Method and system for measuring eye property value

Abstract

Disclosed is a method of measuring an eye property value. The method comprises a. analyzing a spectrum of light intensity (214, 306) received by illuminating an eye (210) with a confocal chromatic sensor (202), b. identifying a first peak (302) and a second peak (304) from the measured spectrum of light intensity, wherein the first peak is associated with an anterior surface (206) of a cornea (208) and the second peak is associated with a posterior surface (212) of the cornea, c. calculating a thickness of the cornea based on a difference between the first peak and the second peak, d. repeating steps a – c to determine a change of the thickness as a function of time.

Description

[0001] METHOD AND SYSTEM FOR. MEASURING EYE PROPERTY VALUE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to methods of measuring eye property values. Moreover, the present disclosure relates to systems of measuring eye property values.

[0004] BACKGROUND

[0005] The eye of a subject (namely, a living organism, a human, or a user) is examined by measuring various properties thereof. For example, the property is a pressure within the eye, known as an intraocular pressure (IOP). The measured eye properties help in diagnosing and managing various eye conditions, including glaucoma, which can lead to vision loss if left untreated. Moreover, the measurement and understanding of the intraocular pressure (IOP) in the context of a cardiac cycle presents a crucial aspect of an ocular health of the eye. The fluctuations in the IOP during the cardiac cycle, ranging from diastolic to systolic bounds, create an ocular pulse amplitude (OPA).

[0006] There exist tonometers for measuring the intraocular pressure (IOP) in the eye. A tonometer provides IOP value during the contact time with the eye. Tonometer is typically in contact with the eye for a period exceeding several heartbeat cycles thus reading from the tonometer provides average IOP value with no indication on possible variations resulting from heart beat cycle variations (such as systolic and diastolic peaks). Therefore, such tonometers fail to provide consistently precise IOP readings in the subjects, regardless of corneal thickness or other individual factors thereof. Moreover, such tonometers require direct contact with the cornea, which can cause discomfort and potential damage to the corneal surface. Furthermore, when measuring the IOP of the eye using a rebound tonometer, the rebound tonometer value depends on a time instant the measurement is done. This is due to OPA induced changes in the IOP. In practice a reading from the rebound tonometer depends on which phase of heartbeat cycle the measurement is done.

[0007] Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks.

[0008] SUMMARY

[0009] The aim of the present disclosure is to provide a method and a system to accurately measure intraocular pressure (IOP) in the eye. The aim of the present disclosure is achieved by a method and a system of measuring an eye property value as defined in the appended independent claims to which reference is made to. Advantageous features are set out in the appended dependent claims.

[0010] 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] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is an illustration of a flowchart depicting steps of a method of measuring an eye property value, in accordance with an embodiment of the present disclosure; FIG. 2 is an illustration of a system of measuring an eye property value, in accordance with an embodiment of the present disclosure;

[0013] FIG. 3 is a graphical representation of a first peak and a second peak from a measured spectrum of light intensity, in accordance with an embodiment of the present disclosure;

[0014] FIG. 4A, 4B is a simulated distance measurement and corneal thickness as function of time; and

[0015] FIG. 5A, 5B is a simulated distance measurement including movement of sensor and patient as a function of time.

[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 method of measuring an eye property value, the method being carried out by a processor and the method comprising a. analyzing a spectrum of light intensity received by illuminating an eye with a confocal chromatic sensor (CCS), b. identifying a first peak and a second peak from the measured spectrum of light intensity, wherein the first peak is associated with an anterior surface of a cornea and the second peak is associated with a posterior surface of the cornea, c. calculating a thickness of the cornea based on a difference between the first peak and the second peak, d. repeating steps a - c to determine a change of the thickness as a function of time. The aforementioned method precisely identifies the first and the second peak associated with the anterior and posterior surfaces of the cornea, respectively, by employing a confocal chromatic sensor (CCS) to analyze the spectrum of light intensity. The calculated thickness of the cornea, derived from the difference between (wavelengths associated with) the first peak and the second peak, provides an accurate and dynamic measurement. The method enables repeating the aforementioned steps a to c to determine changes in the thickness over time. The step of repeating enhances the method's capability to capture and analyze the dynamic fluctuations in the cornea. The synergy of the aforementioned steps ensures not only high precision in the thickness of the cornea measurement but also the ability to monitor and understand variations over time, making a comprehensive and reliable approach for assessing the eye property values.

