Ophthalmic devices

Abstract

To provide an ophthalmologic apparatus capable of accurately measuring an eye axial length.SOLUTION: An ophthalmologic apparatus includes: an eye refractive power measurement optical system for acquiring an eye refractive power of a subject's eye; a cross-sectional image imaging optical system for acquiring an anterior eye part cross-sectional image of the subject's eye by projecting measurement light to an anterior eye part of the subject's eye and detecting return light of the measurement light from an oblique direction to a projection optical axis of the measurement light; shape information acquisition means for acquiring shape information related to a shape of the anterior eye part and including a plurality of parameters by analyzing the anterior eye part cross-sectional image; and eye axial length acquisition means for controlling the eye refractive power measurement optical system and the cross-sectional image imaging optical system and acquiring an eye axial length of the subject's eye based on the eye refractive power and the plurality of parameters. The eye axial length acquisition means acquires a first eye axial length derived by using measurement values of the plurality of parameters and a second eye axial length derived by using an assumption value obtained by substituting a measurement value of a part of the plurality of parameters.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an ophthalmic apparatus that acquires the axial length of a subject's eye. [Background technology]

[0002] 2. Description of the Related Art There is known an ophthalmic apparatus that illuminates an optical body in an anterior segment of an examinee's eye in a manner that cuts the optical axis of the anterior segment, and captures a cross-sectional image of the anterior segment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-134907 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned ophthalmologic apparatus, the anterior ocular segment cross-sectional image of the subject's eye may not be captured properly. For example, if the subject's eyelids or eyelashes are captured, their shadows may appear in the anterior ocular segment cross-sectional image. Also, a reflection of illumination light reflected by the eyelashes may appear in the anterior ocular segment cross-sectional image. For example, if the pupil state of the subject's eye is not proper, the return light of the illumination light may be vignetted, causing a change in the capture range of the anterior ocular segment in the depth direction.

[0005] On the other hand, in recent years, the prevalence of myopia has increased significantly, especially among young people, and evaluation of myopia progression based on axial length has attracted attention. The inventors have studied a device configuration that acquires both the ocular refractive power and anterior ocular cross-sectional image of the subject's eye and acquires the axial length based on these. However, even with such a device configuration, it is difficult to acquire the axial length unless the anterior ocular cross-sectional image is appropriately captured.

[0006] The present disclosure has been made in consideration of the above circumstances, and has as its technical object to provide an ophthalmic apparatus that can appropriately acquire an anterior segment cross-sectional image and accurately acquire an axial length. [Means for solving the problem]

[0007] The ophthalmic device disclosed herein comprises an eye refractive power measuring optical system for acquiring the eye refractive power of the test eye, a cross-sectional image taking optical system for acquiring a cross-sectional image of the anterior segment of the test eye by projecting measurement light toward the anterior segment of the test eye and detecting the return light of the measurement light from an oblique direction relative to the projection optical axis of the measurement light, a shape information acquiring means for analyzing the anterior segment cross-sectional image and acquiring shape information regarding the shape of the anterior segment, the shape information including a plurality of parameters, and an axial length acquiring means for controlling the eye refractive power measuring optical system and the cross-sectional image taking optical system, and acquiring the axial length of the test eye based on the eye refractive power and the plurality of parameters, wherein the axial length acquiring means acquires a first axial length derived using measured values ​​of the plurality of parameters and a second axial length derived using assumed values ​​replacing measured values ​​of some of the plurality of parameters. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an external view of an ophthalmic apparatus. [Diagram 2] FIG. 2 is a schematic diagram showing an optical system of an ophthalmic apparatus. [Diagram 3] 1 is a schematic diagram showing the relationship between the visibility of a test eye and wavelength. [Figure 4] 2 is a schematic diagram showing the relationship between the light receiving sensitivity of an image sensor and wavelength. FIG. [Diagram 5] FIG. 2 is a simplified schematic diagram of a fixation target presenting optical system. [Figure 6] FIG. 2 is a schematic diagram showing a simplified visual target projection optical system. [Figure 7] 4 is a flowchart showing a control operation of the ophthalmic apparatus. [Figure 8] This is an appropriate cross-sectional image taken when the subject's eye is not miotically constricted. [Figure 9] This is an inappropriate cross-sectional image taken when the subject's eye is in a contracted state. [Figure 10] This is the change in brightness value that corresponds to the appropriate cross-sectional image. [Figure 11]This is a change in brightness value corresponding to an inappropriate cross-sectional image. [Figure 12] FIG. 11 is a schematic diagram for explaining a method for deriving the axial length. [Figure 13] 1 is an example showing the change in axial length over time. [Figure 14] FIG. 1 is a diagram showing refractive power in the meridian direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] "overview" An overview of an ophthalmic device according to an embodiment of the present disclosure will be described. The items classified in < > below can be used independently or in association with each other. In this embodiment, "conjugate" is not necessarily limited to a perfect conjugate relationship, but includes "approximate conjugate." In other words, "conjugate" in this embodiment also includes cases where the position is shifted from the perfect conjugate position within a range permitted in relation to the technical significance of each part.

[0010] The ophthalmic apparatus of the present embodiment is an apparatus capable of acquiring the axial length of the subject's eye. For example, the ophthalmic apparatus may have an optical system used to measure the axial length, a shape information acquiring unit, an axial length acquiring unit, etc. In addition, for example, the ophthalmic apparatus may have a determining unit, a selecting unit, etc.

[0011] <Ocular refractive power measurement optical system> The ophthalmic apparatus of this embodiment may have an eye refractive power measuring optical system (e.g., a measuring optical system 100). The eye refractive power measuring optical system is an optical system for acquiring the eye refractive power of the subject's eye. For example, the apparatus may include a configuration for projecting measuring light (first measuring light) onto the fundus of the subject's eye and acquiring the eye refractive power based on the reflected light of the measuring light reflected by the fundus. The first measuring light may be visible light or infrared light.

[0012] The eye refraction measuring optical system may be a measuring optical system used in an objective eye refraction measuring device (such as an autorefractometer and a wavefront sensor). The projection optical axis of the first measuring light in the eye refraction measuring optical system may be disposed on the surface of a light section formed by a cross-sectional image capturing optical system described later. For this reason, the eye refraction measuring optical system is used to obtain the eye refraction on the light section of the anterior eye (on-surface eye refraction). Of course, the eye refraction measuring optical system may be capable of obtaining the eye refraction on other surfaces.

[0013] <Cross-sectional image capturing optical system> The ophthalmic apparatus of the present embodiment may have a cross-sectional image capturing optical system (for example, a cross-sectional image capturing optical system). The cross-sectional image capturing optical system is an optical system for acquiring a cross-sectional image of an anterior segment of an eye to be examined. For example, the apparatus may include a configuration for acquiring a cross-sectional image of an anterior segment of an eye by projecting a measurement light toward the anterior segment of an eye to be examined and detecting return light (scattered light) due to scattering of the measurement light from an oblique direction with respect to the projection optical axis of the measurement light. In addition, the apparatus may include a configuration for projecting a measurement light (second measurement light) toward the anterior segment of an eye to be examined, forming a light section passing through the optical axis of the eye refractive power measurement optical system on the anterior segment, and acquiring a cross-sectional image of an anterior segment based on scattered light from the light section of the second measurement light. The measurement light (second measurement light) may be visible light or infrared light.

[0014] The cross-sectional image photographing optical system may be an optical system based on the Scheimpflug principle. In this case, the projection optical axis of the first measurement light in the eye refractive power measuring optical system and the projection optical axis of the second measurement light in the cross-sectional image photographing optical system may be arranged coaxially. In this case, the second measurement light may be projected as slit light in the cross-sectional image photographing optical system. For example, the irradiation area of ​​the slit light is set as a light section plane of the anterior eye. In this case, the cross-sectional image photographing optical system may have a lens system and a photodetector arranged in a Scheimpflug relationship with the light section plane formed in the anterior eye. The receiving optical axis of the second measurement light is arranged to be inclined with respect to the light section plane.

[0015] The imaging range of the anterior segment cross-sectional image by the cross-sectional image capturing optical system preferably includes at least the anterior surface of the cornea of ​​the subject's eye to the anterior surface of the crystalline lens. Needless to say, it is even more preferable if it includes the anterior surface of the cornea to the posterior surface of the crystalline lens. In this case, the corneal thickness, the anterior corneal radius of curvature, the posterior corneal radius of curvature, the anterior chamber depth, the crystalline lens thickness, the anterior crystalline lens radius of curvature, and the posterior crystalline lens radius of curvature can be obtained without omission, so that the axial length can be calculated more accurately.

[0016] <Shape information acquisition means> The ophthalmologic apparatus of this embodiment may include a shape information acquiring means (e.g., the control unit 50). The shape information acquiring means acquires shape information related to the shape of the anterior segment, including a plurality of parameters, by analyzing an anterior segment cross-sectional image. For example, the shape information may be information capable of identifying the shape of the translucent body included in the anterior segment. As an example, the shape information may be coordinates at which each translucent body is located, an equation expressing the shape of each translucent body, and a value calculated from the equation (e.g., curvature, thickness, depth, etc.), etc.

[0017] The multiple parameters included in the shape information may include parameters related to the shape of the cornea. For example, the radius of curvature of the anterior surface of the cornea, the radius of curvature of the posterior surface of the cornea, and the corneal thickness may be included. The multiple parameters may also include parameters related to the shape of the crystalline lens. For example, the radius of curvature of the anterior surface of the crystalline lens, the radius of curvature of the posterior surface of the crystalline lens, and the crystalline lens thickness may be included. The multiple parameters may also include parameters related to the depth of the anterior segment. For example, the anterior chamber depth may be included.

