Ophthalmologic imaging apparatus for stimulated eye

An ophthalmologic imaging apparatus includes: a first optical system that applies an accommodation stimulus to a subject's eye; a tomographic image forming unit that includes a second optical system that splits light from a light source into signal light and reference light, and detects interference light between the signal light having travelled via the subject's eye and the reference light, and creates a tomographic image of the subject's eye based on a detection result of the interference light; and an analyzer that compares a first tomographic image with a second tomographic image to acquire change information indicating a change in a tissue of the subject's eye due to an accommodation stimulus change. The first and second tomographic images are respectively created by the tomographic image forming unit for the subject's eye, to which first and second accommodation stimuli are respectively applied by the first and second optical systems.

The present application is a National Stage entry of PCT/JP2013/082646, filed on Dec. 4, 2013, which claims priority from Japanese Patent Application No. 2012-286377, filed Dec. 27, 2012, the contents of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to an ophthalmologic imaging apparatus.

BACKGROUND TECHNOLOGY

The ophthalmologic imaging apparatus is used to capture an image of a subject's eye. Examples of the ophthalmologic imaging apparatus include slit lamps, fundus cameras, scanning laser ophthalmoscopes (SLO), and the like.

In recent years, there has been proposed an apparatus that uses optical coherence tomography (OCT) for imaging the eye fundus and the anterior eye segment (see, for example, Patent Document 1). The OCT apparatus is advantageous in that it can acquire high-resolution images and also tomographic images. The tomographic images of the eye are subjected to various analysis processes to be used as diagnostic materials (see, for example, Patent Document 2).

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The accommodation function is extremely important in the vision. The accommodation function is a function to adjust the focus by changing the refractive power of the eye according to the distance to the object. The crystalline lens, zonule of Zinn and ciliary body contribute to the change in the refractive power of the eye. The crystalline lens is a convex lens with variable refractive power. The zonule of Zinn is a tissue that couples the lens with the ciliary body. The ciliary body is a muscle tissue. For near vision, the ciliary muscle contracts, the zonular fibers relax, and accordingly the lens becomes thicker, which increase the refractive power. On the other hand, for far vision, the ciliary muscle relaxes, then the zonular fibers are stretched, and the lens consequently becomes flatter, which reduce the refractive power.

With the conventional technologies, it has been difficult to determine, in terms of structure, whether the tissues involved in the accommodation function having such a mechanism are functioning properly. For example, it has been difficult to figure out whether the ciliary body, which is a muscle tissue, has a sufficient ability to contract and relax.

Besides, even when the ciliary body is functioning properly, if the flexibility of the lens declines due to a cataract or the like, or if an implanted intraocular lens is not located in a proper position, the focus cannot be suitably adjusted. In the conventional technologies, it has been difficult to specify whether such a problem of the accommodation function is caused by the ciliary body, the zonule of Zinn, or the lens or the intraocular lens. For example, with the conventional technologies, it is difficult to determine whether the accommodative dysfunction is caused by a decline in the function of the ciliary muscle due to aging or the like, the relaxation of the zonule of Zinn, or a decline in the shape-changing function (flexibility) of the lens.

An objective of the present invention is to provide a technology whereby the accommodation function of the eye can be suitably judged.

Means of Solving the Problems

An ophthalmologic imaging apparatus of an embodiment includes: a first optical system configured to apply an accommodation stimulus to a subject's eye; a tomographic image forming unit including a second optical system configured to split light from a light source into signal light and reference light, and detect interference light between the signal light having travelled via the subject's eye and the reference light, the tomographic image forming unit configured to create a tomographic image of the subject's eye based on a detection result of the interference light; and an analyzer configured to compare a first tomographic image with a second tomographic image to acquire change information indicating a change in a predetermined tissue of the subject's eye due to a change of the accommodation stimulus, wherein the tomographic image forming unit is configured to create the first tomographic image of the subject's eye to which a first accommodation stimulus is being applied by the first optical system, and the second tomographic image of the subject's eye to which a second accommodation stimulus is being applied.

MODES FOR CARRYING OUT THE INVENTION

Embodiments of ophthalmologic imaging apparatuses related to the present invention are explained in detail with reference to the accompanying drawings.

FIGS. 1 and 2illustrate an example of the appearance of an ophthalmologic imaging apparatus according to an embodiment. An ophthalmologic imaging apparatus2is placed on an optometry table1, the height of which is adjustable. A subject4is seated in an optometry chair3. The subject4faces toward the front2F of the ophthalmologic imaging apparatus2. The ophthalmologic imaging apparatus2includes a base5a, a drive mechanism5b, a pair of left and right bodies5L and5R, and a face holder6. The bodies5L and5R are supported by struts5pand5q, respectively.

The face holder6includes a pair of left and right struts6aand6b. The struts6aand6bsupport a forehead rest6c. The forehead rest6cis movable in the longitudinal direction. The face holder6further includes a jaw rest6d. The jaw rest6dis moved by a knob6ein the vertical direction.

The drive mechanism5bincludes an XYZ drive mechanism and a rotary drive mechanism. The XYZ drive mechanism drives the struts5pand5qin the horizontal direction (X direction), the vertical direction (Y direction), and the longitudinal direction (Z direction). The XYZ drive mechanism includes, for example, an actuator such as a pulse motor and a power transmission mechanism such as a feed screw. The rotary drive mechanism performs swing operation and tilt operation. The swing operation is intended to rotate the struts5pand5qabout their respective axes (i.e., in the horizontal direction). The tilt operation is intended to tilt the struts5pand5q. The rotary drive mechanism includes, for example, an actuator such as a pulse motor and a power transmission mechanism such as a gear. The drive mechanism5bthus configured moves the bodies5L and5R in the X, Y and Z directions and the rotation direction.

The base5ais provided with a lever6hfor operation input to the ophthalmologic imaging apparatus2. A button6gis arranged on the top of the lever6h. Although not illustrated, an operating unit may be arranged on the back side of the ophthalmologic imaging apparatus2.

On the base5a, a strut7bis erected to support a display7. Various types of information are displayed on a screen7aof the display7. The front surfaces of the left and right bodies5L and5R are respectively provided with displays7L and7R. The left and right displays7L and7R display, for example, the anterior eye image of the left eye and the right eye of the subject4, respectively. The displays7,7L and7R are flat panel displays such as liquid crystal displays. Although not illustrated, there may be a display provided on the back side of the ophthalmologic imaging apparatus2.

[Configuration of Optical System]

A description is given of an optical system provided on the left and right bodies5L and5R.FIG. 3is a top view illustrating an example of an optical system provided on the right body5R. The left body5L is provided with an optical system that is symmetrical to the optical system of the right body5R. Reference sign ER represents the right eye of the subject4(subject's right eye).

The body5R is provided with an imaging optical system10, a measurement optical system30, a visual target projection optical system50, an interference optical system60, and a fixation optical system80. In the example ofFIG. 3, the optical axis of the imaging optical system10, the measurement optical system30and the visual target projection optical system50is oriented in a different direction from the direction of the optical axis of the interference optical system60and the fixation optical system80. The angle formed by these optical axes is represented by θ. The angle θ may be variable or fixed.

The imaging optical system10is used to photograph the anterior segment of the subject's right eye ER. The imaging optical system10includes a prism P, anterior eye illumination light sources11, an objective lens12, relay lenses13and14, an imaging lens15, and an image pickup device16.

