Rebound tonometer and how to use it

Abstract

A rebound tonometer is disclosed. The rebound tonometer includes a body (102, 206, 302), an elongated magnetic probe (104, 208, 304), a measurement coil (106, 210, 306) and a drive coil (108, 212, 308) surrounding the elongated magnetic probe, and a controller (310). The body has a proximal end (110, 214) and a distal end (112, 216), with an opening (114) in the proximal end. The elongated magnetic probe has a first end (116, 218) that projects outwardly from the opening in the body and a second end (118, 220) that remains within the body. The first end is a first distance (D1) from the opening. The elongated magnetic probe is aligned with and movable along an axis of the rebound tonometer. When the rebound tonometer is used, the controller is configured to energize the drive coil to move the elongated magnetic probe so that the first end is at a second distance from the proximal end, measure an induced voltage in the measurement coil, detect contact by comparing the induced voltage with a predetermined criterion, and initiate a measurement cycle of the rebound tonometer upon detecting contact.

Description

[Technical field]

[0001] The subject matter disclosed herein (hereinafter referred to as the present disclosure) relates to a rebound tonometer (sometimes referred to as a rebound tonometer). The present disclosure also relates to a method of using a rebound tonometer to determine a characteristic of an object.

[0002] Over the past few decades, measuring devices have gained favor in various fields such as medicine, engineering, etc. In the field of medicine in particular, measuring devices are often used, for example, by medical professionals (optometrists, ophthalmologists, doctors, etc.) to observe an object (such as a patient's eye, a part of the patient's body, etc.) and measure parameters related to the object. As an example, a rebound tonometer may be employed to measure the intraocular pressure (i.e., fluid pressure within the eye) of a patient's eye by the interaction of the cornea with the indentation of the eye. Generally, when using a rebound tonometer, the rebound tonometer is placed (i.e., set) in front of the object at a specific distance from the object.

[0003] However, there are very specific requirements for the placement of the tonometer relative to the object (to measure a parameter related to the object). In some cases, existing tonometers are placed too far from the object. In such cases, the parameter is measured inaccurately or not at all. In other cases, existing rebound tonometers are placed too close to the object, where one or more parts of the tonometer may inadvertently damage the object while measuring the parameter. In both cases, the result is erroneous and unreliable measurements.

[0004] Some existing rebound tonometers include a holder for contacting a peripheral portion of an object. The holder facilitates positioning the rebound tonometer in front of the object. The holder defines a distance between the rebound tonometer and the object. However, such holders position the rebound tonometer in front of the object in a non-precise and inaccurate manner. This is because the holder is mechanically set on the rebound tonometer and manually positioned relative to the object, and thus is prone to errors due to such mechanical set-up and manual intervention. For example, a rebound tonometer may include a holder that can be contacted with a patient's forehead when measuring the intraocular pressure of the patient's eye. Such a holder cannot compensate for the various shapes and characteristics of various patients' foreheads and cannot accurately align the rebound tonometer with the eye. In addition, tonometers with holders are heavy and expensive. Using typical distance measurement solutions such as ultrasonic sensors, cameras, etc. for existing tonometers is unlikely to be feasible because these solutions are expensive and difficult to implement.

[0005] In light of these considerations, a need exists to overcome the aforementioned shortcomings associated with existing rebound tonometers.

[0006] The present disclosure seeks to provide a rebound tonometer. The present disclosure also seeks to provide a method of using a rebound tonometer to determine a property of an object. It is an object of the present disclosure to provide a solution that at least partially overcomes the problems encountered in the prior art.

[0007] According to one aspect, an embodiment of the present disclosure provides a rebound tonometer. The rebound tonometer comprises: a body having a proximal end and a distal end opposite the proximal end, the body having an opening at the proximal end; with an elongated magnetic probe; a measurement coil and a drive coil, both disposed within the body and partially surrounding the elongated magnetic probe; With the controller; Equipped with The elongated magnetic probe comprises: a first end and a second end opposite the first end; a first end portion of the first end protruding from an opening in the body to an exterior of the body at a first distance from the opening and a second end portion of the second end portion of the first ... aligned with and movable along an axis of the rebound tonometer; The controller: When the rebound tonometer is in use, contact between an object and the first end is energizing the drive coil to move the elongated magnetic probe relative to the body such that the first end is at a second distance from the proximal end, the second distance being greater than the first distance; measuring a first induced voltage in the measurement coil as a function of time during a first time period; comparing the first induced voltage measured as a function of time to a predetermined reference; if the predetermined criterion is satisfied based on the comparison, using the satisfaction as an indication that contact between the first end and the object has been detected; By detecting; when said contact is detected, initiating a measurement cycle of said rebound tonometer; The device is configured to:

[0008] Viewed another way, embodiments of the present disclosure provide a method of using a rebound tonometer to determine a property of an object, the rebound tonometer comprising a body, an elongated magnetic probe, a measurement coil, and a drive coil, the method comprising: disposing the elongated magnetic probe at least partially within a body, a first end of the elongated magnetic probe protruding from an opening in the body exterior to the body at a first distance from the opening and a second end of the elongated magnetic probe interior to the body, the elongated magnetic probe being movable along an axis of the rebound tonometer; detecting contact between the object and a short-term first end; and initiating a measurement cycle of the rebound tonometer when the contact is detected; and detecting contact between the object and the short-term first end includes: moving the elongated magnetic probe relative to the body so that the first end is at a second distance from the proximal end, the second distance being greater than the first distance; moving the rebound tonometer relative to the object during a first period of time; measuring a first induced voltage as a function of time during a first period that the rebound tonometer is moved; comparing the first induced voltage measured as a function of time to a predetermined reference; if the predetermined criterion is satisfied based on the comparison, using the satisfaction as an indication that contact between the first end and the object has been detected; This is carried out by.

[0009] Embodiments of the present disclosure substantially eliminate or at least partially address the aforementioned problems in the prior art and enable accurate and reliable alignment of a rebound tonometer with respect to an object during a measurement cycle for measuring a property of the object.

[0010] Further aspects, advantages, features and objects of the present disclosure will become apparent from the accompanying drawings and detailed description of illustrative embodiments, taken in conjunction with the appended claims.

