Method and apparatus for accurately measuring the transmittance of blood within a retinal vessel
First Claim
1. A method of measuring the transmittance of blood within a retinal vessel, the method comprising the steps of:
- illuminating the retinal vessel and at least a portion of the background fundus within an eye;
detecting the intensity of light reflected from illuminated portions of the eye;
identifying a portion of the detected light intensities as corresponding to light that has been transmitted through a retinal vessel, wherein said identifying step comprises matching a portion of the detected light intensities with a predetermined pattern corresponding to the intensity of light that has propagated through a retinal vessel;
constructing an intensity profile function based upon the identified portion of the detected light intensities, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, and wherein said constructing step comprises compensating for at least some of the reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel; and
determining the transmittance of blood within the retinal vessel based upon the intensity profile function.
2 Assignments
0 Petitions
Accused Products
Abstract
The method and apparatus for measuring the transmittance of blood within a retinal vessel detects the intensity of light reflected from illuminated portions of an eye, including the retinal vessel and background fundus, and adjusts the corresponding intensity signals to compensate for reflections from the retinal vessel. In particular, the transmittance measuring method and apparatus constructs an intensity profile function based upon the intensity signals. As a result, the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position. During the construction of the intensity profile function, the transmittance measuring method and apparatus can compensate for at least some of the reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel, thereby increasing the accuracy with which the transmittance of blood within a retinal vessel is measured. In addition, the transmittance measuring method and apparatus can compensate for the finite point spread function of the light with which the eye is illuminated in order to further increase the resulting measurement accuracy.
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Citations
39 Claims
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1. A method of measuring the transmittance of blood within a retinal vessel, the method comprising the steps of:
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illuminating the retinal vessel and at least a portion of the background fundus within an eye; detecting the intensity of light reflected from illuminated portions of the eye; identifying a portion of the detected light intensities as corresponding to light that has been transmitted through a retinal vessel, wherein said identifying step comprises matching a portion of the detected light intensities with a predetermined pattern corresponding to the intensity of light that has propagated through a retinal vessel; constructing an intensity profile function based upon the identified portion of the detected light intensities, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, and wherein said constructing step comprises compensating for at least some of the reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel; and determining the transmittance of blood within the retinal vessel based upon the intensity profile function. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of measuring the transmittance of blood within a retinal vessel, the method comprising the steps of:
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illuminating the retinal vessel and at least a portion of the background fundus within an eye; detecting the intensity of light reflected from illuminated portions of the eye; constructing an intensity profile function based upon the detected light intensity, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, and wherein said constructing step comprises compensating for at least some of the reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel; constructing a second intensity profile function which defines a curve and approximates the intensity of light reflected from the background fundus as a function of retinal position; and determining the transmittance of blood within the retinal vessel based upon the intensity profile function, wherein said step of determining the transmittance of blood within the retinal vessel is based upon both the intensity profile function and the second intensity profile function. - View Dependent Claims (8, 9)
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10. A method of measuring the transmittance of blood within a retinal vessel based upon intensity signals representing the intensity of light reflected from illuminated portions of an eye including the retinal vessel and a background fundus, the method comprising the steps of:
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matching a portion of the intensity signals with a predetermined pattern corresponding to the intensity of light that has propagated through a retinal vessel so as to identify that portion of the intensity signals that has been transmitted through a retinal vessel; constructing an intensity profile function based upon the identified portion of the intensity signals representing the intensity of light reflected from illuminated portions of the eye, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, and wherein said constructing step comprises compensating for at least some of the reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel; determining the intensity of light reflected from the background fundus based upon the intensity signals representing the intensity of light reflected from the background fundus; and determining the transmittance of blood within the retinal vessel based upon the intensity profile function and the intensity of light reflected from the background fundus. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method of measuring the transmittance of blood within a retinal vessel based upon intensity signals representing the intensity of light reflected from illuminated portions of an eye including the retinal vessel and a background fundus, the method comprising the steps of:
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constructing an intensity profile function based upon the intensity signals representing the intensity of light reflected from illuminated portions of the eye, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, and wherein said constructing step comprises compensating for at least some of the reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel; determining the intensity of light reflected from the background fundus based upon the intensity signals representing the intensity of light reflected from the background fundus, wherein said step of determining the intensity of light reflected from the background fundus comprises constructing a second intensity profile function which defines a curve and approximates the intensity of light reflected from the background fundus as a function of retinal position; and determining the transmittance of blood within the retinal vessel based upon the intensity profile function and the second intensity profile function. - View Dependent Claims (17, 18, 19, 21)
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20. A method of constructing an intensity profile function based upon intensity signals representing the intensity of light reflected from illuminated portions of an eye including a retinal vessel and a background fundus, wherein the intensity profile function approximates the intensity of light transmitted through a retinal vessel as a function of retinal vessel position, the method comprising the steps of:
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determining the intensity of light transmitted through lateral portions of the retinal vessel based upon intensity signals representing the intensity of light reflected from illuminated portions of the eye, wherein said determining step comprises approximating a portion of the intensity profile function describing the intensity of light transmitted through lateral portions of the retinal vessel as a function of retinal vessel position; and compensating for reflections of light from a central portion of the retinal vessel which occurred prior to propagation of the light through the retinal vessel, wherein said compensating step comprises creating the intensity profile function based upon the intensity of light transmitted through the lateral portions of the retinal vessel such that the intensity profile function approximates the light transmitted through the central portion of the retinal vessel in the absence of reflections from the central portion of the retinal vessel, wherein said creating step comprises fitting a cubic function to the portion of the intensity profile function describing the intensity of light transmitted through lateral portions of the retinal vessel as a function of retinal vessel position.