[0019] In a second aspect, the present disclosure provides a system of measuring an eye property value, the system comprising: a confocal chromatic sensor; at least one processor configured to:

[0020] I analyze a spectrum of light intensity received by illuminating an eye with a confocal chromatic sensor (CCS);

[0021] II. identify a first peak and a second peak from the measured spectrum of light intensity, wherein the first peak is associated with an anterior surface of a cornea and the second peak is associated with a posterior surface of the cornea;

[0022] III. calculate a thickness of the cornea based on a difference between the first peak and the second peak;

[0023] IV. repeat steps I - III to determine a change of the thickness as a function of time. The aforementioned system employs the confocal chromatic sensor (CCS) that enhances precision in analyzing the spectrum of light intensity, thus allowing for the accurate identification of the first peak and the second peaks associated with the anterior and posterior surfaces of the cornea, respectively. It will be appreciated that the confocal chromatic sensor enhances the precision of measuring the thickness of the cornea. Moreover, the system employs the at least one processor which is configured to perform sequential steps from analyzing to calculating and repeating, ensuring an automated and continuous measurement process. The system facilitates the real-time assessment of the thickness of the cornea changes over time. The synergy of the confocal chromatic sensor and the at least one processor in the system promotes a high level of accuracy, reliability, and efficiency in measuring the eye property values.

[0024] The human eye is a complex sensory organ responsible for vision, capturing and processing visual stimuli from the surrounding environment. The eye begins with a transparent and protective outer layer called the cornea, which refracts incoming light. Behind the cornea lies the aqueous humor-filled anterior chamber. The colored iris regulates the amount of light entering through the pupil, a central opening in the iris. The lens, located behind the pupil, further refracts the light to focus it onto the retina at the back of the eye. The retina contains photoreceptor cells called rods and cones, which convert light signals into electrical impulses. The optic nerve transmits these impulses to the human brain for visual interpretation.

[0025] The term "eye property value" as used herein refers to quantitative measurements or characteristics associated with the eye's physiological state or behaviour. Notably, the eye property values provide insights into various aspects of the eye's function and health. In this regard, the eye property values include a diastolic intraocular pressure or a systolic intraocular pressure. It will be appreciated that the method facilitates the calculation of the eye property values selected from at least one of: the diastolic intraocular pressure or the systolic intraocular pressure.

[0026] Herein, the term intraocular pressure refers to a fluid pressure inside the eye of the subject such as a human. Herein, the term diastolic pressure refers to a lowest pressure level reached during a relaxation phase of the heart of the subject. Herein, the term diastolic intraocular pressure indicates a minimum pressure recorded during the given time range. Herein, the term systolic pressure refers to a highest pressure level reached during a contraction phase of the heart. Herein, the term systolic intraocular pressure represents the maximum pressure measured within the given time range.

[0027] The term "spectrum of light intensity" as used herein refers to a distribution of light intensity across different wavelengths. In this regard, the spectrum of light intensity represents the variations in the intensity of light reflected from different layers of the cornea, thus providing valuable information about the optical characteristics of the eye.

[0028] The term "confocal chromatic sensor" as used herein refers to an optical sensor designed to measure distances and surface characteristics with high precision. The confocal chromatic sensor utilizes the principles of confocal microscopy and chromatic aberration to achieve accurate distance measurements. In this regard, the confocal chromatic sensor emits light with varying wavelengths, measures the reflected light, and analyzes intensity peaks related to different wavelengths of reflected light to determine distances and surface features.

[0029] The method comprises illuminating the eye using the confocal chromatic sensor. In this regard, the confocal chromatic sensor is configured to emit a spectrum of light (typically white light comprising a range of wavelengths in continous manner). The emitted spectrum of light is directed towards the cornea of the eye. The emitted light illuminates the cornea of the eye. In this regard, upon hitting the cornea, the illuminated light interacts with the surface of the cornea and layers thereof. The interaction allows a partial absorption of the emitted light and a partial reflection of the emitted light back toward the confocal chromatic sensor. The reflected light spectrum is then analyzed to identify specific features corresponding to different layers of the cornea. Moreover, the intensity of the reflected light is measured at different wavelengths within the spectrum. By analyzing the variations in the intensity as a function of wavelength, information about the distance between the CCS and the cornea can be derived. In practical terms a first peak (from anterior surface of the cornea) corresponds to a first wavelength and a second peak (from posterior of the cornea) corresponds to a second wavelength. Wavelengths correlate with distances from CCS measurement device and the surfaces. Difference between the first wavelength and the second wavelength correlates with thickness of the cornea.

