Methods and systems for alignment of ophthalmic imaging devices

Ophthalmic imaging systems and related methods provide pseudo feedback to aid a user in aligning the user's eye with an optical axis of the imaging system. An ophthalmic imaging system includes an ophthalmic imaging device having an optical axis, a display device, an eye camera, and a control unit. The display device displays a fixation target viewable by the user. The eye camera images the eye to generate eye image data. The control unit processes the eye image data to determine a position of the eye relative to the optical axis, processes the position of the eye relative to the optical axis to generate a pseudo position of the eye relative to the optical axis, and causes the display device to display an indication that provides feedback to the user that the eye is located at the pseudo position of the eye relative to the optical axis.

BACKGROUND

Macular degeneration is the leading cause of vision loss in the United States of America. In macular degeneration, the central portion of the retina (a.k.a., the macula) deteriorates. When healthy, the macula collects and sends highly detailed images to the brain via the optic nerve. In early stages, macular degeneration typically does not significantly affect vision. If macular degeneration progresses beyond the early stages, vision becomes wavy and/or blurred. If macular degeneration continues to progress to advanced stages, central vision may be lost.

Although macular degeneration is currently considered to be incurable, treatments do exist that may slow the progression of the disease so as to prevent severe loss of vision. Treatment options include injection of an anti-angiogenic drug into the eye, laser therapy to destroy an actively growing abnormal blood vessel(s), and photodynamic laser therapy, which employs a light-sensitive drug to damage an abnormal blood vessel(s). Early detection of macular degeneration is of paramount importance in preventing advanced progression of macular degeneration prior to treatment to inhibit progression of the disease.

Early detection of macular degeneration can be accomplished using a suitable retinal imaging system. For example, Optical Coherence Tomography (OCT) is a non-invasive imaging technique relying on low coherence interferometry that can be used to generate a cross-sectional image of the macula. The cross-sectional view of the macula shows if the layers of the macula are distorted and can be used to monitor whether distortion of the layers of the macula has increased or decreased relative to an earlier cross-sectional image to assess the impact of treatment of the macular degeneration.

Existing OCT imaging systems, however, are typically expensive and may have to be operated by a trained technician. For example, a trained technician may be required to properly align an optical axis of the OCT imaging system with the optical axis of the eye examined. As a result, the use of such OCT imaging systems is typically restricted to specialized eye care clinics, thereby limiting use of such OCT imaging systems for widespread screening for early stage macular degeneration.

BRIEF SUMMARY

Ophthalmic imaging systems and related methods employ improved feedback to a user for use in self-alignment of the user's eye with the optical axis of the ophthalmic imaging system. In many embodiments, the user looks into a view port of the imaging device and is instructed to look at a fixation target, and perform a task. In some embodiments of the ophthalmic imaging systems and related methods disclosed herein, the user is shown two fiducials, one representing the optical axis of the device and the other one represents the center of the pupil and the task is to move “pupil” fiducial till the two are coincident. In some embodiments of the ophthalmic imaging systems and related methods disclosed herein, the fiducial representing the center of the pupil is displayed at a location that is, in many instances, offset by a controlled amount from where the fiducial would be displayed to indicate the actual position of the user's pupil relative to the optical axis of the imaging system. Showing an eye position fiducial at a location that is offset by a controlled amount from a location that would indicate the actual position of the user's pupil relative to the optical axis is in contrast to existing approaches. By displaying the eye position fiducial at a location that is offset by a controlled amount from a location at which the fiducial would be displayed to indicate the actual position of the user's pupil relative to the optical axis, the effort required by the user to achieve and maintain sufficient positioning of the user's pupil relative to the optical axis of the imaging device is reduced relative to prior approaches. For example, in some embodiments, the eye position fiducial is displayed coincident with optical axis fiducial when the actual position of the pupil is close enough to the optical axis to enable satisfactory imaging of the user's eye so as to avoid feedback to the user that may induce the user to try to reposition the user's eye when the current position of the user's eye is sufficiently close to the optical axis.

Thus, in one aspect, an ophthalmic imaging system includes an ophthalmic imaging device, a display device, an eye camera, and a control unit. The ophthalmic imaging device has an optical axis. The display device displays a fixation target viewable by an eye of a user. The eye camera is operable to image the eye to generate eye image data. The control unit processes the eye image data to determine a position of the eye relative to the optical axis. The control unit processes the position of the eye relative to the optical axis to generate a pseudo position of the eye relative to the optical axis. The pseudo position of the eye relative to the optical axis is different from the position of the eye relative to the optical axis. The control unit causes the display device to display an indication that provides feedback to the user that the eye is located at the pseudo position of the eye relative to the optical axis.

In many embodiments of the ophthalmic imaging system, the indication is displayed at a position relative to the fixation target. For example, the indication displayed to the user can include an eye pseudo position indicator displayed at a position relative to the fixation target matching the pseudo position of the eye relative to the optical axis. In many embodiments, if a distance between the position of the eye and the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis is generated to lie on the optical axis. In many embodiments, the indication displayed to the user includes an eye pseudo position indicator displayed aligned with the fixation target to provide feedback to the user indicating that the position of the eye is located on the optical axis.