[0018] It is desirable to obtain more parameters (in other words, measured values) in the optical medium from the anterior ocular cross-sectional image analyzed by the shape information acquisition means, but there are cases where parameters cannot be obtained as an analysis result, or where the parameters are inaccurate. This may occur, for example, due to the reflection of the subject's eyelids or eyelashes. In addition, for example, it may change depending on the state of the anterior ocular segment of the subject's eye (for example, the state of the pupil, etc.). When the anterior ocular cross-sectional image cannot be properly acquired due to these influences, valid and invalid parameters may be mixed. However, in this embodiment, the axial length acquisition means described later derives the axial length (second axial length) using the measured values ​​of valid parameters and the assumed values ​​replacing the measured values ​​of invalid parameters, thereby making it possible to properly acquire the axial length. Of course, when the shape information acquisition means effectively obtains the measured values ​​of all parameters, it is also possible to derive the axial length (first axial length) using only the measured values ​​of each parameter.

[0019] <Method for acquiring axial length> The ophthalmologic apparatus of this embodiment may include an axial length acquiring means (for example, the control unit 50). For example, the axial length acquiring means may function as an image processing unit, an axial length acquiring unit, and an arithmetic control unit, etc.

[0020] The axial length acquiring means may acquire the ocular refractive power of the subject's eye by controlling acquisition of the ocular refractive power using the ocular refractive power measuring optical system. More specifically, the axial length acquiring means may acquire the ocular refractive power of the subject's eye by controlling projection of the first measurement light in the ocular refractive power measuring optical system and detection of the fundus reflected light of the first measurement light by the photodetector.

[0021] The axial length acquiring means may acquire the cross-sectional image of the anterior segment of the subject's eye by controlling acquisition of the cross-sectional image of the anterior segment of the subject's eye using the cross-sectional image capturing optical system. More specifically, the cross-sectional image of the anterior segment of the subject's eye may be acquired by controlling projection of the second measurement light in the cross-sectional image capturing optical system and detection of the return light (scattered light) of the second measurement light by the photodetector.

[0022] The axial length acquisition means may continuously project the second measurement light in the cross-sectional image capturing optical system to acquire a plurality of anterior segment cross-sectional images. In this case, the axial length acquisition means may execute projection of the second measurement light and detection of the return light in real time, and acquire a plurality of anterior segment cross-sectional images by capturing the anterior segment cross-sectional images as moving images. In this case, the measurement means may execute projection of the second measurement light and detection of the return light at a predetermined time interval (for example, at one second intervals) and acquire a plurality of anterior segment cross-sectional images by capturing the anterior segment cross-sectional images as still images.

[0023] The axial length acquisition means may acquire the axial length of the subject's eye based on the ocular refractive power and a plurality of parameters included in the shape information acquired by the shape information acquisition means by analyzing the anterior eye cross-sectional image. The axial length acquired by the axial length acquisition means may include a first axial length derived using each measured value as a plurality of parameters. In other words, the first axial length derived without using an assumed value replacing each measured value may be included. The axial length may also include a second axial length derived using a portion of an assumed value as a plurality of parameters. In other words, the second axial length derived using a measured value and an assumed value may be included. The axial length acquisition means may select whether to derive one or both of the first axial length and the second axial length based on an operation signal input by the examiner operating an operation means (e.g., the monitor 16). Also, the axial length acquisition means may select whether to derive one or both of the first axial length and the second axial length based on a selection result of a selection means described later.

[0024] For example, the axial length acquisition means may change some of the ineffective parameters among the multiple parameters in the shape information acquired by the shape information acquisition means from the measured values ​​to assumed values. For example, the assumed values ​​may be standard values ​​adopted in a predetermined eye optical model (e.g., a Gullstrand eye model, etc.). Alternatively, they may be average values ​​based on statistical data on the eye. Alternatively, they may be estimated values ​​that can be obtained by considering the measured values ​​of the effective parameters and the general ratios of the anterior and posterior surfaces of the cornea and the anterior and posterior surfaces of the lens in the eye. Alternatively, they may be measured values ​​of the subject's eye previously obtained by at least one of an ophthalmic device and a device different from the ophthalmic device. A plurality of standard values ​​and average values ​​may be prepared for at least one of age, sex, region, etc., and the examiner may be able to select which value is used to obtain the axial length.

[0025] For example, the axial length acquiring means may acquire the axial length based on the ocular refractive power and a plurality of parameters. For example, the axial length may be derived by ray tracing calculation based on the ocular refractive power and a plurality of parameters. In the ray tracing calculation, when a light ray incident from a far point to a predetermined position of the anterior eye intersects with the optical axis after being refracted by a transparent body, the distance between the intersection point and the corneal apex is derived as the axial length. In this case, the ocular refractive power on the light section (on-surface ocular refractive power) may be used instead of the spherical equivalent power that is generally used in the field of ophthalmology when specifying the far point. This allows the position of the far point of the light ray passing through the section surface to be specified more appropriately. As a result, the axial length can be obtained more appropriately. In this case, the 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 for each light ray. For example, the average value (or weighted average) of the axial lengths obtained by each ray tracing calculation may be obtained as the axial length of the subject eye.

[0026] In the ray tracing calculation, the incident position of the light beam on the boundary surface of each transparent body and the angle change at the boundary surface may be determined taking into consideration the shape of the transparent body on the cross section specified from the anterior eye information. In addition, in the ray tracing calculation, the decentering of the transparent body of the anterior eye may be taken into consideration. The decentering is specified based on the anterior eye information. As a result of taking into consideration the decentering of the transparent body in the cross section, the axial length can be calculated more appropriately. In this case, for example, the ray tracing calculation may be performed for each of a plurality of light beams including at least the first light beam and the second light beam to calculate the axial length for each light beam, and the final measurement value may be calculated based on the plurality of axial lengths. The first light beam and the second light beam are light beams arranged on either side of the axis of the eye on the cross section.

[0027] In this embodiment, the axial length acquisition means may adjust the amount of light of the second measurement light in the cross-sectional image taking optical system based on the anterior segment cross-sectional image. More specifically, an anterior segment cross-sectional image (first anterior segment cross-sectional image) of the subject eye may be acquired, and if this anterior segment cross-sectional image is deemed inappropriate for analysis, the amount of light of the second measurement light may be adjusted to acquire an anterior segment cross-sectional image (second anterior segment cross-sectional image). Also, in this embodiment, the axial length acquisition means may adjust the detection conditions of the photodetector in the cross-sectional image taking optical system based on the anterior segment cross-sectional image. More specifically, if the first anterior segment cross-sectional image is acquired, and if the first anterior segment cross-sectional image is deemed inappropriate for analysis, the detection conditions of the photodetector may be adjusted to acquire a second anterior segment cross-sectional image. This increases the possibility of acquiring appropriate values ​​as the multiple parameters based on the anterior segment cross-sectional image, resulting in improved accuracy of the axial length.

[0028] For example, the axial length acquisition means may adjust the amount of light of the second measurement light within a predetermined range in which the luminance information of each translucent body detected from the second anterior segment cross-sectional image is not saturated. In this case, the axial length acquisition means may increase or decrease the set value of the output of 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. Note that, as an example, the predetermined range may be set in advance based on the detection sensitivity, gain, etc. of the photodetector. Also, for example, the axial length acquisition means may adjust the detection conditions of the photodetector within a predetermined range in which the luminance information of each translucent body detected from the second anterior segment cross-sectional image is not saturated. In this case, the axial length acquisition means may change at least one of the exposure time, gain, etc. of the photodetector.

[0029] The axial length acquisition means may acquire the eye refractive power and the anterior eye cross-sectional image in parallel. In this case, the acquisition means may set the detection timing of the photodetector of the eye refractive power measurement optical system and the detection timing of the photodetector of the cross-sectional image taking optical system to be the same (parallel) when the measurement light is projected from both optical systems onto the subject's eye. Note that the term "same" does not necessarily require that the respective detection timings are completely simultaneous. For example, there may be a time difference between the respective detection timings to the extent that no significant difference occurs in the state of the subject's eye (pupil state or accommodation state).

[0030] In this embodiment, the axial length acquisition means may control the ocular refractive power measurement optical system and the cross-sectional image taking optical system to acquire the ocular refractive power and the cross-sectional image in a state where the test eye is fogging. The first axial length and the second axial length may be acquired based on the anterior segment cross-sectional image acquired in a state where the test eye is fogging. This allows each parameter to be acquired from the anterior segment cross-sectional image acquired with the anterior segment of the test eye in an appropriate state (i.e., a state where accommodation is released by fogging). Furthermore, if there is a parameter that is not valid as a measured value, it can be replaced with an assumed value to satisfactorily derive the axial length.

[0031] <Judgment means> The ophthalmologic apparatus of the present embodiment may include a determination means (for example, a control unit 50). The determination means may determine whether at least one of a plurality of parameters based on an anterior ocular cross-sectional image is good or bad. For example, the determination means may determine whether the parameters are good or bad by determining whether the anterior ocular cross-sectional image is suitable for analysis. In other words, if the anterior ocular cross-sectional image is inappropriate, the parameters may be considered to be poor without obtaining measured values. Also, for example, the determination means may determine whether the parameters are good or bad by determining whether measured values ​​of the plurality of parameters based on the anterior ocular cross-sectional image are appropriate or bad. This makes it easier to obtain appropriate values ​​even when measured values ​​of the plurality of parameters cannot be obtained or are inaccurate.