[0030] The step of analyzing provides a detailed profile of how much light is being reflected from the cornea at each specific wavelength. The technical effect of the step of analyzing is to allow an extraction of detailed information about the thickness of the cornea. The spectrum of light intensity provides a unique fingerprint, allowing the identification of peaks associated with specific corneal surfaces.

[0031] The term "first peak" as used herein refers to the intensity of light that is reflected from a front surface of the cornea. In this regard, the first peak is associated with the reflective properties of the anterior surface of the cornea. The term "anterior surface" as used herein refers to an outermost layer or the front surface of the cornea, facing outward. The anterior surface is the first layer encountered by the light entering the eye. In other words, the reflected light from the anterior surface creates the first peak in the spectrum, with its intensity indicating the characteristics of the anterior surface. The term "second peak" as used herein refers to another distinct intensity point in the spectrum of light intensity and is linked to the reflective characteristics of the posterior surface of the cornea. The term "posterior surface" as used herein refers to an inner surface, facing the interior of the eye. The posterior surface is the second layer encountered by the light after passing through the anterior surface.

[0032] It will be appreciated that the identification of the first peak and the second peak in the spectrum of the light intensity enables the method to determine the wavelengths associated with the anterior and posterior surfaces of the cornea. The first peak and the second peak serve as markers for specific layers within the eye. The technical effect of the step of identification is the accurate peak localization on the spectrum of light intensity.

[0033] Optionally, the first peak has the highest peak intensity value and the second peak has the second highest peak intensity value. In this regard, of all the points where the reflected light intensity reaches its maximum, the first peak has the most intense reflection. The first peak indicates the strength or magnitude of the reflection from the anterior surface. Moreover, the second highest peak intensity value means that, after the first peak, the intensity of reflection reaches its next highest value at the second peak. In other words, the second highest peak intensity value indicates the strength or magnitude of the reflection from the posterior surface of the cornea. Moreover, the method establishes a standardized order for the reflective characteristics, facilitating reliable differentiation between the first peak and the second peak by ensuring that the first peak has the highest intensity, and the second peak has the second- highest intensity. Furthermore, the highest peak intensity value and the second highest peak intensity value are crucial for calculating the thickness of the cornea. The highest peak intensity value and the second highest peak intensity value provide insights into the properties of the cornea. Optionally, changes in the highest peak intensity value and the second highest peak intensity value can indicate abnormalities or variations in the cornea's structure, which might be associated with certain eye conditions. The technical effect of imposing a hierarchy based on the peak intensity values is to enhance the reliability of subsequent calculations, such as the determination of the thickness of the cornea.

[0034] The method comprises calculating or determining the thickness of the cornea by analyzing the difference in wavelengths between the first peak and the second peak in the spectrum of light intensity. In other words, the thickness is a difference between a distance from the confocal chromatic sensor to the posterior surface of the cornea and a distance from the confocal chromatic sensor to the anterior surface of the cornea. The step of calculation converts the information obtained from the first peak and the second peak in the light spectrum into a quantitative measure of the thickness of the cornea. The calculation is essential for obtaining precise numerical data about the thickness of the cornea based on the reflective characteristics of the anterior surface and the posterior surface thereof. The step of calculation involves subtracting the wavelength associated with the second peak from that of the first peak. The difference corresponds to the thickness of the cornea. The technical effect is the accurate determination of the thickness of the cornea. Notably, the possible movements of the confocal chromatic sensor or a subject during the measurement will not influence the accuracy of measuring the thickness of the cornea. The thickness can be measured even when the confocal chromatic sensor would move in respect to the eye during the measurement.

