Noninvasive methods and apparatuses for measuring the intraocular pressure of a mammal eye
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Abstract
Noninvasive methods and apparatuses measuring the intraocular pressure (IOP) of the eye using vibratory excitation are disclosed. Prior art methods teaches that the natural frequencies of the eye vary as a function of the IOP, with each natural frequency being zero at zero IOP. The present invention recognizes that the eye has different and separate classes of natural frequencies that vary as function of the IOP, which have non-zero values for a zero value of IOP, and which have curves that extrapolate to negative IOPs to obtain zero values of frequency. Preferred methods and apparatuses of the present invention measure a first natural frequency of this class at an unknown IOP value, and thereafter compare it to one or more known values of the first natural frequency measured at corresponding known IOPs to estimate value of the unknown IOP. Preferred embodiments include measuring one or more additional natural frequencies.
72 Citations
111 Claims
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1-57. -57. (cancelled without prejudice).
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58. A method of estimating the intraocular pressure of an eye of a mammal with a gaseous environment around a portion of its surface, the gaseous environment having a pressure, the intraocular pressure being the difference between the pressure inside the eye and the pressure of the gaseous environment, said method comprising the steps of:
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(a) measuring a first frequency value of a first vibratory frequency of the eye at a portion of the sclera or cornea of the eye at an unknown intraocular pressure, said first vibratory frequency being associated with a corresponding first vibratory mode of the eye and having a value that varies as a first function of the eye'"'"'s intraocular pressure, the first function having a form that extends or extrapolates to a non-zero frequency value for a zero value of intraocular pressure and to a zero frequency value for a negative value of intraocular pressure; and
(b) comparing the first measured frequency value to one or more known frequency values of the first vibratory frequency measured at corresponding known intraocular pressures to estimate value of the unknown intraocular pressure; and
wherein step (a) comprising the steps of;
applying a plurality of vibrations at a plurality of frequencies to the eye, at least some of the vibrations causing one or more portions of the eye'"'"'s surface to undergo an oscillatory motion;
measuring the phase of the vibratory motion of a portion of the eye'"'"'s surface relative to the applied vibrations, said step including obtaining several phase measurements at each of the vibration frequencies and averaging the phase measurements at each vibration frequency; and
selecting the first measured vibratory frequency as a first frequency of the applied vibrations at which the measured phase of the vibratory motion lags the phase of the applied vibrations by approximately one of a plurality of selected degree amounts. - View Dependent Claims (59, 60, 61, 62, 63, 64, 65, 66)
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67. A method of estimating the intraocular pressure of an eye of a mammal with a gaseous environment around a portion of its surface, the gaseous environment having a pressure, the intraocular pressure being the difference between the pressure inside the eye and the pressure of the gaseous environment, said method comprising the steps of:
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(a) measuring a first frequency value of a first vibratory frequency of the eye at a portion of the sclera or cornea of the eye at an unknown intraocular pressure, said first vibratory frequency being associated with a corresponding first vibratory mode of the eye and having a value that varies as a first function of the eye'"'"'s intraocular pressure, the first function having a form that extends or extrapolates to a non-zero frequency value for a zero value of intraocular pressure and to a zero frequency value for a negative value of intraocular pressure; and
(b) comparing the first measured frequency value to one or more known frequency values of the first vibratory frequency measured at corresponding known intraocular pressures to estimate value of the unknown intraocular pressure; and
wherein step (a) comprising the steps of;
applying a plurality of vibrations at a plurality of frequencies to the eye, at least some of the vibrations causing one or more portions of the eye'"'"'s surface to undergo an oscillatory motion;
measuring the phase of the vibratory motion of a portion of the eye'"'"'s surface relative to the applied vibrations, said measuring step occurring at a pre-selected part of the blood pulsation period of the mammal; and
selecting the first measured vibratory frequency as a first frequency of the applied vibrations at which the measured phase of the vibratory motion lags the phase of the applied vibrations by approximately one of a plurality of selected degree amounts. - View Dependent Claims (68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78)
