JP6589378B2 - Ophthalmic measuring device - Google Patents

Description

  The present disclosure relates to an ophthalmologic measurement apparatus that performs measurement related to an eye to be examined.

  As one of the eye characteristics of the eye to be examined, there is a case where information related to the corneal surface such as the corneal posterior curvature and the corneal posterior surface shape is measured. The corneal posterior curvature is used, for example, for calculating the corneal refractive power, and the calculation result is used for calculating the power of the intraocular lens. Conventionally, information on the posterior surface of the cornea has been acquired by analyzing a cross-sectional image of the cornea imaged by a Shine-Pluke camera, an anterior ocular segment OCT apparatus, or the like.

JP 2012-055337 A

  In the case of the prior art exemplified above, a cross-sectional image of the cornea is required. Therefore, the user must always prepare a device for capturing a cross-sectional image of the cornea.

  Note that when measuring with respect to a plurality of meridian directions on the cornea in a Shine-Pluke camera, it is necessary to rotate the optical system in order to obtain cross-sectional images at different angles, resulting in a complicated apparatus configuration. The anterior segment OCT is relatively expensive because it requires an interference optical system, an optical scanner, and the like.

  In view of the problems of the prior art, the present disclosure aims to obtain information on the posterior corneal surface of the eye to be examined with a simple configuration.

An ophthalmologic measurement apparatus according to a first aspect of the present disclosure includes a projection optical system for projecting an index toward the cornea of an eye to be examined, a first Purkinje image and a second image using the index projected onto the cornea by the projection optical system. An imaging optical system that captures a Purkinje image with an imaging device and an internal fixation target provided in the apparatus main body, and a fixation that can guide the line of sight of the eye to be examined in a direction inclined with respect to the imaging optical axis An optical system for separating the first Purkinje image and the second Purkinje image, and a fixation optical system used to obtain information on the posterior corneal surface based on the separated second Purkinje image; and The second Purkinje image picked up by an element and tilted by the fixation optical system; the second Purkinje image of the eye to be examined; information on the frontal shape of the cornea; and the fixation optical system. Information about the amount of inclination with respect to the tilted the subject's eye the image pickup optical axis of, at least based on an arithmetic means for obtaining information about the posterior surface of the cornea of the eye, Ru comprising a.

An ophthalmologic measurement apparatus according to a second aspect of the present disclosure includes a projection optical system for projecting an index toward the cornea of a subject eye, a first Purkinje image and a second image based on the index projected onto the cornea by the projection optical system. In order to separate the first Purkinje image and the second Purkinje image by the imaging eye, and an imaging optical system that captures the Purkinje image with an imaging device, the line of sight of the eye to be inspected with respect to the imaging optical axis of the imaging optical system Line-of-sight tilting means for tilting the direction, the second Purkinje image of the eye to be examined tilted by the line-of-sight tilting means is captured by the imaging device , the second Purkinje image, information on the frontal shape of the cornea, and information about the tilt with respect to the imaging optical axis of the eye to be examined which is inclined by sight tilting means, based at least on the control hand to obtain information about the posterior surface of the cornea of the eye If, Ru equipped with.

  According to the present disclosure, information related to the corneal posterior surface of the eye to be examined can be acquired favorably.

It is a schematic block diagram of the ophthalmologic measurement apparatus in this embodiment. It is the figure which showed arrangement | positioning of the fixation lamp seen from the to-be-tested eye side. (A) shows the eye to be examined whose gaze direction is guided by the central fixation lamp, and (b) is a diagram showing light rays incident on the cornea of the eye to be examined. (A) shows the eye to be examined whose line-of-sight direction is guided in a direction inclined with respect to the optical axis by the near fixation lamp, and (b) is a diagram showing light rays incident on the cornea of the eye to be examined. is there. It is a schematic diagram of the anterior eye part image imaged with an ophthalmologic measurement apparatus. It is a flowchart which shows the measurement operation | movement of an ophthalmologic measurement apparatus.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings.
<Schematic configuration of the device>
First, with reference to FIG. 1, a schematic configuration of the ophthalmologic measurement apparatus 1 in the present embodiment will be described. The ophthalmologic measurement apparatus 1 shown in FIG. 1 performs measurements on the corneal front surface Ec1 and the corneal rear surface Ec2 (see FIGS. 3 and 4) of the eye E to be examined. As shown in FIG. 1, the ophthalmologic measurement apparatus 1 mainly includes a kerato projection optical system 10, an imaging optical system (light receiving optical system) 20, a fixation optical system 50, and a control unit 100. In addition, the ophthalmic measurement apparatus 1 according to the present embodiment includes an alignment projection optical system 30 and a second measurement optical system 40. These optical systems are built in a housing (not shown). Further, the casing is moved three-dimensionally with respect to the eye E by driving a known alignment moving mechanism 60. The movement of the housing may be performed, for example, according to an examiner's operation on an operation member (for example, a joystick).

  The fixation optical system 50 is used to guide the eye direction of the eye E and fix the eye E during measurement. In the present embodiment, the fixation optical system 50 has an internal fixation target provided in the apparatus main body. That is, the fixation optical system 50 projects a fixation target from within the apparatus main body (in other words, inside the housing). Further, the fixation optical system 50 of the present embodiment guides the line-of-sight direction of the eye E in a plurality of directions by switching the position of the fixation target presented to the eye E. The internal fixation target of the fixation optical system 50 may be provided at a position away from the optical axis L2 of the fixation optical system 50.

  The fixation optical system 50 includes a visible light source (fixation lamp) 51 (51a to 51i), a light projection lens 53, and a dichroic mirror 43 for visible reflection and infrared transmission. In the present embodiment, a light source (fixation lamp) 51 is used as an internal fixation target. Visible light emitted from the light source 51 is converted into a parallel light beam by the light projection lens 53, reflected by the dichroic mirror 43, and projected as a fixation target on the fundus of the eye E to be examined. The dichroic mirror 43 makes the optical axis L2 of the fixation optical system 50 coaxial with the optical axis L1 of the imaging optical system 20.

