Two intensity modes for confocal chromatic sensor pachymeter lightsource

Abstract

The present disclosure relates to a method of measuring a thickness (d2) of a cornea (114). The method comprises: measuring a distance (d1) between a pachymeter (100) and an outer surface (162) of the cornea using a confocal chromatic sensor (102), when a light intensity (302) of a light source (104) of the confocal chromatic sensor is set at a first value (V1); comparing the measured distance with a predetermined distance range; and if the measured distance is in the predetermined distance, measuring the thickness of the cornea with the confocal chromatic sensor, wherein the light intensity of the light source of the confocal chromatic sensor is set at a second value (V2). The present disclosure further includes a pachymeter (100) for measuring the thickness of the cornea.

Description

[0001] TWO INTENSITY MODES FOR. CONFOCAL CHROMATIC SENSOR

[0002] PACHYMETER LIGHTSOURCE

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to methods for measuring a thickness of a cornea. Moreover, the present disclosure relates to pachymeters for measuring a thickness of a cornea.

[0005] BACKGROUND

[0006] In the field of ophthalmology and optometry, corneal measurement, also known as corneal topography or corneal mapping, is essential for various reasons. For example, corneal thickness is essential for contact lens fitting, for analysis of medical conditions of a patient (glaucoma, keratoconus etc.), for devising optimal surgery plans with essential precautionary measures in refractive surgery procedures such as LASIK (laser-assisted in situ keratomileusis), PRK (photorefractive keratectomy), and SMILE (small incision lenticule extraction), corneal cross-linking treatment as well as for observing after-surgery recovery status. Moreover, information on corneal geometry can be used to correct other ophthalmic measurements such as measurements of intra-ocular pressure obtained by for example applanation tonometry, rebound tonometry, or air puff tonometry.

[0007] The corneal measurement includes assessment of the shape, curvature, and (central) thickness of the cornea which are used to assist a healthcare professional to assess any abnormalities resulting from trauma, injuries, irregularities, scarring, infections, inflammations, keratoconus, astigmatism, corneal dystrophies and degenerative diseases in cornea. Accurate corneal measurements help the healthcare professional to monitor disease progression, assess treatment efficacy, and make informed decisions about therapeutic interventions such as corneal crosslinking, orthokeratology, and corneal transplantation. No reliable, fast and comfortable means for measuring the corneal thickness are available.

[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 method and a pachymeter to measure a thickness of a cornea by optimally and dynamically changing intensity of light based on a distance of the pachymeter from an eye of a patient. The aim of the present disclosure is achieved by a method and a pachymeter for measuring a thickness of a cornea 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 the words, for example "comprising" and "comprises", mean "including but not limited to", and do not exclude other components, integers or steps. 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 DRAWINGS

[0013] FIG. 1 is an illustration of a pictorial representation depicting a working principle for measuring a thickness of a cornea, in accordance with an embodiment of the present disclosure; FIG. 2 is an illustration of a flowchart depicting steps of a method for measuring a thickness of a cornea, in accordance with an embodiment of the present disclosure;

[0014] FIG. 3 is a graphical representation of a light intensity of an incident light from a light source of a pachymeter with respect to a distance between the pachymeter and the cornea, in accordance with an embodiment of the present disclosure;

[0015] FIG. 4 is a graphical representation of a reflected light intensity as a function of wavelength of an incident light from a light source of a pachymeter, in accordance with an embodiment of the present disclosure; and

[0016] FIGs. 5A, 5B and 5C are graphical representations of effect of sweeping a second intensity of an incident light from a light source to cover a plurality of wavelengths, in accordance with an embodiment of the present disclosure.

[0017] DETAILED DESCRIPTION OF EMBODIMENT

[0018] 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 practicing the present disclosure are also possible.

[0019] In a first aspect, the present disclosure provides a method of measuring a thickness of a cornea, the method comprising:

[0020] - measuring a distance between a pachymeter and an outer surface of the cornea using a confocal chromatic sensor, wherein a light intensity of a light source of the confocal chromatic sensor is set at a first value,

[0021] - comparing the measured distance with a predetermined distance range, and - if the measured distance is in the predetermined distance, measuring the thickness of the cornea with the confocal chromatic sensor, wherein the light intensity of the light source of the confocal chromatic sensor is set at a second value, wherein the second value is higher than the first value.

