JP2018153692A - Ophthalmologic measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire information on a cornea rear face of the eye to be examined with a simple configuration.SOLUTION: An ophthalmologic measuring device 1 includes: a kerato projection optical system 10 for projecting a pattern index to a cornea Ec of the eye E to be examined; first Purkinje images Ra1,Ra2 and second Purkinje images Rp1,Rp2 on the basis of the pattern index; an imaging optical system 20 for imaging with an image pickup device 27; and a second measurement optical system 40 separated from the imaging optical system 20 and measuring a cornea thickness in a reference position. A control part 100 executes a detection processing of the first Purkinje images Ra1,Ra2 and the second Purkinje images Rp1,Rp2 on the basis of an imaging signal output from the image pickup device 27, and a front eye part information acquisition processing (S10) of acquiring information on a cornea rear surface of the eye to be examined, on the basis of a detection result of the second Purkinje image, considering information on a cornea front surface and cornea thickness information.SELECTED DRAWING: Figure 3

Description

  The present invention 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.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to acquire information related to the corneal posterior surface of an eye to be examined with a simple configuration.

  An ophthalmologic measurement apparatus according to a first aspect of the present invention includes a projection optical system that projects a pattern index toward the cornea of an eye to be examined, and an index that is formed by the pattern index being reflected from the front of the cornea of the eye to be examined. A first Purkinje image that is an image, and a second Purkinje image that is an index image formed by reflecting the pattern index on the corneal posterior surface of the eye to be examined, and an imaging optical system that captures the image with an imaging device; A corneal thickness measuring unit for measuring the corneal thickness at a reference position, the first Purkinje image, and the second Purkinje image based on an imaging signal output from the imaging device. Detection means for performing a Purkinje image detection process, information on the corneal front surface of the eye to be obtained acquired based on the detection result of the first Purkinje image, and corneal thickness information acquired by the corneal thickness measurement unit , Into consideration, to obtain information about the posterior surface of the cornea of the eye based on a detection result of the second Purkinje image, and a rear surface information acquisition means.

  According to the present invention, information related to the corneal posterior surface of the eye to be examined can be acquired with a simple configuration.

It is a schematic block diagram of the ophthalmologic measurement apparatus in this embodiment. It is a schematic diagram of the anterior eye part image imaged with an ophthalmologic measurement apparatus. It is a flowchart which shows the process of CPU regarding the measurement operation | movement of an ophthalmologic measurement apparatus. It is a flowchart which shows an anterior segment information acquisition process. It is a schematic diagram for demonstrating the calculation method of the curvature radius of a cornea back surface. It is a schematic diagram of the anterior segment image in a modification.

  Hereinafter, typical embodiments of the present invention will be described with reference to the drawings. 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 measurement related to the corneal posterior surface 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, and a control unit 100. The ophthalmic measurement apparatus 1 according to this embodiment includes an alignment projection optical system 30, a second measurement optical system 40, and a fixation target projection optical system 50. These optical systems are built in a housing (not shown). Further, the housing is moved three-dimensionally with respect to the subject's eye by driving a known alignment moving mechanism. The movement of the housing may be performed based on an examiner's instruction via an operation member (for example, a joystick), for example.

  The kerato projection optical system 10 projects (projects) a pattern index (measurement index) on the cornea of the eye E to be examined. In the present embodiment, the index from the kerato projection optical system 10 is used for measurement related to the rear surface (back surface) of the cornea. For example, the shape, curvature radius, refractive power, etc. of the corneal posterior surface may be measured with respect to the corneal posterior surface. Further, for example, the corneal thickness, the astigmatic axis angle, and the like may be measured with respect to the corneal rear surface. As will be described later, the pattern index is used for measurement related to the anterior surface (surface) of the cornea (for example, measurement of the shape of the anterior surface of the cornea, the radius of curvature, the refractive power, the corneal thickness, the astigmatic axis angle, etc.). Good.

  The kerato projection optical system 10 has a light source 11. For example, the projection optical system 10 may project a ring-shaped index on the cornea of the eye E. In the present embodiment, the light source 11 includes a first ring light source 11a and a second ring light source 11b. The first ring light source 11a and the second ring light source 11b may be, for example, ring-shaped light sources, or a plurality of LEDs arranged in a ring shape and a ring-shaped pattern arranged in front of the LEDs. The structure which combined opening may be sufficient. Each of the ring light sources 11a and 11b is formed in a ring shape centered on the measurement optical axis L1. In the present embodiment, ring-shaped indicators having different sizes are projected from the two ring light sources 11a and 11b.