[0011] It will also be appreciated that features of the present disclosure can be combined in various combinations without departing from the scope defined by the appended claims. [Brief description of the drawings]

[0012] The foregoing summary, as well as the following detailed description of exemplary embodiments, will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the disclosure, example configurations of the disclosure are shown in the drawings. However, the disclosure is not limited to the specific methods and apparatus disclosed therein. Also, the drawings are not drawn to scale. Similar elements are designated by the same numerals wherever possible. Embodiments of the present disclosure will now be described, by way of example only, with reference to the following drawings, in which: FIG. 1 is an exemplary schematic diagram of a rebound tonometer, according to one embodiment of the present disclosure. 2A, 2B, and 2C are exemplary schematic diagrams of a rebound tonometer in use, according to various embodiments of the present disclosure. FIG. 3 is a block diagram of a rebound tonometer according to one embodiment of the present disclosure. FIG. 4A shows a first waveform of a first voltage induced in a measurement coil as a function of time during a first time period, and FIG. 4B shows a second waveform of a second voltage induced in a measurement coil as a function of time during a second time period, in accordance with an embodiment of the present disclosure. FIG. 5 is a flow chart illustrating steps of a method for using a rebound tonometer to determine a property of an object, according to one embodiment of the present disclosure. In the accompanying drawings, underlined numbers are used to represent the item at which the number is located or adjacent to the number. Numbers without underlines are associated with the item identified by the line extending from the number. When a number is not underlined but is written with an arrow, the number is used to identify the general item to which the arrow points. DETAILED DESCRIPTION OF EMBODIMENTS

[0013] The following detailed description illustrates embodiments of the present disclosure and how they may be practiced. Although several forms for carrying out the present disclosure have been disclosed, those skilled in the art will recognize that other forms for carrying out the present disclosure are possible.

[0014] According to one aspect, an embodiment of the present disclosure provides a rebound tonometer. The rebound tonometer comprises: a body having a proximal end and a distal end opposite the proximal end, the body having an opening at the proximal end; with an elongated magnetic probe; a measurement coil and a drive coil, both disposed within the body and partially surrounding the elongated magnetic probe; With the controller; Equipped with The elongated magnetic probe comprises: a first end and a second end opposite the first end; a first end portion of the first end protruding from an opening in the body to an exterior of the body at a first distance from the opening and a second end portion of the second end portion of the first ... aligned with and movable along an axis of the rebound tonometer; The controller: When the rebound tonometer is in use, contact between an object and the first end is energizing the drive coil to move the elongated magnetic probe relative to the body such that the first end is at a second distance from the proximal end, the second distance being greater than the first distance; measuring a first induced voltage in the measurement coil as a function of time during a first time period; comparing the first induced voltage measured as a function of time to a predetermined reference; if the predetermined criterion is satisfied based on the comparison, using the satisfaction as an indication that contact between the first end and the object has been detected; By detecting; when said contact is detected, initiating a measurement cycle of said rebound tonometer; The device is configured to:

[0015] Viewed another way, embodiments of the present disclosure provide a method of using a rebound tonometer to determine a property of an object, the rebound tonometer comprising a body, an elongated magnetic probe, a measurement coil, and a drive coil, the method comprising: disposing the elongated magnetic probe at least partially within a body, a first end of the elongated magnetic probe protruding from an opening in the body exterior to the body at a first distance from the opening and a second end of the elongated magnetic probe interior to the body, the elongated magnetic probe being movable along an axis of the rebound tonometer; detecting contact between the object and a short-term first end; and initiating a measurement cycle of the rebound tonometer when the contact is detected; and detecting contact between the object and the short-term first end includes: moving the elongated magnetic probe relative to the body so that the first end is at a second distance from the proximal end, the second distance being greater than the first distance; moving the rebound tonometer relative to the object during a first period of time; measuring a first induced voltage as a function of time during a first period that the rebound tonometer is moved; comparing the first induced voltage measured as a function of time to a predetermined reference; if the predetermined criterion is satisfied based on the comparison, using the satisfaction as an indication that contact between the first end and the object has been detected; This is carried out by.

[0016] The present disclosure provides a rebound tonometer and a method as described above, where a controller of the rebound tonometer performs a precise alignment calibration of the rebound tonometer to obtain an optimal required distance of the object from the proximal end of the body. Therefore, when a measurement cycle of the rebound tonometer is started after the calibration, the characteristics of the object are accurately and reliably determined. The measurement cycle is started only after contact between the object and the first end is detected. This is to ensure that the object is within a second distance from the proximal end of the body of the rebound tonometer. As a result, during the measurement cycle, the first end of the rebound tonometer only contacts or hits the object, and does not cause accidental damage to the object. In other words, the elongated magnetic probe is ejected at a required distance that is neither too far from nor too close to the object. This approach of ensuring a precise alignment of the tonometer to the object (i.e., accurately aligning the tonometer to the object) before the measurement cycle is started is extremely simple, easy to implement, and inexpensive. As a result, the examination and / or diagnosis of an object using a rebound tonometer is reliable, accurate and error-free. Moreover, the tonometer is lightweight and cost-effective. Furthermore, the method is fast, effective, reliable and easy to perform.

[0017] Throughout this disclosure, the term "rebound tonometer" refers to an instrument used to measure a characteristic of an object, where the term "characteristic" refers to a physiological parameter of the object. For example, a tonometer can be used to measure physiological parameters of the eye, such as intraocular pressure of the eye and tactile sensitivity of the eye. In some embodiments, a tonometer is used to measure intraocular pressure from an ophthalmic measurement.

[0018] The term "body" refers to the outermost physical structure of the rebound tonometer. The body is a housing in which at least some of the components of the rebound tonometer (e.g., the elongated magnetic probe, the measurement coil, the drive coil, etc.) are disposed. In other words, the body is configured to house (partially or completely) the components of the rebound tonometer. The body has two opposing ends, a proximal end and a distal end, respectively. When the rebound tonometer is in use, the proximal end of the body is located near the object. The body of the rebound tonometer can be attached to an instrument or can be hand-held to utilize the tonometer. In some cases, the rebound tonometer is held manually by a user (e.g., a medical professional, etc.). In such cases, the body may include a groove for gripping the tonometer. Such a groove allows for a better grip of the tonometer manually compared to when such a groove is not provided. In other cases, a mechanical holder-like instrument is used to hold the tonometer. The medical professional could be, for example, a doctor (e.g., an ophthalmologist, an optometrist, a medical practitioner, etc.), a nurse, a medical support staff, etc.

[0019] The rebound tonometer components may be disposed (i.e., held or attached) within the body by adhesive, mechanical, magnetic, etc. In some cases, the rebound tonometer components may be manufactured individually and then assembled within the body, while in other cases at least some of the rebound tonometer components may be manufactured integrally with the body.

[0020] The body has an opening at a proximal end that allows the elongated magnetic probe to be positioned to allow it to move through the opening. In some embodiments, the shape and size of the opening corresponds to the shape and size of the elongated magnetic probe. As an example, the elongated magnetic probe is cylindrical and has a radius, so that the opening has a circular shape with a radius larger than the radius.