[0022] In a second aspect, the present disclosure provides a pachymeter comprising:

[0023] - a confocal chromatic sensor comprising a light source and a spectrometer;

[0024] - a controller communicatively coupled to the confocal chromatic sensor and configured, when in use, to:

[0025] - measure distance from pachymeter to an outer surface of cornea by

[0026] - setting a light intensity of the light source to a first value;

[0027] - receiving a first set of reflected light intensity values from the spectrometer;

[0028] - determining from the first set of values a distance between the pachymeter and an outer surface of a cornea and using the determined distance as the measured distance;

[0029] - compare the measured distance with a predetermined distance;

[0030] - set a light intensity of the light source to a second value if the measured distance is within the predetermined distance;

[0031] - receive a second set of reflected light intensity values from the spectrometer and use the second set of values to determine thickness of the cornea.

[0032] Based on embodiments a confocal chromatic sensor (CCS) may be utilized for measuring thickness. The CCS is an instrument which operates based on the principle of utilizing reflection of light with different wavelengths for measuring shape, curvature, and thickness of the cornea. The basic working involves sending a high-intensity beam of chromatically dispersed light toward the cornea, when the high-intensity light beam reaches the outer surface of cornea then light of certain wavelengths is reflected and light with certain wavelengths pass through the outer layer of cornea into the inner layer of cornea and then get reflected back. Utilizing these information, the CCS measures the thickness of the cornea.

[0033] However, as the CCS-based measurement of cornea thickness (pachymetry) needs to assess the very weak intensity of the reflection signal from the inner surface of the cornea, high intensity light beam is needed. This (high intensity light) might increase patient discomfort and may negatively affect patient's eye safety, and ultimately affects the accuracy of diagnosis of the patient.

[0034] Moreover, it has been observed that there is a substantial difference between the reflection from outer surface of cornea and the inner surface of the cornea due to optical properties of different layers of the cornea, such as the outer epithelial layer, the stroma, and the inner endothelial layer. Such a situation can affect the accuracy of corneal measurements, particularly when assessing corneal thickness or endothelial cell density, unless proper compensation steps are performed during the measurement.

[0035] The present disclosure provides the aforementioned method and the aforementioned pachymeter for a precise and accurate measurement of the thickness of cornea. The method and pachymeter involves using a confocal chromatic sensor to measure the distance between the pachymeter and the outer surface of the cornea. Beneficially, the method utilizes the confocal chromatic sensor (CCS) with adjustable light intensity, to ensure precise distance measurements, and enable the detection of wavelength peaks corresponding to the cornea's outer and inner surfaces. Moreover, the use of a predetermined distance range and higher light intensity during thickness measurement further enhances the accuracy of the measurements, resulting in more reliable data for corneal thickness analysis. Initially, the light intensity of the sensor's light source is set at a lower value, and the measured distance is compared with a predetermined range. Further, when the distance between the aforementioned pachymeter and the outer surface of the cornea is at desired limits i.e., at the predetermined distance, then light intensity of the light source can be set at a higher value for carrying out the measurement of corneal thickness. In other words, only when the desired alignment is achieved, short pulses of increased brightness are emitted for carrying out the corneal measurement. Thus, the aforementioned method assists in reduction of patient discomfort and ensures eye safety.

[0036] Moreover, the present disclosure includes provisions to optimize intensity of an emitted light from the light source for ergonomic measurement of cornea of an eye of a patient while minimizing discomfort to the patient. Advantageously, while carrying out a corneal measurement using the aforementioned method, the light intensity of the light source maintained at a lower level, can be used for distance alignment of the aforementioned pachymeter. As the outer corneal surface reflection is of higher intensity compared to the inner corneal surface reflection, lower light intensity of the light emitted by the source can be utilized for achieving accurate and desired alignment phase of the corneal measurement.

[0037] Throughout the application, the term "corneal measurement" pertains to measurement of the thickness of the cornea of an eye of a patient. The thickness of cornea refers to the distance between the outer surface and the inner surface of the cornea, wherein cornea is a transparent, domeshaped outermost layer of the eye covering the iris, pupil, and anterior chamber of the eye. Cornea is responsible for focusing light and is responsible for a significant portion of the eye's refractive power.

[0038] Throughout the present disclosure, the term "apparatus" refers to the "pachymeter". Optionally, the pachymeter a medical device used for measuring the thickness of the cornea. The pachymeter comprises the confocal chromatic sensor (CCS) having the light source and the spectrometer. The light source of the CCS is configured to emit the incident light of specific intensity (both low and high). The spectrometer of the CCS is configured to disperse the incident light of specific intensity and receive the reflected light from the outer and inner layer of the cornea.

