Ophthalmic device

Abstract

To provide an ophthalmologic apparatus capable of accurately acquiring an eye axial length of a subject's eye.SOLUTION: An ophthalmologic apparatus includes: a fixation mark presenting optical system for projecting a fixation light to a subject's eye and presenting a fixation mark to be used for performing fogging to the subject's eye; an eye refractive power measurement optical system for projecting first measurement light to an eyeground of the subject's eye and acquiring an eye refractive power of the subject's eye based on a reflection light of the first measurement light reflected in the eyeground; and a cross-sectional image imaging optical system for projecting second measurement light to an anterior eye part of the subject's eye, forming a light cut surface passing an optical axis of the eye refractive power measurement optical system in the anterior eye part, and acquiring an anterior eye part cross-sectional image of the subject's eye based on return light of the second measurement light from the light cut surface. The apparatus acquires an eye axial length of the subject's eye based on the eye refractive power and the anterior eye part cross-sectional image, and furthermore includes an optical path connection member for connecting a fixation optical path of fixation light in the fixation mark presenting optical system and a measurement optical path of the second measurement light in the cross-sectional image imaging optical system.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an ophthalmic apparatus for obtaining the axial length of an eye to be examined.

Background Art

[0002] There is known an ophthalmic apparatus that illuminates a transparent body in the anterior segment of an eye to be examined in a form of optical cutting and captures a cross-sectional image of the anterior segment.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, the increase in the myopia prevalence rate centered on the younger generation has been remarkable, and the evaluation of myopia progression based on the axial length has attracted attention. The inventors considered a device configuration for obtaining both the refractive power of an eye to be examined and a cross-sectional image of the anterior segment, and obtaining the axial length based on these.

[0005] The present disclosure has been made in view of the above circumstances, and the technical problem is to provide an ophthalmic apparatus that can accurately obtain the axial length of an eye to be examined.

Means for Solving the Problems

[0006] An ophthalmic apparatus according to a first aspect of the present disclosure includes a fixation target presentation optical system that projects fixation light onto an eye to be examined and presents a fixation target used to perform fogging on the eye to be examined, an eye refractive power measurement optical system that projects first measurement light onto the fundus of the eye to be examined and acquires the eye refractive power of the eye to be examined based on reflected light obtained by reflecting the first measurement light from the fundus, and a cross-sectional image capturing optical system that projects second measurement light onto the anterior segment of the eye to be examined, forms a light cutting plane passing through the optical axis of the eye refractive power measurement optical system on the anterior segment, and acquires a cross-sectional image of the anterior segment of the eye to be examined based on return light of the second measurement light from the light cutting plane. The ophthalmic apparatus acquires the axial length of the eye to be examined based on the eye refractive power and the cross-sectional image of the anterior segment, and is characterized by including an optical path coupling member that couples a fixation optical path of the fixation light in the fixation target presentation optical system and a measurement optical path of the second measurement light in the cross-sectional image capturing optical system.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] 「Overview」 The overview of the ophthalmic device according to the embodiment of the present disclosure will be described. The items classified in the following <> can be used independently or in combination. In this embodiment, the term "conjugate" is not necessarily limited to a complete conjugate relationship, but includes "substantially conjugate". That is, the "conjugate" in this embodiment includes the case where it is arranged deviated from the complete conjugate position within the range allowed in relation to the technical significance of each part.

[0009] The ophthalmic device of this embodiment is a device capable of acquiring the axial length of the eye to be examined. For example, the ophthalmic device may have an optical system used for measuring the axial length, an axial length acquisition means, and the like. Further, for example, the ophthalmic device may have a shape information acquisition means, an anterior eye segment information acquisition means, a specifying means, a setting means, and the like.

[0010] <Fixation Target Presentation Optical System> The ophthalmic device of this embodiment may include a fixation target presentation optical system (for example, the fixation target presentation optical system 150). The fixation target presentation optical system may project fixation light onto the eye to be examined and present a fixation target to the eye to be examined. Note that the fixation target presentation optical system may be able to change the presentation distance of the fixation target. For example, thereby, when acquiring the refractive power of the eye to be examined by the first optical system, the fixation target presentation optical system can be used for fogging the eye to be examined. Also, it can be used for accommodation addition to the eye to be examined. That is, for example, the fixation target may be used to perform fogging on the eye to be examined.

[0011] <Refractive Power Measurement Optical System> The ophthalmic device of this embodiment may have an eye refractive power measurement optical system (for example, the measurement optical system 100). The eye refractive power measurement optical system is an optical system for acquiring the eye refractive power of the eye to be examined. For example, it may be provided with a configuration for projecting measurement light (first measurement light) onto the fundus of the eye to be examined and acquiring the eye refractive power based on the reflected light reflected by the measurement light at the fundus. Note that the first measurement light may be visible light or infrared light.

[0012] The eye refractive power measurement optical system may be a measurement optical system used in an objective type eye refractive power measurement device (such as an autorefractor and a wavefront sensor). The projection optical axis of the first measurement light in the eye refractive power measurement optical system may be arranged on the plane of the optical cutting plane formed by the cross-sectional image photographing optical system described later. For this reason, using the eye refractive power measurement optical system, the eye refractive power (surface eye refractive power) on the optical cutting plane of the anterior segment of the eye is acquired. Of course, the eye refractive power measurement optical system may be capable of acquiring the eye refractive power on other planes.

[0013] <Cross-sectional image photographing optical system> The ophthalmic device of this embodiment may have a cross-sectional image photographing optical system (for example, a cross-sectional photographing optical system). The cross-sectional image photographing optical system is an optical system for acquiring a cross-sectional image of the anterior segment of the eye to be examined. For example, it may be provided with a configuration for projecting measurement light toward the anterior segment of the eye to be examined and detecting the return light (scattered light) due to the scattering of the measurement light from an oblique direction with respect to the projection optical axis of the measurement light to acquire a cross-sectional image of the anterior segment of the eye. Further, for example, it may be provided with a configuration for projecting measurement light (second measurement light) onto the anterior segment of the eye to be examined, forming an optical cutting plane passing through the optical axis of the eye refractive power measurement optical system in the anterior segment of the eye, and acquiring a cross-sectional image of the anterior segment of the eye based on the scattered light from the optical cutting plane of the second measurement light. Note that the measurement light (second measurement light) may be visible light or infrared light.

[0014] The cross-sectional image capturing optical system may be an optical system based on the Schlein-proof principle. In this case, the projection optical axis of the first measurement light in the eye refractive power measurement optical system and the projection optical axis of the second measurement light in the cross-sectional image capturing optical system may be coaxially arranged. Also, in this case, in the cross-sectional image capturing optical system, the second measurement light may be projected as slit light. For example, the irradiation region of the slit light is set as the optical cutting plane of the anterior eye segment. Also, in this case, the cross-sectional image capturing optical system may have a lens system and a photodetector arranged in relation to the optical cutting plane formed in the anterior eye segment and the Schlein-proof. For example, the photodetector may be a two-dimensional imaging device. The light reception optical axis of the second measurement light is arranged to be inclined with respect to the optical cutting plane.

[0015] Note that it is preferable that the imaging range of the anterior eye segment cross-sectional image by the cross-sectional image capturing optical system includes at least from the front surface of the cornea of the eye to be examined to the front surface of the lens. Needless to say, it is more preferable if it includes from the front surface of the cornea to the rear surface of the lens. In this case, the corneal thickness, the anterior corneal curvature radius, the posterior corneal curvature radius, the anterior chamber depth, the lens thickness, the anterior lens curvature radius, and the posterior lens curvature radius can be obtained without omission, so that the eye axis length can be obtained more appropriately.

[0016] <Front image capturing optical system> The ophthalmic apparatus of the present embodiment includes a front image capturing optical system (for example, an index projection optical system 400, an alignment index projection optical system). The front image capturing optical system may project the third measurement light onto the cornea of the eye to be examined and capture a front image of the anterior eye segment including the projected image of the third measurement light projected onto the cornea, thereby obtaining corneal shape information regarding the shape of the cornea. The front image capturing optical system may be a measurement optical system used in a corneal shape measuring device (autokeratometer). Note that the third measurement light in the front image capturing optical system is infrared light, but it is also possible to use visible light.

[0017] <Common use of the fixation target presenting optical system and the cross-sectional image capturing optical system> In this embodiment, the fixation target presentation optical system and the cross-sectional image capturing optical system may share a common optical path. That is, a part of the fixation optical path of the fixation light in the fixation target presentation optical system and the measurement optical path (light projection optical path) of the second measurement light in the cross-sectional image capturing optical system may be a common optical path. For example, an optical path coupling member for coupling the respective optical paths in these optical systems may be arranged. Note that the fixation light projected from the fixation target presentation optical system is focused on the fundus, and the second measurement light projected from the cross-sectional image capturing optical system is focused on the anterior eye segment. For this reason, each optical system becomes a complicated configuration by sharing, but on the other hand, the optical path coupling member can be easily configured. For example, when both the fixation light and the second measurement light are visible light, the optical path coupling member can be configured more easily.

[0018] By using an optical path coupling member for sharing the fixation target presentation optical system and the cross-sectional image capturing optical system, astigmatism may occur in at least one of the fixation light and the second measurement light. Therefore, each optical system may be configured in consideration of the influence of astigmatism.

[0019] The optical path coupling member may be composed of at least one of optical members such as a beam splitter, a dichroic mirror, and a half mirror. In this case, either a prism-type member or a flat-type member can be used for the optical path coupling member.