[0021] Throughout this disclosure, the term "elongated magnetic probe" refers to an elongated tool employed to determine a characteristic of an object. The elongated magnetic probe is arranged to be located partially within an opening in the body. The elongated magnetic probe has two opposing ends, a first end and a second end, the second end being located inside the body and the first end protruding from the opening in the body to the outside of the body. The elongated magnetic probe also has an intermediate portion between the first end and the second end. In some embodiments, the first end of the elongated magnetic probe is made of a biocompatible material and impacts a surface of the object (such as an eye) during use. Having the first portion made of a biocompatible material advantageously allows the probe to function in direct contact with the living tissue of the eye, for example, minimizing discomfort or pain. It is noted that biocompatible materials are non-carcinogenic, non-toxic, and resistant to corrosion. An example of locating the elongated magnetic probe partially within the body is by providing an opening in the body. The opening provides access for inserting the elongated magnetic probe into a cylindrical cavity in the body. The cylindrical cavity has a diameter larger than the diameter of at least the intermediate portion and the second end of the elongated magnetic body, allowing the elongated magnetic body probe to move back and forth within the cavity. In use, initially, the second end and about 80%-90% of the intermediate portion are within the cavity. The first end and the remainder of the intermediate portion are outside the body (protruding through the opening). During a measurement cycle, the probe is ejected from the body cavity through the opening. However, even when the probe is at its furthest distance from the body opening, 40%-80% of the intermediate portion is within the cavity.

[0022] In some embodiments, the elongated magnetic probe (or at least a middle portion of the elongated magnetic probe) is made of a magnetic material. The elongated magnetic probe may be made of, for example, a thin wire of a magnetic material. The elongated magnetic probe may be, for example, 20 millimeters long and 0.5 millimeters wide. The magnetic material of the elongated magnetic probe may be ferromagnetic. The first end and the proximal end are spaced apart by a first distance in a default use state of the rebound tonometer. The default use state may be a state in which the elongated magnetic probe is stationary (i.e., the elongated magnetic probe is not moving). For example, the first distance may be in the range of 3-5 millimeters (mm) from the opening, i.e., from the opening towards the object, i.e., from the opening towards the outside of the body of the rebound tonometer in use. The "axis" of the rebound tonometer refers to an imaginary line that passes through the longitudinal direction of the rebound tonometer, is aligned with the elongated magnetic probe, and defines a path along which the elongated magnetic probe may move. The axis is along a predetermined geometric direction. As an example, the optical axis may be the horizontal axis between the eye of the user of the tonometer and the object.

[0023] The measurement coil is arranged inside the body and partially surrounds the elongated magnetic probe. In some embodiments, the measurement coil has a finite number of loops. The elongated magnetic probe may be partially arranged in a hollow space of the loop of the measurement coil. In such a case, the elongated magnetic probe can move within the loop of the measurement coil. The movement of the elongated magnetic probe within the measurement coil generates an induced voltage in the measurement coil.

[0024] A drive coil is also disposed within the body and partially surrounds the elongated magnetic probe. The drive coil is configured as a series of loops through which the elongated magnetic probe can move. The drive coil has a finite number of loops. When a current is applied to the drive coil, the drive coil moves the elongated magnetic probe. In some embodiments, the drive coil pulls the elongated magnetic probe, causing it to protrude toward a surface of the object. The velocity of the elongated magnetic probe is then equal to the product of the current applied through the drive coil and the magnetization of the elongated magnetic probe. In some embodiments, the drive coil is configured as a series of loops through which the elongated magnetic probe can move. The drive coil has a finite number of loops. The drive coil may be disposed along any point between the first end and the second end. For example, the drive coil may be disposed near the first end.

[0025] In some embodiments, the measurement coil and the drive coil are implemented as separate coils, where the measurement coil and the drive coil are physically separated from one another, or in some embodiments, the measurement coil and the drive coil are implemented as different portions of a single coil, where a portion of the single coil is utilized as the measurement coil and the remaining portion of the single coil is utilized as the drive coil in the operation of the rebound tonometer.

[0026] The term "controller" refers to a computing device operable to control the overall operation of the rebound tonometer. In operation, the controller performs tasks such as, but not limited to, controlling the movement of the elongated magnetic probe, responding to and processing information, etc. In one example, the controller may be an embedded microcontroller, microprocessor, etc. In some embodiments, the controller is coupled to the measurement coil and the drive coil. The controller may be implemented as an internal component of the rebound tonometer, an external component of the rebound tonometer, or a combination thereof.

[0027] The contact between the object and the first end occurs by the first end of the elongated magnetic probe physically contacting the object. The term "object" refers to an element whose characteristics are to be measured. In some embodiments, the object is a physical part of a body of an entity. The entity may be, for example, a human, an animal, or the like. For example, the object is a human eye. The contact between the object and the first end is detected before the initialization of the measurement cycle so that during the measurement cycle, the object is located within a required operating distance from the first end of the elongated magnetic probe. As a result, during the measurement cycle, the elongated magnetic probe is ejected to an appropriate distance to repel the object's surface without damaging or causing discomfort to the object, allowing accurate measurement of the object's characteristics.

[0028] In some embodiments, the drive coil is actuated by a controller. This is done in the form of providing a current to the drive coil, thereby magnetically exciting the drive coil. When the drive coil is magnetically excited, the elongated magnetic probe moves relative to the body toward the object such that a second distance between the first end of the elongated magnetic probe and the proximal end or opening of the body is greater than the first distance. In some embodiments, the second distance is in the range of 6 mm to 8 mm. The second distance can be, for example, from 6, 6.2, 6.4, 6.6, 6.8, 7, or 7.5 mm to 6.5, 7, 7.2, 7.4, 7.6, 7.8, or 8 mm. In some embodiments, the drive coil is magnetically excited such that at least a portion of the drive coil surrounding the second end of the elongated magnetic probe is positively charged with respect to the second end. Such magnetic excitation of the drive coil repels the second end and causes the second end of the elongated magnetic probe to protrude toward the first end.

[0029] It will be appreciated that when the drive coil is energized, a magnetic force is generated that urges the elongated magnetic probe to move towards the first end. Here, energization means switching the supply voltage of the drive coil on or off. When the supply voltage of the drive coil is switched on, an electric field is generated. Typically, the higher the supply voltage of the drive coil, the higher the magnetic force. As a result, the acceleration of the elongated magnetic probe increases. The magnetic force is a function of the magnetization (i.e., magnetic polarization) of the elongated magnetic probe. Here, the term magnetization refers to the density of the dipole moment induced in the elongated magnetic probe. The higher the magnetization, the higher the magnetic force. By energizing the drive coil, the elongated magnetic probe moves towards the first end (in particular towards the surface of the object). If the polarity of the drive coil is reversed by energization, the elongated magnetic probe moves in the opposite direction (i.e., away from the proximal end). The direction of movement of the elongated magnetic probe is controlled by a controller.

[0030] "First induced voltage" refers to a voltage induced in the measurement coil due to the repulsive motion of the elongated magnetic probe when it contacts the object. Upon contacting the object, the first end of the elongated magnetic probe decelerates and then repels to move in the direction of the second end (i.e., towards the distal end of the body). As a result, a first induced voltage is induced in the measurement coil. The first induced voltage is indicative of a distance between the first end of the elongated magnetic probe and the object being equal to or less than a second distance. Here, the measurement of the first induced voltage changes over time due to changes in the velocity and acceleration of the elongated magnetic probe during a first period of time. Here, the first period of time refers to a period of an alignment calibration cycle performed before the measurement cycle, the period of time being the period from the start of the movement of the elongated magnetic probe in the direction of the first end to position the first end at the second distance from the proximal end to the end of the movement of the elongated magnetic probe until the first end is again positioned at the first distance from the proximal end.