[0032] For example, the determination means may determine the acceptability of at least one of the multiple parameters based on the presence or absence of the subject's eyelids or eyelashes in the anterior eye cross-sectional image. Also, for example, the determination means may determine the acceptability of at least one of the multiple parameters based on the horizontal detection width of each translucent body in the anterior eye cross-sectional image. Also, for example, the determination means may determine the acceptability of at least one of the multiple parameters based on pupil information of the subject's eye. Of course, the acceptability of at least one of the multiple parameters may be determined from a combination of these.

[0033] The pupil state of the subject's eye may be information that can grasp the presence or absence of miosis and mydriasis. For example, the pupil diameter, or a determination result of the presence or absence of miosis or mydriasis based on the pupil diameter, etc. may be used. In this case, whether or not the measurement values ​​of the multiple parameters can be considered valid may be associated with the pupil information. As an example, a value that is valid as a measurement value among the multiple parameters may be selected depending on the presence or absence of miosis or mydriasis. Also, as an example, a value that is valid as a measurement value among the multiple parameters may be selected depending on the degree of miosis or mydriasis.

[0034] In this embodiment, the determining means may determine whether at least one of a plurality of parameters included in the shape information of the anterior eye is acceptable based on the luminance information of the anterior eye cross-sectional image. For example, the plurality of parameters may be determined to be acceptable by utilizing a change in the luminance information in the anterior eye cross-sectional image. The luminance information may be information expressed by at least one of luminance, gradation, shade, etc. This makes it easy to know whether the measured value of the parameter is valid or not, taking into consideration the presence or absence of blinking of the subject's eye, the presence or absence and the degree of pupil constriction, etc.

[0035] In the present embodiment, the determining means may determine whether at least one of the multiple parameters is good or bad based on evaluation information for evaluating the reliability of the multiple parameters included in the shape information of the anterior segment. The reliability of the multiple parameters may be anything that can indicate whether the measured value as the parameter in each light-transmitting body is appropriately obtained or not.

[0036] For example, such reliability may be obtained based on luminance information of the anterior-segment cross-sectional image. In this case, as one example, at least one of the presence or absence of reflection of eyelids or eyelashes, the pupil state, the horizontal detection width of each light-transmitting body in the anterior-segment cross-sectional image, and the like may be obtained as information representing the reliability. Also, for example, such reliability may be obtained based on information different from the luminance information of the anterior-segment cross-sectional image. In this case, as one example, the alignment relationship between the subject's eye and the cross-sectional image capturing optical system may be obtained as information representing the reliability.

[0037] The evaluation information for evaluating the reliability may be acquired as an evaluation symbol, an evaluation value, etc. The evaluation information may be bipolarized information based on the presence or absence of reliability, or may be graded information according to the degree of reliability.

[0038] For example, the determination means may acquire the evaluation information by using a correspondence table in which the evaluation information acquired for each light-transmitting body corresponds to the pass / fail of the parameter. Also, for example, the determination means may acquire the evaluation information by using an arithmetic expression in which the evaluation information acquired for each light-transmitting body corresponds to the pass / fail of the parameter. The coefficients of the correspondence table and the arithmetic expression may be set in advance based on experiments, simulations, etc.

[0039] In this embodiment, the determination means may determine the acceptability of each parameter when multiple pieces of shape information are present for each anterior segment cross-sectional image. The determination means may determine the acceptability of each of the parameters obtained for each translucent body, or may average the parameters obtained for each translucent body and determine the acceptability of the averaged parameters. In this case, the determination means may exclude an image having an outlier from the multiple anterior segment cross-sectional images, and determine the acceptability of the parameters for the remaining anterior segment cross-sectional images. For example, the anterior segment cross-sectional image having an outlier may be an image from which multiple parameters included in the shape information of the anterior segment cannot be obtained. As an example, the image may be at least one of an image in which a part of the translucent body is missing due to blinking or miosis of the subject's eye, an image in which the detection width of the translucent body in the horizontal direction is short, and a dark image in which the overall luminance information is insufficient. For example, these anterior segment cross-sectional images may be excluded by statistical processing. This further improves the accuracy of the axial length.

[0040] <Selection method> The ophthalmologic apparatus of the present embodiment may include a selection means (for example, a control unit 50). The selection means may select the derivation of at least one of the first axial length and the second axial length based on the judgment result of the judgment means. For example, the selection means may select the derivation of the first axial length and the second axial length based on the quality of a plurality of parameters corresponding to one anterior segment cross-sectional image. Also, for example, the derivation of the first axial length and the second axial length may be selected based on the quality of a plurality of parameters corresponding to each of a plurality of anterior segment cross-sectional images. For this reason, even if an appropriate anterior segment cross-sectional image cannot be obtained due to the influence of blinking or miosis of the subject's eye, it becomes easier to obtain an accurate axial length.

[0041] <Output method> The ophthalmologic apparatus of the present embodiment may include an output means (e.g., the control unit 50). The output means may output intraocular dimension information. Of course, the output means may output ocular refractive power, an anterior segment cross-sectional image, evaluation information, and the like together with the intraocular dimension information.

[0042] For example, the output means may function as a display control means and cause the intraocular dimensional information to be displayed on a display means (e.g., monitor 16). Also, for example, the output means may function as a print control means and cause a print means (e.g., a printer) to print the intraocular dimensional information. Also, for example, the output means may function as a communication means and cause the intraocular dimensional information to be stored in a storage means (e.g., a memory or a server). The output means may output the intraocular dimensional information in at least any one of these output forms.

[0043] For example, the intraocular dimension information may be the axial length. Also, for example, the intraocular dimension information may be shape information of the anterior segment (i.e., at least one of the radius of curvature of the anterior and posterior surfaces of the cornea, the corneal thickness, the radius of curvature of the anterior and posterior surfaces of the lens, the lens thickness, the anterior chamber depth, etc.). The intraocular dimension information output by the output means may include first dimension information acquired based on the measured values ​​of parameters in the shape information of the anterior segment. For example, this includes the first axial length. Also, the intraocular dimension information may include second dimension information acquired based on the measured values ​​and assumed values ​​of parameters in the shape information of the anterior segment. For example, this includes the second axial length.

[0044] The output means may output, as the intraocular dimension information, first dimension information and second dimension information in a distinguishable manner. More specifically, the output means may output, in a distinguishable manner, first dimension information derived based only on measured values ​​of the multiple parameters and second dimension information derived based on measured values ​​and assumed values ​​of the multiple parameters.

[0045] The output means may output the change over time of the intraocular dimensional information (at least one of the first dimensional information and the second dimensional information) when there is intraocular dimensional information previously obtained for the subject eye. That is, the change over time may be output using two or more pieces of dimensional information obtained on different dates. The change over time of the intraocular dimensional information may be output as information summarizing the dimensional information by time series. As an example, it may be output in the form of a table or graph. This makes it easier to grasp the trend accompanying the change over time, allows efficient follow-up observation, and makes it easier to evaluate the progression of myopia based on the axial length.

[0046] "Example" An example of an ophthalmic apparatus according to the present embodiment will be described.

[0047] <Overall composition> 1 is an external view of an ophthalmic apparatus 10. The ophthalmic apparatus 10 is a combination device of an objective eye refractive power measuring device (particularly, in this embodiment, an autorefractometer) and a Scheimpflug camera. In this embodiment, the ophthalmic apparatus 10 is a stationary examination device, but is not necessarily limited to this and may be a handheld type.

[0048] The ophthalmologic apparatus 10 includes 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 and control unit 50.

[0049] The measurement unit 11 includes a measurement system and an imaging system that are used to examine the subject's eye. In this embodiment, the optical system shown in FIG.

[0050] The alignment drive unit 13 may be capable of moving the measurement unit 11 three-dimensionally relative to the base 12 .

[0051] The face support unit 15 is used to fix the subject's face in front of the measurement unit 11. The face support unit 15 is fixed to the base 12 and supports the subject's face.

[0052] The monitor 16 functions as a touch panel that also serves as an operation unit. The monitor 16 also displays the ocular refractive power, an anterior ocular segment cross-sectional image, axial length, and the like of the subject's eye E on the screen.

[0053] The arithmetic control unit 50 (also called a processor; hereinafter, simply referred to as the control unit 50) is responsible for the overall control of the ophthalmic apparatus 10. In addition, it processes various examination results acquired via the measurement unit 11.

[0054] <Optical system> 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 presenting optical system 150, a front photographing optical system 200, a cross-sectional photographing optical system (an irradiation optical system 300a and a light receiving optical system 300b), an index projecting optical system 400, and an alignment index projecting optical system. The ophthalmic apparatus 10 also includes half mirrors 501, 502, and 503 that branch and combine the optical paths of each optical system, an objective lens 505, and the like. In each optical system, the light source side is upstream and the examined eye side is downstream.

[0055] <Measurement optical system> The measurement optical system 100 is used to objectively measure the ocular refractive power of the subject's eye E. For example, the values ​​of SPH: spherical power, CYL: cylindrical power, and AXIS: cylindrical axis angle may be acquired as the measurement results of the ocular refractive power.

[0056] The measurement optical system 100 includes a projection optical system 100a and a receiving optical system 100b.

[0057] The projection optical system 100a has at least a measurement light source 111, and projects a spot-shaped measurement light onto the fundus of the test eye E through the center of the pupil or the corneal apex of the test eye 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.

[0058] In this embodiment, a prism 115 is disposed on a common path of the projection optical system 100a and the light receiving optical system 100b. The prism 115 is rotated about the optical axis, so that the projection light beam on the pupil is eccentrically rotated at high speed. As an example, in this embodiment, the projection light beam is eccentrically rotated in an area on the pupil of φ2 mm to φ4 mm. This area is the measurement area for the eye refractive power in this embodiment.

