufficient for measurement but not excessive. Such range ensures that the tonometer can reliably detect and quantify corneal responses across a spectrum of the IOP without exceeding safe deformation limits. A technical effect of the aforementioned feature is that the tonometer can provide the excitation air pulse at the pressure which maintains patient comfort and safety while measuring the IOP. It may be appreciated that by limiting corneal deformation to between 1 pm and 300 pm, the disclosed tonometer ensures that the cornea is never subjected to excessive force from the excitation air pulse. Notably, deformations below 1 pm would be too small to detect reliably, leading to inaccurate measurements dominated by sensor noise; and deformations above 300 pm would represent clinically unsafe levels of stress, potentially causing patient discomfort or risk of corneal microtrauma. Thus, the defined range represents an optimal operational window balancing measurement sensitivity and patient safety. Moreover, corneal biomechanics (stiffness, damping, viscoelasticity) can be accurately profiled only when the induced displacement lies within the aforementioned range consistent with the mechanical sensitivity of the cornea, i.e., where the cornea exhibits elastic and measurable deformation behavior.

[0061] Throughout the present disclosure, once the corneal displacement profile is determined, the data points from the corneal displacement profile are then analyzed to extract information that can be used to determine the IOP of the eye. Examples of such information may include, but are not limited to, a magnitude of the peak value of the corneal displacement, a time required to reach the peak value of the corneal displacement, and the like. This information is then compared against reference information comprised in a calibration model or an algorithm model, wherein the reference information is correlated with values of the IOP. The calibration model or the algorithm model is typically derived from empirical data and establishes a relationship between the characteristics of corneal deformation and pressure exerted within the eye. Using the established correlation, the controller is configured to determine the IOP. Then, the IOP is displayed or recorded, providing a measurement that reflects the pressure within the eye.

[0062] Optionally, the controller is configured to: process the corneal displacement profile to perform at least one of:

[0063] (i) identify of a peak value of corneal displacement; (ii) identify of a time taken to reach the peak value of corneal displacement;

[0064] (iii) determine of an acceleration profile of the deformation of the cornea, from the corneal displacement profile; and determine the intraocular pressure, based on at least one of: the peak value of corneal displacement, the time taken to reach the peak value of corneal displacement, and / or the acceleration profile.

[0065] In this regard, the term "peak value of corneal displacement" refers to a maximum extent of deformation that the cornea undergoes as a result of the excitation air pulse applied by the tonometer. The peak value is a critical measurement that indicates highest point of the corneal deformation captured by the displacement sensor during the first time period. Herein, the peak value of corneal displacement is essential for accurately assessing the biomechanical response of the cornea to the excitation air pulse being applied, which in turn is used to determine the IOP. Optionally, the peak value of corneal displacement is independent of applanation state of the eye. Herein, the controller is configured to process the corneal displacement profile, to determine maximum deformation of the eye and the corresponding time when said maximum deformation occurs.

[0066] Herein, when the controller is configured to generate and send the excitation air pulse towards the eye, i.e., when the excitation air pulse is turned ON, the cornea moves inward, thus causing deformation of the eye. This deformation can be represented graphically, in a form of a deformation curve. In this regard, the deformation curve first has a downwards curve, as pressure of the excitation air pulse on the eye increases which deforms the cornea, thus causing displacement. When the deformation curve reaches the peak value, there is no further deformation of the eye. Hence, the controller is configured to stop sending the excitation air pulse towards the eye, i.e., the excitation air pulse is turned OFF. Subsequently, the deformation curve has an upwards curve, as the pressure of the excitation air pulse on the eye decreases. Herein, the cornea returns to its natural position.