[0035] The method comprises repeating the aforementioned steps of analyzing, identifying and calculating to determine a change of the thickness as a function of time. In this regard, the method involves conducting the aforementioned steps at regular intervals, continuously illuminating the eye, identifying peaks from the measured spectrum of light intensities, and calculating the thickness of the cornea. Moreover, the method enables a series of measurements that collectively depict the thickness of the cornea as a dynamic, time-dependent variable by repeating the aforementioned steps over a duration of time.

[0036] The technical effect of the aforementioned step is to observe and quantify changes in the thickness of the cornea over time, providing a dynamic profile of the eye property value. The step of repeating enhances the method's utility for applications where monitoring temporal variations, such as ocular pulse amplitude or other physiological parameters, is critical. Additionally, said iterative approach ensures a comprehensive understanding of how the cornea dynamically responds to various stimuli or conditions.

[0037] Optionally, the method further comprises using the thickness as a function of time as a heart beat related signal. The term "heart beat related signal" as used herein refers to a physiological indicator derived from the dynamic changes associated with a cardiac cycle of the heart. The heart beat related signal is obtained by monitoring variations in the thickness of the cornea over time. As the heart pumps blood, the heart induces fluctuations in the intra-ocular pressure, impacting the thickness of the cornea. The resulting alterations in the thickness of the cornea serve as a proxy for the heartbeat, creating a signal that correlates with the pulsatile activity of the heart. Moreover, the heart rate related signal, extracted from the measured thickness, provides valuable information about the temporal aspects of the cardiac cycle, thus enabling non- invasive monitoring of the heart-related parameters. It will be appreciated that the thickness value is a function of heart beat. Thus, the thickness of the cornea is also the function of the time. Therefore, the thickness as a function time is measured and is used to determine the heart beat. Beneficially, since the confocal chromatic sensor provides real time information on an impact of the heart beat on the eye, the heart beat measured from the cornea of the eye can be used to synchronize the IOP measurements performed with a tonometer in a way that measurement can be precisely performed. For example, for systolic IOP value or diastolic IOP value.

[0038] In this regard, the method includes performing the steps of illuminating the eye, identifying peaks, and calculating the thickness over time repeatedly to observe how the thickness of the cornea changes over time. Each iteration of the aforementioned steps provides a new set of measurements, allowing for the tracking of the thickness of the cornea at different points in time. The resulting measurement data shows the trend or pattern of how the corneal thickness varies over the observed duration. Herein, the function of time represents a mathematical relationship between the measured corneal thickness and the elapsed time. Optionally, the function could take various forms, depending on the behavior of the thickness of the cornea over time. Optionally, the function of time could be a periodic function when there are cyclical changes in the thickness of the cornea. As an example, the thickness would be in its lowest (thinnest) value when intraocular pressure value is highest and it would be in its highest (thickest) value when the intraocular pressure value is in its lowest. The thickness value would then oscillate between the lowest and highest value as function of time (in periodic manner) as the heart beats.

[0039] Moreover, the function of time may have parameters that characterize the behavior of changes in the thickness of the cornea. Some potential parameters include initial thickness To, rate of change, maximum thickness, growth rate, amplitude, frequency, and so forth. It will be appreciated that the function of time, along with its parameters, offers a quantitative and objective way to understand the temporal behavior of corneal thickness, aiding in clinical diagnoses and treatment planning.

[0040] The thickness is then correlated with the temporal aspects of the heart beat, enabling the extraction of the heart beat related signals. This provides a dynamic profile of how the cornea responds to various physiological factors, particularly the rhythmic patterns associated with the heartbeat. The technical effect of using the thickness variations as the heart-related signal is to provide a non-invasive means to indirectly monitor heartbeats. The method allows clinicians to gain valuable insights into cardiovascular health without invasive procedures.

[0041] Optionally, the method further comprises calculating a heart rate based on the heart beat related signal. In this regard, the method includes analyzing the heartbeat-related signal, which is derived from the thickness of the cornea variations over time. Moreover, the method calculates the heart rate (i.e., the number of heartbeats per unit of time) by processing the heart-related signals extracted from the variations in the thickness of the cornea. Optionally, the step of processing involves analyzing the frequency and amplitude characteristics of the heart- related signals. Optionally, the processing may include techniques such as Fourier analysis or wavelet transforms to extract the heart rate information. Optionally, the heart-related signals from the time domain are converted to the frequency domain. In the frequency domain, the heart rate manifests as the distinct peaks corresponding to the frequency of the heartbeat. The calculation of the heart rate is typically expressed in beats per minute (BPM).