In some embodiments of the ophthalmic imaging system, the indication displayed to the user is based on a size of a pupil of the eye. In some embodiments, the acceptable distance is a function of the size of the pupil. For example, in some embodiments of the ophthalmic imaging system, the acceptable distance is smaller for a relatively small pupil and larger for a relatively large pupil. In some embodiments, the control unit processes the eye image data to determine the size of the pupil of the eye.

In some embodiments of the ophthalmic imaging system, the acceptable distance is increased in response to user achieving alignment of the eye of the user with the optical axis. For example, the acceptable distance can be set equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis. The acceptable distance can then be reset to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

In some embodiments of the ophthalmic imaging system, the pre-alignment acceptable distance is based on a size of a pupil of the eye and/or the post-alignment acceptable distance is based on a size of a pupil of the eye. In some embodiments of the ophthalmic imaging system, the control unit processes the eye image data to determine the size of the pupil of the eye.

In some embodiments of the ophthalmic imaging system, the control unit is configured to detect the position of the eye even if a portion of a pupil of the eye is obscured. For example, in some embodiments, the control unit is configured to process the eye image data to (a) detect if a portion of the pupil of the eye is obscured, (b) identify an unobscured portion of the pupil, and (c) determine the position of the eye relative to the optical axis based on the unobscured portion of the pupil.

In many embodiments of the ophthalmic imaging system, the position of the eye relative to the optical axis is repeatedly determined to track the position of the eye relative to the optical axis. For example, in many embodiments the eye camera captures a series of images of the eye and the eye image data includes image data for each of the series of images of the eyes. In many embodiments, for each image of the series of images of the eye, the control unit (a) processes the eye image data to determine a respective position of the eye relative to the optical axis, (b) processes the respective position of the eye relative to the optical axis to generate a respective pseudo position of the eye relative to the optical axis, and (c) causes the display device to display a respective indication that provides feedback to the user that the eye is located at the respective pseudo position of the eye relative to the optical axis. In many embodiments, the respective pseudo position of the eye relative to the optical axis is different from the respective position of the eye relative to the optical axis. In many embodiments, the control unit processes, for the series of images of the eye, a series of positions of the eye relative to the optical axis to detect if the user fails to achieve and/or maintain acceptable positioning of the eye relative to the optical axis. In many embodiments, the control unit, in response to detecting failure of the user to achieve and/or maintain acceptable positioning of the eye relative to the optical axis, increases a size of the fixation target and/or the indication displayed to the user that provides the feedback to the user.

In many embodiments of the ophthalmic imaging system, the pseudo position of the eye is generated as a function of the position of the eye relative to the optical axis. For example, in some embodiments the controller includes a proportional controller and generation of the pseudo position of the eye relative to the optical axis by the control unit comprises multiplying, by the proportional controller, the position of the eye relative to the optical axis by a gain factor not equal to 1.0.

In many embodiments, if a distance of the eye relative to the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis is generated to lie on the optical axis. In many embodiments, the indication displayed to the user includes an eye pseudo position indicator displayed aligned with the fixation target to provide feedback to the user indicating that the eye is located on the optical axis. For example, if the eye and the optical axis are not perfectly aligned but the offset between the optical axis and the pupil is small enough such that an imaging beam of the ophthalmic imaging device enters the pupil without any clipping, the user can be provided feedback that the user's eye is actually aligned with the optical axis so as to induce the user to hold still and avoid frustrating the user via providing feedback to the user suggesting that repositioning by the user is required when no repositioning by the user is actually required. The size of the acceptable offset between the actual position of the user's eye and the optical axis can be dependent on the beam diameter of the ophthalmic imaging device projected to the eye and the pupil diameter. For example, the acceptable offset can be provided by equation (1).
Acceptable Offset=((Pupil Diameter−Beam Diameter)/2)  Equation (1)

In some embodiments, the acceptable offset may vary from 0.1 mm for a combination of a large beam (2.5 mm) and a small pupil diameter (2.7 mm) to 5.0 mm for a combination of a small beam (0.5 mm) and a large pupil (10.5 mm).

In another aspect, a method of providing feedback to a user of an ophthalmic imaging system regarding alignment of an eye of the user with an optical axis of the ophthalmic imaging system is described. The method includes displaying a fixation target on a display device viewable by the eye of the user. Eye image data corresponding to an image of the eye viewing the fixation target is generated by an eye camera. A control unit processes the eye image data to determine a position of the eye relative to the optical axis. The control unit generates a pseudo position of the eye relative to the optical axis based on the position of the eye relative to the optical axis. The pseudo position of the eye relative to the optical axis is generated to be different from the position of the eye relative to the optical axis. The control unit causes display of an indication on the display device to provide feedback to the user indicating that the eye is located at the pseudo position of the eye relative to the optical axis.