[0067] Moreover, when the excitation air pulse is turned OFF, a decay time of the excitation air pulse can either be fast or slow. When the decay time of the excitation air pulse is fast, then corneal oscillations can be distinctly measured, as abrupt cessation of the excitation air pulse allows the cornea to freely oscillate back to its original position. This is depicted as a series of oscillatory waves following an initial corneal displacement, indicating the corneal oscillations over time. These corneal oscillations are essential as they provide additional data points that help in determining biomechanical properties of the cornea hence enhances the IOP measurements. Alternatively, when the decay time of the excitation air pulse is slow, there is a gradual return of the cornea to its natural position, leading to a deformation curve that is smooth and with reduced oscillatory behaviour. This option may be preferred in scenarios where the corneal oscillations are not of primary interest.

[0068] Herein, the peak value of corneal displacement is inversely correlated with the IOP. In this regard, higher the peak value of the corneal displacements, lower will be the IOP, and vice versa. Moreover, the time taken for the cornea to reach the peak value of the corneal displacement is also inversely related to the IOP. In this regard, as the IOP increases, the peak value of the displacement is reached quickly.

[0069] Herein, the term "acceleration profile" refers to a detailed representation of corneal acceleration as the function of time. In other words, the acceleration profile represents a rate of change of velocity of the deformation over the first time period. The acceleration profile captures how quickly the speed of the deformation changes in response to the excitation air pulse, thus providing valuable insights into the biomechanical properties of the cornea. Herein, determining the acceleration profile provides information about dynamic response of the cornea to the excitation air pulse. Herein, the displacement sensor is configured to capture the corneal displacement over time during and after the application of the excitation air pulse. In this regard, the corneal displacement profile is processed to calculate the acceleration at each point in time. This involve by any one of: determining a first derivative of the velocity of the deformation, determining a second derivative of the corneal displacement.

[0070] Optionally, the IOP is determined when the velocity of the deformation is plotted as the function of time, wherein a slope of such plotting represents the acceleration profile of the deformation of the cornea. Herein, steeper the slope, higher will be the IOP.

[0071] A technical effect of determining the IOP based on at least one of: the peak value of corneal displacement, the time taken to reach the peak value of corneal displacement, and / or the acceleration profile is that it enables for a more nuanced and accurate assessment of corneal biomechanics, leading to improved diagnostic precision and better management of ocular conditions like glaucoma.

[0072] Table I provides measured correlations between IOP, peak value of corneal displacement, time to reach the peak value of the corneal displacement and acceleration profile (max acceleration of the corneal surface). As it can be seen by measuring at least one of the values one can derive the IOP.

[0073] TABLE I.

[0074] Optionally, the tonometer further comprises a distance sensor for measuring a distance between the eye and the tonometer, wherein the controller is further configured to perform any one of: open the valve when the distance is within a predetermined distance range 5-15 mm, standardize the deformation of the cornea in the corneal displacement profile based on the distance.

[0075] In this regard, the term "distance sensor" refers to an electronic component integrated into the tonometer, designed to measure the distance between the tonometer and the corneal surface of the eye. Notably, an accurate measurement of the IOP using the tonometer requires precise positioning of the tonometer relative to the eye, as a distance between the tonometer and the eye affects the force exerted by the excitation air pulse on the cornea. Such force consequently influences the deformation of the cornea. Specifically, the peak value of the corneal displacement changes based on the distance between the tonometer and the eye, i.e., as said distance increases, the excitation air pulse loses force, causing less deformation. When such less deformation occurs, the corneal displacement is standardized (namely, normalized) based on the distance to ensure that the IOP is not affected by variations in the distance between the tonometer and the eye.