[0059] The light receiving optical system 100b has at least a ring lens 124 and an image sensor 125. The light receiving optical system 100b extracts the measurement light reflected from the fundus in a ring shape through the periphery of the pupil. The ring lens 124 is disposed at a pupil conjugate position, and the image sensor 125 is disposed at a fundus conjugate position. The eye refractive power is derived by analyzing the ring image formed on the image sensor 125 via the ring lens 124.

[0060] As described above, in this embodiment, since the measurement light is eccentrically rotated at high speed on the pupil, analysis processing is performed on the output image from the image sensor 125 based on an exposure time that is sufficiently long with respect to the rotation period, or on an additive image of image data sequentially output from the image sensor 125, to derive the ocular refractive power. In this embodiment, at least the values ​​of SPH: spherical power, CYL: cylindrical power, and AXIS: cylindrical axis angle are acquired as the results of analysis processing.

[0061] 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 image sensor 125. The measurement light beam from the measurement light source 111 passes through the hole of the hole mirror 113 and the prism 115, and is reflected by the half mirror 502 and the half mirror 501, respectively, to become coaxial with the optical axis L1, and then reaches the fundus via the objective lens 505. The reflected light beam of the measurement light beam reflected by the fundus passes through the optical path that the measurement light beam passed through, is reflected by the mirror of the hole mirror 123, and reaches the image sensor 125 via the ring lens 124.

[0062] <Fixation target presentation optical system> The fixation target presenting optical system 150 presents a fixation target to the subject's eye E. The fixation target is presented on the optical axis of the measurement optical system 100. The fixation target presenting optical system 150 is used to fixate the subject's eye E. It is also used to apply fogging and accommodation load to the subject's eye.

[0063] 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 a position conjugate with the fundus. A 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 a half mirror 503. The fixation light beam also passes through a lens 504, passes through a half mirror 502, and is reflected by a half mirror 501, becoming coaxial with the optical axis L1. The fixation light beam further passes through an objective lens 505 to reach the fundus.

[0064] The measurement light source 111, the ring lens 124, and the image sensor 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 moved integrally along the optical axis by the drive unit 161 as the drive unit 160. For example, the focal length in the drive unit 160 in the measurement optical system 100 and the focal length in the drive unit 160 in the fixation target presenting optical system 150 have a predetermined relationship. For example, by moving the drive unit according to the ocular refractive power of the test eye E, the presentation distance of the fixation target plate 155 relative to the test eye E (i.e., the presentation position of the fixation target) can be changed, and the measurement light source 111 and the image sensor 125 are optically conjugated with the fundus. At this time, regardless of the movement of the drive unit, the hole mirror 113 and the ring lens 124 are pupil conjugated at a constant magnification.

[0065] <Frontal shooting optical system> The front photographing optical system 200 is used to capture a front image of the anterior segment of the subject's eye E. For example, the front photographing optical system 200 includes an image sensor 205 and the like. The image sensor 205 may be disposed at a 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. In addition, an index image (point image) projected onto the cornea from the index projection optical system 400, and an index image (Mayer ring image) projected onto the cornea from the alignment index projection optical system 600 are captured by the front photographing optical system 200.

[0066] <Cross-section imaging optical system> The cross-section photographing optical system is used to photograph a cross-sectional image of the anterior segment of the eye, and includes an irradiation optical system 300a and a light receiving optical system 300b.

[0067] 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 the anterior segment with slit light (illumination light). The irradiation optical system 300a has a light source 311 and a slit 312. 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 peak wavelength of a predetermined wavelength may be used. The slit 312 may be disposed at a pupil conjugate position.

[0068] 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 luminosity of the subject's eye and wavelength. The subject's eye has luminosity in the visible range, which is generally maximum at around 550 nm, which is green visible light, and gradually decreases as the wavelength becomes longer (approaching the infrared range). In other words, the subject's eye is easily dazzled by green visible light, but is not easily dazzled by red visible light. It is said that the subject is not dazzled by infrared light.

[0069] Conventionally, when a cross-sectional image of the anterior eye is obtained based on the Scheimpflug principle, blue visible light, green visible light, white visible light, etc. have been used as illumination light. This is because cataracts and the like tend to appear in cross-sectional images due to the influence of the transmittance of the subject's eye, but the illumination light is dazzling and burdensome to the subject. On the other hand, with the increase in the prevalence of myopia, mainly among young people, in recent years, it is important to measure the axial length of young people, but since young people are less likely to have cataracts, it is possible to use light other than the above as illumination light.

[0070] Therefore, in this embodiment, red visible light to near infrared light, which is less likely to cause glare to the subject's eye, is used as the illumination light. For example, the visibility of red visible light at around 650 nm is approximately 1 / 10 of that of green visible light at around 550 nm, and the visibility of red visible light at around 700 nm is approximately 1 / 200. This significantly reduces the burden on the subject. In particular, when the subject is a young person, including a child, this not only reduces the burden but also leads to more efficient measurement.

[0071] In this embodiment, the cross section through which the slit light passes in the anterior segment is referred to as a "cutting surface." The cutting surface is the object surface of the cross-sectional imaging optical system. In FIG. 2, the opening of the slit 312 has a horizontal direction (depth direction into the paper) as its longitudinal direction. Therefore, in this embodiment, a horizontal plane (XZ cross section) including the optical axis L1 is set as the cutting surface. In this embodiment, the cutting surface is formed at least between the anterior surface of the cornea and the posterior surface of the lens.

[0072] The light receiving optical system 300b includes a lens system 322 and an image sensor 321. In the light receiving optical system 300b, the lens system 322 and the image sensor 321 are arranged in a Scheimpflug relationship with a cut surface set in the anterior segment. That is, the optical arrangement is such that the extension planes of the cut surface, the principal plane of the lens system 322, and the imaging surface of the image sensor 321 intersect at one intersection line (single axis). A cross-sectional image of the anterior segment is acquired based on a signal from the image sensor 321. The image sensor 321 may be formed of a semiconductor substrate made of silicon as a single element.

[0073] 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 and wavelength of the imaging element 321. For example, an imaging element using silicon as a material as a single element has sensitivity to wavelengths around 300 nm to 1000 nm, including wavelengths in the ultraviolet, visible, and infrared regions, but has a maximum sensitivity around 550 nm to 650 nm, including green visible light, and gradually decreases as it approaches the infrared region. However, the sensitivity of 650 nm or more, including 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 eye.

[0074] For example, there are imaging elements whose sensitivity is greatest in the infrared region, but they are expensive. While it is desirable for the device to be used in many facilities such as hospitals and schools, the high cost of the device can hinder its widespread use. If an imaging element made of silicon is used, the device can be made inexpensively.

[0075] In such a cross-section photographing optical system, an illumination light beam from a light source 311 becomes a slit light beam via a slit 312 on an optical axis L3, passes through a lens 313, and is reflected by a half mirror 503 to become coaxial with the optical axis L2. The illumination light beam also passes through a lens 504, passes through a half mirror 502, and is reflected by a half mirror 501 to become coaxial with the optical axis L1. The illumination light beam further passes through an objective lens 505 to reach the anterior segment. Return light from a cut surface formed in the anterior segment reaches an image sensor 321 via a lens 322.

[0076] <Indicator 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 surface facing the subject's eye to the anterior segment.

[0077] The index projection optical system 400 includes a plurality of point light sources 401. The point light sources 401 project an index at infinity by irradiating the cornea with parallel light. The point light sources 401 emit infrared light. However, visible light may be used. The point light sources 401 are arranged symmetrically in the vertical direction and the horizontal direction with respect to the optical axis L1. For example, in this embodiment, two point light sources are provided on each side. This allows four point image indices to be projected onto the cornea. The shape of the indices is not limited to this, and may include linear indices. The number of indices is not limited to this, and may be three or more point image indices.

[0078] In this embodiment, the circumferential region onto which these four point images are projected becomes the measurement region of the corneal shape by the target projecting optical system 400 and the front photographing 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 point image is projected onto a circumferential region of φ3 mm of the corneal model eye.

[0079] <Alignment target projection optical system> The alignment target projection optical system is used to align (position) the measurement unit 11 with respect to the subject's eye E. In this embodiment, the alignment target projection optical system is formed by the alignment light source 601 and the target projection optical system 400. For example, the working distance may be adjusted by moving the measurement unit 11 in the forward / backward direction so that the Purkinje image by the alignment light source 601 and the Purkinje image by the target projection optical system 400 are captured at a predetermined ratio.

[0080] The alignment light source 601 projects a finite index by irradiating the cornea with diffused light. The alignment light source 601 emits infrared light. However, it may also emit visible light. The alignment light source 601 is arranged in a ring shape centered on the optical axis L1. As a result, in this embodiment, a ring index (so-called Mayer ring) is projected onto the cornea.

[0081] <Common optical path for fixation target presentation optical system and cross-sectional imaging optical system> In this embodiment, both the fixation target presenting optical system 150 and the target projection optical system 300a are irradiated with visible light. The optical axis L2 of the fixation target presenting optical system 150 and the optical axis L3 of the target projection optical system 300a are made coaxial by the half mirror 503. The fixation target presenting optical system 150 is disposed on the transmission side of the half mirror 503, and the target projection optical system 300a is disposed on the reflection side of the half mirror 503, so that the optical paths of the fixation target presenting optical system 150 and the target projection optical system 300a are common. For example, the half mirror 503 is a flat type, and astigmatism is likely to occur on the transmission side of the half mirror 503. The target projection optical system 300a requires a certain level of imaging performance in order to form a cut surface in the anterior eye to obtain a clear cross-sectional image 70. For this reason, it is preferable that the target projection optical system 300a is disposed on the reflection side where the influence of astigmatism is small.