[0039] Throughout the present disclosure, the term "confocal chromatic sensor (CCS)" refers to an optical measurement device used for non-contact, high-precision surface profiling and dimensional measurements of the cornea of the eye. In this regard, CCS typically uses chromatic aberration to measure distances with high accuracy and precision. CCS utilizes confocal and chromatic imaging principles in order to capture detailed information about the thickness of the cornea accurately. The term "light source" as used herein refers to to an element from which light emanates. Optionally, the light source is one of a narrowband light-emitting diode (LED), a LASER., a broadband LED, a halogen lamp and any other suitable light source. The light source is selected based on at least one of a desired measurement range, a resolution, and an accuracy of a sensor used in the aforementioned pachymeter.

[0040] Throughout the present disclosure, the term "spectrometer" refers to an optical instrument for measuring properties of light over a specific portion of the electromagnetic spectrum. The spectrometer is configured to disperse light into its component wavelengths (colors) and measures the intensity of each wavelength, allowing for the analysis of spectral features such as absorption, emission, or reflection. Optionally, the spectrometer may be configured to measure the light intensity values of an incident light emitted from the light source as well as a reflected light from the cornea. Beneficially, a synergistic effect of using CCS having the light source and the spectrometer is that the CCS measures the distance between the pachymeter and the outer surface of the cornea by setting the light intensity of the light source to a first value (low intensity, aka "search mode" to search for right distance). It then receives a first set of reflected light intensity values from the spectrometer and determines the distance based on these values. If the measured distance falls within a predetermined range (i.e distance is short enough to measure the thinkness), the light intensity of the light source is set to a second value (high intensity, aka "thickness measurement mode"), which is higher than the first value. The sensor then receives a second set of reflected light intensity values from the spectrometer and uses these values to determine the thickness of the cornea.

[0041] The method comprises measuring the distance between the pachymeter and the outer surface of the cornea using the confocal chromatic sensor, wherein the light intensity of the light source of the CCS is set at a first value. In this regard, the measurements are achieved by sending out the incident light of intensity set at the first value towards the cornea, and receiving the reflected light, namely, a first set of reflected light having the first set of reflected light intensity values, from the outer surface of the cornea at the spectrometer. Notably, the distance between the pachymeter and the outer surface of cornea is measured, by the controller, based on information on the reflected light. Herein, optionally, the information pertains to the wavelength of the reflected light as a function of the distance between the pachymeter and the outer surface of cornea. Throughout the present disclosure, the term "light intensity" refers to the amount of light energy per unit area of the light source. Light intensity is typically measured in units such as lux or candela per square meter. Optionally, the first value is selected to be in a range from 0.05 mW / cm^ up to 5 mW / cm^. Optionally, the first value is in an range from from 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,

[0042] 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2,

[0043] 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8,

[0044] 4.9 mW / cm2up to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7,

[0045] 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3,

[0046] 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, or 5.0 mW / cm2. Notably, the first value of the light intensity is of lower intensity and thus causes minimal to no discomfort to the eye.

[0047] Optionally, the first value is adjusted based on the measured distance. The first value is adjusted to be of lower intensity as the pachymeter approaches near the outer surface of cornea. As the distance between the pachymeter and the outer surface of cornea decreases, even incident light of lower intensity would yield reflection of higher intensity. In other words, while moving the pachymeter towards the outer surface of the cornea, the first value of the light intensity of the incident light is adjusted accordingly. By adjusting the first value of light intensity while aligning the pachymeter with respect to the eye, the discomfort to the eye is reduced. Additionally, the adjustment is made to account for the varying distance and ensure accurate measurements of the corneal thickness while preventing discomfort to the eye.

[0048] Optionally, the method further comprises measuring ambient light and adjusting the first value as a function of the measured ambient light. The term "ambient light" refers to a natural or an artificial illumination present in the environment where corneal thickness measurement is being taken. Ambient light can influence the accuracy and reliability of corneal measurement as the aforementioned pachymeter relies on optical principles or imaging techniques. In this regard, optionally, the confocal chromatic sensors may incorporate additional features or sensors, to measure ambient light in addition to reflected light from the cornea. These could include ambient light sensors or photodiodes that detect the overall ambient light level. By measuring the ambient light level separately, the sensor can differentiate between the ambient light and the reflected light from the object being measured. Moreover, by measuring the ambient light and adjusting the first value accordingly, the method can account for variations in lighting conditions, thereby improving the accuracy of the measurements taken.