The anterior eye illumination light sources11are arranged in a periphery of the optical axis of the imaging optical system10, and output light for illuminating the anterior eye segment. The light output from the anterior eye illumination light sources11is irradiated to the subject's right eye ER via the prism P, and then is reflected by the anterior eye segment. The reflected light passes through the prism P, the objective lens12, the relay lens13, and the imaging lens15, and is detected by the image pickup device16. Note that the light reflected by the anterior eye segment is transmitted through beam splitters38,24and43(described later) and guided to the image pickup device16. An anterior eye image obtained by the image pickup device16is, for example, displayed on the display7L.

The beam splitter24is obliquely arranged between the objective lens12and the relay lens13. Light output from an alignment light source21passes through an alignment target aperture22and a lens23, then is reflected by the beam splitter24, and is projected onto the anterior segment of the subject's right eye ER via the objective lens12and the prism P. As in the conventional manner, based on an alignment target image depicted in the anterior eye image, the alignment of the imaging optical system10is performed for the subject's right eye ER.

The measurement optical system30optically measures an optical property of the subject's right eye ER. The measurement optical system30of this embodiment measures the refractive power of the subject's right eye ER. The measurement optical system30includes a measurement light source31, a collimating lens32, a ring transparent plate33, a relay lens34, a ring-shaped diaphragm35, a perforated prism36, beam splitters37and38, the objective lens12, the prism P, a reflective mirror39, a relay lens40, a movable lens41, a reflective mirror42, the beam splitter43, the imaging lens15, and the image pickup device16.

Light output from the measurement light source31is collimated by the collimating lens32, and becomes a light flux having a ring-shaped cross-section as passing through the ring transparent plate33. The light travels through the relay lens34and the ring-shaped diaphragm35, and is reflected by the perforated prism36, then by the beam splitter37, and by the beam splitter38to be irradiated to the subject's right eye ER via the objective lens12and the prism P.

The measurement light flux having a ring-shaped cross-section irradiated onto the subject's right eye ER is reflected by the fundus, and is output from the subject's right eye ER. At this time, the cross-sectional shape of the measurement light flux is deformed due to the influence of the eye optical system (cornea, lens, etc.).

The measurement light flux output from the subject's right eye ER travels through the prism P, the objective lens12, the beam splitters37and38, passes through a transparent plate36aof the perforated prism36, and is reflected by the reflective mirror39. The light flux then passes through the relay lens40and the movable lens41, and is reflected by the reflective mirror42and the beam splitter43to be detected by the image pickup device16via the imaging lens15. By analyzing the size and shape of the cross section of the detected measurement light flux, the spherical degree, astigmatic degree, astigmatic axis, etc. of the subject's right eye ER are obtained. This process is performed in the conventional manner. In short, the ophthalmologic imaging apparatus2functions as a refractometer.

The visual target projection optical system50presents a variety of visual targets to the subject's right eye ER. The visual target projection optical system50includes a target light source51, a target plate52, relay lenses53and54, a reflective mirror55, the beam splitter38, the objective lens12, and the prism P. The target plate52includes, for example, a turret plate or a transmissive liquid crystal display, and is configured to be capable of selectively positioning various visual targets, such as a fixation target and optotypes, with respect to the optical path. Light output from the target light source51passes through the above components of the visual target projection optical system50, and is projected onto the fundus of the subject's right eye ER.

The target light source51and the target plate52are configured to be movable in the optical axis direction of the visual target projection optical system50. This allows a change of the viewing distance of the subject's right eye ER to the visual target. That is, the visual target projection optical system50can be used to provide an accommodation stimulus to the subject's right eye ER.

The interference optical system60is used for optical coherence tomography (OCT) measurement of the subject's right eye ER. The interference optical system60includes a light source unit61, an optical fiber62, a fiber coupler63, an optical fiber64, a collimating lens65, a galvanometer scanner66, a beam splitter67, a focusing lens68, a relay lens69, a condenser lens70, the prism P, an optical fiber71, a collimating lens72, a beam splitter73, a lens74, a first reference mirror75, a lens76, a second reference mirror77, an optical fiber78, and a detector79.

Any type of OCT measurement may be used in this embodiment. If swept-source OCT is employed, a wavelength-swept light source capable of modulating output wavelength at a high speed is used as the light source unit61, and an optical detector such as a balanced photo detector is used as the detector79. If spectral domain OCT is employed, a broadband light source (low-coherence light source) is used as the light source unit61, and a spectroscope for detecting spectra is used as the detector79.

The galvanometer scanner66includes, for example, two reflective mirrors and actuators for changing the orientations of the respective reflective mirrors. The galvanometer scanner66scans the subject's right eye ER with light (signal light) passing therethrough.

The condenser lens70is removably arranged on the optical path of the interference optical system60. For example, the condenser lens70is arranged on the optical path when an image of the subject's right eye ER is to be captured, while it is retracted from the optical path when the intraocular distance (axial length etc.) is to be measured.

The first reference mirror75is arranged in a position conjugate to a first site of the subject's right eye ER. The first site is a site to be subjected to OCT measurement and may be, for example, the cornea, the ciliary body, the crystalline lens, or the like. The first reference mirror75and the lens74are integrally movable in the optical axis direction.

The second reference mirror77is arranged in a position conjugate to a second site of the subject's right eye ER. The second site is a site to be subjected to OCT measurement and may be, for example, the retina, the choroid, or the like. The second reference mirror77and the lens76are integrally movable in the optical axis direction.

Light output from the light source unit61is guided to the fiber coupler63through the optical fiber62. The fiber coupler63divides the light into two parts.

Light (signal light) guided by the fiber coupler63to the optical fiber64is collimated by the collimating lens65, and directed to a different direction by the galvanometer scanner66. The light is then reflected by the beam splitter67, and passes through the focusing lens68, the relay lens69, (the condenser lens70), and the prism P to be irradiated to the subject's right eye ER. The backscattered light of the signal light from the subject's right eye ER is guided through the same path in the opposite direction, and returns to the fiber coupler63.

Light (reference light) guided by the fiber coupler63to the optical fiber71is collimated by the collimating lens72and guided to the beam splitter73. Component transmitted through the beam splitter73(first reference light) is condensed by the lens74, reflected by the first reference mirror75, collimated by the lens74, and returns to the beam splitter73. Meanwhile, component reflected by the beam splitter73(second reference light) is condensed by the lens76, reflected by the second reference mirror77, collimated by the lens76, and returns to the beam splitter73. The first reference light and the second reference light (collectively referred to as “reference light”) combined by the beam splitter73return to the fiber coupler63via the collimating lens72and the optical fiber71. The optical path of the reference light is referred to as “reference optical path”.

The fiber coupler63makes the signal light having travelled via the subject's right eye ER interfere with the reference light having travelled through the reference optical path. The interference light includes information on the site (the ciliary body etc.) of the subject's right eye ER conjugate to the first reference mirror75and information on the site (the retina etc.) of the subject's right eye ER conjugate to the second reference mirror77. The interference light is led to the detector79through the optical fiber78. In the case of swept-source OCT, the detector79detects the intensity of the interference light. In the case of spectral domain OCT, the detector79detects distribution of spectra of the interference light.

Although not illustrated, the interference optical system60is provided with an attenuator and a polarization controller. The attenuator is located, for example, on the optical fiber71to adjust the amount of the reference light guided to the optical fiber71. The polarization controller applies a stress to, for example, the looped optical fiber71from the outside to adjust the polarization state of the reference light guided to the optical fiber71. In addition to them, the interference optical system60may be provided with various types of known devices applicable to OCT measurement.

The fixation optical system80presents a fixation target to the subject's right eye ER. The fixation optical system80includes a fixation light source81, a beam splitter82, a collimating lens83, the focusing lens68, the relay lens69, and the prism P. Light output from the fixation light source81is reflected by the beam splitter82, and collimated by the collimating lens83. The light is transmitted through the beam splitter67, and travels through the focusing lens68, the relay lens69, and the prism P to be projected onto the fundus of the subject's right eye ER.