[0076] In this regard, the distance sensor measures the distance between the tonometer and the eye. When the distance lies within the predetermined distance range, the controller is configured to open the valve to send the excitation air pulse towards the cornea. Herein, the term "predetermined distance" refers to a pre-set distance between the tonometer and the eye, based on normal measurement conditions, i.e., when the patient has no eye condition. When the distance does not within the predetermined distance, adjustments can be made either by repositioning the tonometer or by repositioning the patient. In other words if the distance between the tonometer and the eye differs from the predefined (optimum) value, this difference can be corrected either by adjusting the air velocity or by normalizing the measured corneal displacement curve with the distance

[0077] Alternatively, the controller is configured to standardize (namely, normalize, compensation) the deformation of the cornea by factoring in the distance and / or angle between the tonometer and the eye. This compensation ensures that regardless of said distance and / or angle, the corneal deformation profile accurately reflects a response of the cornea to the excitation air pulse. Such standardization is performed using any one of: a look up table originating from experiments, a formula, an equation, a rule, a mathematical model, to adjust the deformation measured to account for the distance. Optionally, the controller is further configured to determine a normalization factor that is applied to the peak value of corneal displacement based on the distance and / or angle. Herein, instead of directly increasing the force of the excitation air pulse when the distance between the tonometer and the eye increases, the standardization mathematically adjusts the deformation, thus compensating for weakening of the force as the distance increases. The controller is thus configured optionally to standardize (namely, normalize, compensation) the deformation of the cornea by factoring (by taking in account) angle and / or velocity between the tonometer and the eye. The angle refers to angle between direction of the excitation air pulse and normal of the eye surface at the location of impact. Further, optionally, the distance and / or angle can be used to adjust profile of the excitation air pulse. As an example, duration of the excitation air pulse can be controlled based on distance (longer the distance longer the duration). Other example of adjusting the profile is changing the velocity of the excitation air pulse. The velocity of the air pulse might be increased if angle is large (i.e. angle between the normal of the eye surface and direction of the excitation air pulse is for example 10, 20, 30, 40, 50, 60 degrees).

[0078] A technical effect of the aforementioned feature is that it ensures the tonometer is correctly positioned before releasing the excitation air pulse, hence enhancing measurement accuracy. Moreover, the aforementioned feature ensures measurement accuracy despite patient or device misalignment. Thereby, solving a longstanding limitation in non-contact tonometry that is currently dependent on the operator's judgement.

[0079] Optionally, the controller is further configured to: determine an oscillation frequency of the deformation of the cornea after the first time period; and update the intraocular pressure, based on the oscillation frequency.

[0080] In this regard, the term "oscillation frequency" refers to a number of complete cycles of a periodic motion that occur per unit time. Herein, the oscillation frequency represents the rate at which the cornea oscillates as it returns to its original shape after being deformed by the excitation air pulse. The oscillation frequency is typically measured in Hertz (Hz), where one Hertz equates to one cycle per second. The oscillation frequency serves as a fitting parameter that directly correlates with the IOP. Herein, the oscillation frequency of the corneal deformation or corneal resonance serves as an IOP indicator, beyond applanation. Moreover, measuring the oscillation frequency improves signal-to-noise ratio, since oscillatory patterns persist beyond air turbulence artifacts. Thus, the oscillation frequency of the corneal deformation adds robustness to IOP measurements by cross-validating displacement-based measurement. Notably, a higher oscillation frequency indicates lower IOP, while a lower oscillation frequency indicates higher pressure levels within the eye. This approach provides a non-invasive and precise method for measuring the IOP, essential for diagnosing and managing conditions such as glaucoma. After the cornea is deformed by the excitation air pulse, the cornea undergoes a series of oscillations as it returns to its original shape. Notably, the series of oscillations refers to the repeated motion of the cornea as the cornea vibrates or oscillates after the initial deformation caused by the excitation air pulse. The tonometer detects these oscillations using the displacement sensor, for example, such as the CCS. The displacement sensor captures the displacement of the cornea which is time-varying in nature, and the data is processed by the controller to determine the oscillation frequency. This is achieved by analyzing the displacement data to identify the peaks and troughs of the corneal oscillations over time, which allows the calculation of the frequency of these oscillations. Moreover, similar to the non-contact nature of the excitation air pulse, the non-contact nature of the oscillation frequency measurement enhances the non-invasive / non-contact nature of the measurement that is more comfortable for patients compared to the conventional contact-based systems (such as applanation-based systems).