[0031] When the first end of the elongated magnetic probe is at the second distance from the proximal end of the body, the rebound tonometer and the object may move relative to each other. If the relative position of the object and the rebound tonometer is such that the object just touches the first end, the object is determined to be at a distance equal to the second distance from the proximal end. However, it is also possible that the relative position of the object and the rebound tonometer is such that the elongated magnetic probe is pressed against the object when the first end is at the second distance from the proximal end, indicating that the object is at a distance less than the second distance from the proximal end.

[0032] Throughout this disclosure, the term "predetermined criteria" refers to a predefined criterion utilized to make a decision. In some embodiments, the predetermined criteria is selected to be one of a predetermined voltage threshold, an integral over a first period of the first induced voltage measured as a function of time, a derivative of the first induced voltage as a function of time, or a predetermined pattern. The term "predetermined voltage threshold" refers to a pre-known limit within which the measured first induced voltage is expected to remain when the first end of the elongated magnetic probe is not in contact with an object. When the probe contacts an object, the voltage value is expected to be greater than the predetermined voltage threshold. This value is a function of the impact velocity with the object. The phrase "integral over a first period of the first induced voltage measured as a function of time" refers to an expected cumulative value over a first period of the measured first induced voltage when the first end of the elongated magnetic probe does not contact an object during the first period. Since the induced voltage is a function of velocity, the integral is practically an integral of velocity. Using the integral value is beneficial because the velocity of the probe does not need to exceed a certain threshold value when using the integral value. The integral value indicates whether the probe has moved from its initial position independent of the velocity, and thus provides a means of detecting if the probe has moved slowly towards the object. A further advantage of using the integral value is that the threshold value can be set high. The expression "derivative value of the first induced voltage as a function of time" refers to the expected change in the measured first induced voltage over time. Using the derivative value can increase the sensitivity of the trigger. This is because the derivative value is related to the change in velocity (acceleration). The derivative value can also be used to filter out very fast accelerations, for example due to random vibrations of the device (e.g. due to the shaking of the doctor's hands). The term "predetermined pattern" refers to a pattern of values ​​that is known in advance. Since the comparison of the predetermined criteria is made with the measured induced voltage, the predetermined pattern refers to a pattern of voltage values ​​over time in some embodiments.

[0033] "Meeting the specified criteria" means that any of the following applies: The measured first induced voltage exceeds a predetermined voltage threshold. a calculated integral value obtained by evaluating an integral over a first time period of the first induced voltage measured as a function of time is greater than said integral value. a calculated derivative value obtained by evaluating the derivative of the first induced voltage as a function of time exceeds said derivative value. A pattern of the measured first induced voltage values ​​over time resembles the predetermined pattern (of voltage values ​​over time).

[0034] It will be understood that meeting the predetermined criteria indicates that the first end contacts the object, which means that the object is within or at the required working distance from the proximal end of the body. In this case, the required working distance is the second distance. When contact between the object and the first end is detected, a measurement cycle of the rebound tonometer is initiated. If such contact is not detected, the measurement cycle is not initiated. The term "measurement cycle" refers to an operation cycle in which the elongated magnetic probe is magnetically ejected to impact an object for the purpose of measuring a characteristic of the object. During the measurement cycle, the recoiled elongated magnetic probe is stored in the body so that the rebound tonometer is in a default use state, and then ejected from the body so that the first end is at a third distance from the proximal end. After hitting the object, the elongated magnetic probe rebounds from the object. The magnetic elongated body induces a second voltage in the measurement coil during its motion (ejection into the object, contacting the object, rebounding from the object). This second voltage is a function of time. The second voltage as a function of time indicates the velocity of the probe as a function of time (because a voltage is induced in the coil when the magnetic field changes). The velocity as a function of time can be used to determine a property of the object, for example to determine elasticity or, if the object is an eye, to determine intraocular pressure. It will be appreciated that a measurement cycle is initiated to determine the property of the object. The measurement cycle may be once or may be repeated several times.

[0035] In some embodiments, when initiating a rebound tonometer measurement cycle, the controller is configured as follows. · energizing the measurement coil to draw the elongated magnetic probe into the body so that the first end is located a first distance from the proximal end; Energizing the drive coil to project the elongated magnetic probe from the body and position the first end at a third distance from the proximal end.

[0036] Thus, sequential energization of the measurement coil and the drive coil generates magnetic forces that allow the elongated magnetic probe to move in and out of the body. First, at least a portion of the measurement coil surrounding the second end is negatively charged (in some embodiments) with respect to the elongated magnetic probe to retract the elongated magnetic probe into the body so that the first end is at a first distance from the proximal end. This results in a rebound tonometer in a default use state. Next, at least a portion of the drive coil surrounding the elongated magnetic probe is positively charged (in some embodiments) with respect to the second end to eject the elongated magnetic probe out of the body so that the first end is at a third distance from the proximal end. A current pulse in the drive coil generates a magnetic field that acts on the elongated magnetic probe, which is accelerated by the current pulse in the drive coil.

[0037] In some embodiments, the third distance is in the range of 0.5 to 2.0 times the second distance. As an example, the third distance is in the range of 0.5, 0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 1.8, 1.9, or 2.0 times the second distance. For example, if the second distance is 6 mm, the third distance is in the range of 4.8 mm to 12 mm. As an example, the third distance may be 7.5 mm.

[0038] In some embodiments, when the distance of the object from the proximal end is equal to the second distance, the controller is further configured to: · The third distance is selected to be greater than or equal to the second distance. Completing a rebound tonometer measurement cycle by measuring a second voltage induced in the measurement coil as a function of time during a second period of projection of the elongated magnetic probe, where the second voltage is indicative of impact of the first end with the object.

[0039] Now, if the third distance is selected to be equal to the second distance, the first end just touches the object.

[0040] On the other hand, if the third distance is selected to be greater than the second distance, the first end will contact the object with full force. In both these scenarios, the first end will repel when it contacts the object and a second voltage will be induced in the measurement coil. The measurement cycle is thus completed by measuring the second voltage induced in the measurement coil. The second period refers to the period of the measurement cycle, which period is the period from the start of the movement of the elongated magnetic probe towards the first end to position the first end at the third distance from the proximal end to the end of the movement of the elongated magnetic probe until the first end is again positioned at the first distance from the proximal end.