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22. A method of analyzing blood within a retinal vessel based upon intensity signals representing the intensity of light reflected from illuminated portions of an eye including the retinal vessel and a background fundus, the method comprising the steps of:
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constructing an intensity profile function based upon the intensity signals representing the intensity of light reflected from illuminated portions of the eye, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position; providing a mathematical model of the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, wherein the mathematical model is a cubic function that includes a plurality of parameters including parameters describing the retinal vessel and parameters describing reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel; fitting the mathematical model to a portion of the intensity profile function that describes the intensity of light transmitted through lateral portions of the retinal vessel as a function of retinal vessel position; and determining at least one parameter describing the retinal vessel following said fitting step. - View Dependent Claims (23, 24)
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25. An apparatus for measuring the transmittance of blood within a retinal vessel, the apparatus comprising:
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an optical source for illuminating the retinal vessel and at least a portion of the background fundus within an eye; a detector for measuring the intensity of light reflected from the illuminated portions of the eye; means, responsive to said detector, for matching a portion of the measured light intensities with a predetermined pattern corresponding to the intensity of light that has propagated through a retinal vessel so as to identify that portion of the intensity signals that has been transmitted through a retinal vessel; means, responsive to said detector, for constructing an intensity profile function based upon the matching portion of the measured light intensities, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, and wherein said constructing means comprises means for compensating for at least some of the reflections of light from the retinal vessel produced prior to propagation of the light through the retinal vessel; and means, responsive to said constructing means, for determining the transmittance of blood within the retinal vessel based upon the intensity profile function. - View Dependent Claims (26, 27, 28, 29, 30)
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31. An apparatus for measuring the transmittance of blood within a retinal vessel, the apparatus comprising:
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an optical source for illuminating the retinal vessel and at least a portion of the background fundus within an eye; a detector for measuring the intensity of light reflected from the illuminated portions of the eye; means, responsive to said detector, for constructing an intensity profile function based upon the measured light intensities, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, and wherein said constructing means comprises means for compensating for at least some of the reflections of light from the retinal vessel produced prior to propagation of the light through the retinal vessel; means, responsive to said detector, for constructing a second intensity profile function which defines a curve and approximates the intensity of light reflected from the background fundus as a function of retinal position; and means, responsive to said constructing means, for determining the transmittance of blood within the retinal vessel is based upon both the intensity profile function and the second intensity profile function. - View Dependent Claims (32, 33)
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34. A computer program product for determining the transmittance of blood within a retinal vessel based upon intensity signals representing the intensity of light reflected from illuminated portions of an eye including the retinal vessel and a background fundus, the computer program product comprising a computer-readable storage medium having computer-readable program code means embodied in said medium, said computer-readable program code means comprising:
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first computer-readable program code means for constructing an intensity profile function based upon the intensity signals representing the intensity of light reflected from the illuminated portions of the eye, wherein the intensity profile function approximates the intensity of light transmitted through the retinal vessel as a function of retinal vessel position, wherein said first computer-readable program code means comprises computer-readable program code means for compensating for at least some of the reflections of light from the retinal vessel which occurred prior to propagation of the light through the retinal vessel; second computer-readable program code means for determining the intensity of light reflected from the background fundus based upon the intensity signals representing the intensity of light reflected from the background fundus, wherein said second computer-readable program code means for determining the intensity of light reflected from the background fundus comprises computer-readable program code means for constructing a second intensity profile function which defines a curve and approximates the intensity of light reflected from the background fundus as a function of retinal position; and third computer-readable program code means for determining the transmittance of blood within the retinal vessel based upon the intensity profile function constructed by said first computer-readable program code means and the second intensity profile function constructed by said second computer-readable program code means. - View Dependent Claims (35, 36, 37, 38, 39)
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Specification