In many embodiments of the method, the indication is displayed at a position relative to the fixation target. For example, display of the indication on the display device can include display of a pseudo position indicator at a position relative to the fixation target matching the pseudo position of the eye relative to the optical axis. In many embodiments, the method further includes processing the position of the eye relative to the optical axis to determine if a distance between the position of the eye and the optical axis is less than acceptable distance. In many embodiments of the method, the generation of the pseudo position of the eye relative to the optical axis includes setting the pseudo position of the eye to lie on the optical axis if the distance of the eye relative to the optical axis is less than the acceptable distance. In many embodiments of the method, the display of the indication on the display device includes displaying an eye pseudo position indicator aligned with the fixation target to provide feedback to the user that the position of the eye is located on the optical axis.

In some embodiments, the method further includes determining the acceptable distance based on a size of a pupil of the eye. For example, in some embodiments of the method, the acceptable distance is smaller for a relatively small pupil and larger for a relatively large pupil. In some embodiments, the method further includes processing the eye image data, by the control unit, to determine the size of the pupil of the eye.

In some embodiments of the method, the acceptable distance is increased in response to user achieving alignment of the eye of the user with the optical axis. For example, the acceptable distance can be set equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis. The acceptable distance can then be reset to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

In some embodiments, the method further includes determining the pre-alignment acceptable distance and/or the post-alignment acceptable distance based on a size of a pupil of the eye. In some embodiments, the method further includes processing the eye image data, by the control unit, to determine the size of the pupil of the eye.

In some embodiments of the method, the control unit is configured to detect the position of the eye even if a portion of the pupil is obscured. For example, in some embodiments, the method further includes processing the eye image data, by the controller, to (a) detect if a portion of a pupil of the eye is obscured, (b) identify an unobscured portion of the pupil, and (c) determine the position of the eye relative to the optical axis based on the unobscured portion of the pupil.

In many embodiments of the method, the position of the eye relative to the optical axis is repeatedly determined to track the position of the eye relative to the optical axis. For example, in many embodiments, the method includes generating, by the eye camera, the eye image data so as to comprise image data for each of a series of images of the eyes. In many embodiments, the method includes, for each image of the series of images of the eye, (a) processing the eye image data, by the control unit, to determine a respective position of the eye relative to the optical axis, (b) processing the respective position of the eye relative to the optical axis, by the control unit, to generate a respective pseudo position of the eye relative to the optical axis, the respective pseudo position of the eye relative to the optical axis being different from the respective position of the eye relative to the optical axis, and (c) causing, by the control unit, the display device to display a respective indication that provides feedback to the user that the eye is located at the respective pseudo position of the eye relative to the optical axis. In many embodiments, the method includes processing, by the control unit, for the series of images of the eye, a series of positions of the eye relative to the optical axis to detect if the user fails to achieve and/or maintain acceptable positioning of the eye relative to the optical axis. In many embodiments, the method includes, in response to detecting, by the control unit, failure of the user to achieve and/or maintain acceptable positioning of the eye relative to the optical axis, increasing, by the control unit, a size of the fixation target and/or the indication displayed to the user that provides the feedback to the user.

In many embodiments of the method, the pseudo position of the eye is generated as a function of the position of the eye relative to the optical axis. For example, generating the pseudo position of the eye relative to the optical axis can include multiplying the position of the eye relative to the optical axis by a factor not equal to 1.0. If a distance of the eye relative to the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis can be generated to lie on the optical axis. The indication displayed to the user can include an eye pseudo position indicator displayed aligned with the fixation target to provide feedback to the user that the eye is located on the optical axis.

In another aspect, an ophthalmic imaging system includes an ophthalmic imaging device, a display device, an eye camera, and a control unit. The ophthalmic imaging device has an optical axis. The display device displays a fixation target viewable by an eye of a user. The eye camera is operable to image the eye to generate eye image data. The control unit processes the eye image data to determine a position of the eye relative to the optical axis. The control unit causes the display device to display an indication that provides feedback to the user that the eye is located at the position of the eye relative to the optical axis.

For a fuller understanding of the nature and advantages of the present invention, reference should be made to the ensuing detailed description and accompanying drawings.

DETAILED DESCRIPTION

Referring now to the drawings, in which like reference numerals represent like parts throughout the several views,FIG. 1shows a user12looking into a view port14of a viewing assembly16of an ophthalmic imaging system10, in accordance with many embodiments. In many embodiments, the viewing assembly16is configured to approximately position one eye of the user12on an optical axis of the imaging system10. For example, in the configuration shown inFIG. 1, the viewing assembly16is configured to approximately position the right eye of the user12on the optical axis of the imaging system10. In the illustrated embodiment, the viewing assembly16can be rotated 180 degrees around a pivot axis20so as to reconfigure the viewing assembly16to approximately position the left eye of the user12on the optical axis of the imaging system10. Accordingly, each of the right and the left eye of the user12can be selectively approximately positioned on the optical axis of the imaging system10for imaging of the respective eye by the imaging system10. In embodiments described herein, final positioning and alignment of the optical axis of the respective eye of the user12with the optical axis of the imaging system10is accomplished by the user12adjusting the user's position relative to the view port14in response to feedback provided to the user12as described herein.