  In the present embodiment, the fixation optical system 50 includes a plurality of light sources 51a to 51i as fixation lamps. Each light source 51a-51i is arrange | positioned in a mutually different position regarding the direction which cross | intersects (for example, orthogonal) with respect to the optical axis L1 (optical axis L2). Any one of the light sources 51a to 51i selected by the control unit 100 is turned on. That is, in the present embodiment, the fixation optical system 50 switches the line-of-sight direction of the eye E by switching the fixation lamp that is turned on.

  For example, the light source 51a is a central fixation lamp arranged near the optical axis L1 (optical axis L2). When the fixation lamp 51a is turned on, the fixation optical system 50 guides the line-of-sight direction of the eye E in a direction along the optical axis L1 (that is, the imaging optical axis) (see FIG. 3A). .

  Moreover, each of the light sources 51b to 51i is a proximity fixation lamp. When any one of the light sources 51b to 51i is turned on, the fixation optical system 50 guides the line-of-sight direction of the eye E in a direction inclined with respect to the optical axis L1 (imaging optical axis) (FIG. 4 ( a)). In the present embodiment, the amount of inclination with respect to the optical axis L1 and the direction of inclination in the line-of-sight direction of the subject's eye guided by the near fixation lamp are such that the region near the cornea center is on the optical axis L1 (on the imaging optical axis). It may be set in the range arranged in.

  For example, the plurality of light sources 51b to 51i may be arranged on the same circumference around the optical axis L1 (optical axis L2). More specifically, the light sources 51b to 51i are arranged at predetermined angles as viewed from the subject. For example, in FIG. 2, the light sources 51b to 51i are arranged at 45 degrees at positions of 0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, and 315 degrees. The plurality of light sources 51b to 51i each have a visual axis (line-of-sight direction) of the eye E tilted by a predetermined angle with respect to the central fixation lamp (light source 51) (in other words, with respect to the optical axis L1). It is arranged at a predetermined position to be related. Preferably, a plurality of light sources 51b to 51i may be arranged in a range in which the line-of-sight direction is inclined at an angle of 5 ° to 26 ° with respect to the optical axis L1. For example, in the present embodiment, each of the light sources 51b to 51i may be disposed at a position where the line-of-sight direction is 13 ° with respect to the optical axis L1. In the present embodiment, in this range, the first Purkinje image Ra and the second Purkinje image Rp, which will be described later, can be favorably separated.

  The kerato projection optical system 10 may project (project) a pattern index (measurement index) toward the cornea Ec. As shown in FIG. 1, the kerato projection optical system 10 may project the pattern index from an oblique direction with respect to the optical axis L1. In this case, the region of the cornea Ec on which the pattern index is projected is determined by the case where the gaze direction of the eye E is guided in the direction along the optical axis L1 by the central fixation lamp 51a and the vicinity fixation lamps 51b to 51i. In any case where the line-of-sight direction of the eye E is guided in a direction inclined with respect to the optical axis L1, the pattern index by the kerato projection optical system 10 is set so as to be in the vicinity of the central portion of the cornea. The projection position may be determined.

  The pattern index from the kerato projection optical system 10 is used for measurement related to the corneal front surface Ec1, and the corneal rear surface Ec2 (corneal back surface). For example, the shape, radius of curvature, refractive power, and the like of the corneal front surface Ec1 may be measured with respect to the corneal front surface Ec1. In addition, the shape, the radius of curvature, the refractive power, and the like of the corneal rear surface Ec2 may be measured with respect to the corneal rear surface Ec2. Further, for example, refraction of the entire cornea, distribution of corneal thickness, astigmatic axis angle in the cornea, aberration, and the like may be measured from the measurement result regarding the corneal front surface Ec1 and the measurement result regarding the corneal rear surface Ec2.

  The kerato projection optical system 10 has a light source 11. The light emitted from the light source 11 may be, for example, infrared light or visible light. The kerato projection optical system 10 may be configured to project the light emitted from the light source 11 onto the cornea Ec as a pattern index. The pattern index is preferably a two-dimensional pattern formed by lines or a plurality of (three or more) points. For example, it may be a continuous or intermittent ring pattern, a pattern composed of three or more point indexes arranged concentrically, a dot matrix index in which point indexes are arranged in a grid pattern, and the like.

  As a specific example, the kerato projection optical system 10 in FIG. 1 includes a ring light source as the light source 11 and projects a ring-shaped pattern index onto the cornea Ec. For example, the ring light source may be a light source formed in a ring shape, or a combination of a plurality of point light sources arranged in a ring shape and a ring-shaped pattern opening arranged in front of the point light source It may be.

  As shown in FIGS. 3B and 4B, the ring-shaped first Purkinje image Ra is formed by light reflected (and scattered) by the cornea front surface Ec1 among the light projected by the light source 11a. Can be done. Moreover, the ring-shaped second Purkinje image Rp can be formed by the light reflected (and scattered) by the corneal rear surface Ec2 among the light projected by the ring light source 11. In general, the second Purkinje image Rp has a lower luminance than the first Purkinje image Ra.

  In the present embodiment, the light source 11 includes one ring light source, but may include two or more ring light sources having different radii. In this case, for example, each ring light source may be arranged concentrically with the optical axis L1 as the center, and each ring light source may project a pattern index onto different regions of the cornea Ec. . In addition, each ring light source may be lighted simultaneously, and may be lighted one by one (or one part at a time). However, when a plurality of ring light sources are turned on at the same time, it is preferable that the projection positions of the index images on the cornea Ec do not overlap between the ring light sources that are turned on at the same time.

  The alignment projection optical system 30 projects an alignment target on the cornea Ec. The alignment projection optical system 30 has a light source 31. In the present embodiment, the light source 31 is disposed inside the light source 11 of the kerato projection optical system 10. The light source 31 is a projection light source that emits infrared light, and is used to project an alignment index onto the cornea Ec. The alignment index projected on the cornea Ec is used for alignment of the apparatus with respect to the eye E (for example, automatic alignment, alignment detection, manual alignment, etc.). As shown in FIG. 2, in this embodiment, the alignment projection optical system 30 projects a ring index R3 as an alignment index. The ring index image R3 may also be used as a Mayer ring. In addition, the light source 31 of the alignment projection optical system 30 also serves as anterior segment illumination that illuminates the anterior segment from an oblique direction. In the projection optical system 30, an optical system that projects parallel light onto the cornea Ec may be further provided, and the front-rear alignment may be performed by a combination with the finite light by the alignment projection optical system 30.