[0041] In some embodiments, the controller is further configured to provide an indication on a user interface of the rebound tonometer to increase the distance between the object and the proximal end of the body if the selected third distance is greater than twice the second distance. The selected third distance being greater than twice the second distance means that the third distance may be at least twice the second distance. For example, if the second distance is 6 mm, the selected third distance may be 12 mm or more. In such a case, the impact of the elongated magnetic probe on the object may be too strong. Such an impact may damage the object and / or the elongated magnetic probe, which is undesirable. Thus, for example, an indication is provided to enable a user of the rebound tonometer to increase the distance between the object and the proximal end of the body. Such an indication to increase the distance is provided to prevent the recoiled elongated magnetic probe from impacting the object (which may be a sensitive object such as an eye) too strongly. When the indication is observed, the distance is increased by moving the rebound tonometer or by moving the object. Such a movement may be manual or may be performed by a user of the tonometer. Increasing the distance reduces the force with which the elongated magnetic probe impacts the object, preventing damage to the object and / or the elongated magnetic probe. The term "user interface" refers to an interface through which a user interacts with the rebound tonometer. The user interface is implemented on at least one of the tonometer and a computing device coupled to the tonometer. Examples of computing devices include, but are not limited to, computers, smartphones, smartwatches, tablets, and laptop computers. In some embodiments, the user interface is rendered on a display of the rebound tonometer or the computing device. In this regard, the indication can be a textual display, a pictorial display, an audiovisual display, an error notification, a warning, or the like.Alternatively, the indication may be provided using at least one of an audio device, a light emitting diode (LED), a vibration device, and a tactile device associated with the rebound pressure gauge. As one example, the controller may provide the indication by controlling a vibration device located on the rebound tonometer to vibrate strongly if the selected third distance is greater than twice the second distance. As another example, the controller may provide the indication by controlling an LED located on the rebound tonometer to emit a red light if the selected third distance is greater than twice the second distance.

[0042] In some embodiments, when the distance of the object from the proximal end is less than the second distance, the controller is configured as follows. · The third distance is chosen to be smaller than the second distance. By measuring a second voltage induced in the measurement coil as a function of time during a second period of projection of the long magnetic probe, completing a measurement cycle of the rebound tonometer, where the second voltage is indicative of impact of the first end with the object.

[0043] Here, the third distance is selected to be smaller than the second distance to prevent the rebound elongated magnetic probe from strongly impacting the object. In such a scenario, the third distance may be selected to take into account the possibility that the user may move the rebound tonometer closer to the object or the object closer to the rebound tonometer after the measurement cycle has begun. In this embodiment, the technical advantage of selecting the third distance smaller than the second distance is to ensure that the first end contacts the object with a force required to complete the measurement cycle without damaging the object. When the first end contacts the object, it repels, which induces a second voltage in the measurement coil. Thus, the measurement cycle is completed by measuring the second voltage induced in the measurement coil.

[0044] In some embodiments, the controller is configured to determine a characteristic of the object using the second voltage. The term "characteristic" refers to a physiological parameter of the object. For example, the tonometer can be used to measure physiological parameters of the eye, such as intraocular pressure of the eye or tactile sensitivity (of the eye or skin). For example, the tonometer may be used to measure intraocular pressure of the eye from ophthalmic measurements. The second voltage represents the velocity as a function of time of the elongated magnetic probe repelling from the object when a first end of the elongated magnetic probe impacts (the surface of) the object. The magnitude of the second voltage depends on the magnetic strength and the velocity of the elongated magnetic probe. For example, the magnitude of the second voltage is directly proportional to the velocity of the elongated magnetic probe. As an example, the second voltage may be used to measure intraocular pressure of the eye. The velocity of the elongated magnetic probe and the response of the eye surface to stop the elongated magnetic probe after it is projected towards and impacts the eye surface may be determined by calculating the first derivative of the velocity. Additionally, the speed at which the elongated magnetic probe bounces off the ocular surface may be determined, where if the elongated magnetic probe bounces off quickly (i.e., at a high speed), the intraocular pressure is determined to be high, and if the elongated magnetic probe bounces off slowly (i.e., at a low speed), the intraocular pressure is determined to be low.

[0045] In some embodiments, the rebound tonometer further comprises at least one sensor, and the controller of the rebound tonometer is configured as follows. Collecting sensor data from the at least one sensor during a measurement cycle, the sensor data being indicative of a displacement and / or a velocity of the elongated magnetic probe as a function of time. Determining the velocity and / or acceleration of the elongated magnetic probe based on said sensor data. Determine a characteristic of an object based on changes in velocity and / or acceleration of an elongated magnetic probe.

[0046] In some embodiments, the sensor measures the displacement and / or velocity of the elongated magnetic probe and records sensor data related thereto. The movement of the elongated magnetic probe can be represented by the displacement and / or velocity of the elongated magnetic probe as a function of time. In one embodiment, the sensor is configured to measure the change in magnetic flux in a measurement coil due to the movement of the elongated magnetic probe towards the object. As mentioned above, during the measurement cycle, the magnetic force acts to eject the elongated magnetic probe from the body and impact the object, after which the elongated magnetic probe retracts into the body. The sensor then measures the change in magnetic flux in the measurement coil and the controller uses the measurements to determine the displacement and / or velocity of the probe. In some embodiments, the sensor is implemented using a transducer, an accelerometer, a frequency sensor, a laser surface velocimeter, a piezoelectric sensor.

[0047] In some embodiments, when determining a characteristic of the object based on changes in the velocity and / or acceleration of the elongated magnetic probe, the controller compares the velocity and / or acceleration of the elongated magnetic probe with velocity and / or acceleration data of previously collected medical tests. For example, if the characteristic to be determined is the intraocular pressure of the eye, a high velocity and / or acceleration value would indicate high intraocular pressure, and a low velocity and / or acceleration value would indicate high intraocular pressure, since it has been historically known that when the elongated magnetic probe recoils rapidly (i.e., with high velocity and / or acceleration), intraocular pressure is high, and when the elongated magnetic probe recoils slowly, intraocular pressure is low. Advantageously, determining the characteristic of the object allows further diagnostic developments related to the object.

[0048] In some embodiments, the controller is further configured to compare the first induced voltage measured as a function of time to a second predetermined criterion; If a second predetermined criterion is met based on the comparison, the fulfillment is used as information to provide a warning indicator on a user interface of the rebound tonometer.

[0049] In some embodiments, the second predetermined criterion is selected to be one of a second predetermined voltage threshold, a second integral over a first period of the first induced voltage measured as a function of time, a second derivative of the first induced voltage as a function of time, or a second predetermined pattern. The term "second predetermined voltage threshold" refers to a second pre-known limit within which the measured first induced voltage is expected to remain when the first end of the elongated magnetic probe is not in contact with the object. The phrase "second integral over a first period of the first induced voltage measured as a function of time" refers to an expected second cumulative value of the measured first induced voltage over a first period of time when the first end of the elongated magnetic probe is not in contact with the object during the first period of time. The expression "second derivative of the first induced voltage as a function of time" refers to an expected change over time of the measured first induced voltage. The term "second predetermined pattern" refers to a second pattern of pre-known values, and in some embodiments refers to a second pattern of voltage values ​​over time, since a comparison of the pre-defined criteria is made with the measured induced voltage.