FIG. 2is a simplified schematic illustration of an embodiment of the ophthalmic imaging system10. In the illustrated embodiment, the ophthalmic imaging system10includes a lens assembly22, an ophthalmic imaging device24, an eye camera26, a display device28, a control unit30, a suitable user interface32, a first beam splitter36, and a second beam splitter38. The ophthalmic imaging device24has an optical axis40to which the user12manually aligns a respective eye42of the user12in response to feedback provided to the user12described herein. The control unit30includes a processor33and a data storage device34. A fixation target44is displayed on the display device28and is viewable by the eye42via an optical path46that extends through the lens assembly22and is diverted by each of the first beam splitter36and the second beam splitter38. The display device28, the first and second beam splitters36,38, and the position at which the fixation target44is displayed on the display device28are configured so that the portion of the optical path46between the eye42and the first beam splitter36aligns with the optical axis40of the imaging device24if the eye42is fixated on the fixation target44and the optical center of the eye42is positioned on the optical axis40.

To generate the feedback to the user12to guide self-alignment of the optical center of the eye42with the optical axis40of the imaging device24, the eye camera26images the eye42to generate eye image data corresponding to the captured image of the eye42. The eye image data is transmitted from the eye camera26to the control unit30. The control unit30processes the eye image data to detect the optical center of the eye42using any suitable approach. For example, in some embodiments, the control unit30processes the eye image data to detect the pupil of the eye42and then processes the region of the image of the eye corresponding to the detected pupil to locate the center of the pupil. The location of the detected center of the pupil can then be compared with a known fixed location of the optical axis40to determine the current relative position of the center of the eye42relative to the optical axis40.

In many embodiments, the display device28projects a relatively large beam in the pupil plane (e.g., greater than 10 mm) in order to allow the user to see the projection at every pupil position and correct the pupil position accordingly. In many embodiments, the projection beam always contain the pupil inside in order to avoid a situation that the user cannot see the display or partially sees it.

It should be obvious to a person skilled in the art that any suitable optical assembly that includes the ophthalmic imaging device24, the eye camera26, and the display device28can be employed in the ophthalmic imaging system10. For example,FIG. 3is a simplified schematic illustration of such a suitable optical assembly that includes the ophthalmic imaging device24, the eye camera26, and the display device28and can be employed in the ophthalmic imaging system10. In the illustrated optical assembly, the ophthalmic imaging device24is a spectral domain OCT imaging device that operates in a wavelength range of 800 nm to 900 nm. The illustrated optical assembly includes an eye illuminator49that illuminates the eye42using a suitable wavelength of light (e.g., a wavelength of light above 920 nm). In the illustrated optical assembly, the display device28can project light between any suitable wavelength (e.g., from 400 nm to 700 nm). The illustrated optical assembly includes a dichroic mirror36athat transmits the OCT wavelength and the display wavelength range (400 nm to 900 nm) and reflects the illumination wavelength (e.g., greater than 920 nm) to the eye camera26. The illustrated optical assembly includes a dichroic mirror38athat transmits the display wavelength range and reflects the OCT wavelength.

In many embodiments, the control unit30generates a pseudo position of the eye42relative to the optical axis40as described herein with reference toFIG. 4throughFIG. 7and displays an eye pseudo position indicator48on the display device28so as to provide feedback to the user12that the eye is located at the pseudo position of the eye relative to the optical axis40. Any suitable approach can be used to provide the feedback to the user12. For example, in many embodiments, the eye pseudo position indicator48is positioned on the display device28relative to the fixation target44by the pseudo position of the eye relative to the optical axis40. In such embodiments, the fixation target44represents the location of the optical axis40and the position of the eye pseudo position indicator48relative to the fixation target44provides feedback to the user12indicating if the user12should reposition the user's eye relative to the view port14, and if so, in what direction and by what distance.

In many embodiments, the control unit30is operatively coupled with, and controls operation of, the ophthalmic imaging device24, the eye camera26, and the display device28. For example, in many embodiments, the control unit30receives the eye image data from the eye camera26and processes the eye image data to detect the location of the center of the eye42and determine the position of the center of the eye42relative to the optical axis40. In many embodiments, the optical axis40is disposed at a fixed known position in an image of the eye captured by the eye camera26and the position of the center of the eye42within the image of the eye is compared with the position of the optical axis40within the image to determine the position of the center of the eye42relative to the optical axis40. In some embodiments, the control unit30operates of the ophthalmic imaging device24when the center of the eye42is within an acceptable distance from the optical axis40and blocks operation of the ophthalmic imaging device24when the center of the eye42is not within an acceptable distance of the optical axis40.

In many embodiments, the control unit30is part of a feedback loop that provides the feedback to the user12as described herein. For example,FIG. 4is a simplified schematic illustration of an example feedback loop50that provides the feedback described herein to the user12of the ophthalmic imaging device24regarding alignment of the user's eye42with the optical axis40of the ophthalmic imaging system10. In many embodiments, the display device28displays an indication that is, in many instances, offset from the actual position of the user's eye42relative to the optical axis40by a controlled amount. By displaying an indication that is offset from the actual relative position of the user's eye42by the controlled amount, the effort required by the user12to achieve and maintain sufficient positioning of the user's eye42relative to the optical axis40of the ophthalmic imaging device24may be reduced relative to prior approaches.