  The imaging optical system 20 includes an imaging element 27, and the imaging element 27 captures the first Purkinje image Ra and the second Purkinje image Rp based on the index projected onto the cornea Ec by the kerato projection optical system 10. The imaging optical system 20 in FIG. 1 includes a dichroic mirror (beam splitter) 23, an objective lens 24, a mirror 25, and an imaging lens 26 in addition to the imaging element 27. For example, the image sensor 27 may be disposed at a position conjugate with the anterior segment of the eye to be examined. The beam splitter 23 is an optical path branching member for branching the optical path of the imaging optical system 20 from the optical path of the second measurement optical system 40 (details will be described later). In the example of FIG. 1, the optical axis L1 (imaging optical axis) of the imaging optical system 20 is also used as the projection optical axis L2 of the central fixation lamp 51a.

  In the example of FIG. 1, the imaging optical system 20 images the eye E from the direction along the optical axis L1 (imaging optical axis), and obtains Purkinje images Ra and Rp. That is, when the gaze direction of the eye E is guided by the central fixation lamp 51a in the direction along the optical axis L1, the gaze direction of the eye E is tilted with respect to the optical axis L1 by the neighboring fixation lamps 51b to 51i. The imaging optical system 20 images the eye E from the direction along the optical axis L1 (imaging optical axis). The imaging optical system 20 may also serve as an observation optical system for observing the front image of the anterior segment. At this time, each Purkinje image Ra, Rp may be captured as an image included in an anterior segment front image (hereinafter referred to as anterior segment image A). For example, when the anterior segment illumination is illuminated on the cornea together with the projection of the index by the kerato projection optical system 10, an image including the Purkinje images Ra and Rp is acquired as the anterior segment image A (FIG. 5). reference).

  Further, the imaging optical system 20 can capture the ring index image R3 formed on the cornea Ec by imaging the eye E to which the light from the alignment projection optical system 30 is irradiated (see FIG. 5).

  With respect to the imaging optical system 20, a second measurement optical system 40 is formed in the transmission direction of the beam splitter 23. The second measurement optical system 40 includes a second measurement optical unit 41 and a dichroic mirror 43. Further, the second measurement optical system 40 shares the beam splitter 23 with the imaging optical system 20. The second measurement unit 41 is configured to project the second measurement light onto the subject's eye and receive the reflected light. The second measurement unit 41 has a light source 42 that emits second measurement light.

  As the second measurement optical system 40, for example, an axial length measurement optical system that receives interference light from the measurement light and reference light and measures the axial length, reflected light projected on the fundus of the subject's eye is used. It may be an eye refractive power measurement optical system that receives light and measures the eye refractive power.

  Next, the control system will be described. In this embodiment, the ophthalmologic measurement apparatus 1 includes a calculation control unit 100 (hereinafter, abbreviated as a control unit) that performs control processing of the entire apparatus, various calculations, and the like. The control unit 100 may include a CPU 101, a ROM 102, and a RAM 103. The CPU 101 is a processing device (processor) for executing various processes related to the ophthalmologic measurement apparatus 1. The ROM 102 is a nonvolatile storage device that stores a control program, fixed data, and the like. The RAM 103 is a rewritable volatile storage device. The RAM 103 stores, for example, temporary data used for imaging and measurement of the eye E by the ophthalmic measurement apparatus 1.

  In the present embodiment, the control unit 100 is connected to the light source 11, the image sensor 27, the light source 31, the second measurement optical unit 41, the light source 51, the alignment moving mechanism 60, the monitor 70, the operation unit 80, the storage device 105, and the like. Is done.

  The storage device 105 is a rewritable nonvolatile storage device. In the present embodiment, the storage device 105 may store at least a program for causing the control unit 100 to execute various imaging processes, measurement processes, and the like. The storage device 105 may store an anterior ocular segment image captured by the ophthalmologic measurement apparatus 1.

  The light reception signal (imaging signal) output from the imaging element 27 is processed by the control unit 100 and displayed on the monitor 70. In the present embodiment, the control unit 100 detects the alignment state with respect to the eye E based on the light reception signal output from the image sensor 27.

<Measurement operation>
Operation | movement of the apparatus 1 provided with the above structures is demonstrated. In the present embodiment, an example of the operation of the apparatus relating to the measurement of the anterior segment is shown with reference to the flowchart of FIG.

  First, alignment of the optical system with respect to the eye to be examined is performed (S1). Here, a case where the alignment is automatically performed by the control unit 100 controlling each unit of the apparatus is shown. However, the alignment may be performed manually. Manual alignment (coarse adjustment) and automatic alignment (fine adjustment) may be performed in combination.

  At the time of alignment, the control unit 100 turns on the central fixation lamp 51a and the light source 31 of the alignment projection optical system 30. In addition, the control unit 100 causes the monitor 70 to display a live image (observation image) of the anterior segment image of the eye E based on the imaging signal output from the imaging device 27 when the light source 31 is turned on. In addition, the control unit 100 may electronically display the reticle 13 (see FIG. 5) on the monitor 70. Here, the examiner urges the subject to fixate the fixation target.

  Thereafter, the control unit 100 detects the ring index R3 from the light source 31 based on the imaging signal from the imaging element 27. The control unit 100 drives the alignment moving mechanism 60 based on the detection result to move the optical system of the ophthalmologic measurement apparatus 1 so that the reticle R3 is positioned at the center of the ring index R3. Further, the control unit 100 controls the alignment moving mechanism 60 based on the imaging signal from the imaging element 27 so that the distance from the device to the corneal apex (that is, the working distance) is a predetermined distance. Perform longitudinal alignment. In the present embodiment, the control unit 100 turns off the light source 31 after the alignment is completed.

  Next, the control unit 100 starts projecting the pattern index (S2). The control unit 100 turns on the light source 11 of the kerato projection optical system 10. Thereby, a ring-shaped pattern index is projected onto the cornea Ec.

  Next, the first imaging process (S3) is executed by the control unit 100. In the first imaging process (S3), the control unit 100 images the eye E with the imaging element 27 in a state in which the visual line direction is guided by the fixation optical system 50 in the direction along the optical axis L1. That is, an image including the first Purkinje image Ra and the second Purkinje image Rp in the eye E to be examined in a state where the line-of-sight direction is guided in the direction along the optical axis L1 (for example, the anterior segment image A) is obtained from the imaging device 27. Acquired based on the output imaging signal. For example, the acquired image including the Purkinje images Ra and Rp may be stored in the storage device 105 or the like.