[0020] As an example of the prism-type member, a cube half mirror formed by bonding right-angled prisms, a dichroic prism, or the like may be used. In such a prism-type member, the occurrence of astigmatism is suppressed, so that a good cross-sectional image of the anterior eye segment can be captured. Note that when a prism-type member is used for the optical path coupling member, one of the fixation target presentation optical system and the cross-sectional image capturing optical system may be arranged on the transmission side of the optical path coupling member, and the other of the fixation target presentation optical system and the cross-sectional image capturing optical system may be arranged on the reflection side of the optical path coupling member.

[0021] As an example of the planar member, a plate half mirror, a dichroic mirror, or the like may be used. In such a planar member, either the fixation light or the second measurement light passes through with a large incident angle, so that astigmatism is likely to occur on the transmission side. Therefore, when a planar member is used for the optical path coupling member, it is preferable to arrange the fixation target presenting optical system on the transmission side of the optical path coupling member and arrange the cross-sectional image photographing optical system on the reflection side of the optical path coupling member. By arranging the fixation optical path on the transmission side, the imaging performance of the illumination light is prioritized, and a good cross-sectional image of the anterior eye can be taken. Note that by arranging the measurement optical path on the reflection side, although the imaging performance of the fixation light is reduced, since the performance that allows the fixation target to be fixated is ensured, the influence on visual recognition can be suppressed to a small level.

[0022] In the present embodiment, a common lens may be arranged in the common optical path of the fixation target presenting optical system and the cross-sectional image photographing optical system. More specifically, a common lens having different functions for each optical system may be arranged in the common optical path of the fixation optical path of the fixation light in the fixation target presenting optical system and the measurement optical path of the second measurement light in the cross-sectional image photographing optical system.

[0023] In the present embodiment, the common lens may function as an overall length shortening lens for shortening the overall length of the fixation target presenting optical system. Thereby, without changing the overall focal length (synthetic focal length) of the fixation target presenting optical system, a part of the focal length including the overall length shortening lens is shortened. Also, in the present embodiment, the common lens may function as a field lens for changing the traveling direction of the second measurement light in the cross-sectional image photographing optical system. More specifically, it may function as a field lens for changing the traveling direction of the second measurement light passing outside the optical axis of the cross-sectional image photographing optical system. In other words, it may function as a field lens that substantially coincides with the image plane of the cross-sectional image photographing optical system and transmits the second measurement light without being blocked.

[0024] For example, although the fixation target presenting optical system includes a full-length shortening lens in its configuration, by utilizing the full-length shortening lens as a field lens of the cross-sectional image capturing optical system with the commonization of the fixation optical path and the measurement optical path, it becomes possible to provide an optical member (for example, an objective lens) located downstream of the field lens without increasing its diameter. By arranging a common lens having these functions, the entire optical system can be made more space-saving, and as a result, the ophthalmic device can be miniaturized.

[0025] <Shape information acquisition means> The ophthalmic device of the present embodiment may include a shape information acquisition means (for example, the control unit 50). The shape information acquisition means may acquire anterior eye shape information regarding the shape of the anterior eye by analyzing the anterior eye cross-sectional image. Note that the plurality of parameters are parameters including at least the cornea and the lens. For example, the shape information may be information capable of specifying the shape of the light-transmitting body included in the anterior eye. As an example, it may be the coordinates at which each light-transmitting body is located, an equation representing the shape of each light-transmitting body, and values obtained from the equation (for example, curvature, thickness, depth, etc.).

[0026] The plurality of parameters included in the shape information may include parameters regarding the shape of the cornea. For example, the radius of curvature of the anterior corneal surface, the radius of curvature of the posterior corneal surface, the corneal thickness, etc. may be mentioned. Further, the plurality of parameters may include parameters regarding the shape of the lens. For example, the radius of curvature of the anterior lens surface, the radius of curvature of the posterior lens surface, the lens thickness, etc. may be mentioned. Further, the plurality of parameters may include parameters regarding the depth of the anterior eye. For example, the anterior chamber depth, etc. may be mentioned.

[0027] The shape information acquisition means may perform an analysis using a point on the optical axis of the second measurement light in the cross-sectional image capturing optical system in the anterior eye cross-sectional image. Further, the shape information acquisition means may perform an analysis using a point on the optical axis of the first measurement light in the eye refractive power measurement optical system in the anterior eye cross-sectional image. Note that since the optical axis of the first measurement light is an axis that passes through the center of the pupil (that is, the center of each light-transmitting body), it is easy to capture the apex of the light-transmitting body, and thereby the anterior eye shape information can be accurately acquired.

[0028] The shape information acquisition means may acquire the anterior eye segment shape information by analyzing an analysis region that does not include the reflection image in the anterior eye segment cross-sectional image set by the setting means. In this case, the anterior eye segment shape information may be acquired by changing whether or not to use the point on the optical axis of the second measurement light according to the position of the set analysis region. Also, in this case, the anterior eye segment shape information may be acquired by changing whether or not to use the point on the optical axis of the first measurement light according to the position of the set analysis region. More specifically, for example, when the position of the analysis region overlaps with the center of each light-transmitting body, the analysis may be performed using the point on the optical axis of the first measurement light. For example, when the position of the analysis region does not overlap with the center of each light-transmitting body, the analysis may be performed without using the point on the optical axis of the first measurement light. For example, when the position of the analysis region does not overlap with but is close to the center of each light-transmitting body, the analysis may be performed without using the point on the optical axis of the first measurement light. By appropriately changing the point used for the analysis of the anterior eye segment cross-sectional image, the anterior eye segment shape information can be accurately acquired.

[0029] <Anterior eye segment information acquisition means> The ophthalmic apparatus of the present embodiment may include an anterior eye segment information acquisition means (for example, the control unit 50). The anterior eye segment information acquisition means may acquire anterior eye segment information regarding the anterior eye segment of the subject eye. The anterior eye segment information may include the anterior eye segment shape information (described above) of the subject eye. In this case, as the anterior eye segment information, the corneal radius of curvature, which is one of the parameters in the anterior eye segment shape information, may be acquired. Of course, parameters different from the corneal radius of curvature may be acquired. Also, the anterior eye segment information may include pupil state information regarding the pupil state of the subject eye. For example, the pupil state may be at least one of a constricted state and a dilated state. Note that, as the pupil state information, information capable of grasping the presence or absence of miosis and mydriasis may be used. As an example, a value such as the pupil diameter may be used. Also, as the pupil state information, a determination result obtained by determining the presence or absence of miosis or mydriasis based on the value of the pupil diameter may be used.

[0030] The anterior eye segment information acquisition means may acquire the anterior eye segment information by receiving the anterior eye segment information acquired by a device different from the ophthalmic device. Further, the anterior eye segment information may be acquired by input using an operation means (for example, the monitor 16) by the examiner. Further, the anterior eye segment information may be acquired by analyzing the anterior eye segment cross-sectional image acquired using the cross-sectional image photographing optical system. Further, the anterior eye segment information may be acquired by analyzing the anterior eye segment frontal image acquired using the frontal image photographing optical system.

[0031] <Specific means> The ophthalmic device of the present embodiment may include a specific means (for example, the control unit 50). The specific means may specify the reflected image included in the anterior eye segment cross-sectional image acquired using the cross-sectional image photographing optical system. Note that the specific means may specify the position (for example, coordinates) of the reflected image, or may specify a predetermined range including the position of the reflected image.

[0032] The specific means may specify the position of the reflected image based on an operation signal input by an operation of an operation means (for example, the monitor 16) by the examiner. Further, the specific means may specify the position of the reflected image based on the luminance information (as an example, at least any one of luminance, gradation, shading, etc.) of the anterior eye segment cross-sectional image. Further, the specific means may specify the position of the reflected image based on at least any one of the anterior eye segment information and the anterior eye segment shape information. In this case, the anterior eye segment information, the anterior eye segment shape information, and the position of the reflected image may be associated in advance from experiments or simulations. For example, the position of the reflected image may be specified according to the pupil diameter, the corneal shape, the lens shape, etc.

[0033] For example, the reflected image included in the anterior eye segment cross-sectional image may be a corneal reflection image generated by the second measurement light from the cross-sectional image photographing optical system being reflected (specular reflection) by the cornea. In particular, it may be a slit reflection image generated by projecting slit light as the second measurement light. Also, for example, the reflected image included in the anterior eye segment cross-sectional image may be a corneal reflection image due to specular reflection of the third measurement light from the front image photographing optical system. Of course, it may include corneal reflection images different from the corneal reflection image derived from the second measurement light and the corneal reflection image derived from the third measurement light.

[0034] <Setting means> The ophthalmic apparatus of the present embodiment may include setting means (for example, the control unit 50). The setting means may set an analysis region that does not include a reflected image generated by at least the second measurement light being reflected (specular reflection) by the cornea of the subject eye in the anterior eye segment cross-sectional image obtained using the cross-sectional image photographing optical system. Further, an analysis region that does not include a reflected image generated by the third measurement light being reflected (specular reflection) by the cornea of the subject eye may be set. For example, such an analysis region is set to acquire anterior eye segment shape information (as an example, shape information regarding the cornea and the lens) including the optical axis of the second measurement light in the cross-sectional image photographing optical system.

[0035] The setting means may set an analysis region to be analyzed from the target region where the anterior eye segment cross-sectional image can be analyzed. In this case, as the analysis region that does not include the reflected image, a region excluding the position of the reflected image may be set. Also, as the analysis region that does not include the reflected image, a region excluding a predetermined range including the position of the reflected image may be set. Thereby, the anterior eye segment shape information based on the anterior eye segment cross-sectional image is accurately acquired. Of course, the setting means may indirectly set the analysis region by setting a non-analysis region (that is, the position of the reflected image or a predetermined range including the position of the reflected image) that is not the target of analysis from the target region of the anterior eye segment cross-sectional image.