In the illustrated embodiment of the feedback loop50, the control unit30includes a proportional controller52that generates a pseudo position of the eye42(X′1, Y′ 1) from an actual position of the eye42(X1, Y1) and the position of the optical axis40(X0, Y0). The control unit30processes the eye image data from the eye camera26to determine the actual position of the eye42(X1, Y1). In some embodiments, the proportional controller52multiplies differences between actual position of the eye42(X1, Y1) and the position of the optical axis40(X0, Y0) by a predefined factor, referred to below as gain factor (G). For example, in some embodiments: (a) (X′1, Y′1) are the coordinates sent to the display device28from the proportional controller52at which the eye pseudo position indicator48is displayed to the user12, (b) (X′0, Y′0)=(X0, Y0) (correspond to the location of the optical axis40of the imaging device24and the fixation target44displayed to the user12), (c) (X1, Y1) are the coordinates of the actual position of the center of the eye42relative to the optical axis40of the imaging device24, (d) X′1=X0+(X1−X0)*G is the x-coordinate of the eye pseudo position indicator48displayed to the user12on the display device28, and (e) Y′1=Y0+(Y1−Y0)*G is the y-coordinate of the eye pseudo position indicator48displayed to the user12on the display device28. An example display for a G=1.5 is shown inFIG. 5.

In many embodiments, if the eye42is not exactly positioned on the optical axis40of the ophthalmic imaging device24, but is none-the-less positioned within an acceptable distance from the optical axis40, the eye pseudo position indicator48is displayed on the display device28so as to give a false feedback to the user12that the eye42is centered on the optical axis40. For example, as shown inFIG. 6, when the actual relative position of the pupil is within an acceptable pupil position boundary54(not actually displayed to the user in many embodiments), the eye pseudo position indicator48is displayed on the display device28aligned with the fixation target44, thereby serving to inhibit the user12from further repositioning of the user's eye42relative to the view port14. In many embodiments, the displayed location of the eye position pseudo indicator48changes suddenly when the position of the eye42is repositioned from outside of the acceptable pupil position boundary54to within the boundary54, thereby appearing to the user12to snap between the displayed positions.

For example, in some embodiments the control unit30is configured to check if the current position of the eye42is within the acceptable pupil position boundary54relative to the optical axis40of the ophthalmic imaging device24. If the current position of the eye42is within the acceptable pupil position boundary54, then the control unit30sets X′1=X′0 and Y′1=Y′0 so that the eye pseudo position indicator48is placed on the fixation target44. In other words, when the eye42is within a distance D of the optical axis40of the ophthalmic imaging device24(i.e., ((X1−X0){circumflex over ( )}2±(Y1−Y0){circumflex over ( )}2){circumflex over ( )}0.5<=D), then X′1=X′0 and Y′1=Y′0.

In some embodiments, the size of the acceptable pupil position boundary54is a function of the size of the pupil of the eye42. For example, in some embodiments, the acceptable pupil position boundary is smaller for a relatively small pupil and larger for a relatively large pupil. In some embodiments, the size of the acceptable pupil position boundary54can be based in imaging requirements, which can be changed from one user to another, from one test to another, and/or from one disease state to another.

In some embodiments, the ophthalmic imaging system10is configured to detect when the user12is having trouble achieving and/or maintaining acceptable positioning of the user's eye42relative to the optical axis40of the ophthalmic imaging device24. In response to detecting the user12having difficulty achieving and/or maintaining acceptable positioning of the user's eye42relative to the optical axis40, the feedback provided to the user12via the display device can be modified to further assist the user12. For example, the size of the fixation target44can be increased and/or the size of the eye pseudo position indicator48can be increased, which may further assist a user that has poor vision. Any suitable approach can be used to detect when the user12is having trouble achieving and/or maintaining acceptable positioning of the user's eye42relative to the optical axis40. For example, if the user12fails to achieve acceptable positioning of the user's eye42relative to the optical axis40within a suitable time period and/or fails to maintain the eye42within the acceptable pupil position boundary54for a suitable time period, the system10can make a determination that the user12is having trouble positioning the eye42relative to the optical axis40and make suitable modifications to the feedback provided to the user12, such as those modifications described herein, to aid the user's efforts.

In some embodiments, the control unit30is configured to detect the position of the eye42even if a portion of the pupil of the eye42is obscured (for example, when a drooped eye lid obscures a portion of the pupil). For example, in some embodiments, the control unit30processes the eye image data to detect if a portion of a pupil of the eye42is obscured. If a portion of the pupil of the eye42is obscured, the control unit30can identify an unobscured portion of the pupil, and determine the position of the eye42relative to the optical axis40based on the unobscured portion of the pupil.

In some embodiments, the control unit30is configured to display the actual position of the eye42relative to the optical axis40. For example, the control unit30can be configured to cause the actual relative position of the pupil to be displayed at (X1, Y1) (seeFIG. 4).