  As shown in FIG. 2, a ring-shaped first Purkinje image Ra1 can be formed by light reflected (and scattered) on the front surface of the cornea out of the index luminous flux projected from the first ring light source 11a. Further, among the indexes projected from the first ring light source 11a, the ring-shaped second Purkinje image Rp1 can be formed by the light reflected (and scattered) on the rear surface of the cornea. In general, the second Purkinje image has a lower luminance than the first Purkinje image. In the present embodiment, the second Purkinje image Rp1 is formed inside the first Purkinje image Ra1 by the curve of the cornea Ec. Similarly, the light flux from the second ring light source 11b is reflected on the front surface and the rear surface of the cornea, so that the first Purkinje image Ra2 and the second Purkinje image Rp2 can be formed.

  In the present embodiment, the first ring light source 11a has a larger diameter than the second ring light source 11b. The second Purkinje image Rp1 is generated on the outer periphery of the second Purkinje image Rp2. Although details will be described later, in the present embodiment, measurement on the cornea is performed mainly using the second Purkinje images Rp1 and Rp2.

  In the present embodiment, the projection position of the pattern index is displaced by switching the light source to be lit. The two ring light sources 11a and 11b may be turned on simultaneously. However, it is preferable that the projection positions do not overlap each other when they are lit simultaneously. Further, only one of the two ring light sources 11a and 11b may be turned on. The light emitted from the light source 11 may be, for example, infrared light or visible light.

  The shape and arrangement of the light source 11 are not limited to the configuration having the two ring light sources 11a and 11b. For example, the light source 11 may be one ring light source. Of course, three or more ring light sources may be used. A plurality of point light sources may be used. It is preferable that the point light sources at this time include at least three or more point light sources arranged on the same circumference. The light source 11 may be an intermittent ring light source. That is, the pattern index is a ring-shaped index pattern used in the present embodiment, a pattern composed of three or more point indices arranged concentrically, a dot matrix index in which the point indices are arranged in a grid, Includes shapes such as intermittent ring patterns.

  The alignment projection optical system 30 projects an alignment target on the cornea of the eye E to be examined. 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 includes a projection light source 31 (for example, λ = 970 nm) that emits infrared light, and is used to project an alignment index onto the subject's eye cornea. The alignment index projected onto the cornea is used for alignment with the subject's eye (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 target. 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. The projection optical system 30 may further include an optical system that projects parallel light onto the cornea, and the front-rear alignment may be performed by a combination with the finite light from the alignment projection optical system 30.

  In the present embodiment, the imaging optical system 20 includes a two-dimensional imaging device 27 and can capture an anterior eye front image of the eye to be examined from the front direction. More specifically, the imaging optical system 20 includes a dichroic mirror 23, an objective lens 24, a mirror 25, an imaging lens 26, and a two-dimensional imaging element 27. For example, the two-dimensional imaging device 27 may be disposed at a position conjugate with the anterior eye portion of the eye to be examined. The imaging optical system 20 is arranged so that its optical axis is coaxial with the fixation target projection optical system 50.

  The dichroic mirror (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).

  Here, the anterior ocular segment reflected light of the light projected from the kerato projection optical system 10 and the alignment projection optical system 30 passes through the optical path of the imaging optical system 20, and then the imaging device 27 (for example, a two-dimensional imaging device). Is imaged (received). Therefore, the imaging optical system 20 captures the anterior segment image irradiated with the light from the kerato projection optical system 10 to thereby form an index image (for example, the first Purkinje images Ra1, Ra2, An anterior segment image A including the second Purkinje images Rb1, Rb2) can be captured. The imaging optical system 20 captures the anterior segment image A including the ring index image R3 formed on the cornea Ec by capturing the anterior segment image irradiated with light from the alignment projection optical system 30. it can.

  Regarding the imaging optical system 20, a second measurement optical system 40 is formed in the transmission direction of the dichroic mirror 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 dichroic mirror 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 the reference light and measures the axial length (the wavelength of the light source 42 is, for example, λ = 830 nm). An eye refractive power measurement optical system that receives reflected light projected on the fundus of the subject's eye and measures eye refractive power (the wavelength of the light source 42 is, for example, λ = 870 nm) may be used.

  Regarding the second measurement optical system 40, a fixation target projection optical system 50 is arranged in the reflection direction of the dichroic mirror 43.

  The fixation target projection optical system 50 is used to fix the eye E during measurement at the time of measurement. In the present embodiment, the fixation target projection optical system 50 includes a fixation target unit 51, a lens 54, and a fixation target position adjustment mechanism 55.