[0081] As an example, the oscillation frequency of the deformation of the cornea can be determined using a general form of the equation of motion, wherein the general equation of motion is given by equation (1): mx + ex + kx = 0 (1) wherein, m is a mass of a corneal tissue, c is a damping coefficient, k is a spring constant, x is a corneal displacement, x is a first derivative of the corneal displacement which is a velocity, and % is a second derivative of the corneal displacement which is an acceleration.

[0082] In further example oscillation frequency can be correlated with intraocular pressure using pre-determined look up table. Table II is an example measurement of relationship between the oscillation frequency and intraocular pressure value of an eye (mmHg)

[0083] TABLE II

[0084] Once the oscillation frequency is determined, the IOP can be determined using a pre-determined calibration algorithm that correlates the oscillation frequency with the IOP. The oscillation frequency is then used to update the IOP reading by applying the pre-determined calibration algorithm that correlates the oscillation frequency with intraocular pressure levels. This enables the tonometer to provide an accurate, reliable, and non-contact measurement of IOP, enhancing patient comfort and compliance. A technical effect of the aforementioned feature is that it enables precise determination of the IOP through analysis of the oscillation frequency of the corneal deformation. This approach enhances the accuracy and reliability of the IOP measurements by leveraging the dynamic biomechanical response of the cornea to the excitation air pulse. Optionally, the tonometer further comprises a corneal oscillation measurement sensor, wherein the controller is further configured to: control the corneal oscillation measurement sensor to measure another signal related to the corneal oscillations caused by incidence of the excitation air pulse on the eye, after the first time period; and determine the intraocular pressure from the measured another signal and the measured signal.

[0085] In this regard, 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 the corneal oscillations observed on the corneal surface after the excitation air pulse impacts on the corneal surface. Herein, the term "another signal" refers to a secondary signal detected by the corneal oscillation measurement sensor, which is related to the corneal oscillations occurring after an initial response to the excitation air pulse. Optionally, the various characteristics of the corneal oscillation used herein may refer to: an amplitude, a frequency, 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.

[0086] Herein, the corneal oscillation measurement sensor is communicably coupled with the controller. The controller is further configured to control the corneal oscillation measurement sensor to start capturing data after the first time period. This timing ensures that the another signal corresponds specifically to the corneal oscillations induced by the excitation air pulse. Once activated, the corneal oscillation measurement sensor continuously monitors the corneal surface for oscillatory movements. Specifically, the corneal oscillation measurement sensor detects changes in at least one of: a corneal shape, an amplitude, a frequency, that is indicative of the corneal biomechanical response, which is then sent to the controller. In this regard, to determine the IOP, the controller is further signal to integrate information from both the signal (related to the deformation) and the another signal. The signal and the another signal collectively provide a comprehensive view of the corneal biomechanics influenced by the excitation air pulse.

[0087] Subsequently, the controller is further configured to process this information using algorithms calibrated to correlate specific parameters of the corneal response with the IOP levels. Such algorithms are well- known in the art. Examples of the specific parameters may include, but are not limited to, an oscillation frequency, an amplitude ratio, a phase relationship, and so forth. This approach enhances the accuracy and reliability of the IOP measurements, particularly in capturing nuances of the corneal behavior beyond the immediate impact of the excitation air pulse. It will be appreciated that the tonometer can be used together with an oscillation-based air pulse tonometer to obtain the IOP measurements based on both the signal related to the deformation of cornea and the another signal after the controller is configured to stop sending the excitation air pulse. This combined use enhances the robustness and accuracy of the IOP assessments. A technical effect of the aforementioned feature is that it enables the tonometer to measure and analyze the another signal, thereby enhancing capability of the tonometer to assess biomechanical response of the eye following the initial excitation air pulse.