  In the first imaging process (S3), imaging is performed one or more times in a state where the line-of-sight direction is guided in the direction along the optical axis L1. Here, for convenience of explanation, it is assumed that imaging is performed only once in the first imaging process (S3) (that is, only one image including each Purkinje image Ra, Rp is acquired). In addition, the case where imaging is performed twice or more will be described later in the item of modification examples.

  In the present embodiment, in order to guide the line-of-sight direction of the eye E along the optical axis L1, the control unit 100 turns on the light source 51a, which is a central fixation lamp, in advance. For example, the light source 51a may be continuously turned on from the alignment stage.

  Next, the control unit 100 executes a first index image detection process (S4). In the process of S4, the control unit 100 detects the first Purkinje image Ra and the second Purkinje image Rp from the imaging results in the first imaging process (S3). As a result of the detection process, for example, index position information of the first Purkinje image Ra and the second Purkinje image Rp may be acquired. The index position information may be, for example, two-dimensional position information of each index image.

  Here, various detection processes may be employed as the detection process of S4. For example, each Purkinje image Ra, Rp may be detected based on luminance information in the image. For example, an area having a luminance value equal to or higher than a threshold value on the image may be detected as an area where an index image is formed. The first Purkinje image Ra and the second Purkinje image Rp both have a width in the meridian direction. Therefore, among the regions where each index image is formed in each meridian of the cornea Ec, the detection result indicating the position of the index image on each meridian, such as the position of the luminance peak (maximum value or maximum value), the center position, etc. As may be obtained.

  For example, the control unit 100 can distinguish and detect the first Purkinje image Ra and the second Purkinje image Rp by using the characteristics of the first Purkinje image Ra and the second Purkinje image Rp. For example, the characteristic that the first Purkinje image Ra is a brighter image (having a higher luminance value) than the second Purkinje image Rp can be used. For example, two types of threshold values (first threshold value, second threshold value) having different values may be used to distinguish the first Purkinje image Ra and the second Purkinje image Rp. Further, the characteristic that the first Purkinje image Ra is generally formed outside the optical axis L1 with respect to the second Purkinje image Rp can be used. For example, the control unit 100 may detect the bright line on the outer side as the first Purkinje image Ra and detect the bright line formed on the inner side as the second Purkinje image Rp. Of course, the method of detecting the Purkinje images Ra and Rp is not necessarily limited to this. The control unit 100 stores the detection result in, for example, the RAM 102, the storage device 105, or the like.

  However, even if the above detection method is used, the second Purkinje image Rp may not be detected. For example, when the second Purkinje image Rp and the first Purkinje image Ra overlap on the image, it is difficult to detect the second Purkinje image Rp. Here, the cornea shape of the eye E can be a factor that makes detection difficult.

  For example, generally, the vertex of the corneal front surface Ec1 and the vertex of the corneal posterior surface Ec2 tend to be formed with a deviation in the direction intersecting the visual axis. Thereby, in the imaging result in a state in which the line-of-sight direction of the eye to be examined is guided in the direction along the optical axis L1, the second Purkinje image Rp is formed in one direction with respect to the first Purkinje image Ra. There may be a case where the first Purkinje image Ra and the second Purkinje image Rp partially overlap. Here, in each of the corneal front surface Ec1 and the corneal posterior surface Ec2 of the eye E in which the line-of-sight direction is guided to the optical axis L1, the position where the normal line faces in the direction along the optical axis L1 is referred to as a vertex.

  In addition, for example, in an eye in which the central portion of the cornea has been cut by LASIK surgery, the curvature of the corneal front surface Ec1 and the curvature of the corneal posterior surface Ec2 may be close to each other. In such an eye, at least a part of the first Purkinje image Ra and the second Purkinje image Rp may overlap.

  In addition, there may be a case where the second Purkinje image Rp cannot be detected due to individual differences in corneal shape, abnormal corneal shape, or the like. When the second Purkinje image Rp cannot be detected properly, the control unit 100 may store, for example, information indicating a detection error as a detection result of the second Purkinje image Rp. At least the first Purkinje image Ra can be detected by the first index image detection process (S4). Therefore, even when the second Purkinje image Rp cannot be detected, the detection result of the first Purkinje image Ra may be stored in the storage device 105 or the like.

  Next, the control unit 100 determines whether or not the second Purkinje image Rp can be detected by the first index image detection process (S4) (S5). When it is determined that the second Purkinje image Rp cannot be detected (S5: No), the second imaging process (S6) is executed. On the other hand, when it is determined that the second Purkinje image Rp can be detected (S5: Yes), the second imaging process (S6) is skipped and the anterior ocular segment information acquisition process (S10) is executed.

  In the second imaging process (S6), the control unit 100 images the eye E with the imaging element 27 in a state in which the visual line direction is guided by the fixation optical system 50 in the direction along the optical axis L1. That is, an image (for example, the anterior segment image A) including the Purkinje images Ra and Rp in the eye E whose visual line direction is inclined with respect to the optical axis L1 is acquired based on the imaging signal output from the imaging element 27. Is done. The image acquired in the second imaging process (S6) may be stored in the storage device 105, for example. Further, the control unit 100 may store, in the storage device 105, the amount of inclination in the line-of-sight direction with respect to the optical axis L1 and the amount of inclination information regarding the inclination direction together with the image. The tilt amount information may be information for specifying the tilt amount in the line-of-sight direction guided by the nearby fixation lamps 51b to 51i, and may be information for specifying the fixation lamp that is turned on at the time of imaging. Alternatively, it may be an inclination amount expected based on the position of the fixation lamp, a design value in the inclination direction, and the like. Further, the actual tilt amount and tilt direction in the eye E may be measured, and the measured values may be used.

  In the present embodiment, the controller 100 controls the fixation optical system 50 to separate the first Purkinje image and the second Purkinje image by the eye to be imaged during imaging by the second imaging process (S6). The line-of-sight direction of the eye E is tilted with respect to the axis L1. More specifically, the control unit 100 turns off the central fixation lamp 51a that has been turned on at least in the first imaging process (S3), and turns on any one of the neighboring fixation lamps 51b to 51i.