[0082] In this embodiment, a lens 504a is disposed on the optical axis of the fixation target presenting optical system 150. The lens 504a functions as a lens for shortening the overall length of the fixation target presenting optical system 150. The lens 504a also serves to reduce the diameter of the lens 156 located upstream of the lens 504a.

[0083] Fig. 5 is a schematic diagram of a simplified fixation target presenting optical system 150. Fig. 5(a) shows a case where the lens 504a is not arranged. Fig. 5(b) shows a case where the lens 504a is arranged. Here, the optical path from the subject's eye E to the fixation target plate 155 is a straight line, and some optical members are omitted. The fundus imaging light rays from the center and peripheral parts of the fixation target plate 155 are represented by solid lines and dotted lines, respectively.

[0084] When the working distance from the subject's eye E to the objective lens is a predetermined value, in FIG. 5(a), the distance of the fixation target presenting optical system 150 (particularly, the distance from the fixation target plate 155 to the lens 156) is long. Both light rays from the center and periphery of the fixation target plate 155 reach the lens 156 with a large diameter. On the other hand, as shown in FIG. 5(b), by arranging a lens 504a in the fixation target presenting optical system 150, the distance of the fixation target presenting optical system 150 can be shortened. Both light rays from the fixation target plate 155 reach the lens 156 with a small diameter.

[0085] For example, the fixation target presenting optical system 150 may be a target-side telecentric optical system, and the lens 504a may be disposed at a pupil conjugate position. In this case, the light rays (principal rays) from the center and periphery of the fixation target plate 155 pass through the center of the lens 504a, so that the overall focal length (composite focal length) of the fixation target presenting optical system 150 does not change. Therefore, the relationship between the focal length of the fixation target presenting optical system 150 and that of the drive unit 160 of the measurement optical system 100 is maintained.

[0086] In this way, by arranging the lens 504a in the fixation target presenting optical system 150, the lens 156 can be designed with a small diameter. Also, while maintaining a predetermined working distance of the subject's eye E and a composite focal length of the fixation target presenting optical system 150, the overall length of the fixation target presenting optical system 150 can be shortened. As a result, the ophthalmic apparatus 10 can be made more compact.

[0087] In this embodiment, a lens 504b is disposed on the optical axis of the visual target projection optical system 300a. The lens 504b serves to reduce the diameter of the objective lens 505 located downstream of the lens 504b.

[0088] Fig. 6 is a schematic diagram of a simplified target projection optical system 300a. Fig. 6(a) shows a case where the lens 504b is not arranged. Fig. 6(b) shows a case where the lens 504b is arranged. Here, the optical path from the subject's eye E to the slit 312 is a straight line, and some optical members are omitted. The pupil imaging light rays from the center and periphery of the slit 312 are represented by solid lines and dotted lines, respectively.

[0089] In Fig. 6(a) and Fig. 6(b), the light ray (principal ray) from the center of the slit 312 passes 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 ray from the peripheral part of the slit 312 is refracted at a position farther away from the center of the objective lens 505. In order to allow such a light ray to reach the subject's eye E, an objective lens 505 with a large diameter is required. On the other hand, in Fig. 6(b), the light ray (principal ray) from the peripheral part of the slit 312 is refracted at the center position of the objective lens 505. In order to allow such a light ray to reach the subject's eye E, an objective lens 505 with a small diameter can be used.

[0090] In this way, by arranging the lens 504b in the visual target projection optical system 300a, the objective lens 155 can be designed with a small diameter. Note that the light rays from the central and peripheral parts of the slit 312 may generate larger aberrations as they are refracted in an area farther from the center of the objective lens 505. For this reason, the objective lens 155 may have an appropriate diameter that suppresses the generation of aberrations while miniaturizing the ophthalmic apparatus 10.

[0091] In this embodiment, the lens 504 is arranged in the fixation target presenting optical system 150 and the target projection optical system 300a, sharing the lenses 504a and 504b having different roles. For example, the lens 504 is arranged downstream of the half mirror 503 where the optical axis L2 of the fixation target presenting optical system 150 and the optical axis L3 of the target projection optical system 300a are joined. This further reduces the space inside the optical system.

[0092] <Control action> The control operation of the ophthalmic apparatus 10 will be described with reference to the flowchart shown in Fig. 7. In this embodiment, the ophthalmic apparatus 10 sequentially performs corneal curvature measurement, ocular refractive power measurement, and photographing of an anterior segment cross-sectional image, and obtains the axial length based on the results of the measurement and photographing.

[0093] <Alignment (S1)> First, the measurement unit 11 is aligned with the subject's eye E. The examiner instructs the subject to place his or her face on the face support unit 15. The control unit 50 starts presenting a fixation target and acquiring an anterior eye observation image.

[0094] For example, the control unit 50 adjusts the subject's eye E and the ophthalmic device 10 to a predetermined positional relationship based at least on an observation image of the anterior eye acquired via the front photographing optical system 200. More specifically, alignment in the XY directions is performed so that the optical axis L1 coincides with the corneal apex of the subject's eye E. Also, alignment in the Z direction is performed so that the distance between the subject's eye E and the ophthalmic device 10 is a predetermined working 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.

[0095] <Cornea topography measurement (S2)> Next, the corneal shape of the subject's eye E is measured. The control unit 50 projects a point image index from the index projection optical system 400, and captures a corneal Purkinje image of the point image index using the frontal imaging optical system 200. The control unit 50 also acquires corneal shape information based on the corneal Purkinje image. For example, the corneal shape information is derived based on the image height of the corneal Purkinje image. In this embodiment, at least the values ​​of the corneal curvature, the degree of astigmatism, and the astigmatism axis angle are acquired as the corneal shape information.

[0096] <Eye Refractive Index Measurement (S3)> Next, the ocular refractive power of the subject's eye E is measured. Since infrared light is projected onto the subject's eye E as measurement light, the pupil diameter of the subject's eye E becomes a predetermined size with suppressed miosis (for example, φ2 mm or less). As an example, the pupil diameter becomes any diameter included in the measurement region of the subject's eye E (region on the pupil of φ2 mm to φ4 mm). For example, in measuring the ocular refractive power, a preliminary measurement may be performed first, and then a main measurement may be performed.

[0097] In the preliminary measurement, the eye refractive power of the test eye E is measured with the fixation target positioned at a predetermined presentation distance. During the measurement, the fixation target plate 155 may be positioned at an initial position that is optically far enough away from the test eye E and corresponds to the far point of the 0D eye. A ring image captured by the image sensor 125 based on the measurement light irradiated in this state is image-analyzed by the control unit 50. As a result of the analysis, the value of the refractive power in each meridian direction is obtained. At least the spherical power in the preliminary measurement is obtained by performing a predetermined process on the refractive power in each meridian direction.

[0098] Next, the control unit 50 moves the fixation target plate 155 to the fogging start position where the subject's eye E is in focus, according to the spherical power of the preliminary measurement of the subject's eye E. This allows the fixation target to be clearly observed by the subject's eye E. Thereafter, the control unit 50 adds fogging to the subject's eye E by moving the fixation target from the fogging start position. This releases accommodation of the subject's eye E. Note that while accommodation works on the subject's eye, pupil constriction occurs at the same time, but as accommodation is released by fogging, the pupil does not constrict.

[0099] This measurement is performed with fogging applied to the test eye E. A predetermined analysis process is performed on the ring image captured of the test eye E to which fogging has been applied, thereby obtaining the objective values ​​of the test eye E's SPH: spherical power, CYL: cylindrical power, and AXIS: astigmatism axis angle.

[0100] <Capturing cross-sectional images of the anterior segment (S4)> Next, a cross-sectional image (Scheimpflug image) of the anterior segment of the subject's eye E is captured. The control unit 50 immediately executes capturing of the cross-sectional image of the anterior segment after the main measurement of the eye refractive power is completed. For example, the operation of capturing the cross-sectional image may be triggered by the completion of the main measurement of the eye refractive power. In other words, immediately after the main measurement is completed, illumination light is irradiated from the irradiation optical system 300a and a cross-sectional image of the anterior segment formed on the image sensor 321 is obtained. This reduces alignment deviation between the time of measuring the eye refractive power and the time of capturing the cross-sectional image.

[0101] Note that the cross-sectional image of the anterior segment may not be properly acquired depending on the state of the anterior segment of the subject's eye E. For example, the subject's eyelids or eyelashes may be reflected in the image, or the pupil of the subject's eye E may be in a constricted state (a state in which the pupil diameter PDM is short). In the following, the constriction of the subject's eye E will be taken as an example.

[0102] 8 and 9 are examples of cross-sectional images 70 of the anterior eye. Fig. 8 is an appropriate cross-sectional image 70 captured when the subject's eye E is not miotically contracted. Fig. 9 is an inappropriate cross-sectional image 70 captured when the subject's eye E is miotically contracted.

[0103] For example, compared with pupil diameter PDM1 when the pupil of the subject's eye E is not constricted, pupil diameter PDM2 when the pupil is constricted is shorter. In this state, the returning light that illuminates the anterior segment of the subject's eye is likely to be vignetted by the iris, and the imaging range in the depth direction (Z direction) of the anterior segment may be insufficient. In particular, such vignetting of the returning light has a large effect on deeper positions of the anterior segment, and there are cases where the posterior surface of the crystalline lens is not imaged, or where the posterior surface of the crystalline lens is imaged but is inappropriate for detection using luminance information, which will be described later.