[0088] Optionally, when determining the intraocular pressure, the controller is further configured to: control the displacement sensor to determine a corneal thickness of the eye; determine whether the corneal thickness of the eye lies in a predefined range of average corneal thickness; when the corneal thickness of the eye lies outside the predefined range of average corneal thickness, determine a correction factor based on how much the corneal thickness of the eye deviates from the predefined range of average corneal thickness; and adjust the intraocular pressure, based on the correction factor.

[0089] In this regard, the term "corneal thickness" refers to the measurement of the distance between an anterior and posterior surface of the cornea at a given point. Typically, the corneal thickness of the eye is measured in micrometres (pm) and provides essential information about structural properties of the cornea. However, the corneal thickness can influence the biomechanical response of the eye to applied forces and is an essential parameter in determining the IOP accurately. Variations in the corneal thickness can affect the accuracy of IOP measurements, making it important to measure this parameter precisely. The term "predefined range of average corneal thickness" refers to a specific interval of the corneal thickness measured in micrometres that has been created based on clinical research and empirical data. The predefined range of average corneal thickness accounts for normal variations in the corneal thickness among population and provides boundaries within which the IOP measurements are considered reliable without requiring additional corrections. The term "correction factor" refers to a numerical value or an adjustment applied to account for deviations from a standard or expected measurement. Herein, the correction factor quantifies a discrepancy between the measured corneal thickness and the predefined range of average corneal thickness of the eye. It will be appreciated that a capability to adjust the IOP based on individual thickness of the cornea ensures that each measurement is adjusted to the specific anatomical characteristics of patient's eye, thereby enhancing the precision of the diagnostic process. Herein, the controller is further configured to control the displacement sensor to measure the corneal thickness of the eye accurately. The displacement sensor sends and receives yet another signal (such as ultrasound or optical coherence) to determine the distance between the anterior and the posterior surfaces of the cornea, thus measuring the corneal thickness of the eye. Subsequently, a deviation is determined when the corneal thickness lies outside the predefined range of average corneal thickness. Based on this deviation, the correction factor is determined using at least one of: a formula, a rule (for example, such as for every 20 pm deviation from an average corneal thickness, the IOP may be adjusted by 1 mmHg), that is well-known in the art. The correction factor is then used to adjust the IOP to ensure that the corneal thickness is accounted for, by subtracting the correction factor from the IOP that was initially measured. A technical effect of the aforementioned feature is that it ensures the accuracy and reliability of the IOP measurements by accounting for variations in the corneal thickness. This adjustment process minimizes errors in the IOP readings hence leading to better diagnosis and management of ocular conditions, thereby enhancing patient outcomes.

[0090] Moreover, the aforementioned feature improves accuracy of the IOP measurements across patient groups with thin or thick corneas. Furthermore, the aforementioned feature applies (or implements) a simple, selective, conditional deviation-based correction factor scheme (or approach), only when the measured values of the corneal thickness are outside the normal range, thereby avoiding overcorrection in patients with normal corneal thickness. The dynamic deviation-based correction factor scheme serves as a closed-loop measurement-correction-update cycle that produces patient-specific intraocular pressure values automatically. It may be appreciated that the aforementioned feature is contrary to the existing solutions that ignore pachymetry entirely; apply pachymetry correction universally (i.e., to all measurement values) to obtain accurate IOP regardless of hardness; or focuses on biomechanical stiffness / elasticity instead of thickness. This further reduces false positives or false negatives while maintaining reliability in the normal range. Moreover, the aforementioned feature is a novel and non-obvious refinement that balances accuracy with simplicity. Additionally, the aforementioned feature that leads to more patient-specific diagnosis by measuring anatomical parameters like thickness for individual correction and therefore provides an individualized correction factor approach, thereby extending to personalized IOP measurement and correction.