  In the second imaging process (S6), the Purkinje images Ra and Rp are captured once or more in a state where the line-of-sight direction is inclined with respect to the optical axis L1. Here, for convenience of explanation, it is assumed that imaging is performed only once in the second imaging process (S6) (that is, only one image including each Purkinje image Ra, Rp is acquired). In addition, the case where imaging is performed twice or more will be described later in the item of modification examples.

  In a state of being guided in a certain direction (for example, a direction along the optical axis L1), the second Purkinje image Rp overlaps with another index image (mainly the first Purkinje image Ra) on the image, and the second Purkinje image is obtained. The image Rp may not be detected. Even in this case, the second Purkinje image Rp may be separated from other index images by guiding the line-of-sight direction to another direction. For example, as described above, when the curvature of the corneal front surface Ec1 and the curvature of the corneal rear surface Ec2 are close to each other, the second Purkinje image is in a state in which the line-of-sight direction is guided in the direction along the optical axis L1. Rp overlaps with the first Purkinje image Ra. However, when the line-of-sight direction is inclined with respect to the optical axis L1, the projection position of the pattern index image on the front surface of the cornea Ec1 and the projection position of the pattern index image on the rear surface of the cornea Ec2 are displaced by different amounts of displacement. As a result, the second Purkinje image Rp and the first Purkinje image Ra captured by the imaging optical system 20 can be separated. As a result, an image in which the second Purkinje image Rp is easily detected is obtained.

  Next, the control unit 100 executes a second index image detection process (S7). In the process of S7, the control unit 100 detects the first Purkinje image Ra and the second Purkinje image Rp from the imaging results in the second imaging process (S6). The Purkinje image detection method may be, for example, the same processing as the first index image detection processing (S3), and detailed description thereof is omitted.

  Next, the control unit 100 determines whether or not the second Purkinje image Rp can be detected by the second index image detection process (S7) (S8). When it is determined that the second Purkinje image Rp cannot be detected (S8: No), for example, the fixation lamp that is lit is further switched to another neighboring fixation lamps 51b to 51i (S9), and the second imaging process is performed. (S6) The second index image detection process (S7) may be repeatedly executed. Further, when the second index image detection processing is executed for all the near fixation lamps 51b to 51i, but the second Purkinje image Rp is not detected in any of them, information indicating a measurement error or the like is displayed on the monitor 70. Then, the process of the flowchart may be terminated (not shown). On the other hand, when it is determined that the second Purkinje image Rp can be detected, an anterior segment information acquisition process (S10) is executed.

  In the anterior segment information acquisition process (S10) of the present embodiment, at least information on the corneal posterior surface Ec2 based on the detection result of the second Purkinje image Rp is acquired. Furthermore, in the present embodiment, information regarding the corneal front surface Ec1 is also acquired.

  Here, an example of the anterior segment information acquisition process (S10) will be described. In the present embodiment, first, the control unit 100 obtains the shape of the corneal front surface Ec1. The shape of the corneal front surface Ec1 can be derived based on the index position information of the first Purkinje image Ra obtained by the first index image detection process (S4) or the second index image detection process (S7), for example. For example, the frontal shape of the cornea may be obtained by ray tracing simulation based on the first Purkinje image Ra. In this case, for example, a model of the corneal front surface Ec1 placed near the working distance is assumed. In the present embodiment, the model of the corneal front surface Ec1 is a spherical approximation model. However, it may be a model approximated by a cornea or an aspherical surface (for example, an elliptical spherical surface, a paraboloid, etc.). By changing the curvature of the model of the corneal front surface Ec1, the index position of the first Purkinje image Ra on the imaging surface is projected back onto the corneal front surface Ec1 along the optical path of the imaging optical system 20, and is projected on the corneal front surface Ec1. The condition (here, the radius of curvature) of the shape of the corneal front surface Ec1 that satisfies the light rays reaching the light source 11 by being reflected is obtained. For example, the simulation may be performed using a light ray matrix indicating light rays from the light source 11 to the first Purkinje image Ra. In this ray matrix, the image height of the first Purkinje image Ra is substituted for the ray height at one of the entrance or exit surfaces in the ray matrix, and the light ray height and the inclination of the ray on the other are based on the light source 11. The default value is assigned. In this way, the radius of curvature of the corneal front surface Ec1 can be obtained.

Here, the amount of inclination in the line-of-sight direction and the inclination direction at the time of capturing the first Purkinje image Ra are considered in the position of the model of the corneal front surface Ec1 assumed in the above simulation. That is, when the shape of the corneal front surface Ec1 is obtained from the first Purkinje image Ra detected by the first index image detection process (S4), the line-of-sight direction is the front direction (that is, along the optical axis L1) of the corneal front surface Ec1. The ray tracing simulation described above is performed assuming a model (see FIG. 3B). On the other hand, when the shape of the corneal front surface Ec1 is obtained from the first Purkinje image Ra detected by the second index image detection process (S7), the corneal front surface Ec1 whose visual axis is inclined in the sight line direction and the inclination direction during imaging is obtained. The above ray tracing simulation is performed assuming the above model (see FIG. 4B). The position of the model of the corneal front surface Ec1 can be defined by, for example, the length from the center of eye rotation to the reference point (for example, the corneal apex) in the cornea Ec, the amount of inclination in the line-of-sight direction, and the inclination direction. Here, as the length from the turning center to the reference point in the cornea Ec, for example, a predetermined value such as an average value of the human eye may be used, or a value based on a measured value of an actual eye dimension in the eye E to be examined. It may be. For the tilt amount and the tilt direction, values indicated by the tilt amount information stored together with the Purkinje images Ra and Rp in the second imaging process (S6) may be used.
For example, the radius of curvature of the corneal front surface Ec1 is calculated based on the index position information of the first Purkinje image Ra detected by the first index image detection process (S4) or the second index image detection process (S7). You may ask for. Specifically, the corneal curvature radius r1 is set to the image height of the first Purkinje image Ra (for example, the position of the optical axis L1 on the image (for example, the image center under the condition that the optical axis L1 passes through the center of the cornea) ) To the first Purkinje image Ra). For a specific method, for example, refer to Japanese Patent Application Laid-Open No. 2003-111727 by the present applicant.
For example, the radius of curvature of the corneal front surface Ec1 is calculated based on the index position information of the first Purkinje image Ra detected by the first index image detection process (S4) or the second index image detection process (S7). You may ask for. Specifically, the corneal curvature radius r1 is set to the image height of the first Purkinje image Ra (for example, the position of the optical axis L1 on the image (for example, the image center under the condition that the optical axis L1 passes through the center of the cornea) ) To the first Purkinje image Ra). For a specific method, for example, refer to Japanese Patent Application Laid-Open No. 2003-111727 by the present applicant.