Behind the beam splitter82of the fixation optical system80is arranged an imaging device90. The imaging device90is used to capture an image of the anterior segment of the subject's right eye ER. Since the optical axis of the imaging optical system10and that of the interference optical system60are oriented in different directions, the imaging optical system10and the imaging device90photograph the anterior segment of the subject's right eye ER from different directions.

[Configuration of Control System]

FIGS. 4 and 5illustrate an example of the configuration of the control system of the ophthalmologic imaging apparatus2.

The control system of the ophthalmologic imaging apparatus2is configured centering on the controller100. The controller100includes, for example, a processor, a storage device, a communication interface, and the like. The storage device stores computer programs and data for control/calculation operation. The controller100includes a main controller110and a storage120.

The main controller110controls each unit of the ophthalmologic imaging apparatus2. For example, the main controller110controls the operation of the anterior eye illumination light sources11, the image pickup device16, the alignment light source21, the measurement light source31, the target light source51, the light source unit61, the galvanometer scanner66, the detector79, the fixation light source81, and the imaging device90illustrated inFIG. 3. Although not illustrated, the main controller110controls the attenuator and the polarization controller.

The main controller110controls the movement of the optical element. For example, the main controller110controls a measurement driver30A to move the measurement light source31, the collimating lens32, and the ring transparent plate33in the optical axis direction. The measurement driver30A includes an actuator such as a pulse motor and a power transmission mechanism. The main controller110controls a lens driver41A to move the movable lens41in the optical axis direction. The lens driver41A includes an actuator such as a pulse motor and a power transmission mechanism. The main controller110controls a visual target driver50A to move the target light source51and the target plate52in the optical axis direction. The visual target driver50A includes an actuator such as a pulse motor and a power transmission mechanism. The main controller110controls a focusing driver68A to move the focusing lens68in the optical axis direction. The focusing driver68A includes an actuator such as a pulse motor and a power transmission mechanism. The main controller110controls a placement/removal driver70A to place/remove the condenser lens70with respect to the optical path. The placement/removal driver70A includes an actuator such as a solenoid and a power transmission mechanism. The main controller110controls a reference driver70B to move the lens74and the first reference mirror75in the optical axis direction. Similarly, the main controller110controls a reference driver70C to move the lens76and the second reference mirror77in the optical axis direction. Each of the reference drivers70B and70C includes an actuator such as a pulse motor and a power transmission mechanism.

The main controller110controls the movement of the optical system. For example, the main controller110controls an XYZ drive mechanism130A provided in the drive mechanism5bto move the bodies5L and5R in three dimensions. The XYZ drive mechanism130A includes an actuator such as a pulse motor and a power transmission mechanism. The main controller110controls a rotary drive mechanism130B to rotationally move the bodies5L and5R around the struts5pand5q, respectively. The main controller110controls the rotary drive mechanism130B to tilt the struts5pand5q, thereby tilting the bodies5L and5R. The rotary drive mechanism130B includes an actuator such as a pulse motor and a power transmission mechanism. The main controller110controls an optical axis deflection mechanism130C to relatively change the direction of the optical axis (first optical axis) of the imaging optical system10, the measurement optical system30, and the visual target projection optical system50, and the direction of the optical axis (second optical axis) of the interference optical system60and the fixation optical system80. The optical axis deflection mechanism130C changes either or both the direction of the first optical axis and that of the second optical axis. This changes the angle θ illustrated inFIG. 3. The optical axis deflection mechanism130C includes an actuator such as a pulse motor and a power transmission mechanism.

The main controller110performs writing of data to the storage120as well as reading of data from the storage120.

The storage120stores various types of data. Examples of the data stored in the storage120include image data of an anterior eye image, image data of an OCT image, measurement data of a subject's eye, and subject's eye information. The subject's eye information includes information about a subject such as patient ID and name, and information about the subject's eye such as identification information of the left eye/right eye.

Having detected interference light in OCT measurement, the detector79outputs a signal. This signal is fed to the image forming unit150. The image forming unit150creates image data of a two-dimensional tomogram of the subject's right eye ER based on the signal from the detector79. As in the conventional manner, this image forming process includes noise removal (noise reduction), filtering, fast Fourier transform (FFT), and the like. The image forming unit150includes, for example, a hardware circuit and/or a processor to execute software for image formation. Incidentally, in this specification, “image data” and “image” may sometimes be identified with each other.

The data processor160performs various types of data processing. For example, the data processor160applies various types of image processing and analysis processing to an OCT image and an anterior eye image. Examples of the processing include luminance correction and dispersion correction. The data processor160creates a three-dimensional image based on the two-dimensional tomogram formed by the image forming unit150. The data processor160includes a processor to execute software for data processing. The data processor160is an example of “analyzer”.

The data processor160includes an image area specifying unit161, a change information acquisition unit162, an optical property information acquisition unit163, an intraocular distance calculator164, and an anterior eye change information acquisition unit165.

The ophthalmologic imaging apparatus2applies an accommodation stimulus to the subject's eye. The accommodation stimulus refers to visual information provided to the subject's eye to exert arbitrary accommodation force. The ophthalmologic imaging apparatus2applies an accommodation stimulus by the visual target projection optical system50. More specifically, the ophthalmologic imaging apparatus2moves the target light source51and the target plate52by the visual target driver50A to guide the focus of the subject's eye to a predetermined position.

In this embodiment, an examination is performed as follows. First, OCT measurement is performed while a first accommodation stimulus is being applied to the subject's eye to acquire a first tomographic image of the eye. Then, OCT measurement is performed while a second accommodation stimulus different from the first one is being applied to acquire a second tomographic image of the eye. The first accommodation stimulus and the second accommodation stimulus correspond to different focal positions. For example, the first accommodation stimulus corresponds to a far focal position, while the second accommodation stimulus corresponds to a near focal position. The data processor160performs the following processing to obtain a change in the predetermined tissue of the subject's eye caused by a change of the accommodation stimulus. The information indicating such a change is referred to as “change information”. The predetermined tissue where a change is to be detected may be, for example, tissue related to the accommodation function such as the ciliary body, the crystalline lens, and the zonule of Zinn.

The image area specifying unit161analyzes the first tomographic image to specify an image area corresponding to the predetermined tissue. The image area specifying unit161also analyzes the second tomographic image to specify an image area corresponding to the predetermined tissue. When such processing is performed automatically, the image area specifying unit161distinguishes an image area of the predetermined tissue from other image areas based on the pixel values (luminance values) of the first tomographic image. The processing includes, for example, threshold processing, pattern matching, and the like.

Part of the processing may be performed manually. In this case, the main controller110displays a tomographic image on a display unit181. The user observes the tomographic image displayed and figures out an image area corresponding to the predetermined tissue, thereby designating the image area through an operation unit182. The image area may be specified by, for example, inputting a plurality of points on the contour of the image area corresponding to the predetermined tissue using a pointing device such as a mouse. The image area specifying unit161finds a closed curve that connects the points input. This closed curve is, for example, a spline curve or a Bezier curve. An area surrounded by the closed curve is the image area of interest. For another example, the contour may be input by using a pointing device.

The change information acquisition unit162compares the image area (first image area) specified in the first tomographic image with the image area (second image area) specified in the second tomographic image, and thereby obtains change information indicating a change in the morphology of the predetermined tissue.