[0104] <Analysis of cross-sectional images of the anterior eye segment (S5)> The control unit 50 acquires anterior eye shape information relating to the shape of the anterior eye based on the cross-sectional image 70 of the anterior eye of the subject's eye E. For example, as the anterior eye shape information, a plurality of parameter information is acquired which are measurement values ​​such as the radius of curvature (Ra) of the anterior cornea, the radius of curvature (Rp) of the posterior cornea, the corneal thickness (CT), the anterior chamber depth (ACD), the radius of curvature (ra) of the anterior crystalline lens, the radius of curvature (rp) of the posterior crystalline lens, and the crystalline lens thickness (LT). It is also possible to acquire the radius of curvature of the anterior and posterior corneal surfaces and the corneal thickness using the corneal shape information in step S2.

[0105] The control unit 50 detects each optical body (for example, the cornea, aqueous humor, crystalline lens, etc.) by performing image processing on the cross-sectional image 70, and acquires anterior eye shape information. For example, the control unit 50 may use the luminance information of the cross-sectional image 70 to detect pixel positions corresponding to tissue boundaries (the anterior and posterior surfaces of the cornea, the anterior and posterior surfaces of the crystalline lens, the iris, etc.) and acquire information such as the radius of curvature. In addition, for example, the control unit 50 may obtain the distance of the pixel positions corresponding to the tissue boundaries and acquire information such as the thickness and depth of the tissue.

[0106] <Parameter information pass / fail judgement (S6)> However, as described above, when the subject's eye E is in miosis, some of the multiple parameter information in the anterior eye shape information cannot be correctly acquired. Therefore, the control unit 50 judges the acceptability of the multiple parameter information. For example, the acceptability of each of the multiple parameter information may be judged based on the luminance information of the cross-sectional image 70.

[0107] Fig. 10 and Fig. 11 are schematic diagrams showing changes in luminance values ​​in a cross-sectional image 70. Fig. 10 shows changes in luminance values ​​corresponding to the appropriate cross-sectional image 70 shown in Fig. 8. Fig. 11 shows changes in luminance values ​​corresponding to the inappropriate cross-sectional image 70 shown in Fig. 9.

[0108] The control unit 50 detects the rise and fall of the luminance in the depth direction of the subject's eye at the left-right center of the cross-sectional image 70 (i.e., on the optical axis L1). For example, as shown in Figs. 8 and 10, when the pupil of the subject's eye E is not constricted, the boundaries between the front and rear surfaces of the cornea and the front and rear surfaces of the lens are clearly captured, and the gradient of the rise and fall of the luminance value is steep. On the other hand, as shown in Figs. 9 and 11, when the pupil of the subject's eye E is constricted, the boundaries between the front and rear surfaces of the cornea and the front surface of the lens are clearly captured, but the boundary of the rear surface of the lens may not be clearly captured, and the fall of the luminance value at the rear surface of the lens is gradual. As a result, the rear surface of the lens is detected at a position different from the actual position.

[0109] The control unit 50 judges whether the anterior and posterior surfaces of the cornea and the anterior and posterior surfaces of the crystalline lens have been photographed well from the rise and fall of the brightness values ​​of the tissues in the cross-sectional image 70. For example, a reference angle based on an experiment or a simulation may be set for the gradient of the brightness values ​​of each tissue. If the gradient of the brightness values ​​of a certain tissue is equal to or greater than a predetermined angle, it may be judged that the tissue has been photographed well, and if it is less than the predetermined angle, it may be judged that the tissue has not been photographed well. Note that the rise and fall of the brightness values ​​corresponding to each tissue may be expressed as a slope, not limited to an angle. It is also possible to use the width in the depth direction from the maximum value to the minimum value of the brightness values ​​corresponding to each tissue as a criterion for such judgment.

[0110] Furthermore, the control unit 50 judges whether a plurality of pieces of parameter information included in the anterior eye shape information are good or bad based on the judgment result of whether each tissue in the cross-sectional image 70 has been photographed well. For example, the analysis result of parameter information based on the pixel position of a tissue that has not been photographed well may be judged to be bad. Also, for example, the analysis result of parameter information based on the pixel position of a tissue that has been photographed well may be judged to be good. As an example, when the posterior surface of the lens is not photographed well, the radius of curvature of the posterior surface of the lens and the lens thickness may be regarded as invalid measurement values, and the radius of curvature of the anterior and posterior corneal surfaces, the corneal thickness, the anterior chamber depth, and the radius of curvature of the anterior surface of the lens may be regarded as valid measurement values.

[0111] In this embodiment, an evaluation value for evaluating the reliability of a plurality of pieces of parameter information in the anterior eye shape information may be obtained, and the quality of each piece of parameter information may be determined based on the evaluation value. In this case, the control unit 50 may determine an evaluation value that indicates whether the imaging of each tissue is good or bad according to the degree of gradient of the brightness value of each tissue in the cross-sectional image 70.

[0112] For example, the control unit 50 may express the difference between a reference angle set for the gradient of the brightness value of each tissue and the angle of the actual gradient as a value in five stages. For example, the closer the angle of the actual gradient of the brightness value is to the reference angle, the higher the value in the five stages is set, and the farther it is from the reference angle, the lower the value in the five stages is set. That is, for example, the smaller the difference between the actual gradient angle and the reference angle, the higher the value is set, and the larger the difference, the lower the value is set. Note that such a correspondence relationship between the allowable range of the difference in angle and the value may be stored in the storage unit. When the evaluation value of a certain tissue is below a predetermined value, the control unit 50 may determine that the tissue is not photographed well and may invalidate the analysis result of the related parameter information (i.e., the measurement value).

[0113] <Eye axis length calculation (S7)> Next, the axial length of the subject's eye E is calculated. The control unit 50 calculates the axial length based on the ocular refractive power of the subject's eye E and a plurality of parameter information in the anterior eye shape information of the subject's eye E. For example, the axial length may be calculated using both valid measurement values ​​and invalid measurement values ​​among the plurality of parameter information. Also, for example, the axial length may be calculated using both valid measurement values ​​and assumed values ​​replacing invalid measurement values ​​among the plurality of parameter information.

[0114] In this embodiment, the axial length is calculated using only the measured values ​​or the measured values ​​and the assumed values ​​as multiple parameter information in the anterior eye shape information. The assumed values ​​are estimated values ​​that can be obtained by considering the ratio of a general corneal shape or a lens shape. For example, the radius of curvature (measured value) of the corneal anterior surface can be multiplied by a predetermined ratio value to obtain the radius of curvature (estimated value) of the corneal posterior surface. Similarly, the radius of curvature (measured value) of the lens anterior surface can be multiplied by a predetermined ratio value to obtain the radius of curvature (estimated value) of the lens posterior surface. The control unit 50 may multiply the valid measured values ​​of the parameter information by such a ratio value to obtain an estimated value in place of the invalid measured values.

[0115] First, the control unit 50 determines the position of the far point FP (see FIG. 12) relative to the corneal apex C based on the measurement results of the ocular refractive power of the subject's eye E. For example, if the subject's eye E has no astigmatism, SPH=-5D, and VD=12mm, then the distance from the corneal apex C to the far point FP is 12+1000 / 5=212mm. It is considered that a light ray from the far point FP forms an image on the fundus. Note that VD=12mm is a fixed value indicating the corneal apex distance assuming the wearing of spectacle lenses. VD may vary depending on the device.

[0116] 12 is a schematic diagram for explaining a method for deriving the axial length. In this embodiment, the axial length may be derived based on a ray tracing calculation on a cut surface of the anterior segment. For example, the control unit 50 performs the ray tracing calculation based on the position of the far point FP, the refractive index of each translucent body, and parameter information (measured values ​​or assumed values) in the anterior segment shape information.

[0117] The control unit 50 tracks a light ray (e.g., light ray Lx in FIG. 12) incident from a far point FP toward the subject's eye E, and determines the position of the intersection point where the light ray is refracted by each optically transparent body of the subject's eye E and intersects with the optical axis. Details of the ray tracing calculation will be described later. For example, the position of the fundus Ef is 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.

[0118] <Display output (S8)> 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 ocular refractive power (SPH, CYL, AXIS) of the subject's eye E. In this embodiment, the axial length using only measured values ​​as multiple parameter information and the axial length using measured values ​​and assumed values ​​are displayed so as to be distinguishable from each other.

[0119] Fig. 13 is an example showing the change in axial length over time. If past axial length measurements of the subject eye E exist, the current axial length may be displayed together with the past axial length. Note that, for each of the past and current axial lengths, the axial length using only the measured value (first axial length AL1) and the axial length using the measured value and the assumed value (second axial length AL2) may be displayed so as to be distinguished. For example, here, a graph showing the axial length for each examination date (age) in chronological order is displayed. Of course, the display manner is not limited.

[0120] When there are a plurality of measurement results with different time series, it is possible to predict the future axial length using these axial lengths. In this case, the past and present axial lengths may be displayed so as to be distinguished from the predicted axial length. In addition to the axial length, the change over time may be displayed for each parameter information included in the anterior segment shape information. For example, the change over time of the corneal thickness, the crystalline lens thickness, the anterior chamber depth, etc. may be displayed.

[0121] <Ray tracing calculation> Ray tracing calculation for deriving the axial length will be described. In this embodiment, for convenience of explanation, it is assumed that the refractive index in each transparent body of the subject's eye E is constant and there is no change in refraction inside each body. However, this is not necessarily limited to this, and the axial length may be derived taking into account the change in the refractive index inside the transparent body (for example, the change in the refractive index between the inside and outside of the crystalline lens).