  Next, the shape of the corneal posterior surface Ec2 is derived based on the previously determined shape of the corneal front surface Ec1 and the index position information of the second Purkinje image Rp. For example, the shape of the corneal posterior surface Ec2 may be obtained by a ray tracing simulation based on the second Purkinje image Rp. In this case, a model of the anterior corneal surface Ec1 and a model of the posterior corneal surface Ec2 are assumed based on the previously obtained radius of curvature. In the present embodiment, the model of the corneal front surface Ec2 is, for example, a spherical approximation model. However. A model approximated by an aspherical surface (for example, an elliptical spherical surface, a paraboloid, etc.) may be used.

  The model of the corneal posterior surface Ec2 is arranged closer to the center of eye rotation by the corneal thickness d at the reference position of the cornea Ec (in this embodiment, the corneal center) than the model of the corneal front surface Ec1. As the corneal thickness d, a predetermined value such as an average value of the human eye may be used, or the actual corneal thickness of the eye E may be used. For example, a value obtained by publicly known patch measurement such as an ultrasonic measurement method may be used. Note that a corneal thickness measurement optical system may be provided as the second measurement optical system, and the measurement result may be used as the corneal thickness d.

  Further, the model of the corneal posterior surface Ec2 may be arranged such that the vertex position thereof is shifted with respect to the direction intersecting the visual axis with respect to the vertex position of the model of the corneal front surface Ec1. For example, it may be arranged so as to be shifted by a predetermined angle.

  The controller 100 changes the curvature of the model of the corneal posterior surface Ec2 so that the optical path of the imaging optical system 20 is traced back from the index position of the second Purkinje image Rp on the imaging surface via the corneal front surface Ec1. The condition of the shape of the corneal rear surface Ec2 reflected by the rear surface Ec2 and satisfying the light beam reaching the light source 11 (here, the radius of curvature of the corneal rear surface Ec2) is obtained. Of course, the control unit 100 obtains the condition in consideration of refraction when the light beam passes through the corneal front surface Ec1. For the refractive index of the cornea Ec, for example, a predetermined value (n≈1.376 or the like) such as an average value of the human eye may be used. As a result of this simulation, the radius of curvature of the corneal posterior surface Ec2 can be obtained.

  Note that the amount of inclination in the line-of-sight direction and the inclination direction at the time of imaging of the Purkinje images Ra and Rp are taken into consideration in the positions of the model of the corneal front surface Ec1 and the model of the corneal rear surface Ec2 assumed in the above simulation. . For example, when the shape of the corneal posterior surface Ec2 is obtained based on the second Purkinje image Rp detected in the second index image detection process (S7), the amount of the eye is determined according to the amount of inclination in the line-of-sight direction and the inclination direction during imaging. The above ray tracing simulation is performed assuming a model of the corneal front surface Ec1 and a model of the corneal rear surface Ec2 tilted around the turning center (see FIG. 4B). For example, the radius of curvature of the corneal posterior surface Ec2 is calculated based on the index position information of the second Purkinje image Rp detected by the first index image detection process (S4) or the second index image detection process (S7). You may ask for. In the present embodiment, as a method for obtaining information related to the corneal anterior surface Ec1 and information related to the corneal posterior surface Ec2, first, information relating to the corneal anterior surface Ec1 is acquired, and using the acquired information, a method for determining the shape of the corneal posterior surface Ec2 is used. It was used. However, it is not necessarily limited to this. For example, it is possible to simultaneously acquire information on the corneal front surface Ec1 and the corneal rear surface Ec2 by ray tracing simulation or the like.

  Based on the shape of the corneal front surface Ec1 and the shape of the corneal posterior surface Ec2 thus obtained, the control unit 100 can obtain corneal thickness information, refractive power information of the cornea Ec, and the like.

  For example, the control unit 100 may acquire information indicating the thickness distribution of the cornea Ec in a specific meridian direction as an example of corneal thickness information. The thickness distribution of the cornea Ec in one meridian direction is obtained using, for example, the curvature radius of the corneal front surface Ec1 and the curvature radius r1 of the corneal rear surface Ec2 in one meridian direction and the value of the reference corneal thickness d. Can do. Moreover, the control part 100 may acquire the information which shows the thickness distribution of the whole cornea based on the thickness distribution of the whole cornea in several meridian directions.

  Further, as the refractive power information of the cornea Ec, for example, the refractive power of the entire cornea can be obtained. In this case, for example, power information (for example, power and / or values of S, C, and A) of the corneal front surface Ec1 and power information (for example, power and / or S, C, and A of the corneal rear surface Ec2). Each value) can be obtained from the Purkinje image. In the present embodiment, the values of S, C, and A are, for example, values of the corneal curvature in the strong main meridian direction and the weak main meridian direction when the ring image formed on the cornea Ec is approximated to an ellipse, and the strong principal It can be obtained from the axis angles of meridians and weak main meridians. Then, using the power vector method, the refractive power of the entire cornea can be obtained from the combined value of the power of the corneal front surface Ec1 and the power of the corneal rear surface Ec2. The derivation of the refractive power of the entire cornea is not limited to the above method. For example, the refractive power may be obtained in a ray tracing manner.

  As described above, the ophthalmologic measurement apparatus 1 according to the present embodiment images the eye E with the image sensor 27 whose visual line direction is inclined with respect to the optical axis L <b> 1 by the fixation optical system 50. As a result, when the line-of-sight direction is guided in the direction along the optical axis L1, the second Purkinje image Rp is different from the second Purkinje image Rp even if the eye E is difficult to specify (for example, image detection). Can be separated from the index image (for example, the first Purkinje image Ra). As a result, it is possible to increase the possibility of acquiring information related to the corneal posterior surface Ec2 based on the second Purkinje image.