A change in shape may be cited as an example of morphological change of a predetermined tissue. In this case, the change information acquisition unit162calculates a predetermined evaluation value based on each of the first image area and the second image area, and compares the evaluation values to obtain the change information. Specifically, for example, the change information acquisition unit162calculates evaluation values such as thickness, size (area, volume, etc.), perimeter, and the like of the predetermined tissue based on the contour of each of the first image area and the second image area. Then, the change information acquisition unit162obtains a value (the difference, ratio, etc.) indicating the difference between the evaluation value of the first image area and that of the second image area to use it as the change information. Further, a change of the evaluation value per unit accommodation amount may be obtained by dividing the value indicating the difference by the amount of a change in the accommodation stimulus (i.e., expected accommodation amount). Besides, a statistical value such as an average value and variation may be obtained by performing the above examination a plurality of times. This is effective for evaluating the ciliary body and the crystalline lens. If the zonule of Zinn formed of a fibrous tissue is the predetermined tissue, for example, a wire model of an image area corresponding to the zonule of Zinn may be obtained to compare the shape. Alternatively, two (or more) feature points of the predetermined tissue may be detected to obtain a change in the shape based on the distance(s) between the feature points.

As another example of the morphological change of the predetermined tissue may be cited a change in the density of tissue that constitutes the predetermined tissue. This example is applicable to, for example, the ciliary body. The ciliary body is muscle tissue consisting of a number of muscle fibers. The change information acquisition unit162analyzes each of the first image area and the second image area to specify a number of partial areas corresponding to the muscle fibers. Then, the change information acquisition unit162acquires the number of partial areas existing in an area of a predetermined area in the first image area, and the number of partial areas existing in the area in the second image area. This process is performed by labeling, for example. Further, the change information acquisition unit162obtains a value indicating the difference (variance, ratio, etc.) between these numbers to use it as change information. The change information indicates a change in the density of the muscle fibers due to the contraction or relaxation of the muscle tissue. Note that, by dividing the value representing the difference between the above numbers by the amount of a change in the accommodation stimulus (i.e., expected accommodation amount), expected density change per unit accommodation amount may be obtained. Besides, a statistical value such as an average value and variation of the density variation may be obtained by performing the above examination a plurality of times.

(Optical Property Information Acquisition Unit163)

The optical property information acquisition unit163analyzes the optical property of the subject's eye obtained by the measurement optical system30. The measurement optical system30measures the subject's eye to which the first accommodation stimulus is being applied to acquire a first measurement value, and also measures the subject's eye to which the second accommodation stimulus is being applied to acquire a second measurement value. These measurements are performed in parallel with or at a different time from the OCT measurement. The optical property information acquisition unit163acquires information indicating a change in the optical property of the subject's eye caused by a change of the accommodation stimulus based on the first measurement value and the second measurement value acquired. The information is referred to as “optical property information”.

In this embodiment, the measurement optical system30functions as a refractometer for measuring the refractive power of the subject's eye. The optical property information acquisition unit163obtains the optical property information that indicates a change in the accommodation amount for the subject's eye due to a change of the accommodation stimulus based on the first measurement value and the second measurement of the refractive power of the subject's eye. This process is performed to calculate the difference between the first measurement value and the second measurement value. Note that the actual accommodation amount per expected unit accommodation amount may be obtained by dividing the difference between the two measurement values by the amount of a change in the accommodation stimulus (i.e., expected accommodation amount). Besides, a statistical value such as an average value and variation may be obtained by performing the above examination a plurality of times.

While this embodiment describes the measurement of the refractive power of the subject's eye, other optical properties of the subject's eye may be measured. For example, the aberrations of the subject's eye may be measured. As an example of the technology for the aberration measurement may be cited a wavefront sensor as described in JP 2001-275972 of the present applicant. The wavefront sensor irradiates the fundus of the subject's eye with a light flux from a point light source, and analyzes the distribution of a plurality of point images obtained by detecting the reflected light by an area sensor through a Hartmann plate to determine the aberrations of various orders. With such a wavefront sensor, as well as the spherical degree and astigmatic degree, higher order aberrations can be measured. The optical property information acquisition unit163acquires the optical property information indicating a change in the aberrations of the subject's eye due to a change of the accommodation stimulus with respect to the aberration of each order based on the first measurement value and the second measurement value.

The intraocular distance calculator164calculates the distance between arbitrary sites of the subject's eye based on information acquired by OCT measurement. Such distance is referred to as “intraocular distance”. Although the intraocular distance may be calculated by any method, this embodiment describes the following two methods.

The first intraocular distance calculation method is based on the optical path length difference between the first reference light and the second reference light. Here, the first reference light is reference light travelling via the first reference mirror75, while the second reference light is reference light travelling via the second reference mirror77. As described above, the first reference mirror75is moved by the reference driver70B together with the lens74in the optical axis direction, and the second reference mirror77is moved by the reference driver70C together with the lens76in the optical axis direction. Thereby, the optical path length of the first reference light and that of the second reference light are changed individually.

Since the reference drivers70B and70C operate under the control of the main controller110, the main controller110can recognize the amount of a change in the optical path length made by each of the reference drivers70B and70C. For example, if the reference drivers70B and70C each includes a pulse motor as the actuator, the main controller110can calculate the amount a change in the optical path length based on the operation amount of the pulse motor per one pulse (i.e., unit moving distance of the reference mirror by the pulse motor) and the number of pulses transmitted to the pulse motor. Besides, the main controller110can find the positions of the first reference mirror75and the second reference mirror77, that is, the optical path length of the first reference light and that of the second reference light, based on the control histories (pulse transmission histories) relative to the reference drivers70B and70C.

The reference drivers70B and70C are an example of “optical path length changing unit”. Note that although the optical path length of the reference light is changed in this embodiment, the optical path length of the signal light may be changed. The optical path length of the signal light can be changed by using, for example, a movable corner cube. In addition, both the optical path length of the reference light and that of the signal light may be changed.

In this method, a tomographic image of the first site of the subject's eye and a tomographic image of the second site are acquired by OCT measurement. The two OCT measurements are performed in parallel or at different times. In this embodiment, by virtue of the two reference mirrors75and77, the OCT measurements of different sites of the subject's eye can be performed in parallel. Incidentally, if there are three or more reference mirrors and an optical system which splits the optical path of the reference light according to the number of the reference mirrors, the OCT measurements of three or more sites can be performed simultaneously.

The OCT measurement of the first site is performed so that the backscattered light of the signal light from the first site and the first reference light interfere effectively with each other. In other words, the OCT measurement of the first site is performed such that the optical path length between the fiber coupler63and the first site (the optical path length of the signal light) and the optical path length between the fiber coupler63and the first reference mirror75(the optical path length of the first reference light) match each other. That is, in the OCT measurement of the first site, the first reference mirror75is located in a position substantially conjugate to the first site.

Similarly, the OCT measurement of the second site is performed so that the backscattered light of the signal light from the second site and the second reference light interfere effectively with each other. In other words, the OCT measurement of the second site is performed such that the optical path length between the fiber coupler63and the second site (the optical path length of the signal light) and the optical path length between the fiber coupler63and the second reference mirror77(the optical path length of the second reference light) match each other. That is, in the OCT measurement of the second site, the second reference mirror77is located in a position substantially conjugate to the second site.

The intraocular distance calculator164calculates the distance between the first site and the second site based on the optical path lengths of the first reference light when the tomographic image of the first site is acquired, and the optical path length of the second reference light when the tomographic image of the second site is acquired. This process is accomplished by calculating the difference between the optical path length of the first reference light and that of the second reference light.

