Arrangement and method for detecting physiological factors of the eye

Abstract

An arrangement (100) for ocular tonometry comprising means to move a probe (102) towards an eye (110), means to produce a measurement signal from the movement of the probe (102), wherein the measurement signal representing probe velocity information as function of time, and wherein the measurement signal pertains to a probe (102) traveling to and from the surface of an eye (110), characterized in that the arrangement (100) comprises processing means (108), which are arranged using the measurement signal, to detect rebound of the probe (102) after impact with the eye (110) and separation of the probe (102) contact from the surface of the eye (110), to calculate energy loss (212) between the points of maximum rebound probe velocity before separation and probe rebound velocity at separation, wherein the calculated energy loss is associated with a physiological factor of the eye, the physiological factor representing tear film condition or dryness of the eye Corresponding method (300) and computer program product are also disclosed.

Description

[0001] ARRANGEMENT AND METHOD FOR DETECTING PHYSIOLOGICAL FACTORS OF THE EYE

[0002] FIELD OF THE INVENTION

[0003] Generally, the present disclosure relates to ophthalmological measurement arrangements and methods. Particularly, however not exclusively, the present disclosure pertains to an arrangement, method and use for detecting physiological factors of the eye.

[0004] BACKGROUND

[0005] Dry eye syndrome is a common ocular condition characterized by insufficient lubrication and moisture on the eye's surface, causing discomfort and potentially impairing vision. Accurate assessment and measurement of dry eye conditions are essential for effective diagnosis and management.

[0006] Traditional methods to evaluate dry eye conditions typically include patient questionnaires, where subjective symptoms such as irritation, burning, or blurred vision are reported. Visual inspections performed by ophthalmologists using slit lamps are another conventional technique. This involves directing a narrow beam of light onto the cornea to visually identify areas where the tear film is deficient. Additionally, corneal imaging devices that provide visual animations or images depicting tear film breakup patterns have been utilized.

[0007] While such conventional methods offer valuable information, they suffer from notable limitations. Primarily, these prior solutions fail to accurately account for or measure the adhesion or "stickiness" of probes or instruments to the ocular surface during testing. Although some prior art approaches may consider energy loss during corneal measurements, they predominantly focus on energy loss associated with deformation of the ocular surface rather than specifically addressing energy dissipation due to probe adhesion to the tear film. Consequently, there remains an unmet need for a method and apparatus that effectively and accurately quantify this adhesive interaction, leading to more precise assessments of dry eye conditions.SUMMARY OF THE INVENTION

[0008] The objective of the embodiments of the present disclosure is to at least alleviate one or more of the aforementioned drawbacks evident in the prior art arrangements. The objective is generally achieved with an arrangement, method, and computer program in accordance with the present disclosure.

[0009] One technical advantage of the present disclosure is that it allows measuring of dryness of an eye and potential anomalies in the tear film of the eye in a rebound tonometer.

[0010] In accordance with one aspect of the present disclosure an arrangement for ocular tonometry comprising

[0011] - means to move a probe towards an eye,

[0012] - means to produce a measurement signal from the movement of the probe, wherein the measurement signal representing probe velocity information as function of time, and wherein the measurement signal pertains to a probe traveling to and from the surface of an eye, - characterized in that the arrangement comprises processing means, which are arranged using the measurement signal,

[0013] o to detect rebound of the probe after impact with the eye and separation of the probe contact from the surface of the eye, o to calculate energy loss between the points of maximum rebound probe velocity before separation and probe rebound velocity at separation,

[0014] - wherein the calculated energy loss is associated with a physiological factor of the eye, the physiological factor representing tear film condition or dryness of the eye.

[0015] In accordance with one aspect of the present disclosure a computer-implemented method for ocular measurement comprising

[0016] - receiving a measurement signal representing probe velocity information as function of time, and wherein the measurement signal pertains to a probe traveling to and from the surface of an eye, - characterized in that using the measurement signal,o detecting rebound of the probe after impact with the eye and separation of the probe contact from the surface of the eye, and

[0017] o calculating an energy loss between the points of maximum rebound probe velocity before separation and probe rebound velocity at separation

[0018] - wherein the energy loss is associated with a physiological factor of the eye, the physiological factor representing tear film condition or dryness of the eye.

[0019] In accordance with another aspect of the present disclosure a computer program product embodied in a non-transitory computer readable medium, comprising computer code for causing the computer to execute the method of the present disclosure.

[0020] One example of an embodiment of use of the present disclosure is measuring and monitoring the presence and amount of deterioration of the tear film of the eye. The solution can be used in screening with a tonometer when intraocular pressure is measured.

[0021] As briefly reviewed hereinbefore, the utility of the different aspects of the present disclosure arises from a plurality of issues depending on each particular embodiment.

[0022] Different embodiments of the present disclosure are also disclosed in the attached dependent claims.

[0023] The expression “a number of’ may herein refer to any positive integer starting from one (1). The expression “a plurality of’ may refer to any positive integer starting from two (2), respectively.