[0049] Moreover, the method comprises comparing the measured distance with a predetermined distance range. The predefined distance range is a desired range of alignment of the pachymeter at which the pachymeter is configured to send out short and continuous pulses of incident lights from the light source. Beneficially, by comparing the measured distance with a predetermined range, the method can assess whether the cornea thickness is within the desired parameters, providing reliable and precise measurements.

[0050] Optionally, the predefined distance range is from 1 mm up to 5 mm. Optionally, the predefined distance range is from 1, 1.5, 2, 2.5, 3, 3.5, 4 or 4.5 mm up to 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 mm. In an example, the predetermined distance range is 2 mm between the pachymeter and the outer surface of the cornea.

[0051] Furthermore, upon comparison, if the measured distance is in the predetermined distance range, then the thickness of the cornea is measured with the confocal chromatic sensor, wherein the light intensity of the light source of the CCS is set at a second value, wherein the second value is higher than the first value. Optionally, the measurement of the thickness of the cornea is performed by setting the light intensity of the light source of the CCS at a second value. In this regard, the CCS is configured to send out short and continuous pulses of incident lights of higher light intensity, i.e., light intensity of the second value, from the light source towards the cornea of the eye, which penetrates deeper and reaches the inner surface of the cornea. The CCS of the pachymeter is configured to measure the thickness from information of the reflected light intensity and the measured distance. The total travel distance of the incident light and the reflected light corresponds to the thickness of the cornea. Notably, the second value is higher than the first value. Beneficially, setting the light intensity of the light source at the second value enhances the accuracy and reliability of the corneal thickness measurement, by improving the resolution and sensitivity of the CCS. By increasing the light intensity, the CCS can capture more precise data and obtain more accurate measurements of the cornea's thickness.

[0052] Optionally, the method further comprises moving the pachymeter towards the outer surface of the cornea until the measured distance is within the predetermined distance range before setting the light intensity of the light source at the second value for measuring the thickness of the cornea. For example, if it is determined that the measured distance is not within the predetermined distance range, then the pachymeter is moved further towards the outer surface of the cornea until the measured distance is within the predetermined distance range, before setting the light intensity of the light source at the second value for measuring the thickness of the cornea.

[0053] Optionally, the second value is selected to be in a range from 0.2 mW / cm^ up to 20 mW / cm^. Optionally, the second value is in an range from 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8,

[0054] 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4,

[0055] 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0,

[0056] 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6,

[0057] 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2,

[0058] 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0,

[0059] 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, 12.1, 12.2,

[0060] 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13.0, 13.1, 13.2, 13.3, 13.4,

[0061] 13.5, 13.6, 13.7, 13.8, 13.9, 14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6,

[0062] 14.7, 14.8, 14.9, 15.0, 15.1, 15.2, 15.3, 15.4, 15.5, 15.6, 15.7, 15.8,

[0063] 15.9, 16.0, 16.1, 16.2, 16.3, 16.4, 16.5, 16.6, 16.7, 16.8, 16.9, 17.0,

[0064] 17.1, 17.2, 17.3, 17.4, 17.5, 17.6, 17.7, 17.8, 17.9, 18.0, 18.1, 18.2,

[0065] 18.3, 18.4, 18.5, 18.6, 18.7, 18.8, 18.9, 19.0, 19.1, 19.2, 19.3, 19.4,

[0066] 19.5, 19.6, 19.7, 19.8, 19.9, or 20.0 mW / cm2up to 0.3, 0.4, 0.5, 0.6,

[0067] 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2,

[0068] 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8,

[0069] 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4,

[0070] 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 7.0,

[0071] 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6,

[0072] 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1,

[0073] 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.1, 11.2, 11.3,

[0074] 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, 12.1, 12.2, 12.3, 12.4, 12.5,

[0075] 12.6, 12.7, 12.8, 12.9, 13.0, 13.1, 13.2, 13.3, 13.4, 13.5, 13.6, 13.7,

[0076] 13.8, 13.9, 14.0, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 14.7, 14.8, 14.9,

[0077] 15.0, 15.1, 15.2, 15.3, 15.4, 15.5, 15.6, 15.7, 15.8, 15.9, 16.0, 16.1,

[0078] 16.2, 16.3, 16.4, 16.5, 16.6, 16.7, 16.8, 16.9, 17.0, 17.1, 17.2, 17.3,

[0079] 17.4, 17.5, 17.6, 17.7, 17.8, 17.9, 18.0, 18.1, 18.2, 18.3, 18.4, 18.5,

[0080] 18.6, 18.7, 18.8, 18.9, 19.0, 19.1, 19.2, 19.3, 19.4, 19.5, 19.6, 19.7,

[0081] 19.8, 19.9, or 20.0 ' mW / cm2.