One example of this method is capable of obtaining the axial length of the subject's eye. In this case, the first site is set to the anterior surface of the cornea, and the second site is set to the surface of the fundus. That is, the first reference mirror75is located in a position conjugate to the anterior surface of the cornea, and the second reference mirror77is located in a position conjugate to the surface of the fundus. In this example, a cornea tomographic image depicting the cornea and a fundus tomographic image depicting the fundus are obtained. The intraocular distance calculator164calculates the axial length of the subject's eye based on the position of the first reference mirror75in the OCT measurement for acquiring the cornea tomographic image (i.e., the optical path length of the first reference light), and the position of the second reference mirror77in the OCT measurement for acquiring the fundus tomographic image (i.e., the optical path length of the second reference light). Thus, this method can measure a relatively long intraocular distance.

Another example of this method is capable of obtaining the anterior chamber depth. In this case, the first site is set to the posterior surface of the cornea, and the second site is set to the anterior surface of the crystalline lens. That is, the first reference mirror75is located in a position conjugate to the posterior surface of the cornea, and the second reference mirror77is located in a position conjugate to the anterior surface of the lens. In this example, a cornea tomographic image depicting the cornea and a lens tomographic image depicting the lens are obtained. The intraocular distance calculator164calculates the anterior chamber depth based on the position of the first reference mirror75in the OCT measurement for acquiring the cornea tomographic image (i.e., the optical path length of the first reference light), and the position of the second reference mirror77in the OCT measurement for acquiring the lens tomographic image (i.e., the optical path length of the second reference light).

The second intraocular distance calculation method is intended to find the intraocular distance by analyzing a single tomographic image. In this analysis, first, an image area corresponding to the first site depicted in the tomographic image, and an image area corresponding to the second site are specified. As with the image area specifying unit161, this process is performed automatically or in part manually. The intraocular distance calculator164calculates the distance between the specified two image areas. This process is performed based on a scale which is set in advance for the tomographic image. Besides, this process may include a process of counting the number of pixels existing between the two image areas.

One example of this method is capable of obtaining the anterior chamber depth. In this example, either one of the first reference mirror75or the second reference mirror77is used for OCT measurement (here, it is assumed that the first reference mirror75is used). The first reference mirror75is located in a position which is conjugated with an arbitrary position of the anterior segment. For example, the first reference mirror75is located at a position conjugated with a position between the posterior surface of the cornea and the anterior surface of the lens. The intraocular distance calculator164calculates the depth of the anterior chamber of the subject's eye by calculating the distance between the image area corresponding to the posterior surface of the cornea and the image area corresponding to the anterior surface of the lens.

(Anterior Eye Change Information Acquisition Unit165)

The iris is an example of the predetermined tissue of the anterior eye segment to be analyzed. First, the anterior eye change information acquisition unit165specifies an image area corresponding to the predetermined tissue depicted in the first anterior eye image, and an image area corresponding to the predetermined tissue depicted in the second anterior eye image. As with the image area specifying unit161, this process is performed automatically or in part manually. Further, the anterior eye change information acquisition unit165compares the two image areas specified to obtain morphological changes (changes in pupil diameter, iris pattern, etc.) between the two image areas. Besides, based on a change of the elliptical shape of the pupil (ellipticity, orientation, etc.), a change in the direction of the visual line of the subject's eye (change in the eye axis direction) can be found.

The user interface180is a man-machine interface used to provide information to the examiner and/or the subject, and is also used for operation and information input by the examiner and/or the subject. The user interface180includes the display unit181and the operation unit182.

The display unit181includes the displays7,7L and7R, and the display arranged on the back side of the ophthalmologic imaging apparatus2mentioned above. If a computer is connected to the ophthalmologic imaging apparatus2, the display unit181may include a display of the computer. The display unit181displays information under the control of the main controller110.

The operation unit182is used for information input and the operation of the ophthalmologic imaging apparatus2. The operation unit182includes the lever6hand the button6gmentioned above, and the operation unit on the back side of the ophthalmologic imaging apparatus2. If a computer is connected to the ophthalmologic imaging apparatus2, the operation unit182may include manipulation or input devices of the computer. The main controller110performs control in response to a signal from the operation unit182.

The display unit181and the operation unit182need not be configured as individual devices. For example, like a touch panel, a device with integrated functions of display and operation may be employed.

A description is given of an example of the operation of the ophthalmologic imaging apparatus2.FIG. 6illustrates an example of the operation of the ophthalmologic imaging apparatus2. Here, an example is described in which the subject's right eye ER is examined.

First, an alignment of the optical system is performed with respect to the subject's right eye ER. Specifically, first, the main controller110turns on the anterior eye illumination light sources11and the alignment light source21, and starts the operation of the image pickup device16. Thus, an anterior eye image of the subject's right eye ER where an alignment target image is projected is obtained. The main controller110displays the anterior eye image on the display unit181. The user adjusts the position of the optical system with reference to the position of the alignment target image reflected in the anterior eye image as in the conventional manner to align it with the subject's right eye ER. Incidentally, if the main controller110adjusts the position of the optical system by analyzing the position of the alignment target image, the alignment can be made automatically.

When an accommodation stimulus is applied also to the subject's left eye, the alignment of the optical system for the subject's left eye is performed in the same manner.

FIG. 7illustrates an example of a state where the alignment is completed. Reference sign O1represents the optical axis (the first optical axis) of the imaging optical system10, the measurement optical system30, and the visual target projection optical system50. Reference sign O2represents the optical axis (the second of the optical axis) of the interference optical system60and the fixation optical system80. The main controller110controls the XYZ drive mechanism130A and the rotary drive mechanism130B based on the anterior eye image acquired by the imaging optical system10to match the first optical axis O1with the axis of the subject's right eye ER to accomplish the alignment of the right body5R.

As illustrated inFIG. 3, the second optical axis O2is at an angle θ with respect to the first optical axis O1. The alignment of the second optical axis O2may be performed in a state where the position of the first optical axis O1is fixed. To perform this alignment, for example, the main controller110controls the optical axis deflection mechanism130C based on live OCT images obtained through repetitive OCT measurements and/or the anterior eye image captured by the imaging device90.

When an accommodation stimulus is applied also to the subject's left eye EL, the main controller110performs the alignment of the first optical axis O1of the left body5L in the same manner as in the case of the right body5R. When the OCT measurement of the subject's left eye EL is also conducted, the alignment of the second optical axis (not illustrated) of the left body5L is performed in the same manner as in the case of the right body5R.

The main controller110displays the anterior eye image thus obtained on the display unit181.FIG. 8illustrates an example of the display of the anterior eye image when the alignment is completed. The main controller110displays an anterior eye image G1acquired by the imaging optical system10, and an anterior eye image G2acquired by the imaging device90as moving imaged on the display unit181. Since the first optical axis O1is substantially aligned with the axis of the subject's right eye ER, the anterior eye image G1is an image obtained by photographing the subject's right eye ER from the front. On the other hand, since the second optical axis O2is inclined by an angle θ with respect to the first optical axis O1, the anterior eye image G2is an image obtained by photographing the subject's right eye ER at a diagonal angle.

FIG. 9illustrates an example of the positional relationship between the first optical axis O1and the second optical axis O2after the alignment is completed.FIG. 9is a cross-sectional view of the subject's right eye ER. Reference sign E1represents the cornea. Reference sign E2represents the iris. Reference sign E3represents the crystalline lens. Reference sign E4represents the ciliary body. Reference sign E5represents the zonule of Zinn. The first optical axis O1is arranged in a location passing through the vertex of the cornea E1, passing through the hole surrounded by the iris E2(that is, the pupil), and passing through the vertex of the lens E3. The second optical axis O2that is inclined by an angle θ with respect to the first optical axis O1is arranged in a position passing through the ciliary body.