[0091] As an example, a table III values can be used as a basis for the correction calculation when a central corneal thickness is measured. For example, if the thickness is 485 micrometers then the IOP value is corrected by adding 3 mmHg. The table values should be modified if the measurement point is not central. The table can be used as look up table or, for example, a correction value as function of the corneal thickness can be derived from the values. Technical effect of this is that we can get more accurate measurements of intra ocular pressure.

[0092] TABLE III. Example of IOP value corrections as function of central corneal thickness

[0093] In an example, the predefined range of average corneal thickness may lie from 500 pm to 550 pm. The IOP may be determined to be 15 mmHg. A corneal thickness of 480 pm may be measured, which is below 500 pm. The deviation of the corneal thickness from a lower limit of the predefined range of average corneal thickness may be 20 pm (i.e., 500 pm -480 pm = 20 pm). Then, by employing the aforementioned rule, a correction factor may be determined using following exemplary formula,

[0094] The IOP is then adjusted based on the correction factor, as shown below,

[0095] Adjusted IOP = 15 mmHg — 1 mmHg = 14 mmHg

[0096] Hence, combining the aforementioned features, corresponding to measuring the oscillation frequency, integrated pachymetry-tonometry, and deviation-based correction factor scheme / approach, results in a holistic, multi-parameter IOP determination system that is far more accurate and patient-tailored than prior tonometers.

[0097] 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. Optionally, the method further comprising : processing the corneal displacement profile for performing at least one of:

[0098] (i) identifying a peak value of corneal displacement;

[0099] (ii) identifying a time taken to reach the peak value of corneal displacement;

[0100] (iii) determining an acceleration profile of the deformation of the cornea, from the corneal displacement profile; and determining the intraocular pressure, based on the peak value of corneal displacement, the time taken to reach the peak value of corneal displacement, and the acceleration profile.

[0101] Optionally, the method further comprising : determining an oscillation frequency of the deformation of the cornea after the first period of time; and updating the intraocular pressure value, based on the oscillation frequency.

[0102] DETAILED DESCRIPTION OF THE DRAWINGS

[0103] Referring to FIG. 1A, illustrated is a schematic illustration of a tonometer 100 for measuring an intraocular pressure of an eye 102, and referring to FIG. IB, illustrated is a schematic illustration of an air pulse generator 104 of FIG. 1A, in accordance with an embodiment of the present disclosure. With reference to FIG. 1A, the tonometer 100 comprises an air pulse generator 104, a displacement sensor 106, a controller 108. Herein, the controller 108 is coupled to the air pulse generator 104 and the displacement sensor 106, wherein the controller 108 is configured to: control the air pulse generator 108 to generate an excitation air pulse 110 and control the air pulse generator 104 to send the excitation air pulse 110 towards the eye 102 in a first time period; control the displacement sensor 106 to measure a signal related to deformation of cornea produced by the excitation air pulse 110 during the first time period to form a corneal displacement profile; and determine from the corneal displacement profile, the intraocular pressure of the eye 102. Optionally, the air pulse generator 104 comprises a pressure chamber 112, a nozzle 114, and a valve 116. Optionally, the tonometer 100 further comprises a distance sensor 118 for measuring a distance 120 between the eye 102 and the tonometer 100. The controller 108 is optionally communicably coupled with the distance sensor 118. Optionally, the tonometer 100 further comprises a corneal oscillation measurement sensor 122. The controller 108 is optionally communicably coupled with the corneal oscillation measurement sensor 122.

[0104] With reference to FIG. IB, the valve 116 is arranged between the pressure chamber 112 and the nozzle 114. Optionally, the air pulse generator 104 further comprises a pressure sensor 124 and a pressure regulator 126 arranged in the pressure chamber 112. The controller 108 is optionally communicably coupled with the pressure sensor 124 and the pressure regulator 126. Optionally, the nozzle 114 comprises an exit aperture 128 of a particular diameter.

[0105] FIGs. 1A and IB 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.