[0082] The (first and second) value can be considered as an effective irradiance observed on eye. "Irradiance" as such is the optical power per unit area. By "effective irradiance" we mean the optical power onto a certain area divided by that area. In the context the present disclosure the "effective irradiance" is similar to the "anterior segment irradiance" in the standard (ISO 15004-2:2007), Hence: The effective irradiance is the maximal localized radiant power onto a 1 mm diameter circular area of the cornea divided by that area.

[0083] Optionally, the second value is selected based on a function of the measured distance. Optionally, a specific mathematical function or algorithm may be applied to the measured distance to determine the appropriate value for the second value of the light intensity. Notably, the second value is optimized for the specific distance, leading to improved measurement of the corneal distance. Notably, the analysis is performed by comparing the measured distance between a pachymeter and the outer surface of the cornea using the CCS with a predetermined distance range. If the measured distance falls within this range, the thickness of the cornea is measured using the confocal chromatic sensor. During the measurement of distance, a lower light intensity value is used, while for the thickness measurement, a higher light intensity value is applied. This allows for the capture of a weak peak associated with the inner surface of the cornea.

[0084] In an embodiment, when measuring the thickness of the cornea with the confocal chromatic sensor, the set second value comprises a plurality of intensity values. Optionally, the plurality of intensity values corresponds to the light intensity of the light source of the confocal chromatic sensor. During the measurement of cornea thickness using the confocal chromatic sensor (CCS), the second value of the light intensity of the light source, is set to a range of multiple intensity values by sweeping the second intensity value across a range of values. This enables the detection of various peaks in the wavelength corresponding to reflections from different layers, such as the outer surface, inner surface, or surfaces of the cornea, and potentially other details like the lens of the eye or the retina. In an embodiment, the method further comprises analyzing accuracy of the measured thickness and adjusting the light intensity to a third value based on the analysis.

[0085] The present disclosure also relates to the pachymeter as described above. Various embodiments and variants disclosed above, with respect to the aforementioned method, apply mutatis mutandis to the pachymeter.

[0086] In an embodiment, the controller is further configured to adjust the first value based on the measured distance. As an example, the first value is reduced as the pachymeter is moved closer to the eye, but still enabling to measure distance in accurate manner. This way one can keep the illumination level towards eye minimal during the measurement procedure.

[0087] In an embodiment, the controller is further configured to adjust the second value as the function of the measured distance. In deed if the measurement is done closer to eye the second value can be lower than if the measurement is done further away.

[0088] In an embodiment, the the first value is selected to be in the range from 0.05 mW / cm2up to 5 mW / cm2, the second value is selected to be in the range from 0.2 mW / cm2up to 20 mW / cm2. Optional ranges are as indicated earlier in the application when discussing method.

[0089] In an embodiment, the controller is configured to control the second light intensity value as a sweep to measure corneal thickness values with plurality of light intensity values.

[0090] In an embodiment, the aforementioned pachymeter comprises an ambient light sensor. The controller of the aforementioned pachymeter is communicatively coupled with the ambient light sensor and is configured to adjust at least one of the first value or the second value as function of the ambient light. The "ambient light sensor" refers to a device that measures the intensity of ambient light in the environment where the pachymeter is placed for measuring thickness of the cornea. The ambient light sensor is configured to detect a level of illumination present in the environment and to provide information pertaining to the level of illumination present in the environment to the controller. As a summary a method and pachymeter is disclosed. During use the pachymeter is moved close to patient's eye. Confocal chromatic sensor of the pachymeter is used to measure distance. Since the distance measurement requires only reflection from outer surface of the eye a low intensity (first value of light intensity) light can be used. This way patient does not feel discomfort due to the incident light beam of the CCS. As soon as the distance is close enough to make reliable measurement the CCS is used to measure thickness of the eye using higher (second) light intensity (than during the distance measurement). Higher intensity is needed to capture details of cornea in accurate manner. The thickness measurement is relatively short and can be done in matter of fraction of second thus irradiance to eye is reduced in comparison to setup in which the light intensity would remind same during the entire measurement procedure.