(S2: Application of the First Accommodation Stimulus)

When the alignment is completed, the main controller110applies the first accommodation stimulus to the subject's right eye ER (and the subject's left eye). Specifically, the main controller110turns on the target light source51, and also controls the visual target driver50A to place the target light source51and the target plate52each at a position corresponding to the first accommodation stimulus. The positions of the target light source51and the like corresponding to the first accommodation stimulus are set in advance.

(S3: OCT Measurement, Optical Property Measurement, Photographing of the Anterior Segment of the Subject's Eye)

While the first accommodation stimulus is being applied to the subject's right eye ER (and the subject's left eye), the main controller110performs OCT measurement, optical property measurement, and photographing of the anterior eye segment. Note that all or two of the three operations may be performed in parallel, or they may be performed at different times. In this stage, the condenser lens70is arranged on the optical path of the interference optical system60.

Described below is the OCT measurement. First, the main controller110controls the reference driver70B to arrange the first reference mirror75and the lens74each in a position corresponding to the ciliary body E4. This process is performed with reference to, for example, live OCT images obtained through repetitive OCT measurements. Upon completion of the positioning of the first reference mirror75, the main controller110controls the light source unit61and the galvanometer scanner66to perform the OCT measurement in an area of the subject's right eye ER containing the ciliary body. The detector79detects the interference light between the signal light that has travelled via the subject's right eye ER and the reference light that has travelled via the first reference mirror75. The image forming unit150creates a tomographic image based on a signal output from the detector79. The tomographic image illustrates the morphology of the ciliary body E4in a state where the first accommodation stimulus is being applied. The main controller110stores the acquired tomographic image in the storage120. This tomographic image is used as the first tomographic image.

Described below is the optical property measurement. First, the main controller110turns on the measurement light source31. A measurement light flux output from the measurement light source31is reflected by the fundus of the subject's right eye ER and detected by the image pickup device16. The main controller110sends a signal output from the image pickup device16to the optical property information acquisition unit163. This signal includes information indicating the size and shape of the cross section of the measurement light flux detected by the image pickup device16. The optical property information acquisition unit163analyzes the signal, and thereby calculates the spherical degree, astigmatic degree, and the astigmatic axis of the subject's right eye ER. The main controller110stores the measurement values of the optical properties calculated in the storage120. Such a measurement value indicates the optical property value of the subject's right eye ER to which the first accommodation stimulus is being applied, and is used as the first measurement value.

Described below is photographing of the anterior eye segment. If the anterior eye illumination light sources11are continuously on from step1, the image pickup device16feeds signals to the controller100at predetermined time intervals (frame rate). The main controller110stores image data based on a signal input at a predetermined timing (any time while the first accommodation stimulus is being applied) in the storage120. This image data represents the morphology of the anterior segment of the subject's right eye ER to which the first accommodation stimulus is being applied, and is used as the image data of the first anterior eye image.

If the anterior eye illumination light sources11are not lit at least at a point immediately before the photographing of the anterior eye segment, the main controller110turns on the anterior eye illumination light sources11to photograph the anterior eye segment, and stores image data of the first anterior eye image thus obtained in the storage120.

(S4: Application of the Second Accommodation Stimulus)

Upon completion of the OCT measurement, the optical property measurement, and the photographing of the anterior eye segment, the main controller110applies the second accommodation stimulus to the subject's right eye ER (and the subject's left eye). Specifically, the main controller110controls the visual target driver50A to move the target light source51and the target plate52each arranged at a position corresponding to the first accommodation stimulus to a position corresponding to the second accommodation stimulus. The positions of the target light source51etc. corresponding to the second accommodation stimulus are set in advance.

(S5: OCT Measurement, Optical Property Measurement, Photographing of the Anterior Segment of the Subject's Eye)

While the second accommodation stimulus is being applied to the subject's right eye ER (and the subject's left eye), the main controller110performs OCT measurement, optical property measurement, and photographing of the anterior eye segment. These processes are performed in the same manner as in step3. Thereby, a second tomographic image, a second measurement value, and a second anterior eye image are acquired for the subject's right eye ER to which the second accommodation stimulus is being applied. The information is stored in the storage120.

(S6: Movement of the Optical System)

Upon completion of the OCT measurement, the optical property measurement, and the photographing of the anterior eye segment in step5, the main controller110moves the optical system to a position for intraocular distance measurement. Specifically, the main controller110controls the rotary drive mechanism130B such that the optical axis (the second optical axis O2) of the interference optical system60matches the axis of the subject's right eye ER (seeFIG. 10). This rotational movement of the optical system is intended to rotate the right body5R by the angle θ. The main controller110controls the XYZ drive mechanism130A to adjust the distance from the interference optical system60to the subject's right eye ER. The main controller110controls the placement/removal driver70A to retract the condenser lens70from the optical path of the interference optical system60.

(S7: OCT Measurement for Intraocular Distance Measurement)

After the optical system has been moved, the main controller110controls the reference driver70B to place the first reference mirror75and the lens74each in a position corresponding to the first site of subject's right eye ER (e.g., the anterior surface of the cornea E1). The main controller110also controls the reference driver70C to place the second reference mirror77and the lens76each in a position corresponding to the second site of the subject's right eye ER (e.g., the surface of the fundus). This process is performed with reference to, for example, live OCT images obtained by repetitive OCT measurements. In such OCT measurements, the fixation of the subject's right eye ER is made by the fixation light source81.

Upon completion of the positioning of the first reference mirror75and the second reference mirror77, the main controller110controls the light source unit61and the galvanometer scanner66to perform OCT measurement of the subject's right eye ER. The detector79detects the interference light between the reference light and the signal light having travelled via the subject's right eye ER. The interference light includes interference component (first interference component) of the signal light having travelled via the first site of the subject's right eye ER and the reference light having travelled via the first reference mirror75, and the interference component (second interference component) of the signal light having travelled via the second site and the reference light having travelled via the second reference mirror77.

The image forming unit150creates tomographic images based on signals output from the detector79. In this operation example, the image forming unit150creates a cornea tomographic image illustrating the anterior surface of the corneal E1based on the first interference component, and a fundus tomographic image illustrating the surface of the fundus based on the second interference component. The main controller110stores the cornea tomographic image and the fundus tomographic image thus acquired in the storage120. Incidentally, the OCT measurement of the first site and the OCT measurement of the second site may be performed at different times.

Thus, the optical measurements for the subject's right eye ER are completed, and data processing takes place. Incidentally, the following steps8to11are performed in arbitrary order. In addition, two or more of these steps may be performed in parallel.

(S8: Generation of Change Information)

The data processor160generates change information indicating a change in a predetermined tissue (e.g., the ciliary body) of the subject's right eye ER due to a change of the accommodation stimulus. In this operation example, the change information indicates the difference between the morphology of the predetermined tissue to which the first accommodation stimulus is being applied and the morphology of the predetermined tissue to which the second accommodation stimulus is being applied.

As described below, step8includes two stages of processes. In the first stage, the image area specifying unit161analyzes the first tomographic images acquired in step3to specify a ciliary body area, and analyzes the second tomographic image acquired in step5to specify a ciliary body area. In the second stage, the change information acquisition unit162compares the ciliary body area in the first tomographic image and the ciliary body area in the second tomographic image, and thereby obtains the change information indicating a change in the morphology of the ciliary body E4(shape, the density of muscle fibers, etc.). The main controller110stores the change information thus acquired in the storage120.