  In the present embodiment, the control unit 100 controls the fixation optical system 50 to guide the eye direction of the eye E in a plurality of directions with different inclination amounts with respect to the optical axis L1, and the respective eye directions. Thus, an image including the second Purkinje image Rp is captured. The possibility of obtaining the second Purkinje image Rp separated from other index images is increased by performing imaging in a plurality of line-of-sight directions. As a result, the possibility of acquiring information related to the corneal posterior surface Ec2 is further improved.

  In addition, when calculating | requiring the curvature of the cornea back surface Ec2, calculation using the corneal thickness of the eye E to be examined is preferable. Therefore, by providing the corneal thickness measurement optical system as the second measurement optical system, it is not always necessary to use another device. For the corneal thickness measurement optical system, for example, the configuration described in JP 2012-143492 A is used.

  Even in this case, the corneal thickness measurement optical system only needs to measure the corneal thickness of at least one point on the cornea, and is complicated such as a shine-proof camera having a rotation mechanism and an anterior segment OCT that requires two-dimensional scanning. It is not always necessary to provide an optical system.

  Moreover, in the said embodiment, the synthetic | combination power of the cornea Ec is obtained as information regarding the cornea back surface Ec. Here, the power of the entire cornea can also be calculated based on a cross-sectional image captured by a shine-proof camera, an anterior ocular segment OCT, or the like. However, as in this embodiment, it is easier to obtain accurate power when the calculation is performed based on the second Purkinje image Rp. Therefore, the power obtained by the ophthalmologic measurement apparatus 1 is useful, for example, when selecting an IOL having an appropriate power for the eye to be examined.

In general, as a Purkinje image formed by reflecting a light beam projected onto the eye E to be examined by the anterior eye part, in addition to the first Purkinje image Ra and the second Purkinje image Rp, the front reflection of the crystalline lens. And the fourth Purkinje image by reflection of the back surface of the crystalline lens are known. As described above, when the ophthalmic measuring apparatus 1 tilts the line-of-sight direction of the eye E with respect to the optical axis L1 by the fixation target, the first Purkinje image Ra and the second Purkinje image Rp are separated. Although useful, it is also useful for separating at least one of the third Purkinje image and the fourth Purkinje image from the second Purkinje image Rp. That is, the ophthalmologic measurement apparatus 1 of the present embodiment can obtain the second Purkinje image Rp that is well separated from both the third Purkinje image and the fourth Purkinje image, and from the result, information on the corneal posterior surface is favorably obtained. You can get it.
<Modification>
As mentioned above, although demonstrated based on embodiment, this indication is not limited to the said embodiment, A various deformation | transformation is possible.

  For example, the second Purkinje image is an upright image, while the fourth Purkinje image is an inverted image. When a pattern index symmetrical to the optical axis L1 is projected, a fourth Purkinje image may be formed near the second Purkinje image. As a result, it is important to distinguish the second Purkinje image from the fourth Purkinje image.

  On the other hand, for example, the kerato projection optical system 10 (an example of a light projection optical system) may be configured such that an asymmetric index pattern is projected with respect to the meridian of the cornea Ec. In addition, the second Purkinje image detection process (for example, the process of S9) may be configured such that the second Purkinje image is detected from the erect reflected image of the index light beam. As a configuration in which the projection is asymmetric with respect to the meridian of the cornea Ec, for example, the ring light sources 11a and 11b may be partially (or intermittently) lit. Further, the ring light sources 11a and 11b may be replaced by a plurality of point light sources and the like arranged asymmetrically with respect to the meridian of the cornea Ec. In this case, when the second Purkinje image is an erect image, the fourth Purkinje image is obtained as an inverted image. Therefore, the control unit 100 can distinguish and detect the second Purkinje image and the fourth Purkinje image based on the positional relationship between the optical axis L1 and each image.

  Moreover, although the said embodiment demonstrated the case where the corneal thickness in the cornea center part was used as a corneal thickness in the reference | standard position of the cornea Ec, it is not necessarily limited to this, The corneal thickness in a reference | standard position is used. The corneal thickness in a region away from the center of the cornea may be used.

  In the above embodiment, in each process of the first imaging process (S2) and the second imaging process (S6), the control unit 100 receives an image (for example, the anterior segment image A) including the Purkinje images Ra and Rp. It has been described that one image is taken for each eye-gaze direction of the optometry. However, the present invention is not necessarily limited to this, and a plurality of images may be taken for each line-of-sight direction.

  When performing imaging twice or more with respect to one gaze direction, different imaging conditions may be set for each imaging. The imaging conditions here may mainly be conditions relating to the brightness of the index image formed on the cornea Ec. Such conditions may be, for example, the light amount of the light beam output from the light source 11 and the gain in the image sensor 27. In general, the second Purkinje image Rp is formed with lower luminance than the first Purkinje image Ra. For this reason, for example, it may be difficult to detect both the first Purkinje image Ra and the second Purkinje image Rp from one image. On the other hand, an image for detecting the first Purkinje image Ra and an image for detecting the second Purkinje image Rp may be acquired as separate images by performing imaging under some imaging conditions.

  Further, for example, in a configuration including a plurality of light sources for projecting the pattern index, the light source that is turned on for each imaging may be switched when imaging is performed twice or more in one gaze direction. In this case, the index images formed on the cornea Ec are prevented from overlapping in each image. That is, the overlap between the first Purkinje image and the second Purkinje image, the overlap between the first Purkinje images, and the overlap between the second Purkinje images are suppressed. As a result, the index image can be easily detected from each image.

  In the embodiment described above, the line-of-sight direction of the eye E guided by the fixation optical system 50 is automatically set by the control unit 100. However, for example, the examiner may manually set the line-of-sight direction of the eye E to be guided by the fixation optical system 50. At this time, for example, the first Purkinje image Ra and the second Purkinje image Rp captured by the imaging optical system 20 may be displayed on the monitor 50. The examiner instructs the apparatus to change the line-of-sight direction via the operation unit 80 while confirming the degree of separation of the Purkinje images Ra and Rp displayed on the monitor 50. The control unit 100 controls the fixation optical system 50 based on the signal input from the operation unit 80 to change the line-of-sight direction of the eye E to be guided by the fixation optical system 50. Furthermore, the control unit 100 acquires information related to the corneal front surface Ec1 and information related to the corneal rear surface Ec2 based on the adjusted line-of-sight direction.