FIG. 7is a simplified schematic block diagrams of acts of a method100of providing feedback to a user of an ophthalmic imaging system regarding alignment of an eye of the user with an optical axis of the ophthalmic imaging system, in accordance with some embodiments. Any suitable ophthalmic imaging system, such as the ophthalmic imaging system10described herein, can be employed in the practice of the method100. In the method100, a fixation target is displayed to a user on a display device (act102). Eye image data corresponding to an image of the eye viewing the fixation target is generated (act104). The eye image data is processed to determine a position of the eye relative to the optical axis (act106). A pseudo position of the eye relative to the optical axis is generated based on the position of the eye relative to the optical axis (act108). An indication is displayed on the display device to provide feedback to the user indicating that the eye is located at the pseudo position of the eye relative to the optical axis (act110).

FIG. 8is a simplified schematic block diagrams of additional acts that can be practiced in the method100, in accordance with some embodiments. In act112, if the position of the eye is within an acceptable distance from the optical axis, the pseudo position of the eye can be set to lie on the optical axis. In act114, the acceptable distance is determined based on a size of the pupil of the user's eye. In act116, the eye image data is processed to determine the size of the pupil of the user's eye. In act118, the position of the eye is based on a portion of the pupil excluding an obscured portion of the pupil. In act120, the pseudo position of the eye relative to the optical axis is repeatedly updated for each of a series of images of the eye. In act122, a series of images of the eye is processed to detect if the user fails to achieve and/or maintain acceptable positioning of the eye relative to the optical axis.

In some embodiments of the ophthalmic imaging system10, the acceptable distance is increased in response to user12achieving an initial acceptable alignment of the eye42with the optical axis40. For example,FIG. 9illustrates a pre-alignment acceptable alignment area56and a post-alignment acceptable area58relative to an imaging area60of the ophthalmic imaging system10. The acceptable distance is set equal to a pre-alignment acceptable distance (corresponding to the pre-alignment acceptable alignment area56) prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis40to being equal to or less than the pre-alignment acceptable distance from the optical axis40. The acceptable distance is then reset to a post-alignment acceptable distance (corresponding to the post-alignment acceptable alignment area58) in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis40to being equal to or less than the pre-alignment acceptable distance from the optical axis40. The post-alignment acceptable distance is greater than the pre-alignment acceptable distance. By allowing the user increased movement following achievement of the initial acceptable alignment of the user's eye42with the optical axis40, the user is presented with decreased repositioning commands, and thereby experiences a more stable imaging session. The diameters of the pre-alignment acceptable alignment area56and the post-alignment acceptable area58can be based on the size of the pupil62. For example, if the pupil62is relatively large, the diameters of the pre-alignment acceptable alignment area56and the post-alignment acceptable area58can be increased relative to those for smaller pupils so as to enable quicker alignment and improved experience for the user. Alternatively, the diameters of the pre-alignment acceptable alignment area56and the post-alignment acceptable area58can be based on size of the smallest pupil expected in a selected population of users.

In some embodiments of the ophthalmic imaging system10, the control unit is configured to guide the user12to position the user's pupil based on an unobscured portion of the pupil instead of the center of the pupil. By guiding the user to position the user's pupil based on the unobscured portion of the pupil, blocking of the OCT imaging beam by the user's eyelid can be reduced. For example,FIG. 10illustrates an acceptable alignment area64for a partially obscured pupil relative to the imaging area60of the ophthalmic imaging system10. The acceptable alignment area64is shaped to overlay an unobstructed portion of a partially obscured pupil relative to the imaging area60of the ophthalmic imaging system10. In many existing ophthalmic imaging systems, a pupil detection algorithm is employed that processes an image of the eye to identify the pupil by searching for a black circle or almost black circle feature in the image of the eye; the imaging beam is then aligned with the center of the pupil. The use of such an existing approach with an elderly user having a droopy eyelid, however, can result in a significant percentage of the light beam being blocked by the user's eyelid and the resulting OCT signal may be very weak or nonexistent. By shaping the acceptable alignment area64to overlay an unobstructed portion of a partially obscured pupil relative to the imaging area60, the user12is provided feedback to align the imaging area60with the unobstructed portion of the user's pupil, thereby avoiding blockage of the OCT imaging beam via the user's eyelid. As another example,FIG. 11illustrates that the pre-alignment acceptable alignment area56and the post-alignment acceptable alignment area58can be shaped to overlay an unobstructed portion of a partially obscured pupil.

Examples of the embodiments of the present disclosure can be described in view of the following clauses:

Clause 1. An ophthalmic imaging system, comprising an ophthalmic imaging device having an optical axis, a display device displaying a fixation target viewable by an eye of a user, an eye camera operable to image the eye to generate eye image data, and a control unit. The control unit processes the eye image data to determine a position of the eye relative to the optical axis. The control unit processes the position of the eye relative to the optical axis to generate a pseudo position of the eye relative to the optical axis. The pseudo position of the eye relative to the optical axis is different from the position of the eye relative to the optical axis. The control unit causes the display device to display an indication that provides feedback to the user that the eye is located at the pseudo position of the eye relative to the optical axis.

Clause 2. The ophthalmic imaging system of clause 1, comprising a view port that is coupled to the ophthalmic imaging device.

Clause 3. The ophthalmic imaging system of any preceding clause, wherein the indication displayed to the user comprises an eye pseudo position indicator displayed at a position relative to the fixation target matching the pseudo position of the eye relative to the optical axis.