[0042] The technical effect of the calculation of the heart rate enhances the diagnostic capabilities of the method, thus offering insights into cardiovascular function without the need for direct cardiac measurements. An example could be the continuous and non-invasive monitoring of the heart rate during a clinical study or routine eye examination.

[0043] Optionally, the method further comprises using the heart beat related signal to synchronize operations of a tonometer. Pursuant to the embodiments of the present disclosure, the term "tonometer" as used herein refers to an instrument that is used for measuring the intraocular pressure. Optionally, the tonometer is a rebound tonometer, a corneal tonometer or an oscillation based tonometer. Preferably the tonometer is a rebound tonometer. The term "rebound tonometer" as used herein refers to a tonometer that measures the intraocular pressure by utilizing a rebound principle. In this regard, the rebound tonometer works by projecting a small probe onto the cornea, and upon contact, the probe rebounds or bounces back. The rebound tonometer measures the speed and changes in the probe's rebound, which are directly related to the intraocular pressure. The technical effect of implementing the tonometer as the rebound tonometer is that it provides way to time measurement of intraocular pressure value precisely to target point of time. Optionally, the rebound tonometer is user friendly and may provide quick measurements without the need for anesthesia. Further benefit of using heartbeat related signal which is derived from the corneal thickness changes is to eliminate jitter which would take place, if heartbeat related signal would be measured for example from a finger. As an example, heart rate pulse maximum peak measured from finger can be 20msec- 30msec or larger offset from pulse maximum peak at cornea due to speed of blood pulse in blood vessel system.

[0044] The term "corneal tonometer" as used herein refers to a tonometer that measures intraocular pressure by assessing the biomechanical properties of the cornea. Optionally, the corneal tonometer may use different techniques, such as applanation or indentation, to evaluate the response of the cornea to the applied force by the probe. The technical effect of using the corneal tonometer is that it provides direct contact measurements, allowing for precise assessment of the intraocular pressure value. Typically, the corneal tonometer takes into account factors such as the thickness of the cornea and biomechanical characteristics, which may influence intraocular pressure measurements. The term "oscillation-based tonometer" as used herein refers to a tonometer that utilizes the principle of corneal resonance or natural frequency of the eye to estimate intraocular pressure. Typically, the oscillation-based tonometer applies a small oscillating force to the cornea and measures the response or vibrations caused by this force. The technical effect of using the oscillation-based tonometer is that it offers a non-contact method for measuring the intraocular pressure. Optionally, the oscillation-based tonometer may provide rapid and reproducible measurements without the need for anesthesia or corneal contact.

[0045] In this regard, the method includes integrating the heart rate information obtained from the heartbeat-related signal with the operations of the tonometer. Optionally, the synchronization is achieved by configuring the tonometer to conduct measurements at strategic moments within the cardiac cycle, determined by the heart rate information. In an implementation, the heart-related signals, which are variations in corneal thickness over time, serve as the basis for said synchronization. Moreover, as the thickness of the cornea changes with each heart beat, the method uses the dynamic thickness as the function of time to precisely time the tonometer measurements. For example, the method might trigger the tonometer to measure the IOP at specific intervals during the cardiac cycle, as indicated by the fluctuations in the thickness. This ensures that the tonometer operates in synchrony with the heart's activity, optimizing the accuracy and reliability of the IOP measurements. Further technical effect of using heartbeat-related signal which is derived from cornea is that there is no, or very minimal, jitter between the heartbeat signal and its impact to intra ocular pressure value. If heartbeat related signal would be measured for example using pulse meter in a finger it would be challenging to synchronize the IOP measurement since it is unknown when "pulse of blood" arrives to eye in comparison to finger. The technical effect of the synchronization is to improve the accuracy and reliability of intra-ocular pressure measurements. Moreover, the method optimizes the timing of the IOP measurements, allowing for more precise assessments of ocular health by synchronizing the tonometer operations with the cardiac cycle. Optionally, the synchronization ensures that measurements correspond to specific physiological states, such as the systolic or the diastolic phases, resulting in more clinically relevant data.

[0046] Optionally, the method further comprises at least one of:

[0047] - measuring a systolic intraocular pressure (IOP) at a highest value of the heart beat related signal,

[0048] - measuring a diastolic intraocular pressure at a lowest value of the heart beat related signal.