[0122] Incidentally, in the widely used expression format of ocular refractive power by SPH, CYL, and AXIS, SPH indicates the refractive power related to the strong meridian (or weak meridian), so it is not necessarily an appropriate value in ray tracing on a cut surface of the anterior eye. For example, consider a case where SPH=-5D, CYL=-2D, and AXIS=30°. In this case, if a horizontal cross section is obtained in the above optical system example, the refractive power on this cross section is neither -5D nor -7D with CYL added.

[0123] In contrast, in this embodiment, the on-surface ocular power, which is the ocular power on the cut surface, is calculated, and the position of the far point FP is set based on the on-surface ocular power. Here, the refractive power P on an arbitrary surface is expressed by the following formula. Here, θ is an angle with respect to the horizontal plane, and the horizontal direction is set to 0°.

[0124] P(θ)=SPH+CYL×[sin2(θ-A)]

[0125] 12 is a diagram showing the refractive power in each meridian direction when the subject's eye E has SPH=-5D, CYL=-2D, and AXIS=30°. For example, the cutting plane in this embodiment is a horizontal plane (θ=0°). Therefore, if the subject's eye E has SPH=-5D, CYL=-2D, and AXIS=30°, P(0°)=-5.5D is calculated. In this case, if VD=12mm, the distance from the corneal apex C to the far point FP on the cutting plane is 12+1000 / 5.5=194mm.

[0126] The control unit 50 tracks a ray from the far point FP thus set. For example, it guides a ray (e.g., a ray Lx in FIG. 12) from the far point FP toward a fixed position (as an example, a position of φ6 mm at the position of the pupil of the subject's eye (approximately 3 mm behind the cornea)). Note that setting the fixed position to φ6 mm at the position of the pupil of the subject's eye is merely an example and can be changed as appropriate.

[0127] This light ray is first refracted at the front surface of the cornea. The intersection of the light ray and the front surface of the cornea is calculated based on the radius of curvature Ra of the front surface of the cornea, the position of the far point FP, and the light ray angle at the far point FP. Furthermore, the angle of incidence of the light ray at the intersection is calculated. The light ray that reaches the front surface of the cornea changes its direction at a refraction angle determined with respect to the angle of incidence based on Snell's law. In this manner, the light ray is tracked successively at each transparent body boundary surface. At that time, the anterior eye shape information (Ra, Rp, CT, ACD, ra, rp, LT) acquired based on the corneal shape information and the cross-sectional image 70 (Scheimpflug image) is appropriately used to give the intersection of each boundary surface and the light ray. In this embodiment, the intersection (i.e., the position of the fundus Ef) where the light ray intersects with the axis of the eye (here, the visual axis) after leaving the rear surface of the crystalline lens is finally obtained. The distance from the intersection to the corneal apex C (here, the origin) is used as the axial length AL.

[0128] In addition, when the above-mentioned anterior eye shape information (Ra, Rp, CT, ACD, ra, rp, LT) is used in the ray tracing calculation, in this embodiment, for at least the radius of curvature Ra of the corneal anterior 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 (Scheimpflug image) are used. This is because, for the corneal anterior surface shape, the measurement accuracy based on the corneal Purkinje image is generally higher than that based on the Scheimpflug image. As described above, in this embodiment, at least the values ​​of the corneal curvature, the astigmatism degree, and the astigmatism axis angle are obtained as the corneal shape information. The corneal curvature (curvature of the corneal anterior surface) at the cut surface can be obtained from these values ​​using a method similar to the method of obtaining the refractive power for the cut surface. The reciprocal of the obtained value may be used as Ra.

[0129] The axial length AL of the subject's eye E can be obtained by tracing rays directed toward such a fixed position. However, the method of ray tracing is not limited to the above method. For example, the point at which an image is formed from the far point FP may be obtained by paraxial calculation. Also, the point at which an image is formed from the far point FP may be obtained by considering a plurality of rays that are incident on the subject's eye E at different positions. For example, ray tracing for each of a paraxial ray and a ray directed toward a fixed position other than the paraxial ray may be combined. When ray tracing for a plurality of rays is performed, the final measurement value (calculated value) of the axial length may be the average value (weighted average value) of the axial lengths obtained by each ray tracing.

[0130] The axial length AL may also be obtained by tracing rays directed toward a 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 toward a region on the pupil of φ2 mm to φ4 mm, and the average value of the axial length obtained by each ray tracing may be obtained as the calculation result. Since ray tracing is performed under more appropriate conditions, the axial length can be obtained more accurately.

[0131] A predetermined offset value may be added to the axial length value obtained in this embodiment, which corrects the error between the calculated value and the actual measured value.

[0132] Ray tracing may also be performed by tracing a ray that is emitted from the far point FP and passes through a circumferential region onto which a point image index for corneal shape measurement is projected. This makes the conditions for ray tracing more appropriate, making it easier to obtain the axial length with higher accuracy.

[0133] As described above, for example, the ophthalmologic apparatus of this embodiment acquires the ocular refractive power of the subject eye and shape information including a plurality of parameters based on an anterior segment cross-sectional image of the subject eye, and derives the axial length (first axial length) based on the ocular refractive power and the measured values ​​of the plurality of parameters. In addition, the axial length (second axial length) is derived based on the ocular refractive power and an assumed value replacing some of the measured values ​​of the plurality of parameters. In deriving the axial length, it is desirable to acquire as many shape information of the translucent body in the anterior segment as possible as parameters, but there are cases where no measured value can be obtained or the measured value is inaccurate. By deriving at least one of the first axial length and the second axial length, the axial length can be acquired with high accuracy.

[0134] In addition, for example, the ophthalmologic apparatus of the present embodiment judges whether at least one of a plurality of parameters in the shape information of the anterior eye is good or bad, and selects derivation of at least one of the first axial length and the second axial length based on the judgment result. Therefore, even if an appropriate anterior eye cross-sectional image is not obtained due to the influence of blinking or miosis of the subject's eye, or if there are inappropriate parameter measurement values, it becomes easier to obtain an accurate axial length.

[0135] In addition, for example, the ophthalmologic apparatus of the present embodiment judges whether a plurality of parameters in the shape information of the anterior eye segment are acceptable based on luminance information of the anterior eye segment cross-sectional image. Alternatively, the ophthalmologic apparatus judges whether a plurality of parameters in the shape information of the anterior eye segment are acceptable based on evaluation information for evaluating reliability. This makes it easy to grasp the presence or absence of blinking in the subject's eye, the presence or absence and degree of miosis, etc.

[0136] In addition, for example, the ophthalmologic apparatus of the present embodiment outputs the first dimension information acquired based on the measured values ​​of the multiple parameters in the shape information of the anterior eye segment and the second dimension information acquired based on the assumed values ​​replacing some of the measured values ​​of the multiple parameters in a distinguishable manner, so that the examiner can easily determine the value to be adopted as the axial length of the subject eye by comparing the respective values.

[0137] Furthermore, for example, the ophthalmologic apparatus of this embodiment outputs the change over time in the intraocular dimension information (the first dimension information and the second dimension information), which makes it easier for the examiner to evaluate the progression of myopia based on the axial length.

[0138] <Example of transformation> In this embodiment, the cross-section photographing optical system is described as using red visible light or infrared light as illumination light, but is not limited thereto. The cross-section photographing optical system may be configured to use visible light other than red as illumination light. When visible light (especially light with high luminosity) is irradiated to the subject's eye E, the pupil contracts, so it is preferable to photograph the cross-section image 70 immediately before or simultaneously with the irradiation of visible light.

[0139] In this embodiment, the configuration is described as an example in which the rise and fall of the brightness value in each tissue is used to determine whether the anterior eye shape information based on the cross-sectional image 70 is good or bad, but the present invention is not limited to this. For example, the configuration may be such that the pupil state of the subject eye is used to determine whether the anterior eye shape information is good or bad. In this case, the control unit 50 may obtain the pupil diameter as the pupil state by detecting the pixel position corresponding to the iris based on the brightness information of the cross-sectional image 70. In addition, based on this pupil diameter, it may be determined whether the anterior and posterior surfaces of the cornea and the anterior and posterior surfaces of the crystalline lens have been photographed well. The control unit 50 may also obtain pupil state information (pupil diameter) using an observation image photographed by the front photographing optical system 200.

[0140] For example, when the pupil diameter of the subject's eye E is small, the detection width in the horizontal direction (X direction) of the front and rear surfaces of the crystalline lens becomes narrow. In other words, the number of pixels in the longitudinal direction of the slit light on the front and rear surfaces of the crystalline lens becomes small. Also, when the pupil diameter of the subject's eye E is small, the boundary of the rear surface of the crystalline lens may not be clearly captured. For this reason, the control unit 50 may change the tissues that are considered to have been photographed well according to the pupil diameter of the subject's eye E. As an example, if the pupil diameter is φ2 mm or less, the front and rear surfaces of the cornea may be considered to have been photographed well, and the front and rear surfaces of the crystalline lens may be considered to have been photographed poorly. Also, the control unit 50 may determine whether the multiple parameter information included in the anterior eye shape information is good or bad based on the determination result of whether each tissue has been photographed well. As an example, the radius of curvature of the front and rear surfaces of the cornea, the corneal thickness, and the anterior chamber depth may be considered to be valid measurement values, and the radius of curvature of the front and rear surfaces of the crystalline lens and the crystalline lens thickness may be considered to be invalid measurement values.

[0141] In addition, if the horizontal detection width of each tissue is narrow, an error in the calculation of the radius of curvature is likely to occur. For example, in fitting a circle using at least three pixel positions, a deviation of one pixel is more likely to appear as an error in the radius of curvature when three narrow points are used than when three wide points are used. By considering the change in detection width due to the change in pupil diameter and correlating the quality of imaging of each tissue with the pupil diameter, the validity of the parameter information can be determined with high accuracy.