[0106] Referring to FIG. 2A, illustrated is a graphical representation of a corneal deformation profile 202, and referring to FIGs. 2B and 2C, illustrated are graphical representations of excitation air pulse as a function of time, in accordance with an embodiment of the present disclosure. With reference to FIG. 2A, a vertical axis (Y-axis) represents the corneal deformation, and a horizontal axis (X-axis) represents a time. Herein, a corneal displacement (as shown by the dashed box 204) of the eye occurs when the excitation air pulse is generated and then stopped. In this regard, when the controller is configured to generate and send the excitation air pulse towards the eye, i.e. when the excitation air pulse is turned ON, a cornea moves inward, thus causing deformation of the eye. Herein, the corneal deformation profile comprises a downwards curve (as shown by a curve 206). In this regard, the downwards curve 206 is formed as a pressure of the excitation air pulse on the eye increases which deforms the cornea, thus causing corneal displacement. When the downwards curve 206 reaches a peak value P of the corneal displacement 204, there is no further deformation of the eye. Hence, the controller is configured to stop sending the excitation air pulse towards the eye, i.e., the excitation air pulse is turned OFF. Herein, the corneal deformation profile comprises an upwards curve (as shown by curve 208). In this regard, the upwards curve 208 is formed as the pressure of the excitation air pulse on the eye decreases. Hence, the cornea begins to return to its natural position.

[0107] Moreover, when the excitation air pulse is turned OFF, a decay time of the excitation air pulse can either be fast (as shown in FIG. 2B) or slow (as shown in FIG. 2C). In FIGs. 2B and 2C, respective decay times of the excitation air pulse corresponds to the upwards curve 208 of the corneal deformation profile 202 of FIG. 2A. Herein, the Y-axis represents an intensity of the excitation air pulse, and the X-axis represents the time. In FIG. 2B, the decay time 210 of the excitation air pulse is fast, which enables measurement of corneal oscillations after the excitation air pulse, as abrupt cessation of the excitation air pulse allows the cornea to freely oscillate back to its original position. In FIG. 2C, the decay time 212 of the excitation air pulse is slow, which means that there is a gradual return of the cornea to its natural position, leading to a deformation curve that is smooth and with reduced oscillatory behaviour. FIGs. 2A-2C 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. Referring to FIG. 3, 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 302, the tonometer is aligned with respect to the eye. At step 304, an excitation air pulse is provided towards the eye in a first time period. At step 306, a signal related to a deformation of cornea produced by the excitation air pulse is measured during the first time period to form a corneal displacement profile. At step 308, the intraocular pressure of the eye is determined from the corneal displacement profile.

[0108] 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 displacement sensor (106); a controller (108) coupled to the air pulse generator and the displacement sensor, wherein the controller is configured to: control the air pulse generator to generate an excitation air pulse (110) and control the air pulse generator to send the excitation air pulse towards the eye in a first time period lying in a range of 1 millisecond - 15 milliseconds; control the displacement sensor to measure a signal related to deformation of cornea produced by the excitation air pulse during the first time period to form a corneal displacement profile; and determine, from the corneal displacement profile, the intraocular pressure of the eye.

2. A tonometer according to claim 1, wherein the corneal displacement profile is determined as a function of time during the first time period.

3. A tonometer according to any of the preceding claims, wherein the controller is configured to: process the corneal displacement profile to perform at least one of:(i) identify a peak value of corneal displacement;(ii) identificy a time taken to reach the peak value of corneal displacement;(iii) determine c an acceleration profile of the deformation of the cornea, from the corneal displacement profile; anddetermine the intraocular pressure, based on at least one of: the peak value of corneal displacement, the time taken to reach the peak value of corneal displacement, and / or the acceleration profile.

4. A tonometer (100) according to any of the preceding claims, wherein the air pulse generator (104) comprises: a pressure chamber (112), a nozzle (114), and a valve (116) 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 within the pressure chamber to regulate a force of the excitation air pulse (110) emitted from the nozzle; regulate a duration of the excitation air pulse by controlling opening and closing of the valve; and adjust a velocity of air through the nozzle to achieve the peak value of corneal displacement.