[0036] Further, the setting means may set the analysis region by excluding the position of the reflection image (or a predetermined range including the position of the reflection image) in the anterior eye segment image and interpolating using the data around the excluded part. That is, the reflection image may be removed from the anterior eye segment image by image processing, and the analysis region may be set for the obtained anterior eye segment image without the reflection image. In this case, all of the above-described target regions can be set as the analysis region without the reflection image. Of course, a part of the target region can also be set as the analysis region.

[0037] The setting means may set the analysis region based on the anterior eye information acquired by the anterior eye information acquisition means. For example, the analysis region may be set based on the pupil state (for example, pupil diameter, etc.) of the eye to be examined. Further, for example, the analysis region may be set based on the shape of each light-transmitting body (for example, corneal radius of curvature, etc.) in the anterior eye of the eye to be examined. Thereby, a region suitable for the analysis of the anterior eye segment image can be easily grasped. Note that the setting means may set the analysis region by excluding the position of the reflection image (or a predetermined range including the position of the reflection image) specified by the specifying means.

[0038] <Axial length acquisition means> The ophthalmic apparatus of the present embodiment may include an axial length acquisition means (for example, the control unit 50). For example, the axial length acquisition means may also serve as an image processing unit, an axial length acquisition unit, a calculation control unit, and the like.

[0039] The axial length acquisition means may acquire the refractive power of the eye to be examined by controlling the acquisition of the refractive power of the eye using the ophthalmic refractive power measurement optical system. More specifically, the refractive power of the eye to be examined may be acquired by controlling the projection of the first measurement light in the ophthalmic refractive power measurement optical system and the detection of the fundus reflection light of the first measurement light by the photodetector.

[0040] Further, the axial length acquisition means may acquire a cross-sectional image of the anterior eye of the eye to be examined by controlling the acquisition of a cross-sectional image of the anterior eye using the cross-sectional image photographing optical system. More specifically, the cross-sectional image of the anterior eye of the eye to be examined may be acquired by controlling the projection of the second measurement light in the cross-sectional image photographing optical system and the detection of the return light (scattered light) of the second measurement light by the photodetector.

[0041] The axial length acquisition means may acquire the axial length of the eye to be examined based on the refractive power of the eye and a plurality of parameters included in the shape information acquired by the shape information acquisition means analyzing the cross-sectional image of the anterior eye. For example, the axial length acquisition means may derive the axial length by ray tracing calculation based on the refractive power of the eye and a plurality of parameters. In the ray tracing calculation, the distance between the intersection point and the corneal apex when the light ray incident from the far point to a predetermined position of the anterior eye is refracted by the transparent body and intersects on the optical axis is derived as the axial length. At this time, instead of the equivalent spherical power generally used when specifying the far point in the field of ophthalmology, the refractive power of the eye on the light cut surface (surface refractive power of the eye) may be used. Thereby, the position of the far point in the light ray passing through the cut surface is specified more appropriately. As a result, the axial length can be obtained more appropriately. At this time, ray tracing calculation may be performed for each of the plurality of light rays, and the axial length may be obtained as a result of the ray tracing calculation of each light ray. For example, the average value (weighted average is also acceptable) of the axial lengths obtained by each ray tracing calculation may be obtained as the axial length of the eye to be examined.

[0042] In the ray tracing calculation, the incident position of the ray on the interface of each transparent body and the angular change at the interface may be determined in consideration of the shape of the transparent body on the cross section specified from the anterior eye part information. Further, in the ray tracing calculation, the eccentricity of the transparent body of the anterior eye part may be considered. The eccentricity is specified based on the anterior eye part information. As a result of considering the eccentricity of the transparent body within the cross section, the axial length of the eye can be obtained more appropriately. In this case, for example, ray tracing calculations may be performed for each of a plurality of rays including at least a first ray and a second ray, the axial length of the eye may be obtained for each ray, and a final measurement value may be obtained based on the plurality of axial lengths. The first ray and the second ray are rays arranged with the eye axis interposed therebetween on the cross section.

[0043] In the present embodiment, the axial length acquisition means may adjust the light amount of the second measurement light in the cross-sectional image photographing optical system based on the anterior eye part cross-sectional image. More specifically, an anterior eye part cross-sectional image (first anterior eye part cross-sectional image) of the eye to be examined is acquired, and when this anterior eye part cross-sectional image is determined to be inappropriate for analysis, the light amount of the second measurement light may be adjusted, and again an anterior eye part cross-sectional image (second anterior eye part cross-sectional image) may be acquired. Further, in the present embodiment, the axial length acquisition means may adjust the detection conditions of the photodetector in the cross-sectional image photographing optical system based on the anterior eye part cross-sectional image. More specifically, the first anterior eye part cross-sectional image is acquired, and when the first anterior eye part cross-sectional image is determined to be inappropriate for analysis, the detection conditions of the photodetector may be adjusted to acquire the second anterior eye part cross-sectional image. As a result, the possibility of obtaining appropriate values as a plurality of parameters based on the anterior eye part cross-sectional image is increased, and as a result, the accuracy of the axial length is improved.

[0044] Note that the axial length acquisition means may determine whether the first anterior eye part cross-sectional image is suitable for analysis based on whether the first anterior eye part cross-sectional image is obtained well. Further, the axial length acquisition means may determine whether the first anterior eye part cross-sectional image is suitable for analysis based on whether a plurality of parameters based on the first anterior eye part cross-sectional image are obtained well. As a result, even when measurement values of a plurality of parameters cannot be obtained or when the measurement values are not accurate, appropriate values are likely to be obtained.

[0045] For example, the axial length acquisition means may adjust the light quantity of the second measurement light within a predetermined range where the luminance information of each light-transmitting body detected from the second anterior eye segment image does not reach the saturation state. In this case, the axial length acquisition means may increase or decrease the set value of the output in the light source, or may insert or remove an optical member in the optical path of the second measurement light projected from the light source. As an example, the predetermined range may be set in advance based on the detection sensitivity, gain, etc. of the photodetector. Further, for example, the axial length acquisition means may adjust the detection conditions of the photodetector within a predetermined range where the luminance information of each light-transmitting body detected from the second anterior eye segment image does not reach the saturation state. In this case, the axial length acquisition means may change at least any one of the exposure time, gain, etc. of the photodetector.

[0046] Note that the ophthalmic apparatus in the present embodiment may have a configuration including at least an eye refractive power acquisition means for acquiring the eye refractive power of the eye to be examined, an anterior eye segment image acquisition means for acquiring a cross-sectional image of the anterior eye of the eye to be examined, a setting means for setting an analysis region not including the corneal reflection image in the anterior eye segment image, a shape information acquisition means for analyzing the analysis region to acquire anterior eye shape information, and an axial length acquisition means for acquiring the axial length based on the eye refractive power and the anterior eye shape information.

[0047] In this case, the eye refractive power acquisition means may acquire the eye refractive power by receiving measurement results using a device different from the ophthalmic apparatus, calling from an electronic medical record, etc., input using an operation means by an examiner, etc. Of course, when the ophthalmic apparatus includes an eye refractive power measurement optical system, the eye refractive power as the measurement result using this optical system may be acquired. Similarly, the anterior eye segment image acquisition means may acquire the eye refractive power by receiving a photographed image using a device different from the ophthalmic apparatus, calling from an electronic medical record, etc. When the ophthalmic apparatus includes a cross-sectional image photographing optical system, the anterior eye segment cross-sectional image as the photographing result using this optical system may be acquired.

[0048] "Example" An example of the ophthalmic apparatus in the present embodiment will be described.

[0049] <Overall Configuration> FIG. 1 is an external view of the ophthalmic apparatus 10. The ophthalmic apparatus 10 is a composite machine of an objective-type eye refractive power measuring device (particularly, in this embodiment, an autorefractor) and a shine-proof camera. In this embodiment, the ophthalmic apparatus 10 is a stationary inspection device, but it is not necessarily limited to this, and it may be a handheld type.

[0050] The ophthalmic apparatus 10 has at least a measurement unit 11, a base 12, an alignment drive unit 13, a face support unit 15, a monitor 16, and an arithmetic control unit 50.

[0051] The measurement unit 11 includes a measurement system, a photographing system, etc. used for the examination of the eye to be examined. In this embodiment, the optical system shown in FIG. 2 is arranged.

[0052] The alignment drive unit 13 may be capable of moving the measurement unit 11 three-dimensionally with respect to the base 12.

[0053] The face support unit 15 is used to fix the face of the subject in front of the measurement unit 11. The face support unit 15 is fixed to the base 12 and supports the face of the subject.

[0054] The monitor 16 functions as a touch panel that also serves as an operation unit. Further, the monitor 16 displays on the screen the refractive power of the eye to be examined E, a cross-sectional image of the anterior eye segment, the axial length of the eye, etc.

[0055] The arithmetic control unit 50 (also referred to as a processor. Hereinafter, simply referred to as the control unit 50) controls the entire ophthalmic apparatus 10. Further, it processes various examination results obtained via the measurement unit 11.

[0056] <Optical System> FIG. 2 is a schematic diagram showing the optical system of the ophthalmic apparatus 10. As an example, the ophthalmic apparatus 10 includes a measurement optical system 100, a fixation target presentation optical system 150, a front imaging optical system 200, a cross-sectional imaging optical system (an irradiation optical system 300a and a light receiving optical system 300b), an index projection optical system 400, and an alignment index projection optical system. Further, it has half mirrors 501, 502, 503 for branching and combining the optical paths of each optical system, an objective lens 505, and the like. In each optical system, the light source side is the upstream and the eye to be examined side is the downstream.