[0142] In the present embodiment, the cross-sectional image 70 is captured using the cross-sectional image capturing optical system, but the present invention is not limited thereto. For example, the cross-sectional image 70 may be captured by capturing multiple cross-sectional images. In this case, the control unit 50 may cause the image sensor 321 to capture the return light of the illumination light every time a predetermined time elapses (for example, every second). The illumination light from the light source 311 may be projected at a predetermined time interval in accordance with the image capturing timing of the image sensor 321, or may be projected constantly. For example, by continuously acquiring multiple cross-sectional images of the subject's eye, it becomes easier to include appropriate cross-sectional images such as images without reflections of eyelids or eyelashes, images in which the subject's eye does not contract, etc. The control unit 50 may use luminance information and evaluation information in the multiple cross-sectional images to determine whether the parameter information corresponding to each image is good or bad.

[0143] By acquiring a plurality of anterior segment cross-sectional images, the control unit 50 can acquire at least one of the first axial length AL1 and the second axial length AL2 based on the quality of a plurality of parameters corresponding to each of the images. For example, it is possible to average the values ​​of the parameters for each tissue that are good, and acquire each axial length based on this. Note that such an average may be an average excluding outliers, which will be described later. Also, for example, it is possible to acquire each axial length using the value of the parameter for each tissue that is the best. This allows the axial length to be acquired with high accuracy.

[0144] When multiple cross-sectional images are continuously obtained using the cross-sectional image capturing optical system, outliers in the cross-sectional images or outliers in the anterior eye shape information based on the cross-sectional images may be excluded in advance. For example, the control unit 50 may identify and exclude these outliers by statistical processing. As an example, luminance information or evaluation information obtained from multiple cross-sectional images that is significantly outside the allowable range may be excluded. By obtaining multiple anterior eye cross-sectional images and further eliminating the outliers, the accuracy of the axial length can be further improved.

[0145] In this embodiment, the cross-sectional image 70 is captured once using the cross-sectional image capturing optical system in the flowchart shown in Fig. 7, but the present invention is not limited to this. For example, the cross-sectional image 70 may be captured again based on the quality of the parameter information. In other words, the cross-sectional image 70 may be captured twice.

[0146] For example, the control unit 50 may perform image processing on the cross-sectional image 70 acquired using the cross-sectional photographing optical system, and adjust the amount of illumination light from the irradiation optical system 300a based on the brightness information detected by the image processing. As an example, when the boundary of a predetermined tissue cannot be detected or the boundary of a predetermined tissue is not clear, the amount of light from the light source 311 may be increased, or an optical member such as a filter may be inserted or removed in the optical path. In addition, for example, the control unit 50 may photograph the cross-sectional image 70 again after adjusting the amount of illumination light from the irradiation optical system 300a. This makes it possible to obtain a second cross-sectional image in which the photographing state of each tissue is improved compared to the first cross-sectional image. In other words, even if at least some of the multiple parameters are not obtained well, and therefore no measurement value can be obtained, or the measurement value is not accurate, there is a high possibility that an appropriate value can be obtained. As a result, each of the multiple parameter information included in the anterior eye shape information can be obtained well, and the axial length can be obtained with high accuracy.

[0147] In addition, in such an adjustment of the light amount in the irradiation optical system 300a, it is preferable that infrared light is irradiated from the light source 311. For example, with infrared light, the subject is less likely to feel dazzled even if the light amount increases, and miosis of the subject's eye can be suppressed.

[0148] In this embodiment, a configuration has been described in which some of the parameters included in the anterior eye shape information are automatically changed from measured values ​​to assumed values ​​based on the analysis result of the cross-sectional image information in the cross-sectional image 70, but the present invention is not limited to this. For example, the examiner may manually change whether to use measured values ​​or assumed values ​​for some of the parameters by operating the operation unit (monitor 16). In this case, the control unit 50 may display guide information on the monitor 16 to assist the examiner in making a judgment based on the quality of the parameter information in the anterior eye shape information.

[0149] In this embodiment, a configuration in which some of the parameters included in the anterior eye shape information are replaced with an estimated value, which is one of the assumed values, has been described as an example, but the present invention is not limited to this. For example, a configuration in which an examiner can operate an operation unit to select a value to be used as the assumed value may be used. As an example, a configuration in which at least one of a standard value based on a model eye, an average value based on statistical data, etc., past measurement values ​​of the subject eye, and an estimated value, etc. may be selected.

[0150] In this embodiment, the configuration in which the ocular refractive power of the test eye is measured and then the cross-sectional image 70 of the test eye is acquired is described as an example, but the present invention is not limited thereto. For example, the ocular refractive power of the test eye and the cross-sectional image 70 of the test eye may be acquired in parallel (at the same timing). In this case, the control unit 50 controls both the measurement light from the measurement light source 111 in the projection optical system 100a and the illumination light from the light source 311 in the irradiation optical system 300a to project both lights toward the test eye. The projection of the lights does not necessarily have to start at the same time. In addition, the control unit 50 controls both the image sensor 125 in the light receiving optical system 100b and the image sensor 321 in the light receiving optical system 300b to capture the ring image and the cross-sectional image 70 at the same timing. For example, the ocular refractive power and the cross-sectional image 70 are acquired in a state in which the test eye is clouded.

[0151] The state of the subject's eye may differ at each acquisition timing, and it is difficult to avoid the influence of pupil constriction and accommodation on the eye refractive power and the anterior eye shape information based on the cross-sectional image 70. For example, in measuring the eye refractive power of the subject's eye, pupil constriction is suppressed and accommodation is released, but when a cross-sectional image of the anterior eye is subsequently acquired, pupil constriction and accommodation may occur again. However, if the measurement of eye refractive power (acquisition of a ring image) and acquisition of a cross-sectional image are performed simultaneously, the pupil state and accommodation state of the subject's eye can be easily matched, and the cross-sectional image is acquired with the subject's eye being clouded and the anterior eye in an appropriate state (i.e., the accommodation of the subject's eye is released and the crystalline lens thickness is thin). Therefore, the control unit 50 can acquire the measured values ​​of parameters suitable for calculating the axial length, and the axial length can be calculated with high accuracy. Furthermore, if the measured values ​​of the parameters are not valid, they can be replaced with assumed values ​​to calculate the axial length with high accuracy.

[0152] In this embodiment, the refractive index of each translucent body of the subject's eye E is constant, but the present invention is not limited to this. For example, refractive index information on the refractive index of the translucent body may be obtained separately from the cross-sectional image 70 of the anterior eye, and the refractive index information may be used to derive the axial length AL. In other words, in obtaining the axial length AL, the refractive index of the translucent 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 age. Therefore, the storage unit of the ophthalmic device 10 may have a calculation formula or a lookup table in which the refractive index of the crystalline lens is associated with each age. In this case, the age of the subject is input, and the refractive index according to the age can be obtained. The control unit 50 may perform ray tracing calculation using such a refractive index of the crystalline lens. [Explanation of symbols]

[0153] 10 Ophthalmology equipment 50 Control section 100 Measurement optical system 150 Fixation target presentation optical system 200 Frontal Shooting Optical System 300a Irradiation optical system 300b Light receiving optical system 400 Index Projection Optics

Claims

1. an eye refractive power measuring optical system for acquiring an eye refractive power of a subject's eye; a cross-sectional image photographing optical system for projecting measurement light toward an anterior segment of the subject's eye and detecting return light of the measurement light from an oblique direction with respect to an optical axis of the projection of the measurement light, thereby acquiring a cross-sectional image of the anterior segment of the subject's eye; a shape information acquiring means for analyzing the anterior ocular segment cross-sectional image and acquiring shape information regarding the shape of the anterior ocular segment, the shape information including a plurality of parameters; an axial length acquiring means for controlling the eye refractive power measuring optical system and the cross-sectional image taking optical system, and acquiring an axial length of the subject's eye based on the eye refractive power and the plurality of parameters; Equipped with The ophthalmologic apparatus, characterized in that the axial length acquisition means acquires a first axial length derived using measured values ​​of the plurality of parameters, and a second axial length derived using assumed values ​​that replace some of the measured values ​​of the plurality of parameters.

2. 2. The ophthalmic apparatus of claim 1, A determination means for determining whether or not at least one of the plurality of parameters is acceptable; a selection means for selecting derivation of at least one of the first axial length and the second axial length based on a result of the determination by the determination means; An ophthalmic apparatus comprising:

3. 3. The ophthalmic apparatus according to claim 2, The ophthalmologic apparatus according to claim 1, wherein the determining unit determines whether the plurality of parameters are good or bad based on evaluation information for evaluating reliability of the plurality of parameters.

4. 3. The ophthalmic apparatus according to claim 2, The axial length acquisition means acquires a plurality of the anterior segment cross-sectional images, The determining means determines whether a plurality of parameters corresponding to each of the anterior segment cross-sectional images are good or bad, The ophthalmologic apparatus according to claim 1, wherein the selection means selects the derivation of the first axial length and the second axial length based on the quality of the plurality of parameters corresponding to the plurality of anterior eye cross-sectional images.

5. In the ophthalmic apparatus according to any one of claims 2 to 4, The axial length acquiring means adjusts the amount of the measurement light in the cross-sectional image capturing optical system based on the determination result of the determining means, the shape information acquisition means analyzes the anterior segment cross-sectional image acquired after the adjustment of the light amount by the axial length acquisition means, and acquires a plurality of adjusted parameters; The ophthalmologic apparatus according to claim 1, wherein the determining unit determines whether the plurality of parameters after the adjustment are acceptable or not.

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