[0049] In this regard, the method utilizes the heart beat related signal to identify the highest value, corresponding to the systolic phase. Optionally, at this point, the method conducts a measurement of the intraocular pressure. The measurement of the systolic intraocular pressure enhances the precision of IOP measurements, as it captures data during a specific physiological state associated with the systole, thus providing insights into the dynamic behavior of ocular pressure during the heart's contraction.

[0050] Optionally, the method uses the heart beat related signal to identify the lowest value, corresponding to the diastolic phase. Subsequently, the method performs a measurement of the intraocular pressure during the diastolic phase. The measurement of the diastolic intraocular pressure enhances the specificity of the IOP measurements by capturing data during the diastolic phase. It will be appreciated that said measurement provides a comprehensive understanding of the ocular pressure dynamics during the heart's relaxation phase.

[0051] Optionally, the change of the thickness as a function of time is used for determining a point in time for measuring the intraocular pressure (IOP). In this regard, the method comprises continuously monitoring the change in the thickness of the cornea over time. Optionally, analyzing the temporal evolution allows the method to identify a given point in the cardiac cycle where the cornea exhibits characteristics that enhance the precision of the IOP measurements. The given point is then chosen for conducting the IOP measurement.

[0052] The technical effect of selecting the given point in time based on the dynamic changes in the thickness of the cornea is to allow the method to optimize the conditions for the IOP assessment. This synchronization ensures that measurements are taken at a moment when the cornea is in a state that provides the most meaningful information about the ocular pressure, contributing to enhanced diagnostic capabilities and more effective management of the ocular health conditions.

[0053] The present disclosure also relates to the system of measuring the eye property value as described above. Various embodiments and variants disclosed above, with respect to the aforementioned method of measuring the eye property value, apply mutatis mutandis to the system of measuring the eye property value.

[0054] The term "processor" as used herein refers to a device or set of devices that perform functions such as computation, data processing, and the execution of instructions. The system comprises one or more processors to carry out the specified operations, such as the analysis of the spectrum of light intensity and the calculation of the thickness of the cornea. This enhances the system's ability to rapidly and accurately process the thickness, contributing to the real-time monitoring of dynamic changes in the thickness of the cornea as the function of time. The technical effect of employing the at least one processor is to enable the system to deliver precise and timely measurements of the eye property value.

[0055] Optionally, the at least one processor is further configured to use the thickness as a function of time as a heart beat related signal. In this regard, the at least one processor enables the extraction of the heart rate-related signal from the measured corneal thickness data. Herein, the cornea exhibits slight thickness variations due to pulsations associated with the heartbeat. Thus, by analyzing the subtle changes, the at least one processor can potentially derive a signal reflecting the heart beat related signal.

[0056] Optionally, the heartbeat related signal derived from the thickness is used to correct intraocular pressure value. In this regard if the heartbeat phase indicates contribution of heartbeat induced variation to intraocular pressure value. This can be used then to provide intraocular pressure value from which heartbeat related contribution is removed or taken in account. As discussed earlier, a setup enables to get heartbeat related signal timing in respect to changes of IOP precisely thus this type of correction is feasible.

[0057] Optionally, the at least one processor is further configured to calculate a heart rate based on the heart beat related signal. The technical effect of employing the at least one processor to calculate the heart rate is to provides additional physiological data that could be valuable for various applications, such as health monitoring or biometric identification.

[0058] Optionally, the at least one processor is further configured to use the heart beat related signal to synchronize operations of a tonometer. It will be appreciated that by synchronizing the tonometer measurement with the heartbeat cycle, the system aims to minimize potential artifacts caused by the physiological fluctuations and potentially improve the accuracy and reliability of the IOP measurements.

[0059] Optionally, the at least one processor is further configured to:

[0060] - measure a systolic intraocular pressure (IOP) at a highest value of the heart beat related signal,

[0061] - measure a diastolic intraocular pressure at a lowest value of the heart beat related signal. In this regard, the cornea thins slightly during peak systolic pressure and thickens slightly during diastolic pressure. Moreover, by identifying the lowest value of the heart beat related signal and highest value of the heart beat related signal in the heart rate-related signal, the at least one processor of the system can potentially measure the corresponding IOP values.