Clause 4. The ophthalmic imaging system of any preceding clause, wherein, if a distance between the position of the eye and the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis is generated to lie on the optical axis.

Clause 5. The ophthalmic imaging system of clause 4, wherein the indication displayed to the user comprises an eye pseudo position indicator displayed aligned with the fixation target to provide feedback to the user indicating that the position of the eye is located on the optical axis.

Clause 6. The ophthalmic imaging system of clause 4, wherein the acceptable distance is based on a size of a pupil of the eye.

Clause 7. The ophthalmic imaging system of clause 6, wherein the control unit processes the eye image data to determine the size of the pupil of the eye.

Clause 8. The ophthalmic imaging system of clause 4, wherein the acceptable distance is equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, and the acceptable distance is set to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

Clause 9. The ophthalmic imaging system of clause 8, wherein the pre-alignment acceptable distance is based on a size of a pupil of the eye and/or the post-alignment acceptable distance is based on a size of a pupil of the eye.

Clause 10. The ophthalmic imaging system of clause 9, wherein the control unit processes the eye image data to determine the size of the pupil of the eye.

Clause 11. The ophthalmic imaging system of any preceding clause, wherein the control unit is configured to process the eye image data to detect if a portion of a pupil of the eye is obscured, identify an unobscured portion of the pupil, and determine the position of the eye relative to the optical axis based on the unobscured portion of the pupil.

Clause 12. The ophthalmic imaging system of clause 11, wherein if a distance between the position of the eye and to the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis is generated to lie on the optical axis.

Clause 13. The ophthalmic imaging system of clause 12, wherein the acceptable distance is equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, and the acceptable distance is set to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

Clause 14. The ophthalmic imaging system of clause 13, wherein the pre-alignment acceptable distance is based on a size of a pupil of the eye and/or the post-alignment acceptable distance is based on a size of a pupil of the eye.

Clause 15. The ophthalmic imaging system of clause 14, wherein the control unit processes the eye image data to determine the size of the pupil of the eye.

Clause 16. The ophthalmic imaging system of any preceding clause, wherein the eye camera captures a series of images of the eye, and the eye image data comprises image data for each of the series of images of the eyes. For each image of the series of images of the eye, the control unit processes the eye image data to determine a respective position of the eye relative to the optical axis, and processes the respective position of the eye relative to the optical axis to generate a respective pseudo position of the eye relative to the optical axis. The respective pseudo position of the eye relative to the optical axis being different from the respective position of the eye relative to the optical axis. For each image of the series of images, the control unit causes the display device to display a respective indication that provides feedback to the user that the eye is located at the respective pseudo position of the eye relative to the optical axis.

Clause 17. The ophthalmic imaging system of clause 16, wherein the control unit processes, for the series of images of the eye, a series of positions of the eye relative to the optical axis to detect if the user fails to achieve and/or maintain acceptable positioning of the eye relative to the optical axis. The control unit, in response to detecting failure of the user to achieve and/or maintain acceptable positioning of the eye relative to the optical axis, increases a size of the fixation target and/or the indication displayed to the user that provides the feedback to the user.

Clause 18. The ophthalmic imaging system of any preceding clause, wherein the control unit comprises a proportional controller, and generation of the pseudo position of the eye relative to the optical axis by the control unit comprises multiplying, by the proportional controller, the position of the eye relative to the optical axis by a gain factor not equal to 1.0.

Clause 19. The ophthalmic imaging system of clause 18, wherein, if a distance between the position of the eye and the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis is generated to lie on the optical axis.

Clause 20. The ophthalmic imaging system of clause 19, wherein the indication displayed to the user comprises an eye pseudo position indicator displayed aligned with the fixation target to provide feedback to the user indicating that the eye is located on the optical axis.

Clause 21. The ophthalmic imaging system of clause 19, wherein the acceptable distance is equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, and the acceptable distance is set to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

Clause 22. The ophthalmic imaging system of any preceding clause, wherein the ophthalmic imaging device comprises a spectral domain optical coherence tomography (OCT) imaging device that operates in a wavelength range of 800 nm to 900 nm, and the display device projects light in a wavelength range of 400 nm to 800 nm. The ophthalmic imaging system comprises an eye illuminator, a first dichroic mirror, and a second dichroic mirror. The eye illuminator illuminates the eye with light including a wavelength greater than 920 nm. The first dichroic mirror transmits light in a wavelength range of 400 nm to 900 nm and reflects light with a wavelength above 920 nm. The second dichroic mirror transmits light in a wavelength range between 400 nm to 800 nm and reflects light in a wavelength range between 800 nm and 900 nm.

Clause 23. The ophthalmic imaging system of any preceding clause, wherein the display device projects a beam in the plane of the pupil that extends beyond a 10 mm diameter circle.