(S9: Generation of Optical Property Information)

The data processor160generates optical property information that indicates a change in the optical property of the subject's right eye ER due to a change of the accommodation stimulus. In this operation example, the optical property information acquisition unit163obtains the optical property information indicating a change in the amount of accommodation of the subject's right eye ER caused by a change of the accommodation stimulus based on the first measurement value of the ocular refractive power obtained in step3, and the second measurement value obtained in step5. The main controller110stores the optical property information thus acquired in the storage120.

(S10: Generation of Anterior Eye Change Information)

The data processor160generates anterior eye change information indicating a change in the predetermined tissue of the anterior segment of the subject's right eye ER due to a change of the accommodation stimulus. In this operation example, the anterior eye change information acquisition unit165obtains the anterior eye change information that indicates changes in the pupil diameter of the subject's right eye ER, in the iris pattern, in the direction of the visual line, and the like based on a first anterior eye image obtained in step3and a second anterior eye image obtained in step5. The main controller110stores the anterior eye change information thus acquired in the storage120.

(S11: Calculation of the Intraocular Distance)

The data processor160calculates the intraocular distance of the subject's right eye ER. In this operation example, the intraocular distance calculator164calculates the axial length of the subject's right eye ER, that is, the distance between the anterior surface of the cornea and the surface of the fundus based on the positions of the first reference mirror75and the second reference mirror77when the corneal tomographic image and the fundus tomographic image are obtained in step7. The main controller110stores the intraocular distance calculated in the storage120.

(S12: Display of Information)

The main controller110retrieves the information obtained in steps8to11from the storage120and displays it on the display unit181. With this, the operation example is completed.

Described below are the actions and effects of the ophthalmologic imaging apparatus2.

The ophthalmologic imaging apparatus2includes a first optical system, a tomographic image forming unit, and an analyzer. The first optical system includes the visual target projection optical system50configured to apply an accommodation stimulus to a subject's eye. The first optical system is an example of a stimulating unit for stimulating the subject's eye. The tomographic image forming unit includes the interference optical system60. The interference optical system60, which corresponds to a second optical system, splits light from a light source (the light source unit61) into signal light and reference light, and detects interference light between the signal light having travelled via the subject's eye and the reference light. The tomographic image forming unit creates a tomographic image of the subject's eye based on a detection result of the interference light obtained by the interference optical system60. The analyzer includes the data processor160. The analyzer is configured to compare a first tomographic image of the subject's eye to which a first accommodation stimulus is being applied with a second tomographic image of the subject's eye to which a second accommodation stimulus is being applied, and thereby obtain change information indicating a change in a predetermined tissue of the subject's eye caused by a change of the accommodation stimulus.

The data processor160may include the image area specifying unit161and the change information acquisition unit162. The image area specifying unit161analyzes the first tomographic image corresponding to the first accommodation stimulus and the second tomographic image corresponding to the second accommodation stimulus, and specifies image areas corresponding to the predetermined tissue of the subject's eye. The change information acquisition unit162compares the image area specified in the first tomographic image with the image area specified in the second tomographic image, and thereby obtains information indicating a change in the morphology of the predetermined tissue of the subject's eye as the above change information.

The change information acquisition unit162may acquire, as the change information, information indicating a change in the shape of the predetermined tissue of the subject's eye and/or a change in the density of tissues that constitute the predetermined tissue. Thereby, it is possible to figure out how the shape and/or density of the predetermined tissue change according to the accommodation stimulus.

When the ciliary body is used as the predetermined tissue, the following configuration may be applicable. The image area specifying unit161specifies a ciliary body area corresponding to the ciliary body as the image area. Then, the change information acquisition unit162compares the ciliary body area in the first tomographic image and the ciliary body area in the second tomographic image, and thereby obtains information indicating a change in the shape of the ciliary body of the subject's eye and/or a change in the density of the muscle fibers of the ciliary body as the change information. Thus, it is possible to figure out how the shape of the ciliary body and/or the density of muscle fibers change according to the accommodation stimulus.

When the ciliary body is used as the predetermined tissue, the application of the accommodation stimulus to the subject's eye and the OCT measurement of the ciliary body may be performed while the optical axis (first optical axis O1) of the first optical system and the optical axis (second optical axis O2) of the second optical system are oriented in different directions. Thereby, it is possible to suitably carry out the application of the accommodation stimulus and the OCT measurement of the ciliary body in parallel. In other words, while the accommodation stimulus is being applied from the front of the subject's eye, the OCT measurement can be suitably performed from the direction inclined with respect to the eye axis.

When the ciliary body is used as the predetermined tissue, there may be provided an optical system moving mechanism that relatively changes the direction of the first optical axis O1and the direction of the second optical axis O2. In this embodiment, the optical axis deflection mechanism130C corresponds to the optical system moving mechanism. Thereby, it is possible to suitably carry out the application of the accommodation stimulus and the OCT measurement of the ciliary body. In other words, while the accommodation stimulus is being applied from the front of the subject's eye, the OCT measurement can be suitably performed from the direction appropriate to the imaging of the ciliary body.

The predetermined tissue is not limited to the ciliary body. For example, the crystalline lens may be used as the predetermined tissue. It is then possible to use the following configuration. That is, the image area specifying unit161specifies a lens area corresponding to the lens as the image area. Then, the change information acquisition unit162compares the lens area in the first tomographic image and the lens area in the second tomographic image, and thereby acquires information indicating a change in the shape of the crystalline lens as the change information. This change information includes the thickness, the size (area, volume, etc.), the perimeter, etc. of the lens. Thereby, it is possible to figure out how the shape of the tissue of the lens or the like changes according to the accommodation stimulus. Note that in this embodiment, the lens refers not only to a biological lens but also to an artificial lens (i.e., intraocular lens).

The first optical system may include a pair of right and left optical systems that simultaneously apply the accommodation stimulus to the subject's left eye EL and right eye ER. Thereby, as compared with the case of applying the accommodation stimulus only to one of the subject's eyes, the accommodation can be suitably induced. In the case of applying the accommodation stimulus to both the eyes, the positions of the pair of left and right optical systems may be adjusted such that the subject's left and right eyes are congested. In this case, the convergence angle may be changed according to the accommodation stimulus. As a specific example, a first convergence angle related to the viewing distance corresponding to the first accommodation stimulus and a second convergence angle related to the viewing distance corresponding to the second accommodation stimulus may be obtained in advance so that the first and second convergence angles can be switched for use depending on a change of the accommodation stimulus.

The first optical system may include a measurement optical system configured to optically measure the optical properties of the subject's eye. In this embodiment, the measurement optical system30measures the subject's eye to which the first accommodation stimulus is being applied and thereby obtains first measurement values of the optical properties. Further, the measurement optical system measures the subject's eye to which the second accommodation stimulus is being applied and thereby obtains second measurement values of the optical properties. The optical property information acquisition unit163of the data processor160acquires optical property information indicating a change in the optical properties due to a change of the accommodation stimulus based on the first measurement values and the second measurement values. Thus, it is possible to figure out how the optical properties of the subject's eye change according to the accommodation stimulus.

The measurement optical system may measure the refractive power of the subject's eye as the optical properties. In this case, the optical property information acquisition unit163can acquire the optical property information that indicates a change in the amount of accommodation of the subject's eye due to a change of the accommodation stimulus based on the first and second measurement values of the refractive power. Thus, it is possible to figure out how the refractive power of the subject's eye changes according to the accommodation stimulus.

The measurement optical system may measure the aberration of the subject's eye as the optical properties. In this case, the optical property information acquisition unit163can obtain the optical property information that indicates a change in the aberration of the subject's eye due to a change of the accommodation stimulus based on the first and second measurement values of the aberration. Thus, it is possible to figure out how the aberration of the subject's eye changes according to the accommodation stimulus.

