Eye fixation monitor and tracker
First Claim
1. An apparatus for assessing the fixation state of at least one eye, each eye having a corneal birefringence meridional direction, a fundus, a fovea having a projection, lutein pigment having a dichroic effect, and a fixation state, said apparatus comprising:
- a) an illumination system, comprising at least one light source, for providing at least one beam of incident light to each of said at least one eye;
b) a detection system, synchronously operable with said illumination system and comprising at least one photodetector, each of said at least one photodetector comprising a detection surface, for detecting incident light reflected from the fundus of each of said at least one eye; and
c) an analysis system, operably connected with both said illumination system and said detection system, for determining polarization-related changes that have occurred between the incident light and the reflected light and for assessing foveal projection information for each of said at least one eye from said polarization-related changes detected in the reflected light, wherein said foveal projection information indicates the fixation state of the eye, said fixation state of the eye varying from a fixated condition to a non-fixated condition.
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Accused Products
Abstract
Apparatus and method are provided for assessing the direction of fixation of an eye by detecting polarization-related changes in light retroreflected from the fundus of the eye. Nerve fibers in the retina of the eye are birefringent and alter the polarization state of light traversing them as a function of their orientation. The nerve fibers are arrayed in a characteristic pattern in the retina, specifically radiating outward from the fovea and converging to the optic nerve head. By assessment of polarization-related changes in rctroreflected light from multiple retinal areas either sequentially or simultaneously, characteristic birefringence signatures of portions of the retina can be identified which are used to assess the direction of fixation of the eye. In addition, interference from the corneal birefringence is reduced by using incident light having a polarization state that is substantially independent of meridional direction. Circularly polarized light or non-polarized light is used for the assessment. Interference from the corneal birefringence is reduced still further by detecting polarization-related changes that are substantially independent of the meridional direction of the corneal birefringence. This is accomplished by detecting changes in ellipticity by measuring solely the Stokes parameter S3 or by measuring any two Stokes parameters. An alternative is measuring the overall intensity of the retroreflected light when the dichroism of the lutein pigment particles in the vicinity of the fovea is used for the assessment.
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Citations
64 Claims
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1. An apparatus for assessing the fixation state of at least one eye, each eye having a corneal birefringence meridional direction, a fundus, a fovea having a projection, lutein pigment having a dichroic effect, and a fixation state, said apparatus comprising:
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a) an illumination system, comprising at least one light source, for providing at least one beam of incident light to each of said at least one eye; b) a detection system, synchronously operable with said illumination system and comprising at least one photodetector, each of said at least one photodetector comprising a detection surface, for detecting incident light reflected from the fundus of each of said at least one eye; and c) an analysis system, operably connected with both said illumination system and said detection system, for determining polarization-related changes that have occurred between the incident light and the reflected light and for assessing foveal projection information for each of said at least one eye from said polarization-related changes detected in the reflected light, wherein said foveal projection information indicates the fixation state of the eye, said fixation state of the eye varying from a fixated condition to a non-fixated condition. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method for assessing the fixation state of at least one eye, each eye having a comeal birefringence meridional direction, a fundus, a fovea, lutein pigment having a dichroic effect, and a fixation state, comprising the steps of:
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a) producing and directing at least one beam of incident light from an illumination system, said illumination system comprising at least one light source, toward each of said at least one eye to illuminate the area of the fundus of the eye which is aligned with said at least one beam of incident light; b) isolating and detecting light reflected from the illuminated area of the fundus of each of said at least one eye by a detection system, said detection system comprising at least one photodetector, each of said at least one photodetector comprising a detection surface; c) determining polarization-related changes that have occurred between the incident light and the reflected light; and d) correlating the polarization-related changes that are observed with polarization-related changes known to occur with known fixation states of the eye in order to determine fixation state information for each of said at least one eye, wherein said fixation state varies from a fixated condition to a non-fixated condition. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64)
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Specification