[0057] <Measurement optical system> The measurement optical system 100 is used for objectively measuring the refractive power of the eye to be examined E. For example, each value of SPH: spherical power, CYL: cylindrical power, AXIS: astigmatism axis angle may be obtained as the measurement result of the refractive power of the eye.

[0058] The measurement optical system 100 has a projection optical system 100a and a light receiving optical system 100b.

[0059] The projection optical system 100a has at least a measurement light source 111, and projects spot-like measurement light onto the fundus of the eye to be examined E through the center of the pupil or the corneal apex in the eye to be examined E. The measurement light source 111 may be an SLD light source, an LED light source, or other light sources. In this embodiment, infrared light is used as the measurement light. For example, near-infrared light having a peak wavelength between 800 nm and 900 nm may be used. As an example, near-infrared light having a peak wavelength of 870 nm may be used.

[0060] In this embodiment, a prism 115 is disposed on the common path of the projection optical system 100a and the light receiving optical system 100b. By rotating the prism 115 around the optical axis, the projection light beam on the pupil is rapidly eccentrically rotated. As an example, in this embodiment, in the region of φ2 mm to φ4 mm on the pupil, the projection light beam is eccentrically rotated. This region becomes the measurement region of the refractive power of the eye in this embodiment.

[0061] The light-receiving optical system 100b includes at least a ring lens 124 and an imaging device 125. The light-receiving optical system 100b extracts the reflected light beam of the measurement light beam reflected from the fundus in a ring shape through the peripheral portion of the pupil. The ring lens 124 is disposed at the pupil conjugate position, and the imaging device 125 is disposed at the fundus conjugate position. By analyzing the ring image formed on the imaging device 125 through the ring lens 124, the eye refractive power is derived.

[0062] As described above, in this embodiment, since the measurement light is rapidly eccentrically rotated on the pupil, an output image from the imaging device 125 based on an exposure for a time sufficiently long with respect to the rotation period, or an addition image of image data sequentially output from the imaging device 125, is subjected to analysis processing, and the eye refractive power is derived. In this embodiment, at least the values of SPH (spherical power), CYL (cylindrical power), and AXIS (astigmatism axis angle) are obtained as a result of the analysis processing.

[0063] Note that the measurement optical system 100 may have optical elements such as lenses and diaphragms in addition to the measurement light source 111, the prism 115, the ring lens 124, and the imaging device 125. The measurement light beam from the measurement light source 111 passes through the hole portion of the hole mirror 113 and the prism 115, and is reflected by the half mirror 502 and the half mirror 501, respectively, to be coaxial with the optical axis L1, and further reaches the fundus through the objective lens 505. The reflected light beam reflected by the fundus when the measurement light beam reaches the fundus passes through the optical path through which the measurement light beam has passed, is reflected by the mirror portion of the hole mirror 123, and reaches the imaging device 125 through the ring lens 124.

[0064] <Fixation target presentation optical system> The fixation target presentation optical system 150 presents a fixation target to the eye to be examined E. The fixation target is presented on the optical axis of the measurement optical system 100. The fixation target presentation optical system 150 is used to fixate the eye to be examined E. Further, it is used to impose a clouding and an accommodation load on the eye to be examined.

[0065] For example, the fixation target presenting optical system 150 includes at least a light source 151 and a fixation target plate 155. The fixation target plate 155 may be disposed at the fundus conjugate position. The fixation light beam from the light source 151 passes through the fixation target plate 155 and the lens 156 on the optical axis L2, and then passes through the half mirror 503. Further, it passes through the lens 504, passes through the half mirror 502, and is reflected by the half mirror 501 to be coaxial with the optical axis L1. The fixation light beam reaches the fundus through the objective lens 505.

[0066] In addition, the measurement light source 111, the ring lens 124, and the imaging device 125 in the measurement optical system 100, and the light source 151 and the fixation target plate 155 in the fixation target presenting optical system 150 can be integrally moved along the optical axis by the driving unit 161 as the driving unit 160. For example, the focal length in the driving unit 160 in the measurement optical system 100 and the focal length in the driving unit 160 in the fixation target presenting optical system 150 are in a predetermined relationship. For example, by moving the driving unit according to the refractive power of the eye E to be examined, the presentation distance of the fixation target plate 155 with respect to the eye E to be examined (that is, the presentation position of the fixation target) can be changed, and further, the measurement light source 111 and the imaging device 125 are optically conjugate to the fundus. At this time, regardless of the movement of the driving unit, the hole mirror 113 and the ring lens 124 are pupil conjugate at a constant magnification.

[0067] <Front imaging optical system> The front imaging optical system 200 is used to capture a front image of the anterior segment of the eye E to be examined. For example, the front imaging optical system 200 includes an imaging device 205 and the like. The imaging device 205 may be disposed at the pupil conjugate position. As the front image, an observation image of the anterior segment may be acquired. The observation image is used for alignment and the like. Further, the index image (dot image) projected from the index projection optical system 400 onto the cornea and the index image (Meyer's ring image) projected from the alignment index projection optical system 600 onto the cornea are captured by the front imaging optical system 200.

[0068] <Cross-sectional imaging optical system> The cross-sectional imaging optical system is used to capture cross-sectional images of the anterior eye segment. The cross-sectional imaging optical system includes an irradiation optical system 300a and a light-receiving optical system 300b.

[0069] The irradiation optical system 300a is coaxial with the projection optical axis (optical axis L1) of the measurement light in the measurement optical system 100, and irradiates slit light (illumination light) onto the anterior eye segment. The irradiation optical system 300a includes a light source 311, a slit 312, etc. The light source 311 may be an SLD light source, an LED light source, or other light sources. In this embodiment, red visible light or near-infrared light is used as the illumination light. For example, red visible light or near-infrared light having a peak wavelength between 650 nm and 800 nm may be used. As an example, red visible light having a peak wavelength of 730 nm may be used. Of course, near-infrared light having a predetermined wavelength as the peak wavelength may also be used. The slit 312 may be disposed at the pupil conjugate position.

[0070] The light source 311 of the irradiation optical system 300a will be described in detail. FIG. 3 is a schematic diagram showing the relationship between the visual sensitivity of the eye to be examined and the wavelength. The eye to be examined has visual sensitivity in the visible region, generally reaching a maximum near 550 nm, which is green visible light, and gradually decreasing as the wavelength becomes longer (as it approaches the infrared region). That is, the eye to be examined is more likely to feel dazzled by green visible light and less likely to feel dazzled by red visible light. It is noted that it is said that the eye to be examined does not feel dazzled by infrared light.

[0071] Conventionally, when acquiring cross-sectional images of the anterior eye segment based on the principle of shine-proof, blue visible light, green visible light, white visible light, etc. have been used as the illumination light. This is because due to the influence of the transmittance of the eye to be examined, cataracts, etc. are likely to appear in the cross-sectional image, but the illumination light is dazzling and burdensome to the subject. On the other hand, with the increase in the myopia prevalence rate, especially among the younger generation in recent years, the measurement of the axial length of the eye for the younger generation has been emphasized. However, since the possibility of cataracts in the younger generation is low, it is also possible to use light different from the above as the illumination light.

[0072] Therefore, in this embodiment, red visible light to near-infrared light that is less likely to cause glare to the eye to be examined is used as illumination light. For example, compared with the visual sensitivity near 550 nm, which is green visible light, the visual sensitivity near 650 nm, which is red visible light, is reduced to about one-tenth, and the visual sensitivity near 700 nm is reduced to about one-two-hundredth. Therefore, the burden on the subject is greatly reduced. In particular, when the target is the younger generation including children, it leads to an improvement in measurement efficiency along with a reduction in burden.

[0073] In this embodiment, the cross-section through which the slit light passes in the anterior segment of the eye is referred to as the "cutting plane". The cutting plane serves as the object plane of the cross-sectional imaging optical system. In FIG. 2, the opening of the slit 312 has its longitudinal direction in the horizontal direction (the depth direction of the paper). Therefore, in this embodiment, the horizontal plane (XZ cross-section) including the optical axis L1 is set as the cutting plane. In this embodiment, at least a cutting plane is formed between the anterior surface of the cornea and the posterior surface of the lens.

[0074] The light receiving optical system 300b includes a lens system 322, an imaging element 321, and the like. In the light receiving optical system 300b, the lens system 322 and the imaging element 321 are arranged in a relationship that is shine-proof with respect to the cutting plane set in the anterior segment of the eye. That is, the optical arrangement is such that the extension planes of the cutting plane, the principal plane of the lens system 322, and the imaging plane of the imaging element 321 intersect at a single intersection line (a single axis). Based on the signal from the imaging element 321, a cross-sectional image of the anterior segment of the eye is acquired. The imaging element 321 may be composed of a semiconductor substrate made of silicon as a single element.

[0075] The imaging element 321 of the light receiving optical system 300b will be described in detail. FIG. 4 is a schematic diagram showing the relationship between the light receiving sensitivity of the imaging element 321 and the wavelength. For example, an imaging element using silicon as a single element has sensitivity to wavelengths in the vicinity of 300 nm to 1000 nm, including wavelengths in the ultraviolet region, visible region, and infrared region, but it is maximum near 550 nm to 650 nm including green visible light, and gradually decreases as it approaches the infrared region. However, the sensitivity at 650 nm or more, including the red visible light to near-infrared light used in the irradiation optical system 300a, is sufficient for acquiring a cross-sectional image of the anterior segment of the eye.

[0076] Note that, for example, there are imaging elements whose sensitivity is maximized in the infrared region, but they are expensive. While it is desired that the device be popularized in many facilities such as hospitals and schools, the high cost of the device can hinder its popularization. By using an imaging element made of silicon, the device can be kept at a low cost.