[0091] DETAILED DESCRIPTION OF DRAWINGS

[0092] Referring to FIG. 1, illustrated is a pictorial representation of a working principle for measuring a thickness D2 of a cornea 114 using a pachymeter 100, in accordance with an embodiment of the present disclosure. According to FIG.l, the method is executed by the pachymeter 100 comprising a confocal chromatic sensor (CCS) 102. The CCS 102 includes a light source 104 configured to emit an incident light 106. The CCS 102 also includes a spectrometer 108 configured to receive a reflected light 110. Moreover, the pachymeter 100 comprises a controller 112 communicatively coupled to the CCS 102. Moreover, the incident light 106 is reflected, namely, reflected light 110, from the cornea 114 of an eye 150. According to FIG. 1, the cornea 114 of an eye 116, include an outer surface 118 and an inner surface 120. The thickness D2 is measured as a distance between the outer surface 118 and the inner surface 120. As shown, the pachymeter 100 is placed at a distance DI from the outer surface 118 of the cornea 114. As shown, the pachymeter 100 further comprises an ambient light sensor 122 for measuring ambient light.

[0093] Referring to FIG. 2, illustrated is a flowchart 200 depicting steps of a method for measuring a thickness D2 of a cornea 114, in accordance with an embodiment of the present disclosure. At 202, a distance DI between the pachymeter 100 and the outer surface 118 of the cornea 114 is measured using the CCS 102. The CCS 102 includes the light source 104 which is configured to emit the incident light 106 of a light intensity set at a first value. At 204, the measured distance DI is compared with a predetermined distance range. At 206, if the measured distance DI is in the predetermined distance, the thickness D2 of the cornea 114 is measured with the CCS 102, wherein the light intensity of the light source 104 of the CCS 102 set at a second value, wherein the second value is higher than the first value.

[0094] Referring to FIG.3, illustrated is a graphical representation of a light intensity 302 of an incident light from the light source 104 of the pachymeter 100 with respect to a distance DI between the pachymeter 100 and the cornea 116, in accordance with an embodiment of the present disclosure. As shown, during the alignment of the pachymeter 100 for measuring the distance DI between the pachymeter 100 and the outer surface of the cornea 118, the light intensity 302 of the light source 104 is set at the first value VI, which is of lower intensity. When the distance DI is optimum, i.e., within the predetermined distance range, which may be between 1 mm up to 5 mm, then thickness D2 is measured while the light source 104 is set at the light intensity 302 of the second value V2, which is higher intensity. Thus, the weak peak of the reflected light 110 associated with the inner surface 120 of the cornea 114 is captured. The dashed line indicates a "minimum" intensity as the function of distance DI from the outer surface 118 of the cornea 114. As shown, the intensity value of incident light 106 can be set lower and optimum intensity of the reflected light 110 can be obtained, when the distance DI is shorter, thus ensuring that lower light intensity VI can be used for measurement of distance from eye and minimizing patient's discomfort. At the moment when distance is less than a threshold distance which pertains to the higher range of the predetermined distance range, light intensity is increased to V2 to obtain reflections from the inner surface 118 of the cornea 114 as well.

[0095] Referring to FIG. 4, illustrated is a graphical representation of a reflected light intensity as a function of wavelength of an incident light 106 from the light source 104 of the pachymeter 100, in accordance with an embodiment of the present disclosure. As shown, a peak at wavelength LI is associated with the outer surface 118 of the cornea 114 and a peak at wavelength L2 is associated with the inner surface 120 of the cornea 114. A difference 'dL' between the wavelengths LI and L2 corresponds to the thickness D2 of the cornea 114. In general, depending on how the CCS 102 is set up, each wavelength (LI and L2) corresponds to a specific distance from the light source 104 of the CCS 102. In an embodiment, when the second peak L2 is of a low intensity value, then the light intensity 302 of the light source 104 is set to the third value V3 which is higher than the second value V2 to increase signal to noise ratio.