[0050] "Meeting the second specified criterion" means that either of the following is true: The measured first induced voltage exceeds a second predetermined voltage threshold. a calculated integral value obtained by evaluating an integral over a first time period of the first induced voltage measured as a function of time is greater than the second integral value. A calculated derivative value obtained by evaluating the derivative of the first induced voltage as a function of time exceeds the second derivative value. A pattern of measured first induced voltage values ​​over time resembles said second predetermined pattern (of voltage values ​​over time).

[0051] It will be appreciated that if the measured first induced voltage exceeds the second predetermined voltage threshold, it indicates that the rebound tonometer is being moved too quickly toward the object, which may cause harm to the object. The calculated differential value exceeding the second differential value also means that the rebound tonometer is being moved too quickly toward the object (i.e., is being moved too quickly). The calculated integral value being greater than the second integral value means that the first end is too close to the object. Similarly, a pattern of values ​​of the measured first induced voltage similar to the second predetermined pattern means that the first end is too close to the object. Thus, meeting the second predetermined criterion indicates that the rebound tonometer is moving in an undesirable, unsafe manner.

[0052] The term "warning indicator" refers to an indication provided to a user of the rebound tonometer when the first induced voltage measured as a function of time meets a second predetermined criterion, the indication indicating that the rebound tonometer is moving in an undesirable, unsafe manner. Upon observing the warning indicator, the user of the rebound tonometer may take corrective action to prevent damage to the object (e.g., de-energizing the drive coil, moving the object away from the rebound tonometer, etc.). The warning indicator is provided to the user through a user interface. The warning indicator may be in the form of a textual display, a visual display, an audiovisual display, etc. Alternatively, the warning indicator may be provided to at least one of an audio device, a light emitting diode (LED), a vibration device, and a tactile device associated with the rebound pressure gauge. As another example, the controller may provide the warning indicator by controlling an LED located on the rebound tonometer to emit a blue light when the first induced voltage measured as a function of time meets a second predetermined criterion.

[0053] In some embodiments, the controller may be further configured to display the magnitude of the given voltage over a given time as a waveform on at least one display. The display may be at least one of an oscilloscope display, a rebound tonometer display, and a computing device display. The "magnitude" of the given voltage refers to the measurement of the given voltage. In other words, the intensity represents how high or low the voltage is at a given time. By displaying the waveform representing the intensity of the given voltage over time on at least one display, a user of the rebound tonometer can easily see and identify when the given voltage was induced and can easily see the intensity of the given voltage. The user can then change the relative positioning of the rebound tonometer and the object or provide a diagnosis based on the intensity. The present disclosure also relates to the above-mentioned method. The various embodiments and variations disclosed above with respect to the first approach above apply mutatis mutandis to the present method.

[0054] In some embodiments, in the method, the predetermined criterion is selected to be one of a predetermined voltage threshold, an integral over a first period of the first induced voltage measured as a function of time, a derivative of the first induced voltage as a function of time, or a predetermined pattern.

[0055] In some embodiments, in the method, the measurement cycle comprises: energizing the measurement coil to draw the elongated magnetic probe into the body and position the first end at a first distance from the proximal end; Energizing the drive coil to project the elongated magnetic probe from the body and position the first end at a third distance from the proximal end. completing the measurement cycle by measuring a second voltage induced in the measurement coil as a function of time during a second period of projection of the elongated magnetic probe, wherein the second voltage is indicative of impact of the first end with the object. Using the second voltage to determine a characteristic of an object.

[0056] The second voltage is indicative of the velocity of the elongated probe as a function of time. This information can be used to determine a property of the object. For example, a high second voltage indicates that the probe bounced off the object quickly, and therefore the object is harder than a slower bounce (low second voltage). As an example of a measurement cycle, a tonometer can be used to measure, for example, intraocular pressure in an eye. As another example of a measurement cycle, a recoil tonometer can be used to impact the skin of a target user to measure the touch sensitivity of the skin. In some embodiments, in the method, the third distance is in the range of 0.5 to 2.0 times the second distance.

[0057] In some embodiments, when the distance of the object from the proximal end is equal to the second distance, the method further includes selecting a third distance to be equal to or greater than the second distance.

[0058] In some embodiments, the method further includes providing an indication on a user interface of the rebound tonometer to increase the distance between the object and the proximal end of the body if the third distance is greater than twice the second distance.

[0059] In some embodiments, if the distance of the object from the proximal end is less than the second distance, the method further includes selecting the third distance to be less than the second distance.

[0060] In some embodiments, the method further comprises: During a measurement cycle, sensor data indicative of displacement and / or velocity of the elongated magnetic probe as a function of time is collected from at least one sensor of the rebound tonometer. Determining the velocity and / or acceleration of the elongated magnetic probe based on said sensor data. Determine a characteristic of an object based on changes in velocity and / or acceleration of an elongated magnetic probe.

[0061] In some embodiments, the method further includes comparing the first induced voltage measured as a function of time to a second predetermined criterion; If a second predetermined criterion is met based on the comparison, the fulfillment is used as information to provide a warning indicator on a user interface of the rebound tonometer.

[0062] In some embodiments, in the method, the second predetermined criterion is selected to be one of a second predetermined voltage threshold, a second integral over a first period of the first induced voltage measured as a function of time, a second derivative of the first induced voltage as a function of time, or a second predetermined pattern.

[0063] As a further example, the present disclosure provides a rebound tonometer that can automatically detect the distance between the rebound tonometer and the object, and therefore automatically initiate a measurement cycle. This (detecting the distance) is important because if the distance is too short, the probe may hit the object (such as an eyeball) too quickly and cause damage. Furthermore, if the measurement cycle is too far from the object, the probe may hit the object too late or not at all. The distance of the object is detected by moving a first end of the probe away from the body of the rebound tonometer (towards the object) and contacting the first end of the probe with the object. The probe is arranged to move within the body (opening / cavity / pathway of the body) and is surrounded by a measurement coil so that the contact can be detected. The induced voltage in the measurement coil is used to initiate the measurement cycle. [Detailed description of the drawing]

[0064] Referring to FIG. 1, an exemplary schematic diagram of a rebound tonometer 100 according to an embodiment of the present disclosure is shown. The rebound tonometer 100 includes a body 102, an elongated magnetic probe 104, a measurement coil 106, a drive coil 108, and a controller (not shown). The body 102 has a proximal end 110 and a distal end 112 opposite the proximal end 110. The body 102 also has an opening 114 (shown in dotted lines) at the proximal end 110. The elongated magnetic probe 104 has a first end 116 and a second end 118 opposite the first end 116, and is at least partially disposed within the body 102 such that the first end 116 protrudes outside the body 102 through the opening 114 of the body 102. The measurement coil 106 and the drive coil 108 are disposed within the body 102 to partially surround the elongated magnetic probe 104. The controller is coupled to the measurement coil 106 and the drive coil 108. The first end 116 is a first distance DI from the opening 114 and the second end 118 is interior to the body 102. The elongated magnetic probe 104 is aligned with and movable along an axis 120 (shown by a dashed dotted line) of the rebound tonometer 100.