[0062] Optionally, the at least one processor is further configured to use the change of the thickness as a function of time for determining a point in time for measuring an intraocular pressure (IOP). In this regard, the IOP measurements are more accurate during specific phases of the heartbeat cycle when the cornea exhibits minimal movement or distortion. It will be appreciated that the at least one processor could potentially select a more stable time window for the IOP measurement by analyzing the thickness data, thereby potentially improving the accuracy and reliability of the measurement of the intraocular pressure (IOP). Furthermore the heart beat related signal derived from the thickness is used to correct intraocular pressure value.

[0063] Typically heartbeat (pulse) related variations to intraocular pressure are in range of 2-10 mmHg i.e. the variation is significant. The setup provided in present disclosure provides means to differentiate between these variations and "basic" intraocular pressure. Corneal movements of 1 to 10 micrometers are associated with ocular pulse amplitude OPA.

[0064] DETAILED DESCRIPTION OF THE DRAWINGS

[0065] Referring to FIG. 1, illustrated is a flowchart depicting steps of a method of measuring an eye property value, in accordance with an embodiment of the present disclosure. At step 102, a spectrum of light intensity received by illuminating an eye with a confocal chromatic sensor (CCS) is analyzed. At step 104, a first peak and a second peak from the measured spectrum of light intensity are identified, wherein the first peak is associated with an anterior surface of a cornea and the second peak is associated with a posterior surface of the cornea. At step 106, a thickness of the cornea based on a difference between the first peak and the second peak is calculated. At step 108, the aforementioned steps are repeated to determine a change of the thickness as a function of time.

[0066] 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.

[0067] Referring to FIG. 2, illustrated is a system 200 of measuring an eye property value, in accordance with an embodiment of the present disclosure. The system 200 comprises a confocal chromatic sensor 202 and at least one processor 204. As shown, the confocal chromatic sensor 202 is measuring a distance DI and D2. Herein, DI is the distance between an anterior surface 206 of a cornea 208 of an eye 210 and the confocal chromatic sensor 202. Herein, D2 is the distance between a posterior surface 212 of the cornea 208 of the eye 210 and the confocal chromatic sensor 202. Moreover, the confocal chromatic sensor 202 is configured to illuminate the eye 210 by emitting a spectrum of light intensity 214 and measure a reflected light from the cornea 208 of the eye 210. Herein, the spectrum of light intensity includes an emitted light 216A by the confocal chromatic sensor 202. Herein, the spectrum of light intensity includes a light 216B received from the eye. The distance from the confocal chromatic sensor 202 can be derived by analysing amplitudes of reflected light as a function of wavelength. Notably, the cornea 208 is transparent in nature. The at least one processor 204 is configured to analyze the spectrum of light intensity 214 received by illuminating the eye 210 with the confocal chromatic sensor 202; identify a first peak and a second peak from the measured spectrum of light intensity, wherein the first peak is associated with an anterior surface 206 of the cornea 208 and the second peak is associated with the posterior surface 212 of the cornea 208; calculate a thickness of the cornea 208 based on a difference between the first peak and the second peak; and repeat the aforementioned steps to determine a change of the thickness as a function of time.

[0068] Referring to FIG. 3, illustrated is a graphical representation 300 of a first peak 302 and a second peak 304 from a measured spectrum of light intensity (y-axis) , in accordance with an embodiment of the present disclosure. Herein, the x axis represents a wavelength of the first peak 302 and the second peak 304. Herein, the y axis represents an amplitude of the first peak 302 and the second peak 304. There is shown a difference between the first peak wavelengths LI and the second peak wavelengths L2. Said difference corresponds to a thickness of the cornea.

[0069] FIG 4A is an illustration of simulated measured distance (D2) from CCS sensor to posterior surface of the cornea of the eye and simulated measured distance (DI) to anterior surface of the cornea of the eye. It can be seen that distances are periodic and correspond to heart beat signal of the person. FIG 4B is illustration of corneal thickness (D2-D1) as function of time. We can see that thickness is higher when heart beat related signal is lowest and vice versa. This is due to higher intraocular "expanding" the eye thus making cornea thinner. In this example simulation target person and CCS are not moving in respect to each other's.