Clause 24. A method of providing feedback to a user of an ophthalmic imaging system regarding alignment of an eye of the user with an optical axis of the ophthalmic imaging system. The method comprises displaying a fixation target on a display device viewable by the eye of the user; generating, by an eye camera, eye image data corresponding to an image of the eye viewing the fixation target; processing the eye image data, by a control unit, to determine a position of the eye relative to the optical axis; generating, by the control unit, a pseudo position of the eye relative to the optical axis based on the position of the eye relative to the optical axis, the pseudo position of the eye relative to the optical axis being different from the position of the eye relative to the optical axis; and causing, by the control unit, display of an indication on the display device to provide feedback to the user indicating that the eye is located at the pseudo position of the eye relative to the optical axis.

Clause 25. The method of clause 24, wherein display of the indication on the display device comprises display of an eye pseudo position indicator at a position relative to the fixation target matching the pseudo position of the eye relative to the optical axis.

Clause 26. The method of any of clause 24 and clause 25, further comprising processing the position of the eye relative to the optical axis to determine if a distance between the position of the eye and the optical axis is less than an acceptable distance, and wherein, if the distance between the position of the eye and the optical axis is less than the acceptable distance, the generation of the pseudo position of the eye relative to the optical axis comprises setting the pseudo position of the eye to lie on the optical axis.

Clause 27. The method of clause 26, wherein the display of the indication on the display device comprises displaying an eye pseudo position indicator aligned with the fixation target to provide feedback to the user that the eye is located on the optical axis.

Clause 28. The method of clause 27, further comprising determining the acceptable distance based on a size of a pupil of the eye.

Clause 29. The method of clause 28, further comprising processing the eye image data, by the control unit, to determine the size of the pupil of the eye.

Clause 30. The method of any of clause 26 through clause 29, wherein the acceptable distance is equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, and the acceptable distance is set to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

Clause 31. The method of clause 30, further comprising determining the pre-alignment acceptable distance and/or the post-alignment acceptable distance based on a size of a pupil of the eye.

Clause 32. The method of clause 31, further comprising processing the eye image data, by the control unit, to determine the size of the pupil of the eye.

Clause 33. The method of any of clause 24 through clause 32, further comprising processing the eye image data, by the controller, to detect if a portion of a pupil of the eye is obscured, identify an unobscured portion of the pupil, and determine the position of the eye relative to the optical axis based on the unobscured portion of the pupil.

Clause 34. The method of clause 33, wherein if a distance between the position of the eye and the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis is generated to lie on the optical axis.

Clause 35. The method of clause 34, wherein the acceptable distance is equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, and the acceptable distance is set to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

Clause 36. The method of clause 35, further comprising determining the pre-alignment acceptable distance and/or the post-alignment acceptable distance based on a size of a pupil of the eye.

Clause 37. The method of clause 36, further comprising processing the eye image data, by the control unit, to determine the size of the pupil of the eye.

Clause 38. The method of any of clause 24 through clause 37, comprising generating, by the eye camera, the eye image data so as to comprise image data for each of a series of images of the eyes. The method further comprising, for each image of the series of images of the eye, processing the eye image data, by the control unit, to determine a respective position of the eye relative to the optical axis; processing the respective position of the eye relative to the optical axis, by the control unit, to generate a respective pseudo position of the eye relative to the optical axis, the respective pseudo position of the eye relative to the optical axis being different from the respective position of the eye relative to the optical axis; and causing, by the control unit, the display device to display a respective indication that provides feedback to the user that the eye is located at the respective pseudo position of the eye relative to the optical axis.

Clause 39. The method of clause 38, comprising processing, by the control unit, for the series of images of the eye, a series of positions of the eye relative to the optical axis to detect if the user fails to achieve and/or maintain acceptable positioning of the eye relative to the optical axis; and in response to detecting, by the control unit, failure of the user to achieve and/or maintain acceptable positioning of the eye relative to the optical axis, increasing, by the control unit, a size of the fixation target and/or the indication displayed to the user that provides the feedback to the user.

Clause 40. The method of any of clause 24 through clause 39, wherein the generation of the pseudo position of the eye relative to the optical axis comprises multiplying the position of the eye relative to the optical axis by a factor not equal to 1.0.

Clause 41. The method of clause 40, wherein, if a distance of the eye relative to the optical axis is less than an acceptable distance, the pseudo position of the eye relative to the optical axis is generated to lie on the optical axis.

Clause 42. The method of clause 41, wherein the indication displayed to the user comprises an eye pseudo position indicator displayed aligned with the fixation target to provide feedback to the user that the eye is located on the optical axis.

Clause 43. The method of any of clause 41 and clause 42, wherein the acceptable distance is equal to a pre-alignment acceptable distance prior to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis; and the acceptable distance is set to a post-alignment acceptable distance in response to the position of the eye being repositioned from being greater than the pre-alignment acceptable distance from the optical axis to being equal to or less than the pre-alignment acceptable distance from the optical axis, the post-alignment acceptable distance being greater than the pre-alignment acceptable distance.

Clause 44. An ophthalmic imaging system, compromising an ophthalmic imaging device having an optical axis, a display device displaying a fixation target viewable by an eye of a user, an eye camera operable to image the eye to generate eye image data, and a control unit. The control unit processes the eye image data to determine a position of the eye relative to the optical axis, and causes the display device to display an indication that provides feedback to the user that the eye is located at the position of the eye relative to the optical axis.