5. A tonometer (100) according to claim 4, wherein the air pulse generator (104) further comprises: a pressure sensor (124); and a pressure regulator (126) arranged in the pressure chamber (112); wherein the controller (108) is configured to adjust the pressure within the pressure chamber to maintain the pressure within a range of 0.05 to 5 bars to achieve the peak value of corneal displacement.

6. A tonometer (100) according to any of claim 4 or 5, wherein the nozzle (114) is detachably attached to the pressure chamber (112) to change the nozzle between nozzles of different exit aperture diameters.

7. A tonometer (100) according to any of claims 2-4, wherein the controller (108) is configured to: control the valve (116) to remain open during the first time period; and control the valve to be closed after the first time period.

8. A tonometer (100) according to any preceding claims, wherein the tonometer further comprises a distance sensor (118) for measuring a distance (120) between the eye (102) and the tonometer, wherein the controller (108) is further configured to perform any one of: open the valve (116) when the distance is within a predetermined distance range, standardize the deformation of the cornea in the corneal displacement profile based on the distance or adjust profile of the excitation air pulse based on the distance.

9. A tonometer (100) according to any preceding claims, wherein the tonometer further comprises an angle sensor (118) for measuring an angle (120) between the eye (102) and the tonometer, wherein the controller (108) is further configured to perform any one of: standardize the deformation of the cornea in the corneal displacement profile based on the angle or adjust profile of the excitation air pulse based on the angle.

10. A tonometer (100) according to any of the preceding claims, wherein the controller (108) is further configured to: determine an oscillation frequency of the deformation of the cornea after the first time period; and update the intraocular pressure, based on the oscillation frequency.

11. A tonometer (100) according to any of the preceding claims, further comprising a corneal oscillation measurement sensor (122), wherein the controller (108) is further configured to: control the corneal oscillation measurement sensor to measure another signal related to corneal oscillations caused by incidence of the excitation air pulse (110) on the eye, after the first time period; and determine the intraocular pressure from the measured another signal and the measured signal.

12. A tonometer (100) according to any of the preceding claims, wherein when determining the intraocular pressure, the controller (108) is further configured to: control the displacement sensor (106) to determine a corneal thickness of the eye (102); determine whether the corneal thickness of the eye lies in a predefined range of average corneal thickness; when the corneal thickness of the eye lies outside the predefined range of average corneal thickness, determine a correction factor based on how much the corneal thickness of the eye deviates from the predefined range of average corneal thickness; and adjust the intraocular pressure, based on the correction factor.

13. A tonometer (100) according to any of the preceding claims, wherein a pressure of the excitation air pulse (110) at a surface of the eye produces the deformation of the cornea, wherein said deformation lies in a range of 1 micrometre to 300 micrometres.

14. A tonometer (100) according to any of the preceding claims, wherein the displacement sensor (106) is a confocal chromatic sensor (CCS).

15. 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 (110) towards the eye during a first time period lying in a range of 1 millisecond -15 milliseconds; measuring a signal related to a deformation of cornea produced by the excitation air pulse during the first time period to form a corneal displacement profile; and determining the intraocular pressure of the eye from the corneal displacement profile.

16. A method according to claim 15, further comprising: processing the corneal displacement profile to perform at least one of:(i) identification of a peak value of corneal displacement;(ii) identification of a time taken to reach the peak value of corneal displacement;(iii) determination of an acceleration profile of the deformation of the cornea, from the corneal displacement profile; and determining the intraocular pressure, based on at least one of: the peak value of corneal displacement, the time taken to reach the peak value of corneal displacement, and the acceleration profile.

17. A method according to any of claims 15-16, further comprising: determining an oscillation frequency of the deformation of the cornea after the first period of time; and updating the intraocular pressure value, based on the oscillation frequency.

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