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79. A method of estimating the intraocular pressure of an eye of a mammal within a gaseous environment around a portion of the eye, the gaseous environment having a pressure, the intraocular pressure being the difference between the pressure inside the eye and the pressure of the gaseous environment, said method comprising the steps of:
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(a) measuring a first vibratory frequency and a second vibratory frequency of an eye at an unknown intraocular pressure which is to be estimated to generate a first measured vibratory frequency and a second measured vibratory frequency, respectively, said step including the steps of applying a plurality of vibrations at a plurality of frequencies to the eye, at least some of the vibrations causing one or more portions of the eye'"'"'s surface to undergo an oscillatory motion, measuring the phase of the vibratory motion of a portion of the eye'"'"'s surface relative to the applied vibrations, selecting the first measured vibratory frequency as a first frequency of the applied vibrations at which the measured phase of the vibratory motion lags the phase of the applied vibrations by approximately one of a plurality of selected degree amounts, and selecting the second measured vibratory frequency as a second frequency of the applied vibrations at which the measured phase of the vibratory motion lags the phase of the applied vibrations by approximately by one of said plurality of selected degree amounts, wherein the step of measuring the phase comprises obtaining several phase measurements at each of the vibration frequencies and averaging the phase measurements at each vibration frequency;
(b) generating a first implied pressure value of the unknown intraocular pressure by comparing the first measured vibratory frequency to one or more measured values of a first previously-measured vibratory frequency measured at one or more corresponding known intraocular pressures;
(c) generating a second implied pressure value of the unknown intraocular pressure by comparing the second measured vibratory frequency to one or more measured values of a second previously-measured vibratory frequency measured at one or more corresponding known intraocular pressures;
(d) generating a third implied pressure value of the unknown intraocular pressure by comparing the first measured vibratory frequency to one or more measured values of the second previously-measured vibratory frequency;
(e) generating a fourth implied pressure value of the unknown intraocular pressure by comparing the second measured vibratory frequency to one or more measured values of a third previously-measured vibratory frequency measured at one or more corresponding known intraocular pressures;
(f) generating a first estimated pressure from the first and second implied pressure values as an average thereof, and generating a first deviation value representative of a deviation of the first and second implied pressure values from the first estimated pressure;
(g) generating a second estimated pressure from the third and fourth implied pressure values as an average thereof, and generating a second deviation value representative of a deviation of the third and fourth implied pressure values from the second estimated pressure; and
wherein each of the vibratory frequencies has a value that varies as a respective function of the eye'"'"'s intraocular pressure, each respective function extending or extrapolating to a non-zero frequency value for a zero value of intraocular pressure and to a zero frequency value for a negative value of intraocular pressure. - View Dependent Claims (80, 81, 82, 83, 84, 85)
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86. A method of estimating the intraocular pressure of an eye of a mammal within a gaseous environment around a portion of the eye, the gaseous environment having a pressure, the intraocular pressure being the difference between the pressure inside the eye and the pressure of the gaseous environment, said method comprising the steps of:
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(a) measuring a first vibratory frequency and a second vibratory frequency of an eye at an unknown intraocular pressure which is to be estimated to generate a first measured vibratory frequency and a second measured vibratory frequency, respectively, said step including the steps of applying a plurality of vibrations at a plurality of frequencies to the eye, at least some of the vibrations causing one or more portions of the eye'"'"'s surface to undergo an oscillatory motion, measuring the phase of the vibratory motion of a portion of the eye'"'"'s surface relative to the applied vibrations, selecting the first measured vibratory frequency as a first frequency of the applied vibrations at which the measured phase of the vibratory motion lags the phase of the applied vibrations by approximately one of a plurality of selected degree amounts, and selecting the second measured vibratory frequency as a second frequency of the applied vibrations at which the measured phase of the vibratory motion lags the phase of the applied vibrations by approximately by one of said plurality of selected degree amounts, wherein the step of measuring the phase comprises occurs at a pre-selected part of the blood pulsation period of the mammal;
(b) generating a first implied pressure value of the unknown intraocular pressure by comparing the first measured vibratory frequency to one or more measured values of a first previously-measured vibratory frequency measured at one or more corresponding known intraocular pressures;