[0065] 2A, 2B, and 2C, exemplary schematic diagrams of a rebound tonometer 202 in use are shown, according to various embodiments of the present disclosure. The rebound tonometer 202 is used to determine a characteristic of an object 204 (depicted as an eye). The rebound tonometer 202 includes a body 206, an elongated magnetic probe 208, a measurement coil 210, a drive coil 212, and a controller (not shown). The body 206 has a proximal end 214 and a distal end 216 opposite the proximal end 214. The body 206 also has an opening (not shown) at the proximal end 214. The elongated magnetic probe 208 has a first end 218 and a second end 220 opposite the first end 218, and is at least partially disposed within the body 206 such that the first end 218 protrudes outside the body 206 from the opening in the body 206. A measurement coil 210 and a drive coil 212 are disposed within the body 206 to partially surround the elongated magnetic probe 208. A controller is coupled to the measurement coil 210 and the drive coil 212.

[0066] In FIG. 2A, the rebound tonometer 202 is shown in a first use state (e.g., a standby state). In the standby state, the first end 218 is a first distance DI from the opening and the second end 220 is inside the body 206. The elongated magnetic probe 208 is aligned with and movable along an axis (not shown) of the rebound tonometer 202. The first end 218 is spaced from (i.e., not in contact with) the object 204. In FIG. 2B, the rebound tonometer 202 is shown in a second use state. To transition from the first use state to the second use state, the controller energizes the drive coil 212 to move the elongated magnetic probe 208 relative to the body 206 to position the first end 218 a second distance D2 from the proximal end 214. The second distance D2 is greater than the first distance D1 (shown in FIG. 2A). In the second use state, the first end 218 of the rebound tonometer 202 is closer to the object 204 than the first use state shown in FIG. 2A. FIG. 2B illustrates an example in which the distance from the proximal end 214 to the object 204 is greater than the second distance D2. However, when the distance from the proximal end 214 to the object 204 is equal to or less than the second distance D2, the first end 218 contacts the object 204 in the second use state. When contact between the object 204 and the first end 218 is detected, a measurement cycle of the rebound tonometer 202 is initiated.

[0067] In FIG. 2C, the rebound tonometer 202 is shown in a third use state. To transition from the first use state to the third use state, the controller energizes the drive coil 212 to eject the elongated magnetic probe 208 from the body 206 and position the first end 218 a third distance D3 from the proximal end 214. Here, the third distance D3 is shown to be greater than the second distance D2. In this case, the first end 218 contacts the object 204 with full force. During a second period of ejection of the elongated magnetic probe 208, a second voltage is induced in the measurement coil 210 as a function of time. The measurement cycle of the rebound tonometer 202 is completed by measuring this second voltage. The second voltage is indicative of an impact of the first end 218 with the object 204.

[0068] 1, a block diagram of a rebound tonometer 300 according to one embodiment of the present disclosure is shown. The rebound tonometer 300 comprises a body 302, an elongated magnetic probe 304, a measurement coil 306, a drive coil 308, a controller 310, and at least one sensor (depicted as sensor 312). The controller 310 is coupled to the measurement coil 306, the drive coil 308, and the sensor 312.

[0069] 1, 2A-2C, and 3 are merely examples and should not unduly limit the scope of the claims. Rebound tonometers 100, 202, 300 are provided as examples and should not be construed as limiting the number or types of components of a rebound tonometer. One of ordinary skill in the art will recognize many variations, alternatives, and modifications of the embodiments of the present disclosure.

[0070] 4A and 4B, FIG. 4A shows a first waveform of a first voltage induced in a measurement coil as a function of time during a first time period, and FIG. 4B shows a second waveform of a second voltage induced in a measurement coil as a function of time during a second time period, according to an embodiment of the present disclosure. The waveforms given represent the value / amplitude of the voltage at a certain time. The Y-axis represents the magnitude of the voltage, and the X-axis represents time.

[0071] In FIG. 4A, portions 402 and 404 of the first waveform show a (near) constant voltage magnitude throughout the corresponding time. This means that no voltage is induced in the measurement coil during the times corresponding to portions 402 and 404. Portions 406, 408, 410 (depicted as peaks and valleys) of the first waveform show a first induced voltage. For example, portion 406 may correspond to a time when a first end of an elongated magnetic probe contacts an object and the first end is pressed into the object, portion 408 may correspond to a time when the first end moves away from the object but is still in contact with the object, and portion 410 may correspond to a time when the first end moves away from the object and is no longer in contact with the object. In FIG. 4B, point 412 of the second waveform shows a time when the first end is at a first distance from an opening in the proximal end of the body of the rebound tonometer. At point 412, no voltage is induced in the measurement coil. Point 414 in the second waveform indicates another time when the first end is a first distance from the aperture. At point 414, no voltage is induced in the measurement coil. Portion 416 of the second waveform between points 412 and 414 indicates a second voltage induced in the measurement coil. The second voltage varies as a function of time, as shown in portion 416 depicted by peaks and valleys. The second voltage is induced when the elongated magnetic probe is ejected from the body with the first end at a third distance from the proximal end, impacts an object, and rebounds from impact with the object.

[0072] 5, a flow chart illustrating steps of a method of using a rebound tonometer to determine a property of an object is shown, according to one embodiment of the present disclosure. The rebound tonometer includes a body, an elongated magnetic probe, a measurement coil, and a drive coil. In step 502, the elongated magnetic probe is at least partially disposed within the body, a first end of the elongated magnetic probe protruding outside the body from an opening at a proximal end of the body, a second end of the elongated magnetic probe being inside the body, the first end being a first distance from the opening, and the elongated magnetic probe being movable along an axis of the rebound tonometer.

[0073] Contact between an object and the first end is detected in step 504. This detection includes the following steps: moving the elongated magnetic probe relative to the body such that the first end is a second distance from the proximal end, the second distance being greater than the first distance; Moving a rebound tonometer relative to the object for a first period of time. A first induced voltage is measured as a function of time during a first period that the rebound tonometer is moved. Comparing the first induced voltage measured as a function of time with a predetermined reference. If the predetermined criterion is satisfied based on the comparison, then using the satisfaction as an indication that contact between the first end and the object has been detected.

[0074] If contact is detected, then in step 506 a rebound tonometer measurement cycle is initiated.

[0075] Steps 502, 504, and 506 are merely exemplary, and other options may be provided. That is, one or more steps may be added, one or more steps may be removed, or one or more steps may be performed in a different order without departing from the scope of the appended claims. The embodiments of the present disclosure described above may be modified without departing from the scope defined by the appended claims. The terms "including," "comprising," "incorporating," "having," "being," and the like, used to describe and claim the present disclosure, are intended to be interpreted in a non-exclusive manner, i.e., allowing for the presence of items, parts, or components not expressly described. The absence of a plurality of elements does not preclude the presence of a plurality of the elements.