  The fixation target unit 51 includes a light source 52 and a target plate 53. The fixation target formed on the target plate 53 is projected onto the eye E through the lens 54 and the like when light is emitted from the light source 52. Further, the fixation target position adjusting mechanism 55 can displace the fixation target unit 51 along the optical axis L4 of the fixation target projection optical system 50. Thereby, the presentation position (presentation distance) of the fixation target for the eye E is adjusted.

  Next, the control system will be described. In the ophthalmic measurement apparatus 1 according to the present embodiment, the control unit 100 performs overall control of the ophthalmic measurement apparatus 1 and calculation of measurement results.

  In the present embodiment, the control unit 100 includes the light source 11, the image sensor 27, the light source 31, the second measurement optical unit 41, the light source 52, the fixation target position adjustment mechanism 55, the monitor 70, the operation unit 80, the storage device 105, and the like. Connected.

  The control unit 100 includes 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.

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

  Here, 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. Further, 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.

  The operation of the ophthalmologic measurement apparatus 1 having the above configuration will be described.

  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, the CPU 101 performs an optical system alignment process (S1). During the alignment, the CPU 101 turns on the light source 31 of the alignment projection optical system 30 and also displays a live image of the eye E on the monitor 70 based on the light reception signal output from the image sensor 27 when the light source 31 is turned on. (Observation image) is displayed. Further, the CPU 101 electronically displays the reticle 13 (see FIG. 2) on the monitor 70.

  Further, the CPU 101 detects the ring index R <b> 3 by the light source 31 based on the imaging signal from the imaging element 27. The CPU 101 moves the optical system of the ophthalmologic measurement apparatus 1 so that the ring index R3 is arranged concentrically with the rectile LT by driving a drive unit (not shown) based on the detection result. Further, the CPU 101 performs alignment in the front-rear direction based on the imaging signal from the imaging element 27 so that the distance from the device to the corneal apex becomes a predetermined working distance.

  Note that the alignment does not necessarily have to be performed automatically. For example, the alignment may be performed based on an instruction input from the examiner. At this time, for example, the CPU 101 may receive an examiner's instruction input via an operation member (for example, a joystick), and may move the optical system of the ophthalmologic measurement apparatus 1 based on the instruction input.

  The examiner can perform alignment of the optical system until an instruction to start measurement is input via the operation unit (S2: No). CPU101 performs each process after S3 based on the instruction | indication of the measurement start from an examiner (S2: Yes).

  In the present embodiment, the presentation position (presentation distance) of the fixation target with respect to the eye E is set prior to measurement of the anterior segment (S3). At this time, the fixation target is brought closer to the far point of the eye E. For example, in the present embodiment, the CPU 101 controls the fixation target position adjustment mechanism 55 based on the position information of the far point of the eye to be examined and places the fixation target at the far point of the eye E to be examined. As a result, the action of adjusting the eye to be examined by fixation is suppressed. Therefore, measurement of the anterior segment is performed in a state where miosis is reduced. Note that the CPU 101 acquires the position information of the far point as follows, for example. For example, if the second measurement unit 40 is configured to perform measurement related to the far point position of the eye E (for example, measurement of eye refractive power), the position information of the far point based on the measurement result of the second measurement unit 40 May be acquired by the ophthalmologic measurement apparatus 1. In addition, by transferring the result of the measurement related to the far point position of the eye E to be examined using other examination equipment to the ophthalmologic measurement apparatus 1 or by the examiner directly inputting it via the operation unit, The position information of the far point may be acquired by the ophthalmologic measurement apparatus 1.

  Next, in the present embodiment, the CPU 101 sets the acquisition condition (for example, the state of the optical system) of the index pattern image by the ophthalmologic measurement apparatus 1 to the first Purkinje image imaging mode (first mode) (S4). . This mode is a mode for the apparatus main body (for example, the control unit 100) to acquire data used in the detection process (for example, the position and shape detection process) of the first Purkinje images Ra1 and Ra2. As will be described later, as an example of the present embodiment, in the first Purkinje image capturing mode, an anterior eye image including the first Purkinje images Ra1 and Ra2 is captured (captured). In the process of S4, the amount of light flux output from the light source 11, the gain in the image sensor 27, and the like are adjusted so that an anterior ocular segment image including clear first Purkinje images Ra1 and Ra2 is captured. Is preferred. In the process of S4, a light amount adjusting filter may be switched on the optical paths of the kerato projection optical system 10 and the imaging optical system 20 to limit the light received by the imaging element 27.