  In the above-described embodiment, the fixation optical system 50 includes a plurality of fixation lamps 51 a to 51 i in a direction intersecting with the optical axis L <b> 1 (optical axis L <b> 2). The direction in which the eye direction of the eye E is guided is changed. However, the fixation optical system 50 is not necessarily limited to this. For example, the fixation optical system 50 replaces the plurality of fixation lamps 51a to 51i with the fixation target (fixation lamp) and the relative position between the fixation target and the eye to be examined in a direction intersecting the optical axis L1. And a drive mechanism for displacing. In this case, the drive mechanism may be a drive mechanism that moves the fixation target in the apparatus main body (inside the housing). Further, a mechanism for changing the relative position between the apparatus main body (housing) and the eye E without moving the fixation target within the apparatus main body may be used. For example, it may be a drive mechanism (for example, the alignment movement mechanism 60 in FIG. 1) that moves the apparatus main body in the XY directions (up, down, left and right directions), or a chin rest 65 (FIG. 1) that supports the face of the subject. (See) may be a drive mechanism that moves in the XY directions. For example, the ophthalmologic measurement apparatus 1 may have a display instead of the fixation lamps 51a to 51i. The gaze direction of the eye E may be guided by moving the fixation target (for example, a figure, a character, etc.) on the display by the control unit 100.

  In the above embodiment, when the fixation optical system 50 guides the eye direction of the eye to be tilted with respect to the optical axis L1, the ophthalmic measurement apparatus 1 is configured to be able to adjust the amount of tilt in the eye direction. You may have. For example, the fixation target may be presented by the fixation optical system 50 at different positions in the respective radial directions around the optical axis L1 (optical axis L2). In this case, the fixation optical system 50 may further include a second proximity fixation lamp having a radius different from that of the proximity fixation lamps 51b to 51i, or the fixation target and the eye to be examined. A configuration provided with a drive mechanism that displaces the relative position in a direction intersecting the optical axis L1 (optical axis L2) may be used, or a configuration in which the fixation lamp 51 is replaced with the above display may be used. For example, the control unit 100 controls the fixation optical system 50 so that the fixation target presentation position is centered on the optical axis L1 (optical axis L2) at a position away from the optical axis L1 (optical axis L2). By switching in the radial direction, the amount of inclination of the eye E in the line-of-sight direction is adjusted. This increases the possibility that the second Purkinje image Rp can be more preferably separated from other index images. Such a tilt amount adjustment in the line-of-sight direction may be executed based on, for example, an examiner's operation. At this time, for example, the first Purkinje image Ra and the second Purkinje image Rp captured by the imaging optical system 20 may be displayed on the monitor 50. The examiner instructs the apparatus to change the tilt amount via the operation unit 80 while confirming the degree of separation of the Purkinje images Ra and Rp displayed on the monitor 50. The control unit 100 adjusts the amount of inclination in the line-of-sight direction in the eye E based on a signal input from the operation unit 80, and further, information on the corneal front surface Ec1 and the posterior corneal surface based on the adjusted amount of inclination. Information on Ec2 is acquired.

  In the above embodiment, the case where the second Purkinje image is detected from the image itself captured by the image sensor 27 has been described. However, the second Purkinje image Rp may be detected from an image obtained by further processing the image captured by the image sensor 27. For example, after capturing a plurality of images, an added image of these images may be generated, and the detection process of the second Purkinje image Rp may be performed on the added image. By adding a plurality of images, an added image including a clear second Purkinje image is obtained, so that the second Purkinje image Rp can be easily detected. Note that the first Purkinje image Ra may also be detected from the added image.

  Further, at the time of capturing an image for detecting the second Purkinje image Rp, the eye E is examined by an optical system other than the kerato projection optical system 10 (for example, the alignment projection optical system 30 and the second measurement optical system 42). It is preferable to suppress the irradiated light. At this time, it is sufficient that the second Purkinje image is captured, and each part of the anterior segment may not be confirmed in the image. That is, the image for detecting the second Purkinje image Rp is not necessarily limited to the anterior segment image.

DESCRIPTION OF SYMBOLS 10 Kerato projection optical system 20 Imaging optical system 27 Imaging device 30 Alignment projection optical system 50 Fixation optical system 100 Control part Ra 1st Purkinje image Rp 2nd Purkinje image

Claims (2)

A projection optical system for projecting an index toward the cornea of the eye to be examined;
An imaging optical system that captures an image of the first Purkinje image and the second Purkinje image based on the index projected onto the cornea by the projection optical system;
A fixation optical system comprising an internal fixation target provided in the apparatus main body and capable of guiding the line-of-sight direction of the eye to be examined in a direction inclined with respect to the imaging optical axis , wherein the first Purkinje image and the first eye A fixation optical system used to separate two Purkinje images and obtain information on the posterior corneal surface based on the separated second Purkinje images ;
By the second Purkinje image captured by the imaging device, the second Purkinje image of the eye to be examined tilted by the fixation optical system, information on the frontal shape of the cornea, and the fixation optical system information about the amount of inclination with respect to the tilted the subject's eye the image pickup optical axis of, at least based on an arithmetic means for obtaining information about the posterior surface of the cornea of the eye, Ru comprising an ophthalmic measurement apparatus. A projection optical system for projecting an index toward the cornea of the eye to be examined;
An imaging optical system that captures an image of the first Purkinje image and the second Purkinje image based on the index projected onto the cornea by the projection optical system;
Line-of-sight tilting means for tilting the line-of-sight direction of the eye to be imaged with respect to the imaging optical axis of the imaging optical system in order to separate the first Purkinje image and the second Purkinje image by the eye to be examined;
The second Purkinje image of the eye to be examined tilted by the line-of-sight tilting means is picked up by the imaging device , and the second Purkinje image, information on the frontal shape of the cornea, and the subject tilted by the line-of-sight tilting means. Control means for acquiring information relating to the posterior corneal surface of the eye to be examined, based at least on information relating to the amount of inclination of the optometry to the imaging optical axis
Ophthalmology measuring device Ru equipped with.

Images