Method and apparatus for examining an eye
First Claim
1. A method of measuring an ocular pulse pressure (OPP) of an eye, the method using a tonometer having an actuator pressing a prism with a variable force against a cornea of the eye while a source directs light to reflect from an applanation surface of the prism to a detector producing a detected light signal received by a programmed microprocessor and representing an applanated area of the cornea, the method comprising:
- recognizing a preliminary value of the detected light signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined;
pressing the prism applanation surface against the cornea with increasing force applied during a time interval to change the detected light signal from the preliminary value through a range of values including the preliminary value extending by a predetermined amount from the preliminary value;
determining an intra ocular pressure (IOP) from changes in the detected light signal corresponding to prism pressure force changes in the range of values so that the IOP determination is substantially unaffected by thickness and curvature of the cornea of the eye being examined;
pressing the applanation surface against the cornea long enough for at least two systolic pulses to occur within the eye being examined; and
determining OPP from departures of the detected light signal from the determined IOP during the systolic pulses.
2 Assignments
0 Petitions
Accused Products
Abstract
An applanation tonometer and its operation involve an actuator pressing a prism with a variable and determinable force against a cornea of an eye while a source directs light to reflect from an applanation surface of the prism to a detector producing a detected light signal received by a microprocessor. Such a tonometer produces a diastolic phase signal and a systolic phase signal representing the complete intra ocular pressure experience of the eye being examined. The signal information allows combined diastolic and systolic IOP to be determined in several corroborating ways and also yields measures of ocular blood flow and tonography.
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Citations
25 Claims
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1. A method of measuring an ocular pulse pressure (OPP) of an eye, the method using a tonometer having an actuator pressing a prism with a variable force against a cornea of the eye while a source directs light to reflect from an applanation surface of the prism to a detector producing a detected light signal received by a programmed microprocessor and representing an applanated area of the cornea, the method comprising:
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recognizing a preliminary value of the detected light signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined; pressing the prism applanation surface against the cornea with increasing force applied during a time interval to change the detected light signal from the preliminary value through a range of values including the preliminary value extending by a predetermined amount from the preliminary value; determining an intra ocular pressure (IOP) from changes in the detected light signal corresponding to prism pressure force changes in the range of values so that the IOP determination is substantially unaffected by thickness and curvature of the cornea of the eye being examined; pressing the applanation surface against the cornea long enough for at least two systolic pulses to occur within the eye being examined; and determining OPP from departures of the detected light signal from the determined IOP during the systolic pulses. - View Dependent Claims (2, 3)
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4. A method of measuring ocular pulse pressure (OPP) of an eye, the method using a tonometer that presses an applanation surface with a variable force against the cornea of an eye while a detector receives reflected light representing a varying size of an applanated area of the cornea and produces an applanated area signal delivered to a programmed microprocessor, the method comprising:
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recognizing a preliminary value of the applanated area signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined; pressing the applanation surface against the cornea with increasing force applied during a time interval to change the applanated area signal from its preliminary value through a range of values that include and extend from the preliminary value by a predetermined amount; determining an intra ocular pressure (IOP) from changes in the applanated area signal corresponding to changes in the range of values so that the IOP determination is substantially unaffected by thickness and curvature of the eye being examined; and pressing the applanation surface against the cornea long enough for the microprocessor to detect from the applanated area signal at least two systolic pulses departing from the determined IOP; and determining the OPP from the departures of the applanated area signal occurring during the systolic pulses. - View Dependent Claims (5, 6, 7, 8)
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9. A method of measuring intraocular pressure (IOP) of an eye, the method using a tonometer that presses an applanation surface with a variable force against the cornea of an eye while a detector receives reflected light representing a varying size of an applanated area of the cornea and produces an applanated area signal delivered to a programmed microprocessor, the method comprising:
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recognizing a preliminary value of the applanated area signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined; pressing the applanation surface against the cornea with increasing force during a time interval long enough for at least two systolic pulses to occur to change the applanated area signal from the preliminary value through a range of values that include and extend from the preliminary value by a predetermined amount while including values for the systolic pulses; and determining an IOP from changes in the applanated area signal corresponding to changes in the range of values so that the IOP determination includes a diastolic IOP value and a systolic IOP value and is substantially unaffected by thickness and curvature of the cornea of the eye being examined. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A method of measuring ocular blood flow (OBF) of an eye, the method using a tonometer that presses an applanation surface with a variable force against the cornea of an eye while a detector receives reflected light representing a varying size of an applanated area of the cornea and produces an applanated area signal delivered to a programmed microprocessor, the method comprising:
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recognizing a preliminary value of the applanated area signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined; pressing the applanation surface against the cornea with increasing force applied during a time interval to change the applanated area signal from the preliminary value through a range of values that include and extend from the preliminary value by a predetermined amount; determining an intra ocular pressure (IOP) from changes in the applanated area signal corresponding to changes in the range of values so that the IOP determination is substantially unaffected by thickness and curvature of the cornea of the eye being examined; holding the prism against the cornea for a long enough duration for the applanated area signal to indicate that at least two-systolic pulses have occurred; and determining OBF from a rate of the systolic pulses and from a systolic departure of the applanated area signal from a diastolic phase. - View Dependent Claims (17)
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18. A method of measuring the tonography of an eye, the method using a tonometer that presses an applanation surface with a variable force against the cornea of an eye while a detector receives reflected light representing a varying size of an applanated area of the cornea and produces an applanated area signal delivered to a programmed microprocessor, the method comprising:
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recognizing a preliminary value of the applanated area signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined; pressing the applanation surface against the cornea with increasing force applied during a time interval to change the applanated area signal from the preliminary value through a range of values that include and extend from the preliminary value by a predetermined amount; selecting the time interval to include a peak value of a systolic pulse; determining an intra ocular pressure (IOP) from changes in the applanated area signal corresponding to prism pressure force changes in the range of values so that the IOP determination is substantially unaffected by thickness and curvature of the cornea of the eye being examined; and determining a tonography measure based on a return of the applanated area signal from the peak value of the systolic pulse to a diastolic value occurring during absence of a systolic pulse. - View Dependent Claims (19, 20)
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21. A tonometer that presses an applanation surface with a variable and determinable force against a cornea of an eye while a detector receives reflected light representing a varying size of an applanated area of the cornea and produces an applanated area signal delivered to a programmed microprocessor, the tonometer comprising:
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the microprocessor being programmed to determine an intra ocular pressure (IOP) based on both the applanated area signal received during a diastolic phase and the applanated area signal received during a systolic phase; the applanation surface being pressed against the cornea of the eye for a long enough duration for the applanated area signal to indicate that at least two systolic phases have occurred; the microprocessor being programmed to recognize a preliminary value of the applanated area signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined; the microprocessor being programmed to press the applanation surface against the cornea with increasing force applied during a time interval to change the applanated area signal from the preliminary value through a range of values that include and extend from the preliminary value by a predetermined amount; and the microprocessor being programmed to determine from the applanated area signal an average or mean IOP, and an ocular pulse pressure (OPP) occurring during a systolic phase, these determinations being substantially unaffected by thickness and curvature of the cornea of the eye being examined. - View Dependent Claims (22, 23)
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24. A tonometer comprising:
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an applanation surface arranged to be pressed against a cornea of an eye being examined, the applanation surface being supported on a rotationally moveable arm; an electromagnetic actuator arranged for pressing the applanation surface against the cornea with a predetermined and variable force; the electromagnetic actuator including a permanent magnet and a coil one of which is mounted on the arm supporting the applanation surface and the other of which is mounted in a fixed position; a counterbalance applying a rotational moment arm to return the movable arm to a starting position without requiring a return spring; a detector receiving reflected light indicating a varying size of an area of the cornea applanated by the applanation surface; a microprocessor programmed to recognize a preliminary value of the applanated area signal occurring upon preliminary contact of the applanation surface with the cornea, the preliminary value varying from one eye to another based on specific corneal thickness and curvature of the eye being examined; the microprocessor being programmed to press the applanation surface against the cornea with increasing force applied during a time interval to change the applanated area signal from the preliminary value through a range of values that include and extend from the preliminary value by a predetermined amount; and the microprocessor being programmed to determine an intra ocular pressure (IOP) from changes in the applanated area signal corresponding to changes in the range of values so that the IOP determination is substantially unaffected by thickness and curvature of the cornea of the eye being examined. - View Dependent Claims (25)
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Specification