[0096] Referring to FIGs. 5A, 5B and 5C, illustrated are effects of sweeping a second intensity of an incident light 106 from a light source 104 (i.e. using different intensity values) in accordance with an embodiment of the present disclosure. As shown, FIGs. 5A, 5B and 5C depict graphical representations of the reflected light intensity as a function of wavelength of the incident light 106 at different second intensity values.. In FIG. 5A, illustrated is a functional relation between the reflected light intensity as a function of wavelength of the incident light at the second intensity, when the incident light 106 is fired with low intensity. The obtained reflected light 106 for firing the incident light 106 with low intensity results in weak peak of wavelength. In other words, the second intensity value is too low and there is only a small peak at L2. FIG. 5B illustrates as the intensity is increased also the reflected intensity of L2 is higher (and LI) thickness can be measured more accurately. In FIG. 5C, ss the intensity is increased, a third peak of wavelength L3 is detected in addition to the second peak. This way further details of eye structure can be obtained. The scanning of the cornea 114 by sweeping values (of the second inventisity) by the pachymeter 100 results in efficient measurement of thickness D2 of cornea 114.

[0097] 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.

[0098] Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a nonexclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural.

Claims

1. CLAIMS1. A method of measuring a thickness (D2) of a cornea (114), the method comprising- measuring a distance (DI) between a pachymeter (100) and an outer surface (118) of the cornea (114) using a confocal chromatic sensor (102), wherein a light intensity (302) of a light source (104) of the confocal chromatic sensor is set at a first value (VI),- comparing the measured distance with a predetermined distance range, and- if the measured distance is in the predetermined distance range, measuring the thickness of the cornea with the confocal chromatic sensor, wherein the light intensity of the light source of the confocal chromatic sensor is set at a second value (V2), wherein the second value is higher than the first value.

2. A method according to claim 1, wherein the first value (VI) is adjusted based on the measured distance (DI).

3. A method according to any of the preceding claims, wherein the second value (V2) is selected based on a function of the measured distance (DI).

4. A method according to any of the preceding claims, further comprising analysing accuracy of the measured thickness (D2) and adjusting the light intensity (302) to a third value (V3) based on the analysis.

5. A method according to any of the preceding claims, wherein- the first value (VI) is selected to be in a range from 0.05 mW / cm2up to 5 mW / cm2,- the second value (V2) is selected to be in a range from 0.2 mW / cm2up to 20 mW / cm2.

6. A method according to any of the preceding claims, wherein the predefined distance range is from 1 mm up to 5 mm.

7. A method according to any of the preceding claims, further comprising measuring ambient light and adjusting the first value (VI) as a function of the measured ambient light.

8. A method according to any of the preceding claims, wherein when measuring the thickness (D2) of the cornea (114) with the confocal chromatic sensor (102), the set second value comprises a plurality of intensity values.

9. A pachymeter (100) comprising- a confocal chromatic sensor (102) comprising a light source (104) and a spectrometer (108);- a controller (112) communicatively coupled to the confocal chromatic sensor and configured, when in use, to: measure distance (DI) from pachymeter to an outher surface of cornea (114) by- setting a light intensity (302) of the light source to a first value (VI);- receiving a first set of reflected light intensity values from the spectrometer;- determing from the first set of values a distance (DI) between the pachymeter and an outer surface (120) of a cornea and using the determined distance as the measured distance; compare the measured distance with a predetermined distance range; set a light intensity of the light source to a second value (V2) if the measured distance is within the predetermined distance;and receive a second set of reflected light intensity values from the spectrometer and use the second set of values to determine thickness (D2) of the cornea (114).

10. A pachymeter (100) according to claim 9, wherein the controller (112) if further configured to adjust the first value (VI) based on measured distance (DI).

11. A pachymeter (100) according to claim 9 or 10, wherein the controller (112) is further configured to adjust the secod value as function of the measured distance.

12. A pachymeter (100) according to any of the claims 9 to 11 wherein- the first value (VI) is selected to be in a range from 0.05 mW / cm2up to 5 mW / cm2, - the second value (V2) is selected to be in a range from 0.2 mW / cm2up to 20 mW / cm2.

13. A pachymeter(lOO) according to any of the claims 9 to 12, wherein the pachymeter comprises an ambient light sensor (122) and the controller (112) is configured to adjust at least one of the first value (VI) or the second value (V2) as function of the abmient light.

14. A pachymeter (100) according to any of the claims 9 to 13, wherein the controller (112) is configured to control the second value (V2) as a sweep to measure corneal thinkness values with plurality of light intensity values.

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