[0077] In such a cross-sectional imaging optical system, the illumination light beam from the light source 311 becomes a slit light beam through the slit 312 on the optical axis L3, and after passing through the lens 313, it is reflected by the half mirror 503 to be coaxial with the optical axis L2. Further, it passes through the lens 504, transmits through the half mirror 502, and is reflected by the half mirror 501 to be coaxial with the optical axis L1. The illumination light beam further reaches the anterior eye part through the objective lens 505. The return light from the cross-section formed in the anterior eye part reaches the imaging element 321 through the lens 322.

[0078] <Index Projection Optical System> The index projection optical system 400 is used to measure the corneal shape. The index projection optical system 400 projects an index for measuring the corneal shape from the front facing the test eye to the anterior eye part.

[0079] The index projection optical system 400 includes a plurality of point light sources 401. The point light source 401 projects an infinite distance index by irradiating the cornea with parallel light. The point light source 401 emits infrared light. However, it may also be visible light. The point light sources 401 are arranged symmetrically above and below and symmetrically left and right around the optical axis L1. For example, in this embodiment, two point light sources are provided on each side left and right. As a result, four point image indices are projected onto the cornea. Note that the shape of the index is not limited to this, and an index such as a linear shape may be included. Also, the number of indices is not limited to this, and it may be composed of three or more point image indices.

[0080] In this embodiment, the circumferential region on which these four dot images are projected becomes the measurement region of the corneal shape by the index projection optical system 400 and the front imaging optical system 200. As an example, when a corneal model eye having a predetermined radius of curvature is placed at a predetermined working distance, each dot image is projected onto the φ3 mm circumferential region of the corneal model eye.

[0081] <Alignment Index Projection Optical System> The alignment index projection optical system is used to align (position) the measurement unit 11 with respect to the eye to be examined E. In this embodiment, the alignment index projection optical system is formed by the alignment light source 601 and the index projection optical system 400. For example, the operating distance may be adjusted by moving the measurement unit 11 in the front-rear direction so that the Purkinje image by the alignment light source 601 and the Purkinje image by the index projection optical system 400 are photographed at a predetermined ratio.

[0082] The alignment light source 601 projects a finite-distance index by irradiating the cornea with diffused light. The alignment light source 601 emits infrared light. However, it may be visible light. The alignment light source 601 is arranged in a ring shape around the optical axis L1. As a result, in this embodiment, a ring index (so-called Meyer's ring) is projected onto the cornea.

[0083] <Common Optical Path of Fixation Target Presentation Optical System and Cross-Sectional Imaging Optical System> In this embodiment, the fixation target presentation optical system 150 and the visual target projection optical system 300a are both irradiated with visible light. The optical axis L2 of the fixation target presentation optical system 150 and the optical axis L3 of the visual target projection optical system 300a are made coaxial by the half mirror 503. By arranging the fixation target presentation optical system 150 on the transmission side of the half mirror 503 and the visual target projection optical system 300a on the reflection side of the half mirror 503, the optical paths of each are shared. For example, the half mirror 503 is planar, and astigmatism is likely to occur on the transmission side of the half mirror 503. The visual target projection optical system 300a requires a certain imaging performance in order to form a cross-sectional image 70 with a clear cross-section on the anterior eye. For this reason, it is preferable to arrange the visual target projection optical system 300a on the reflection side where the influence of astigmatism is small.

[0084] Also, in this embodiment, a lens 504a is arranged on the optical axis of the fixation target presentation optical system 150. The lens 504a functions as a lens for shortening the overall length to shorten the overall length of the fixation target presentation optical system 150. Further, the lens 504a also serves to reduce the diameter of the lens 156 located upstream of the lens 504a.

[0085] FIG. 5 is a schematic diagram of the simplified fixation target presentation optical system 150. FIG. 5(a) shows the case where the lens 504a is not arranged. FIG. 5(b) shows the case where the lens 504a is arranged. Here, the optical path from the eye under examination E to the fixation target plate 155 is regarded as a straight line, and some optical members are omitted. The fundus imaging light rays from the central part and the peripheral part of the fixation target plate 155 are represented by solid lines and dotted lines, respectively.

[0086] When the distance from the eye E to the objective lens is set as a predetermined operating distance, in Fig. 5(a), the distance of the fixation target presentation optical system 150 (particularly, the distance from the fixation target plate 155 to the lens 156) becomes long. The light rays from the central part and the peripheral part of the fixation target plate 155 both reach the lens 156 with a large diameter. On the other hand, as shown in Fig. 5(b), when the lens 504a is arranged in the fixation target presentation optical system 150, the distance of the fixation target presentation optical system 150 can be shortened. This is because the focal length when the lens 156 and the lens 504a are combined is shorter than the focal length of only the lens 156. Each light ray from the fixation target plate 155 reaches the lens 156 with a small diameter.

[0087] Note that, for example, the fixation target presentation optical system 150 may be a telecentric optical system on the target side, and the lens 504a may be arranged at the pupil conjugate position. At this time, since the light rays from the central part and the peripheral part of the fixation target plate 155 pass through the center of the lens 504a, the overall focal length (combined focal length) of the fixation target presentation optical system 150 does not change. Therefore, the relationship of the focal lengths in the driving unit 160 of the fixation target presentation optical system 150 and the measurement optical system 100 is maintained.

[0088] Thus, if the lens 504a is arranged in the fixation target presentation optical system 150, the lens 156 can be designed with a small diameter. Also, while maintaining the predetermined operating distance of the eye E and the combined focal length of the fixation target presentation optical system 150, the overall length of the fixation target presentation optical system 150 can be shortened. As a result, it leads to miniaturization of the ophthalmic device 10.

[0089] Also, in this embodiment, the lens 504b is arranged on the optical axis of the target projection optical system 300a. The lens 504b serves to reduce the diameter of the objective lens 505 located downstream of the lens 504b.

[0090] FIG. 6 is a schematic diagram of the simplified target projection optical system 300a. FIG. 6(a) shows the case where the lens 504b is not arranged. FIG. 6(b) shows the case where the lens 504b is arranged. Here, the optical path from the eye E to be examined to the slit 312 is regarded as a straight line, and some optical members are omitted. The pupil imaging light rays from the central part and the peripheral part of the slit 312 are represented by solid lines and dotted lines, respectively.

[0091] In FIGS. 6(a) and 6(b), the light rays from the central part of the slit 312 pass through the center of the objective lens 505 regardless of the presence or absence of the lens 504b. However, in FIG. 6(a), the light rays from the peripheral part of the slit 312 are refracted at a position farther from the center of the objective lens 505. In order to allow such light rays to reach the eye E to be examined, an objective lens 505 with a large diameter is required. On the other hand, in FIG. 6(b), the light rays from the peripheral part of the slit 312 are refracted at the position of the center of the objective lens 505. In order to allow such light rays to reach the eye E to be examined, an objective lens 505 with a small diameter can be used.

[0092] Thus, if the lens 504b is arranged in the target projection optical system 300a, the traveling direction of the light rays passing outside the optical axis L3 can be changed without changing the traveling direction of the light rays passing through the optical axis L3. Therefore, the objective lens 155 can be designed with a small diameter. Note that the larger the aberration is likely to occur as the light rays from the central part and the peripheral part of the slit 312 are refracted in a region away from the center of the objective lens 505. For this reason, an objective lens 155 with an appropriate diameter that suppresses the occurrence of aberration while miniaturizing the ophthalmic apparatus 10 may be used.

[0093] Note that in this embodiment, in the fixation target presentation optical system 150 and the target projection optical system 300a, the lens 504 that shares the lenses 504a and 504b having different roles described above is arranged. For example, the lens 504 is arranged downstream of the half mirror 503 where the optical axis L2 of the fixation target presentation optical system 150 and the optical axis L3 of the target projection optical system 300a are combined. Thereby, the inside of the optical system is made more space-saving.

[0094] <Control Operation> The control operation of the ophthalmic device 10 will be described with reference to the flowchart shown in FIG. 7. In this embodiment, the ophthalmic device 10 sequentially performs corneal curvature measurement, eye refractive power measurement, and anterior eye segment image capture, and the axial length of the eye is obtained based on the results of the measurement and capture.

[0095] <Alignment (S1)> First, alignment of the measurement unit 11 with respect to the eye E to be examined is performed. The examiner instructs the subject to place their face on the face support unit 15. The control unit 50 starts presenting the fixation target and acquiring the anterior eye observation image.

[0096] For example, the control unit 50 adjusts the eye E to be examined and the ophthalmic device 10 to a predetermined positional relationship based at least on the observation image of the anterior eye obtained through the front imaging optical system 200. More specifically, alignment in the XY direction is performed so that the optical axis L1 coincides with the corneal apex of the eye E to be examined. Also, alignment in the Z direction is performed so that the distance between the eye E to be examined and the ophthalmic device 10 becomes a predetermined operating distance. At this time, an alignment index may be projected onto the cornea, and the alignment may be adjusted based on the alignment index detected in the observation image.

[0097] <Corneal shape measurement (S2)> Next, the corneal shape of the eye E to be examined is measured. The control unit 50 projects a point image index from the index projection optical system 400, and photographs the corneal Purkinje image of the point image index with the front imaging optical system 200. Also, the control unit 50 acquires corneal shape information based on the corneal Purkinje image. For example, corneal shape information is derived based on the image height of the corneal Purkinje image. In this embodiment, at least the values of corneal curvature, astigmatism degree, and astigmatism axis angle are acquired as the corneal shape information.