[0070] FIG 5A is an illustration of realistic measurement situation (as per comparison to FIG 4A in which it is assumed that CCS sensor and eye do not have any relative movement between them). As one can see in the figure, random movements (due to target person moving in respect to measurement device) result to a situation that periodicity of the corneal distance in respect to CCS is lost. DIS is distance from CCS sensor to anterior surface of cornea and D2S is distance from CCS sensor to posterior surface of the cornea. FIG 5B is an illustration of difference between D2S and DIS. Random movements are eliminated and the difference signal i.e thickness signal provides reliable heartbeat related signal even if the CCS sensor is moving in respect to persons eye. Typically movements can be in range of millimeteres or less, wherein the distance variation of corneal surface to CCS changes during heart beat cycle only in range of few micrometres. For this reason thickness value provides reliable indicator of heart beat cycle. Indeed even a very small movement in range of few or tens of micrometres might have negative impact on measuring of a periodic movements of the corneal surface due to small movements of the cornea due to heart beat.

[0071] FIG 4A, 4B, 5A, and 5B all units are arbitrary units which have been scaled in order to illustrate technical benefit of using corneal thickness variation as heart beat related signal indicator.

Claims

CLAIMS1. A method of measuring an eye property value, the method being carried out by a processor and the method comprising a. analyzing a spectrum of light intensity (214, 306) received by illuminating an eye (210) with a confocal chromatic sensor (CCS) (202), b. identifying a first peak (302) and a second peak (304) from the measured spectrum of light intensity, wherein the first peak is associated with an anterior surface (206) of a cornea (208) and the second peak is associated with a posterior surface (212) of the cornea, c. calculating a thickness of the cornea based on a difference between the first peak and the second peak, d. repeating steps a - c to determine a change of the thickness as a function of time (D2-D1, D2S-D1S).

2. A method according to claim 1, further comprising using the thickness as a function of time as a heart beat related signal.

3. A method according to claim 2, further comprising calculating a heart rate based on the heart beat related signal.

4. A method according to any of the preceding claims, wherein the first peak (302) has the highest peak intensity value and the second peak (304) has the second highest peak intensity value.

5. A method according to any of the claims 2-4, further comprising using the heart beat related signal to synchronize operations of a tonometer.

6. A method according to claim 5, further comprising at least one of:- measuring a systolic intraocular pressure (IOP) at a highest value of the heart beat related signal,- measuring a diastolic intraocular pressure at a lowest value of the heart beat related signal.

7. A method according to any of the preceding claims, wherein the change of the thickness as a function of time is used for determining a point in time for measuring an intraocular pressure (IOP).

8. A method according to any of the claims 2-7, wherein the heart beat related signal derived from the thickness is used to correct intra ocular pressure value.

9. A system (200) of measuring an eye property value, the system comprising: a confocal chromatic sensor (202); at least one processor (204) configured to:I. analyze a spectrum of light intensity (214, 306) received by illuminating an eye (210) with the confocal chromatic sensor (CCS);II. identify a first peak (302) and a second peak (304) from the measured spectrum of light intensity, wherein the first peak is associated with an anterior surface (206) of a cornea (208) and the second peak is associated with a posterior surface (212) of the cornea;III. calculate a thickness of the cornea based on a difference between the first peak and the second peak;IV. repeat steps I - III to determine a change of the thickness as a function of time.

10. The system (200) of claim 9, wherein the at least one processor (204) is further configured to use the thickness as a function of time as a heart beat related signal.

11. The system (200) of claim 9, wherein the at least one processor (204) is further configured to calculate a heart rate based on the heart beat related signal.

12. The system (200) of any of claims 9-11, the at least one processor (204) is further configured to use the heart beat related signal to synchronize operations of a tonometer.

13. The system (200) of claim 9, wherein the at least one processor (204) is further configured to:- measure a systolic intraocular pressure (IOP) at a highest value of the heart beat related signal,- measure a diastolic intraocular pressure at a lowest value of the heart beat related signal.

14. The system (200) of any of claims 9-11, the at least one processor (204) is further configured to use the change of the thickness as a function of time for determining a point in time for measuring an intraocular pressure (IOP).

15. The system (200) of any of the claims 10-14, wherein the heart beat related signal derived from the thickness is used to correct intraocular pressure value.

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