(c) generating a second implied pressure value of the unknown intraocular pressure by comparing the second measured vibratory frequency to one or more measured values of a second previously-measured vibratory frequency measured at one or more corresponding known intraocular pressures;
(d) generating a third implied pressure value of the unknown intraocular pressure by comparing the first measured vibratory frequency to one or more measured values of the second previously-measured vibratory frequency;
(e) generating a fourth implied pressure value of the unknown intraocular pressure by comparing the second measured vibratory frequency to one or more measured values of a third previously-measured vibratory frequency measured at one or more corresponding known intraocular pressures;
(f) generating a first estimated pressure from the first and second implied pressure values as an average thereof, and generating a first deviation value representative of a deviation of the first and second implied pressure values from the first estimated pressure;
(g) generating a second estimated pressure from the third and fourth implied pressure values as an average thereof, and generating a second deviation value representative of a deviation of the third and fourth implied pressure values from the second estimated pressure; and
wherein each of the vibratory frequencies has a value that varies as a respective function of the eye'"'"'s intraocular pressure, each respective function extending or extrapolating to a non-zero frequency value for a zero value of intraocular pressure and to a zero frequency value for a negative value of intraocular pressure. - View Dependent Claims (87, 88, 89, 90, 91)
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92. A tonometer which measures the intraocular pressure of an eye of a mammal within a gaseous environment around a portion of its surface, the gaseous environment having a pressure, the intraocular pressure being the difference between the pressure inside the eye and the pressure of the gaseous environment, said tonometer comprising:
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a processor having a first memory and a second memory;
a controllable frequency generator having a control input coupled to the processor and an output;
a vibratory exciter having an electric input coupled to the output of frequency generator and an output which delivers vibrations to the eye;
a displacement detector which detects vibratory displacements of a surface area of the eye, said displacement detector having an electrical output which provides a signal representative of the vibratory displacements;
a phase detector having a first input which receives a signal related to the output of the controlled frequency generator, a second input coupled to the electrical output of the displacement detector, and an output coupled to processor which provides a value related to the phase difference between the signals at the detector'"'"'s first and second inputs;
a model of the pressure of the eye based on one or more vibratory frequencies of the eye, the model comprising a first set of instructions stored in said first memory, and a set of data parameters stored in said second memory for each vibratory frequency, the first set of instructions operating on the corresponding data parameters of a vibratory frequency to generate a pressure value as a function of the parameters and an input frequency value, each said function corresponding to a vibratory frequency and having a form that extends or extrapolates to a non-zero frequency value for a zero value of intraocular pressure and to a zero frequency value for a negative value of intraocular pressure;
a second set of instructions stored in the first memory that directs the processor to command the controlled frequency generator to output a plurality of waveforms at a plurality of different frequencies for a plurality of periods of time, each period of time corresponding to a respective frequency;
a third set of instructions which directs the processor to monitor the output of the phase detector and to detect one or more vibratory frequencies therefrom, the third set of instructions including instructions that direct the processor to average the measurements at the output of the phase detector during at least a portion of each respective period of time; and
a fourth set of instructions stored in the first memory that directs the processor to compute an estimated pressure from a set of detected vibratory frequencies and the model, the fourth set directing the processor to execute the first set of instructions using at least one set of stored parameters. - View Dependent Claims (93, 94, 95, 96, 97, 98, 99)
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100. A tonometer which measures the intraocular pressure of an eye of a mammal within a gaseous environment around a portion of its surface, the gaseous environment having a pressure, the intraocular pressure being the difference between the pressure inside the eye and the pressure of the gaseous environment, said tonometer comprising:
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a blood pulse detector having an output that is representative of the mammal'"'"'s blood pulse cycle;
a processor having a first memory and a second memory;
a controllable frequency generator having a control input coupled to the processor and an output;