[0098] <Eye refractive power measurement (S3)> Next, the refractive power of the eye E to be examined is measured. Since infrared light is projected onto the eye E to be examined as measurement light, the pupil diameter of the eye E to be examined becomes a predetermined size in which miosis (for example, φ2 mm or less) is suppressed. As an example, it becomes any diameter included in the measurement region of the eye E to be examined (the region of φ2 mm to φ4 mm on the pupil). For example, in the measurement of refractive power, preliminary measurement may be performed first and then main measurement may be performed.

[0099] In the preliminary measurement, the refractive power of the eye E to be examined is measured with the fixation target arranged at a predetermined presentation distance. At the time of measurement, the fixation target plate 155 may be arranged at an initial position that is an optically sufficient distant distance from the eye E to be examined and corresponds to the far point of a 0D eye. The ring image captured by the imaging element 125 based on the measurement light irradiated in this state is subjected to image analysis by the control unit 50. As an analysis result, the values of the refractive power in each meridian direction are obtained. By performing a predetermined process on the refractive power in each meridian direction, at least the spherical diopter in the preliminary measurement is acquired.

[0100] Subsequently, the control unit 50 moves the fixation target plate 155 to the clouding start position where the eye E to be examined is in focus according to the spherical diopter of the preliminary measurement of the eye E to be examined. As a result, the fixation target can be clearly observed in the eye E to be examined. Then, the control unit 50 adds clouding to the eye E to be examined by moving the fixation target from the clouding start position. Thereby, the accommodation of the eye E to be examined is released.

[0101] The main measurement is performed with clouding added to the eye E to be examined. By performing a predetermined analysis process on the ring image captured of the eye E to be examined with clouding added, objective values of SPH: spherical diopter, CYL: cylindrical diopter, and AXIS: astigmatic axis angle of the eye E to be examined are acquired.

[0102] <Taking a cross-sectional image of the anterior segment of the eye (S4)> Next, a cross-sectional image (Shine-proof image) of the anterior eye segment of the eye E to be examined is taken. After the completion of the main measurement of the eye refractive power, the control unit 50 immediately executes the taking of the cross-sectional image of the anterior eye segment. For example, the operation of taking the cross-sectional image may be executed using the completion of the main measurement of the eye refractive power as a trigger. That is, immediately after the completion of the main measurement, illumination light is irradiated from the irradiation optical system 300a, and a cross-sectional image of the anterior eye segment is obtained by imaging the scattered light scattered by the cornea and the lens on the imaging element 321. Thereby, the alignment deviation is reduced between the time of measuring the eye refractive power and the time of taking the cross-sectional image.

[0103] FIG. 8 is an example of a cross-sectional image 70 of the anterior eye segment. Artifacts may be reflected in the cross-sectional image 70 together with the cornea, iris, lens, etc. For example, the slit light (illumination light) irradiated from the irradiation optical system 300a forms a cut surface on the anterior eye segment, but a part of it may be reflected (specular reflection) by the cornea. When the imaging element 321 of the light receiving optical system 300b images the return light from the cut surface of the slit light and the corneal reflected light of the slit light, the image of this corneal reflected light is reflected in the cross-sectional image 70 as an artifact 75. In the subsequent analysis of step S5, if the artifact 75 exists, it becomes difficult to accurately obtain the anterior eye segment shape information.

[0104] <Analysis of the anterior eye segment cross-sectional image (S5)> The control unit 50 acquires anterior eye segment shape information regarding the shape of the anterior eye segment based on the cross-sectional image 70 of the anterior eye segment of the eye E to be examined. For example, the anterior eye segment shape information may include a plurality of parameter information which are measurement values such as the radius of curvature (Ra) of the anterior surface of the cornea, the radius of curvature (Rp) of the posterior surface of the cornea, the corneal thickness (CT), the anterior chamber depth (ACD), the radius of curvature (ra) of the anterior surface of the lens, the radius of curvature (rp) of the posterior surface of the lens, and the lens thickness (LT). Note that it is also possible to use the corneal shape information acquired in step S2 as the anterior eye segment shape information.

[0105] The control unit 50 detects each light-transmitting body (e.g., cornea, aqueous humor, lens, etc.) by performing image processing on the cross-sectional image 70 and acquires anterior eye shape information. For example, by using the luminance information of the cross-sectional image 70, the pixel positions corresponding to the boundaries of tissues (front and rear surfaces of the cornea, front and rear surfaces of the lens, iris, etc.) may be detected, and information such as the radius of curvature may be acquired. Also, for example, the distance of the pixel positions corresponding to the boundaries of tissues may be obtained, and information such as the thickness and depth of the tissues may be acquired.

[0106] In this embodiment, the control unit 50 sets an analysis region that does not include the artifact 75 during the image processing of the cross-sectional image 70. This is because the artifact 75 may cause misdetection of the boundaries of each tissue or may reduce the detection accuracy of the boundaries of each tissue. In particular, when at least a part of the artifact 75 is close to or overlaps with the boundary of the tissue, the influence on the detection is significant. Therefore, the pixel positions of the artifact 75 are specified, and the artifact 75 is excluded from the analysis region for image processing.

[0107] FIG. 9 is a diagram for explaining the analysis region of the cross-sectional image 70. The control unit 50 may specify the pixel positions of the artifact 75 by using the luminance information of the cross-sectional image 70. For example, the corneal reflection light of the slit light is the light that does not pass through the cornea or the lens and is not attenuated. On the other hand, the return light from the cut surface of the slit light is the light that has been attenuated by passing through the cornea or the lens and is also a part of the light scattered by the cornea or the lens. Therefore, the luminance appearing in the cross-sectional image 70 as an image is different between the corneal reflection light and the return light (scattered light). As an example, the control unit 50 may specify the pixel positions of the artifact 75 by detecting whether the luminance value exceeds a preset threshold for each pixel position of the cross-sectional image 70.

[0108] Subsequently, the control unit 50 excludes the pixel positions of at least the artifacts 75 from the target region Q for analysis in the cross-sectional image 70 (i.e., the target region Q including all pixel positions). In this embodiment, based on the pixel positions of the artifacts 75, a range having a predetermined number of pixels in the vertical and horizontal directions is set as a non-analysis region Q1 (the solid line portion in FIG. 9) to be excluded from the target region Q. As a result, an analysis region Q2 that is the target of the image processing of the cross-sectional image 70 and from which the non-analysis region Q1 is excluded from the target region Q (the dotted line portion in FIG. 9) is set.

[0109] Based on the luminance information of the analysis region Q2, the control unit 50 may detect the pixel positions corresponding to the boundaries of the tissue and specify at least three pixel positions of each boundary. When the boundary of the tissue detected in the analysis region Q2 includes the pixel position on the optical axis L1, at least three pixel positions may be specified so as to necessarily include the intersection of the boundary of the tissue and the optical axis L1. The control unit 50 can obtain a circle passing through the specified at least three points, and information such as the center point and radius of this circle, and can also obtain information such as the thickness and depth of the tissue by obtaining the distance of the pixel positions corresponding to the boundary of the tissue.

[0110] When some of the luminance values of the cross-sectional image 70 are low (for example, when the eyelids or eyelashes of the subject are reflected), or when the setting of the non-analysis region Q1 is inappropriate, the error due to the fitting of the circle using at least three pixel positions may increase. In this case, the control unit 50 may change the points specified on the cross-sectional image 70. For example, for this, the similarity between the cross-sectional image 70 and the structure of the anterior eye predicted by the image processing of the cross-sectional image 70 may be used. If the specified point is in a region with low similarity, that point may be deleted and reselected from a region with high similarity. Also, when the control unit 50 specifies four or more pixel positions in the cross-sectional image 70, it may delete a predetermined point so that at least three pixel positions remain. That is, if a point not along the curved surface of the cornea or lens is specified in the cross-sectional image 70, it may be deleted as appropriate.

[0111] <Axial length calculation (S6)> Next, the axial length of the eye E to be examined is calculated. The control unit 50 calculates the axial length based on the refractive power of the eye E to be examined and a plurality of parameter information in the anterior eye shape information of the eye E to be examined.

[0112] First, the control unit 50 determines the position of the far point FP (see FIG. 10) with respect to the corneal apex C based on the measurement result of the refractive power of the eye E to be examined. For example, if there is no astigmatism in the eye E to be examined, SPH = -5D, and VD = 12 mm, then 12 + 1000 / 5 = 212 mm is the distance from the corneal apex C to the far point FP. It is considered that the light rays from the far point FP form an image on the fundus. Note that VD = 12 mm is a constant value indicating the corneal vertex distance on the premise of wearing spectacle lenses. VD may vary depending on the device.

[0113] FIG. 10 is a schematic diagram for explaining the method of deriving the axial length. In this embodiment, the axial length may be derived based on ray tracing calculation on the cross-section of the anterior eye. For example, the control unit 50 performs ray tracing calculation based on the position of the far point FP, the refractive index of each light-transmitting body, and the parameter information in the anterior eye shape information.

[0114] The control unit 50 traces the light rays (for example, the light ray Lx in FIG. 10) incident from the far point FP toward the eye E to be examined, determines the position of the intersection point where the light rays are refracted by each light-transmitting body of the eye E to be examined and the light rays intersect the optical axis. The details of the ray tracing calculation will be described later. For example, the position of the fundus Ef can be determined by such ray tracing calculation. The control unit 50 derives the distance between the corneal apex C and the fundus Ef as the axial length AL. <C

[0115] <Display output (S6)> Finally, the axial length AL is displayed on the monitor 16. In this embodiment, the axial length AL is displayed together with at least one of the corneal shape information and the eye refractive power (SPH, CYL, AXIS) of the eye to be examined E. If there are past axial length measurement results for the eye to be examined E, the current measurement result may be displayed together with the past measurement results. For example, the measurement results may be displayed by a trend graph with the age (measurement date) on the horizontal axis and the axial length AL on the vertical axis. Of course, the display mode of the measurement results is not limited to these.