[0024] The term “exemplary” refers herein to an example or example-like feature, not the sole or only preferable option.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Some exemplary embodiments of the present disclosure are reviewed more closely with reference to the attached drawings, whereinFig. 1 depicts a general view of the operating concept of the arrangement in accordance with the present disclosure,

[0027] Fig. 2 depicts an exemplary measurement time-velocity curve and the general principle in accordance with an embodiment of the present disclosure, and

[0028] Fig. 3 depicts a flow chart for the method of calculating energy loss in accordance with an embodiment of the present disclosure.

[0029] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Fig. 1 depicts a general view of the operating concept of the arrangement in accordance with the present disclosure. In one aspect, an embodiment of the present disclosure provides an arrangement for ocular tonometry, which arrangement is a rebound tonometer. The arrangement (100) of this embodiment may comprise a body having a proximal end and a distal end opposite to the proximal end, wherein the body has an opening at the proximal end, wherein a magnetic elongated probe (102) having a first end and a second end opposite to the first end is arranged to be inserted at least partially in the body in a manner that the first end protrudes outside of the body from the opening of the body, the first end is at a first distance from the opening, and the second end is inside the body, and wherein the magnetic elongated probe (102) is arranged to be aligned with and movable along an axis of the rebound tonometer; a measurement coil, i.e. means to produce a measurement signal (106) from the movement of the probe (102), and a drive coil, i.e. means to move a probe (104) towards an eye (110), arranged inside the body and to partially surround the magnetic elongated probe (102); and processing means (108), such as a controller configured to: produce a measurement signal from the movement of the probe (102), wherein the measurement signal representing probe (102) velocity information as function of time, when the rebound tonometer is in use, by: energizing the drive coil to move the magnetic elongated probe (102) in respect to the body; and detecting rebound of the probe (102) after impact with the eye (110) and separation of the probe (102) contact from the surface of the eye (110), i.e. the cornea (112) and the tear film thereon, and calculating energy loss between the points of maximum rebound probe velocity before separation and probe rebound velocity at separation. The calculated energy loss is associated with a physiological factor of the eye (110), such as the condition of the tear filmof the eye (110). Further, the arrangement (100) may be used to determine the physiological factor of the eye together with other functionalities of the arrangement (100), such as calculation of an intraocular pressure value. These functions of the arrangement (100) need not be connected and they may be executed separately irrespective of each other or they may be carried out simultaneously and / or related to each other.

[0031] The calculated energy loss is associated with a physiological factor of the eye (110), such as tear film condition or dryness of the eye (110). As used herein, 'associated with' is intended to encompass any meaningful relationship between the calculated energy loss and the physiological factor, including but not limited to a correlation, a direct or indirect indicative relationship, or a translation of the calculated energy loss into a physiological assessment.

[0032] In the context of the present disclosure, 'tear film condition' refers to the state of the tear film of the eye (110), including the presence, thickness and integrity of the tear film. The calculated energy loss is sensitive to the condition of the surface with which the probe (102) interacts, such that a change in tear film condition is reflected in a corresponding change in the calculated energy loss. For example, the calculated energy loss may be indicative of the tear film condition of the eye (110), with a higher energy loss at separation potentially being indicative of a healthier or thicker tear film and a lower energy loss potentially being indicative of reduced tear film presence or dryness of the eye (110).

[0033] It has been observed that a reduction in the presence of tear film on the surface of the eye (110), for example as simulated by applying a drying agent to an artificial eye membrane, noticeably reduces the energy loss effect, suggesting that the energy loss is correlated with the condition of the tear film. Such an association may be established by comparison with reference energy loss values, for example energy loss values obtained using artificial eye membranes.

[0034] The arrangement (100) may thus be used as a screening tool, for example to notify an operator that a patient's corneal surface appears dry and that further examination may be warranted, without requiring any hardware modifications to existing rebound tonometer platforms. The physiologicalfactor determination may be implemented as a software module operating on the existing measurement signal of a rebound tonometer.

[0035] In other embodiments, the arrangement (100) may be another type of ocular tonometer, which produces a measurement signal representing probe velocity information as function of time. Such tonometers are widely known in the state of art.

[0036] Fig. 2 depicts an exemplary measurement time-velocity curve and the general principle in accordance with an embodiment of the present disclosure. First, a probe is ejected from a tonometer arrangement and is in a free flight state towards cornea of an eye (202). At the point of impact (204) with the cornea the velocity decreases and thereafter reaches a zero-velocity point (206) after which the probe is rebounded followed by maximum rebound velocity before separation from the eye (208) and a free flight away from the cornea after separation from the eye (210). Fig. 2 further shows energy loss during separation (212) and energy loss during rebound (214). The illustrated energy loss during separation (212) causes delayed separation of the probe from the cornea (216) before the probe travels free away from cornea. The dotted line (218) depicts what would be the probe in a free-flight if the separation from the surface of the eye happened with no energy loss. The arrow (220) extending from the point before impact (204) down to a symmetric point negative velocity value in reference to the zero velocity represents ideal symmetric speed range during fully elastic rebound and shows what the return velocity would be in an ideal elastic collision without energy losses caused by the non-elastic collision with the eye and separation from the surface of the eye. It will be appreciated that the values shown on the axes of Fig. 2 are arbitrary and are provided for illustrative purposes only.