a vibratory exciter having an electric input coupled to the output of frequency generator and an output which delivers vibrations to the eye;
a displacement detector which detects vibratory displacements of a surface area of the eye, said displacement detector having an electrical output which provides a signal representative of the vibratory displacements;
a phase detector having a first input which receives a signal related to the output of the controlled frequency generator, a second input coupled to the electrical output of the displacement detector, and an output coupled to processor which provides a value related to the phase difference between the signals at the detector'"'"'s first and second inputs;
a model of the pressure of the eye based on one or more vibratory frequencies of the eye, the model comprising a first set of instructions stored in said first memory, and a set of data parameters stored in said second memory for each vibratory frequency, the first set of instructions operating on the corresponding data parameters of a vibratory frequency to generate a pressure value as a function of the parameters and an input frequency value, each said function corresponding to a vibratory frequency and having a form that extends or extrapolates to a non-zero frequency value for a zero value of intraocular pressure and to a zero frequency value for a negative value of intraocular pressure;
a second set of instructions stored in the first memory that directs the processor to command the controlled frequency generator to output a plurality of waveforms at a plurality of different frequencies;
a third set of instructions that directs the processor to monitor the output of the phase detector and to detect one or more vibratory frequencies therefrom, the third set of instructions including instructions that direct the processor to monitor the output of the blood pulse detector and to monitor the output of the phase detector at a selected part of the mammal'"'"'s blood pulse cycle; and
a fourth set of instructions stored in the first memory that directs the processor to compute an estimated pressure from a set of detected vibratory frequencies and the model, the fourth set directing the processor to execute the first set of instructions using at least one set of stored parameters. - View Dependent Claims (101, 102, 103, 104, 105, 106)
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107. A tonometer which measures the intraocular pressure of an eye of a mammal within a gaseous environment around a portion of its surface, the gaseous environment having a pressure, the intraocular pressure being the difference between the pressure inside the eye and the pressure of the gaseous environment, said tonometer comprising:
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a processor having a first memory and a second memory;
a controllable frequency generator having a control input coupled to the processor and an output;
a vibratory exciter having an electric input coupled to the output of frequency generator and an output which delivers vibrations to the eye;
a displacement detector which detects vibratory displacements of a surface area of the eye, said displacement detector having an electrical output which provides a signal representative of the vibratory displacements;
a phase detector having a first input which receives a signal related to the output of the controlled frequency generator, a second input coupled to the electrical output of the displacement detector, and an output coupled to processor which provides a value related to the phase difference between the signals at the detector'"'"'s first and second inputs;
a model of the pressure of the eye based on one or more vibratory frequencies of the eye, the model comprising a first set of instructions stored in said first memory, and a set of data parameters stored in said second memory for each vibratory frequency, the first set of instructions operating on the corresponding data parameters of a vibratory frequency to generate a pressure value as a function of the parameters and an input frequency value, each said function corresponding to a vibratory frequency and having a form that extends or extrapolates to a non-zero frequency value for a zero value of intraocular pressure and to a zero frequency value for a negative value of intraocular pressure;
a second set of instructions stored in the first memory that directs the processor to command the controlled frequency generator to output a plurality of waveforms at a plurality of different frequencies for a plurality of periods of time, each period of time corresponding to a respective frequency;
a third set of instructions which directs the processor to monitor the output of the phase detector and to detect one or more vibratory frequencies therefrom, the third set of instructions including instructions that direct the processor to detect a periodic pattern in the variation of the phase measurements during at least one period of time, and to use phase measurements within a part of the detected periodic pattern; and
a fourth set of instructions stored in the first memory that directs the processor to compute an estimated pressure from a set of detected vibratory frequencies and the model, the fourth set directing the processor to execute the first set of instructions using at least one set of stored parameters. - View Dependent Claims (108, 109, 110, 111)
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Specification