[0116] <Ray tracing calculation> The ray tracing calculation for deriving the axial length will be described. In this embodiment, for the sake of convenience of explanation, it is assumed that the refractive index in each light-transmitting body of the eye to be examined E is constant and there is no refractive change inside each. However, it is not necessarily limited to this, and the axial length may be derived in consideration of the change in the refractive index inside the light-transmitting body (for example, the change in the refractive index between the inside and the outside of the lens).

[0117] By the way, in the widely used expression form of eye refractive power by SPH, CYL, and AXIS, since SPH indicates the refractive power related to the strong principal meridian (or weak principal meridian), it does not necessarily become an appropriate value in the ray tracing on the cross-section of the anterior eye part. For example, consider the case where SPH = -5D, CYL = -2D, and AXIS = 30°. In this case, assuming that a horizontal cross-section was obtained in the above optical system example, the refractive power in this cross-section is neither -5D nor -7D with CYL added.

[0118] [[ID=I4]]In contrast, in this embodiment, the refractive power on the surface, which is the eye refractive power on the cross-section, is obtained, and based on the refractive power on the surface, the position of the far point FP is set. Here, the refractive power P at an arbitrary surface is expressed by the following formula. However, θ is the angle with respect to the horizontal plane, and the horizontal direction is 0°.

[0119] P(θ)=SPH+CYL×[sin2(θ - A)]

[0120] FIG. 11 is a diagram showing refractive powers in each meridian direction when the eye E to be examined has SPH = -5D, CYL = -2D, and AXIS = 30°. For example, the cutting plane in this embodiment is the horizontal plane (θ = 0°). Therefore, if the eye E to be examined has SPH = -5D, CYL = -2D, and AXIS = 30°, P(0°) is calculated to be -5.5D. In this case, if the distance from the corneal vertex C to the far point FP on the cutting plane is VD = 12 mm, it becomes 12 + 1000 / 5.5 = 194 mm.

[0121] The control unit 50 tracks the light rays from the thus-set far point FP. For example, it guides a light ray (for example, the light ray Lx in FIG. 10) from the far point FP toward a certain position (as an example, the position of the pupil of the eye to be examined (about 3 mm behind the cornea) at a position of φ6 mm). Note that setting the certain position to the position of the pupil of the eye to be examined at φ6 mm is merely an example and can be changed as appropriate.

[0122] This light ray first undergoes the first refraction at the anterior corneal surface. The intersection point of the light ray and the anterior corneal surface is calculated based on the radius of curvature Ra of the anterior corneal surface, the position of the far point FP, and the light ray angle at the far point FP. Further, the incident angle of the light ray at the intersection point is calculated. The light ray reaching the anterior corneal surface changes its direction at a refraction angle determined with respect to the incident angle based on Snell's law. In this way, the light rays at each light-transmitting body interface are sequentially tracked. At that time, the anterior eye shape information (Ra, Rp, CT, ACD, ra, rp, LT) obtained based on the corneal shape information and the cross-sectional image 70 (Shine-proof image) is appropriately used to provide the intersection points between each interface and the light ray. In this embodiment, finally, after exiting the posterior lens surface, the intersection point (that is, the position of the fundus Ef) that intersects the eye axis (here, the visual axis) is obtained. The distance from the intersection point to the corneal vertex C (here, the origin) is used as the eye axis length AL.

[0123] In addition, in the ray tracing calculation, when using the above anterior eye shape information (Ra, Rp, CT, ACD, ra, rp, LT), in this embodiment, for at least the radius of curvature Ra of the anterior corneal surface, a value based on the corneal Purkinje image of the point image index is used, and for the remaining values, values based on the cross-sectional image 70 (shine proof image) are used. Generally, for the anterior corneal shape, the measurement accuracy based on the corneal Purkinje image is higher than that based on the shine proof image. As described above, in this embodiment, at least the values of corneal curvature, astigmatism degree, and astigmatism axis angle are acquired as corneal shape information. Using a method similar to the method for obtaining the refractive power with respect to the cross-section, the corneal curvature (curvature of the anterior corneal surface) in the cross-section can be obtained from these values. The reciprocal of the obtained value may be used as Ra.

[0124] The axial length AL of the eye to be examined E can be obtained by tracing the rays directed to such a fixed position. However, the ray tracing method is not limited to the above method. For example, the point where an image is formed from the far point FP may be obtained by paraxial calculation. Also, considering a plurality of rays having different incident positions on the eye to be examined E, the point where an image is formed from the far point FP may be obtained. For example, ray tracing for each of a paraxial ray and a ray directed to a fixed position different from the paraxial may be combined. When ray tracing is performed for a plurality of rays, the final measured value (calculated value) of the axial length may be the average value (or weighted average value) of the axial lengths obtained by each ray tracing.

[0125] Also, the axial length AL may be obtained by tracing the rays directed to the measurement region (φ2 mm to φ4 mm on the pupil) by the measurement optical system 100. For example, ray tracing may be performed for each of a plurality of rays directed to the region of φ2 mm to φ4 mm on the pupil, and the average value of the axial lengths obtained by each ray tracing may be acquired as the calculation result. Since ray tracing is performed under more appropriate conditions, the axial length is more likely to be acquired with higher accuracy.

[0126] In addition, a predetermined offset value may be added to the axial length value obtained in this embodiment. The offset value corrects the error between the calculated value and the actually measured value.

[0127] Also, ray tracing may be performed by tracing a ray that exits from the far point FP and passes through a circumferential region where a point image index for corneal shape measurement is projected. As a result, the conditions for ray tracing become more appropriate, and the axial length is more easily obtained with higher accuracy.

[0128] As described above, for example, the ophthalmic device in this embodiment includes an optical path coupling member that couples the fixation optical path of the fixation light in the fixation target presentation optical system and the measurement optical path (light projection optical path) of the measurement light (illumination light) in the cross-sectional image imaging optical system. Thereby, a fixation target can be appropriately presented to the eye to be examined, a cross-sectional image of the anterior eye segment can be taken well, and the axial length can be accurately obtained. Since the fixation light is focused on the fundus and the illumination light is focused on the anterior eye segment, each optical system has a complicated configuration due to commonization. On the other hand, the optical path coupling member can be easily configured. When both the fixation light and the illumination light are visible lights, the optical path coupling member can be configured more easily.

[0129] Also, for example, the ophthalmic device in this embodiment arranges a common lens that functions as a total length shortening lens for shortening the total length of the fixation target presentation optical system and functions as a field lens for changing the traveling direction of the measurement light (illumination light) in the cross-sectional image imaging optical system in the common optical path between the fixation optical path and the measurement optical path. For example, although the fixation target presentation optical system includes a total length shortening lens in its configuration, by utilizing the total length shortening lens as a field lens of the cross-sectional image imaging optical system with the commonization of the fixation optical path and the measurement optical path, it is possible to design without increasing the size of the objective lens. Therefore, the configuration of the optical system is made space-saving, and the ophthalmic device is miniaturized.

[0130] Also, for example, the ophthalmic device in this embodiment uses a planar member as the optical path coupling member. Note that in a planar member, astigmatism is likely to occur on the transmission side, and astigmatism is less likely to occur on the reflection side. For this reason, the imaging performance of the light arranged on the transmission side is lower than that of the light arranged on the reflection side. In this embodiment, by arranging the fixation optical path on the transmission side, the imaging performance of the illumination light is prioritized, and the anterior eye segment image can be taken well. Note that by arranging the measurement optical path on the reflection side, although the imaging performance of the fixation light is reduced, since the performance that allows the fixation target to be fixated is ensured, the influence on visual recognition can be suppressed to a small level.

[0131] Also, for example, the ophthalmic device in this embodiment identifies artifacts included in the anterior eye segment image and sets an analysis region excluding the artifacts. Thereby, the anterior eye shape information can be accurately acquired using only the region suitable for the analysis of the anterior eye segment image.

[0132] Also, for example, the ophthalmic device in this embodiment changes whether or not to use a point on the optical axis of the measurement light in the eye refractive power measurement optical system according to the position of the analysis region with respect to the anterior eye segment image. For example, when an artifact is detected at a location close to the curved surface of each tissue, or when an artifact is detected overlapping the curved surface of each tissue, the accuracy of the anterior eye shape information may decrease. By appropriately changing the point used for the analysis of the anterior eye segment image, the anterior eye shape information can be accurately acquired.

[0133] [[ID=**12**]]<Modification Example> In this embodiment, the configuration in which the optical axes of the fixation target presentation optical system 150 and the visual target projection optical system 300a are branched or combined by the planar half mirror 503 has been described as an example, but the present invention is not limited thereto. In this embodiment, a prism-type half mirror may be used to branch or combine each optical axis. In the prism type, regardless of whether it is the transmission side or the reflection side, astigmatism is less likely to occur. Therefore, no matter how the fixation target presentation optical system 150 and the visual target projection optical system 300a are arranged with respect to the half mirror, the imaging performance of the visual target projection optical system 300a can be maintained. As a result, the anterior eye cross-sectional image can be taken well.

[0134] In this embodiment, the configuration in which the shared lens 504 is arranged on the common optical axis of the fixation target presentation optical system 150 and the visual target projection optical system 300a has been described as an example, but the present invention is not limited thereto. In this embodiment, lenses (lenses 504a and 504b) with different roles may be arranged on the optical axes of the respective optical systems. That is, the lenses 504a and 504b may be arranged upstream of the half mirror 503 that branches or combines the optical axes of the respective optical systems. However, in order to miniaturize the ophthalmic device 10, it is preferable to use the shared lens 504 that shares the lenses 504a and 504b.