Claims

1. A rebound tonometer, a body having a proximal end and a distal end opposite the proximal end, the body having an opening at the proximal end; an elongated magnetic probe; a measurement coil and a drive coil, both disposed within the body and partially surrounding the elongated magnetic probe; a controller; Equipped with The elongated magnetic probe comprises: a first end and a second end opposite the first end; a first end portion of the first end portion of the second ... aligned with and movable along the axis of the rebound tonometer; The controller When the rebound tonometer is in use, contact between an object and the first end is energizing the drive coil to move the elongated magnetic probe relative to the body so that the first end is at a second distance from the proximal end, the second distance being greater than the first distance; measuring a first induced voltage in the measurement coil as a function of time during a first time period; comparing the first induced voltage measured as a function of time with a predetermined reference; If the predetermined criterion is met based on the comparison, using the fulfillment as an indication that contact between the first end and the object has been detected. Detecting by; When said contact is detected, initiating a measurement cycle of said rebound tonometer; configured to: Rebound tonometer.

2. 2. The rebound tonometer of claim 1, wherein the predetermined criterion is selected to be one of a predetermined voltage threshold, an integral of the first induced voltage measured as a function of time over the first period, a derivative of the first induced voltage as a function of time, or a predetermined pattern.

3. When starting the measurement cycle, the controller: energizing the measurement coil to retract the elongated magnetic probe into the body so that the first end is positioned at the first distance from the proximal end; energizing the drive coil to project the elongated magnetic probe from the body and position the first end at a third distance from the proximal end; The rebound tonometer of claim 1 , configured as follows:

4. The rebound tonometer of claim 3 , wherein the third distance is in the range of 0.5 to 2.0 times the second distance.

5. The controller, when the distance of the object from the proximal end is equal to the second distance, selecting the third distance to be equal to or greater than the second distance; completing the measurement cycle of the rebound tonometer by measuring a second voltage induced in the measurement coil as a function of time during a second period of ejection of the elongated magnetic probe; 4. The rebound tonometer of claim 3, wherein the second voltage indicates a collision of the first end with the object.

6. The rebound tonometer of claim 5, wherein the controller is configured to provide an indication on a user interface of the rebound tonometer to increase the distance between the object and the proximal end of the body if the selected third distance is greater than twice the second distance.

7. When the distance of the object from the proximal end is less than the second distance, the controller selecting the third distance to be less than the second distance; completing a measurement cycle of the rebound tonometer by measuring a second voltage induced in the measurement coil as a function of time during a second period of ejection of the elongated magnetic probe; 4. The rebound tonometer of claim 3, wherein the second voltage indicates a collision of the first end with the object.

8. The rebound tonometer of claim 5 , wherein the controller is configured to use the second voltage to determine a property of the object.

9. and a controller configured to: collecting sensor data from the at least one sensor during a measurement cycle indicative of displacement and / or velocity of the elongated magnetic probe as a function of time; determining a velocity and / or acceleration of the elongated magnetic probe based on the sensor data; determining a property of the object based on changes in velocity and / or acceleration of the elongated magnetic probe; The rebound tonometer of claim 1 , configured as follows:

10. the controller is further configured to compare the first induced voltage measured as a function of time with a second predetermined criterion; and if the second predetermined criterion is met based on the comparison, the fulfillment is configured to be used as information to provide a warning indicator on a user interface of the rebound tonometer. The rebound tonometer of claim 1.

11. 11. The rebound tonometer of claim 10, wherein the second predetermined criterion is selected to be one of a second predetermined voltage threshold, a second integral of the first induced voltage measured as a function of time over the first period, a second derivative of the first induced voltage as a function of time, or a second predetermined pattern.

12. 1. A method of using a rebound tonometer to determine a property of an object, the rebound tonometer comprising a body, an elongated magnetic probe, a measurement coil, and a drive coil, the method comprising: disposing the elongated magnetic probe at least partially within the body, wherein a first end of the elongated magnetic probe protrudes outside the body from an opening at a proximal end of the body and is a first distance from the opening, and a second end of the elongated magnetic probe is inside the body, the elongated magnetic probe being movable along an axis of the rebound tonometer; detecting contact between the object and a short-term first end; initiating a measurement cycle of the rebound tonometer when the contact is detected; and detecting contact between the object and the short-term first end includes: moving the elongated magnetic probe relative to the body so that the first end is at a second distance from the proximal end, the second distance being greater than the first distance; moving the rebound tonometer relative to the object during a first period of time; measuring a first induced voltage as a function of time during a first period of time that the rebound tonometer is moved; comparing the first induced voltage measured as a function of time with a predetermined reference; If the predetermined criterion is satisfied based on the comparison, using the satisfaction as information indicating that contact between the first end and the object has been detected; carried out by method.

13. 13. The method of claim 12, wherein the predetermined criterion is selected to be one of a predetermined voltage threshold, an integral over the first time period of the first induced voltage measured as a function of time, a derivative of the first induced voltage as a function of time, or a predetermined pattern.

14. The measurement cycle comprises: energizing the measurement coil to retract the elongated magnetic probe into the body and position the first end at the first distance from the proximal end; energizing the drive coil to project the elongated magnetic probe from the body and position the first end a third distance from the proximal end; completing the measurement cycle by measuring a second voltage induced in the measurement coil as a function of time during a second period of emission of the elongated magnetic probe; using the second voltage to determine a property of an object; wherein the second voltage indicates a collision of the first end with the object. The method of claim 12.

15. 15. The method of claim 14, further comprising selecting the third distance to be equal to or greater than the second distance if the distance of the object from the proximal end is equal to the second distance.

16. 16. The method of claim 15, further comprising: if the third distance is greater than twice the second distance, providing an indication on a user interface of the rebound tonometer to increase the distance between the object and the proximal end of the body.

17. The method of claim 14 , further comprising selecting the third distance to be less than the second distance if the distance of the object from the proximal end is less than the second distance.

18. collecting sensor data from at least one sensor of the rebound tonometer during the measurement cycle, the sensor data indicative of displacement and / or velocity of the elongated magnetic probe as a function of time; determining a velocity and / or acceleration of the elongated magnetic probe based on the sensor data; determining a property of the object based on changes in velocity and / or acceleration of the elongated magnetic probe; The method of claim 12 further comprising:

19. further comprising comparing the first induced voltage measured as a function of time to a second predetermined criterion; and if a second predetermined criterion is met based on the comparison, using the met criterion as information to provide a warning indicator on a user interface of the rebound tonometer. The method of claim 12.

20. 20. The method of claim 19, wherein the second predetermined criterion is selected to be one of a second predetermined voltage threshold, a second integral over a first period of the first induced voltage measured as a function of time, a second derivative of the first induced voltage as a function of time, or a second predetermined pattern.

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