[0037] The moment of separation (216) of the probe (102) from the surface of the eye (110) and the tear film thereon is identifiable from the measurement signal as the point at which the velocity of the rebounding probe departs from the delayed separation trajectory (216) and resumes a free-flight velocity profile (210). The energy loss during separation (212), illustrated in Fig. 2 as the difference between the actual probe velocity at separation (210) and the maximum rebound velocity before separation (208), thus reflectsenergy dissipated during the separation of the probe (102) from the surface of the eye (110) and the tear film thereon.

[0038] Fig. 3 depicts a flow chart for the method of calculating energy loss in accordance with an embodiment of the present disclosure.

[0039] The method (300) of the present disclosure may be provided as a computer implemented method, which may be carried out on a computer, computer network or the like computing means. Therein the method (300) may receive the measurement signal representing probe velocity information as function of time (302) from an arrangement for ocular tonometry, wherein the method (300) may be executed in the arrangement or externally from the arrangement on another computing entity such as terminal device connected to the ocular tonometer or a remote computing entity receiving data from the ocular tonometer. The method (300) and the essential step of calculating energy loss between the points of maximum probe velocity before separation and probe velocity at separation may be implemented in the ocular tonometer arrangement or as a remote software executable with an ocular tonometer arrangement.

[0040] The method (300) is executed by detecting the probe tip contact and separation with the cornea of an eye (304) and calculating the energy loss of the probe movement during when the probe tip separates from the surface of the eye, i.e. the cornea and tear film thereof. The energy loss is calculated (306) from the maximum probe velocity before separation and probe velocity at separation as the ratio of the values or by subtraction of the values. The calculated energy loss (306) can be further correlated with a physiological factor of the eye (308) for example by comparison with energy loss information representing a healthy eye or by comparison with energy loss information measured by using artificial eye membranes.

[0041] The method (300) of calculating the energy loss may be used to detect tear film condition and possible deterioration or biomarker thereof. For example, the method (300) may be used to detect tear film thickness or dryness of an eye. The method (300) may be used as a plurality of measurements carried out by a physician or the person to-be-measured by themselves over time, which may be used to determine the progress of deterioration or lack thereof of a person’s eye or eyes. In particular, a series of successivemeasurements taken in quick succession may be implemented which may be a preferable embodiment to assess the rate of deterioration of the tear film, and the change in calculated energy loss between successive measurements may reflect the rate at which the tear film deteriorates.

[0042] The scope of the invention is determined by the attached claims together with the equivalents thereof. The skilled persons will again appreciate the fact that the disclosed embodiments were constructed for illustrative purposes only, and the innovative fulcrum reviewed herein will cover further embodiments, embodiment combinations, variations and equivalents that better suit each particular use case of the invention.

Claims

CLAIMS1. An arrangement (100) for ocular tonometry comprising- means to move a probe (102) towards an eye (110),- means to produce a measurement signal from the movement of the probe (102), wherein the measurement signal representing probe velocity information as function of time, and wherein the measurement signal pertains to a probe (102) traveling to and from the surface of an eye (110),- characterized in that the arrangement (100) comprises processing means (108), which are arranged using the measurement signal, o to detect rebound of the probe (102) after impact with the eye (110) and separation of the probe (102) contact from the surface of the eye (110),o to calculate energy loss (212) between the points of maximum rebound probe velocity before separation and probe rebound velocity at separation,- wherein the calculated energy loss is associated with a physiological factor of the eye (110), the physiological factor representing tear film condition or dryness of the eye (110).

2. The arrangement (100) of claim 1, wherein the means to move the probe (102) comprise a drive coil (104) for inducing magnetisation to the probe (102) having a magnetic part, and wherein the means to produce the measurement signal comprise a measurement coil (106) arranged to detect the movement of said probe (102) having a magnetic part.

3. A computer- implemented method (300) for ocular measurement comprising- receiving a measurement signal representing probe velocity information as function of time, wherein the measurement signal pertains to a probe traveling to and from the surface of an eye (302), - characterized in that using the measurement signal,o detecting rebound of the probe after impact with the eye and separation of the probe contact from the surface of the eye (304), ando calculating an energy loss (212) between the points of maximum rebound probe velocity before separation and probe rebound velocity at separation (306),- wherein the energy loss is associated with a physiological factor of the eye, the physiological factor representing tear film condition or dryness of the eye (308).

4. The method (300) of claim 5, wherein further acquiring probe geometry, probe weight and / or probe velocity information and including said information to the calculation of energy loss (212).

5. The method (300) of any one of claims 5 and 6, wherein a series of successive measurements is taken in quick succession to assess the rate of deterioration of the tear film of the eye (110), wherein the change in calculated energy loss between successive measurements reflects the rate at which the tear film deteriorates.

6. A computer program product embodied in a non-transitory computer readable medium, comprising computer code which, when executed by a computer, causes the computer to carry out the method (300) of any one of claims 5 to 7.

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