[0135] In this embodiment, the configuration in which the pixel position of the artifact 75 is specified using the threshold value of the luminance value in the cross-sectional image of the anterior eye 70 has been described as an example, but the present invention is not limited thereto. In this embodiment, the pixel position of the artifact 75 may be specified by calculating the similarity based on the luminance values of the cross-sectional image 70 and the template image. As an example, in this case, the control unit 50 may move the template image to be overlapped with the cross-sectional image 70 pixel by pixel (so-called pattern matching) and detect a combination in which the similarity based on the difference in each luminance value becomes zero (or a value closest to zero). Note that the storage unit (memory) of the ophthalmic device 1 may have a template image.

[0136] For example, since the shape, size, luminance value, etc. of the artifact 75 reflected in the cross-sectional image 70 can be predicted in design, a template image for detecting the artifact 75 may be used. In this case, the control unit 50 may specify the pixel position of the template image corresponding to the cross-sectional image 70 as the pixel position of the artifact 75. Further, the control unit 50 may set the non-analysis region Q1 based on the pixel position of the artifact 75 in the cross-sectional image 70.

[0137] Also, for example, a template image representing a standard cross-sectional image of the eye, which models the general eye structure, may be used. The control unit 50 specifies the pixel position of the template image corresponding to the cross-sectional image 70. However, when the cross-sectional image 70 includes an artifact 75 or the like, a difference occurs in each luminance value, and they do not partially match. Therefore, the control unit 50 may set the pixel position where the template image matches in the cross-sectional image 70 as the analysis region Q2 of the cross-sectional image 70. Alternatively, the control unit 50 may specify the pixel position where the template image does not match in the cross-sectional image 70 as the pixel position of the artifact 75, and based on this, set the non-analysis region Q1 of the cross-sectional image 70. That is, the template image may be used for indirect detection of the artifact 75.

[0138] In this embodiment, a configuration in which the non-analysis region Q1 and the analysis region Q2 are set using the luminance information in the cross-sectional image 70 of the anterior eye segment has been described as an example, but it is not limited thereto. In this embodiment, a configuration in which each region is set using the anterior eye segment information regarding the anterior eye segment of the eye to be examined E may be used. The anterior eye segment information may be information including anterior eye segment shape information (corneal shape information, lens shape information, etc.), information regarding the pupil state (for example, miosis or mydriasis), and the like. Thereby, it is possible to easily grasp a region suitable for analysis of the anterior eye segment cross-sectional image and accurately acquire the anterior eye segment shape information.

[0139] For example, the control unit 50 may set at least the non-analytical region Q1 in the cross-sectional image 70 based on the radius of curvature of the anterior corneal surface, which is one of the anterior eye shape information of the eye E to be examined. In this case, the control unit 50 acquires the radius of curvature of the anterior corneal surface of the eye E to be examined and also acquires the pixel position of the artifact 75 corresponding to the radius of curvature. For example, from the radius of curvature of the anterior corneal surface, the approximate pixel position where the artifact 75 is reflected can be predicted. Note that the storage unit of the ophthalmic apparatus 1 may have a correspondence table in which the pixel positions changing for each radius of curvature are associated in advance. Thereby, it is also possible to determine the non-analytical region Q1 without using the luminance information of the cross-sectional image 70.

[0140] Further, for example, the control unit 50 may set at least the analytical region Q2 in the cross-sectional image 70 based on the pupil diameter, which is one of the pupil state information of the eye E to be examined. In this case, the control unit 50 acquires the pupil diameter PDM (see FIG. 8) by detecting the iris of the eye E to be examined, and may set the region inside the pupil diameter PDM as the analytical region Q2. Note that the region inside the pupil diameter PDM may be limited to the same region as the measurement region of the eye refractive power by the measurement optical system 100 (for example, φ2 mm to φ4 mm on the pupil).

[0141] Of course, in the cross-sectional image 70, a configuration may be adopted in which the non-analytical region Q1 and the analytical region Q2 are set by combining the luminance information and the anterior eye information.

[0142] In this embodiment, the case where the artifact 75 is reflected in the cross-sectional image 70 of the anterior eye by the slit light irradiated from the irradiation optical system 300a has been described as an example, but the present invention is not limited to this. For example, the measurement light irradiated from the index projection optical system 400 or the measurement light irradiated from the alignment index projection optical system is reflected by the cornea and imaged by the imaging element 321, whereby the reflection of the artifact may occur.

[0143] FIG. 12 is an example of a cross-sectional image 70 of the anterior eye segment. For example, in the cross-sectional image 70, there may occur a dot-shaped artifact 76 derived from the light source 401, a ring-shaped artifact 77 derived from the alignment light source 601, etc. (the shapes of the respective artifacts are not limited to this). Therefore, similar to the artifact 75, the control unit 50 may also exclude the artifact 76 and the artifact 77 from the target region Q as the non-analysis region Q1, and perform image processing on the analysis region Q2 that does not include them. Thereby, the anterior eye segment shape information of the eye to be examined can be acquired more accurately, and an appropriate axial length can be acquired.

[0144] In addition, in the photographing of the cross-sectional image of the anterior eye segment, by turning off the light source 401, the reflection of the artifact 76 into the cross-sectional image 70 can be suppressed. Also, by turning off the alignment light source 601, the reflection of the artifact 77 into the cross-sectional image 70 can be suppressed.

[0145] In this embodiment, in order to appropriately acquire the anterior eye segment shape information, a configuration in which artifacts are excluded from the analysis region of the cross-sectional image 70 has been described as an example, but it is not limited to this. For example, an optical member for blocking at least any one of the slit light from the irradiation optical system 300a, the measurement light from the index projection optical system 400, the measurement light from the alignment index projection optical system, etc., i.e., corneal reflection light, may be arranged in the optical path of the optical system provided in the ophthalmic apparatus 10. Thereby, the reflection of the artifact into the cross-sectional image 70 is suppressed, and the anterior eye segment shape information based on the cross-sectional image 70 can be appropriately acquired.

[0146] In this embodiment, the case where the refractive index of each light-transmitting body of the eye E to be examined is constant is taken as an example for explanation, but the present invention is not limited thereto. For example, separately from the cross-sectional image 70 of the anterior eye segment, refractive index information regarding the refractive index of the light-transmitting body may be acquired, and the refractive index information may be used for deriving the axial length AL of the eye. That is, when acquiring the axial length AL of the eye, the refractive index of the light-transmitting body based on the refractive index information may be further considered. As an example, the refractive index information may include the refractive index of the crystalline lens. It is known that the refractive index of the crystalline lens changes with aging. Therefore, the storage unit of the ophthalmic apparatus 10 may have a calculation formula or a look-up table in which the refractive index of the crystalline lens is associated with each age. In this case, by inputting the age of the subject, the refractive index corresponding to the age can be acquired. The control unit 50 may perform ray tracing calculation using such a refractive index of the crystalline lens.

[0147] In this embodiment, the configuration in which measured values are all applied to the anterior eye segment shape information (Ra, Rp, CT, ACD, ra, rp, LT) used for the ray tracing calculation of the axial length AL has been described by taking an example, but the present invention is not limited thereto. In this embodiment, the anterior eye segment shape information may be configured such that assumed values are applied to a part thereof. The assumed value can be selected from at least any one of a standard value based on a model eye, an average value based on statistical data, etc., a past measured value of the eye to be examined, an estimated value that can be obtained in consideration of the general ratio of each tissue, etc.

Explanation of Reference Numerals

[0148] 10 Ophthalmic apparatus 50 Control unit 100 Measurement optical system 150 Fixation target presentation optical system 200 Frontal imaging optical system 300a Irradiation optical system 300b Light receiving optical system 400 Index projection optical system

Claims

Claim 1: A fixation target presenting optical system that projects fixation light onto an eye to be examined and presents a fixation target used for creating a haze for the eye to be examined, an eye refractive power measurement optical system that projects first measurement light onto the fundus of the eye to be examined and acquires the eye refractive power of the eye to be examined based on the reflected light obtained by reflecting the first measurement light from the fundus, a cross-sectional image capturing optical system that projects second measurement light onto the anterior segment of the eye to be examined, forms a light cutting plane passing through the optical axis of the eye refractive power measurement optical system on the anterior segment, and acquires a cross-sectional image of the anterior segment of the eye to be examined based on the return light of the second measurement light from the light cutting plane, and having, an ophthalmic device that acquires the axial length of the eye to be examined based on the eye refractive power and the cross-sectional image of the anterior segment, the ophthalmic device being characterized by including an optical path coupling member that couples the fixation optical path of the fixation light in the fixation target presenting optical system and the measurement optical path of the second measurement light in the cross-sectional image capturing optical system. Claim 2 In the ophthalmic device according to Claim 1, a common lens is disposed in the common optical path in which the fixation optical path and the measurement optical path are coupled by the optical path coupling member, the common lens being a total length shortening lens for shortening the total length of the fixation target presenting optical system and a field lens for changing the traveling direction of the measurement light in the cross-sectional image capturing optical system. The ophthalmic device is characterized by this. Claim 3 In the ophthalmic device according to Claim 1 or 2, the optical path coupling member is a prism-type member. The ophthalmic device is characterized by this. Claim 4 In the ophthalmic device according to any one of Claims 1 to 3, the optical path coupling member is a planar member. The ophthalmic device is characterized by this. Claim 5 In the ophthalmic device according to any one of Claims 1 to 4, the fixation optical path is disposed on the transmission side of the optical path coupling member, and the measurement optical path is disposed on the reflection side of the optical path coupling member. The ophthalmic device is characterized by this.

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