The second optical system may include an optical path length changing unit configured to change the length of the optical path of the signal light and/or the length of the optical path of the reference light. In this embodiment, the interference optical system60is provided with the reference driver70B (70C) for changing the optical path length of the reference light. The tomographic image forming unit acquires a tomographic image of the first site and that of the second site of the subject's eye. The intraocular distance calculator164of the data processor160calculates the distance between the first site and the second site based on the optical path length when the tomographic image of the first site is acquired, and the optical path length when the tomographic image of the second site is acquired. Thus, it is possible to determine the distance between the first site and the second site of the subject's eye.

The anterior surface of the cornea may be used as the first site, while the surface of the fundus may be used as the second site. In this case, the intraocular distance calculator164obtains the axial length of the subject's eye.

The intraocular distance calculator164may be configured to analyze a single tomographic image of the subject's eye acquired by the tomographic image forming unit to calculate the distance between the first site and the second site depicted in this tomographic image. Thus, it is possible to determine the distance between the first site and the second site of the subject's eye.

The posterior surface of the cornea may be used as the first site, while the anterior surface of the crystalline lens may be used as the second site. In this case, the anterior chamber depth of the subject's eye can be obtained by the intraocular distance calculator164.

The first optical system may include an imaging optical system configured to photograph the anterior segment of the subject's eye. In this embodiment, the imaging optical system10and an optical system including the imaging device90correspond to the imaging optical system. The imaging optical system captures a first anterior eye image of the subject's eye to which the first accommodation stimulus is being applied, a second anterior eye image of the subject's eye to which the second accommodation stimulus is being applied. The data processor160compares the first anterior eye image with the second anterior eye image, and thereby acquires anterior eye change information indicating a change in the predetermined tissue of the anterior eye segment due to a change of the accommodation stimulus. Thus, it is possible to figure out how the predetermined tissue of the anterior eye segment varies depending on the accommodation stimulus.

With the ophthalmologic imaging apparatus2configured as above, it is possible to determine whether the tissue related to the accommodation function of the subject's eye is functioning properly based on a structural change of the subject's eye. For example, it is possible to figure out whether the ciliary body as a muscle tissue has a sufficient ability to contract and relax. Further, it is also possible to comprehensively determine if the ciliary body is functioning properly, if the flexibility of the lens is reduced by the cataract, if the implanted intraocular lens is placed in a proper position, and the like. Thus, it is possible to specify a cause for that the accommodation function is not acting favorably.

As described above, with the ophthalmologic imaging apparatus2, it is possible to suitably judge the accommodation function of the subject's eye.

Described below is the usage of the ophthalmologic imaging apparatus2according to the embodiment. With the use of the ophthalmologic imaging apparatus2for treatment related to the accommodation function and the follow-up of surgery, it is possible to comprehensively judge a change of the accommodation function due to treatment, surgery, and the passage of time. Further, it is also possible to obtain a time-series change in the accommodation function.

The ophthalmologic imaging apparatus2may be used to measure the efficiency of rehabilitation and training. In this case, the visual target projection optical system50may present a visual target for subjective optometry, such as Landolt rings, to the subject's eye. Then, it is possible to obtain a time-series change in the result of the subjective optometry and in the result of accommodation function measurement.

The ophthalmologic imaging apparatus2may be used for the evaluation of accommodating intraocular lenses. The accommodating intraocular lens is an intraocular lens having accommodation functions. As an example of the evaluation of the accommodating intraocular lens, it is possible to evaluate whether the accommodating intraocular lens implanted is functioning properly according to the movement of the ciliary body or the like. Besides, it is also possible to determine whether the ciliary body or the like of the subject's eye has a sufficient capacity for the implantation of the accommodating intraocular lens before the transplantation of the intraocular lens.

The embodiments described above are mere examples for embodying or carrying out the present invention, and therefore susceptible to several modifications and variations (omission, substitution, addition, etc.). Modifications described below come within the scope of the invention.

The wavelengths of light output from the light source unit61are arbitrarily set. For example, considering that the axial length measurement is performed by using OCT, a light source capable of outputting light having wavelengths of not more than 1.1 um may be used as the light source unit61. Incidentally, the light source for OCT measurement intended to obtain a tomographic image, and the light source for OCT measurement intended to measure the intraocular distances may be separately provided.

In the above embodiment, an example is described in which an accommodation stimulus is applied to the subject's eye by using a visual target; however, the method of applying the accommodation stimulus to the subject's eye is not limited to this. For example, electrical stimulation, ultrasonic stimulation, or light stimulation may be applied to the subject's eye. The electrical stimulation is applied by, for example, applying an electrode to a site to be stimulated. The ultrasonic stimulation is applied by, for example, irradiating a site to be stimulated with ultrasonic waves by using an ultrasonic transducer. The light stimulation is applied by using a light source.

The site of the subject's eye to be stimulated is not limited to the sites related to the accommodation function (lens, zonule of Zinn, ciliary body). For example, a stimulus may be applied to the retina.

Such an ophthalmologic imaging apparatus includes a stimulating unit, a tomographic image forming unit, and an analyzer. The stimulating unit applies a stimulus to the subject's eye. The stimulus includes the presentation of a visual target, electrical stimulation, ultrasonic stimulation, light stimulation, and the like. The stimulating unit includes a means for presenting a visual target to the subject's eye, a means for applying electrical stimulation to the subject's eye, a means for applying ultrasound stimulation to the subject's eye, a means for applying light stimulation to the subject's eye, and the like. The tomographic image forming unit includes an optical system configured to split light from a light source into signal light and reference light, and detect interference light between the signal light having travelled via the subject's eye and the reference light. The tomographic image forming unit creates a tomographic image of the subject's eye based on a detection result of the interference light. The analyzer is configured to compare a first tomographic image of the subject's eye to which a first accommodation stimulus is being applied by the stimulating unit with a second tomographic image of the subject's eye to which a second accommodation stimulus is being applied, both of which are obtained by the tomographic image forming unit, and thereby obtain change information indicating a change in a predetermined tissue of the subject's eye caused by a change of the accommodation stimulus. With this ophthalmologic imaging apparatus, it is possible to judge a change of the subject's eye due to a change of the stimulus.

In the above embodiment, although the change information is acquired based on the tomographic image of the subject's eye, it may be acquired based on data detected by the interference optical system in the OCT measurement, intermediate information from the detected data to the tomographic image, or information obtained from the tomographic image. For example, in the above embodiment, the change information may be obtained based on a signal output from the detector79of the interference optical system60, the change information may also be obtained based on information (intermediate information from the signal to the tomographic image) acquired by the image forming unit150which has received the signal, and further, the change information may also be obtained based on information generated by the data processor160from the tomographic image. In addition, the change information may be obtained based on phase information acquired by OCT of phase detection type. In this case, it is possible to figure out a slight change in the subject's eye (a change of wavelength scale or less) caused by a change in the stimulus.

In the above embodiment, an example is described in particular detail in which two pieces of information corresponding to two stimulating conditions are compared to each other; however, this is not so limited. For example, the change information may be obtained from three or more pieces of information corresponding to three or more stimulating conditions. That is, by acquiring the i-th information (tomographic images etc.) on the subject's eye to which the i-th stimulus is being applied (i=1 to K), the change information may be obtained based on K pieces of information. Further, the change information may be obtained based on three or more pieces of information corresponding to two or more stimulating conditions. For example, the change information may be obtained based on information of the subject's eye that has been repeatedly acquired over a period including the transition from the first stimulating condition to the second stimulating condition. For example, the change information may be obtained based on a moving image acquired by repeatedly capturing tomographic images at a predetermined repetition frequency over a period including the transition from the first stimulating condition to the second stimulating condition.

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