  Next, the CPU 101 captures an anterior ocular segment image used in the detection processing of the first Purkinje images Ra1 and Ra2 (S5). In the process of S5, the CPU 101 may selectively project at least one of a plurality of ring index patterns. More specifically, the first ring light source 11a and the second ring light source 11b are turned on one by one in order, whereby the first Purkinje image Ra1 based on the light flux from the first ring light source 11a and the second ring light source 11a. The first Purkinje image Ra2 based on the luminous flux from the image may be captured so as to be included in separate images. Alternatively, the first Purkinje images Ra1 and Ra2 may be imaged so as to be included in one image by simultaneously lighting the two ring light sources 11a and 11b. However, when a plurality of first Purkinje images are captured as one image, it is preferable that the first Purkinje images do not overlap each other.

  After the process of S5, the CPU 101 executes a first Purkinje image detection process (S6). In the present embodiment, in the first Purkinje image detection process (S6), in the second Purkinje image detection process (S9), the first Purkinje images Ra1 and Ra2 are detected based on the imaging signal output from the image sensor 27. More specifically, the first Purkinje images Ra1 and Ra2 are detected using the image captured by the process of S5. In the present embodiment, the index position information of the first Purkinje images Ra1 and Ra2 is acquired as a result (detection result) of S6. The index position information may be, for example, two-dimensional position information of the first Purkinje images Ra1 and Ra2.

  Various processes can be used as the process of S6. For example, detection may be performed based on luminance information in the anterior segment image. As shown in FIG. 2, the first Purkinje images Ra1 and Ra2 have a width in the meridian direction. Therefore, for example, in the luminance distribution on the meridian of the cornea in the image, the positions of the first Purkinje images Ra1 and Ra2 may be detected from an area in which luminance values equal to or higher than a predetermined threshold are continuously included. At this time, more specifically, the position of the distribution peak (maximum value or maximum value), the center position, and the like in a region where luminance values equal to or greater than a predetermined threshold value are continuously included are the first Purkinje images Ra1, Ra2. It may be detected as the position. The detection result is stored in the RAM 102, the storage device 105, and the like by the CPU 101, for example. The detection result of the first Purkinje images Ra1 and Ra2 is not limited to the index position information, and may be information on the front surface of the cornea, for example. The information regarding the front surface of the cornea may be, for example, the radius of curvature of the front surface of the cornea, the three-dimensional shape of the front surface of the cornea, the power of the front surface of the cornea, and the like.

  Next, in the present embodiment, the CPU 101 changes the imaging condition (or acquisition condition, for example, the state of the optical system) of the index pattern image by the ophthalmologic measurement apparatus 1 to the second Purkinje image imaging mode (second mode). Set (S7). This mode is a mode for the apparatus main body to acquire data used in detection processing (for example, position and shape detection processing) of the second Purkinje images Rp1 and Rp2. As an example of the present embodiment, in the second Purkinje image imaging mode, an anterior eye image including the second Purkinje images Rp1 and Rp2 is captured (captured). In the process of S7, it is preferable to adjust the light amount of the light beam output from the light source 11, the gain in the image sensor 27, and the like so that an image including clear second Purkinje images Rp1 and Rp2 is captured. For example, the CPU 101 may increase at least one of the light amount from the light source 11 and the gain of the image sensor 27 with respect to the first Purkinje imaging mode.

  Although details will be described later, in the process of S7, the light irradiated to the eye E is suppressed 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 do. For example, in order to reduce miosis due to glare, the CPU 101 may reduce the amount of light output from the light source 52 in order to project a fixation target. At this time, the anterior segment illumination (for example, the light source 31) may be turned off. That is, it is sufficient that the second Purkinje image is captured, and each part of the anterior segment may not be confirmed in the image.

  In addition, for example, it is preferable that transillumination (light that illuminates the cornea from the fundus side) is suppressed by being reflected by the fundus. For example, the light quantity of the light source 31, the light source 42, etc. may be reduced. As a result, the second Purkinje images Rp1 and Rp2 are easily captured with a difference from the background.

  Next, the CPU 101 captures an anterior segment image used in the detection process of the second Purkinje images Rp1, Rp2 (S8). In the process of S8, the CPU 101 may selectively project at least one of a plurality of ring index patterns. More specifically, the two Purkinje images Rp1 based on the light beam from the first ring light source 11a and the second light beam based on the light beam from the second ring light source 11b are turned on by alternately lighting the two ring light sources 11a and 11b. The Purkinje image Rp2 may be captured so as to be included in separate images. In this case, it can suppress that each 2nd Purkinje image Rp1, Rp2 overlaps with the reflective image formed with the light beam from another light source. Accordingly, the second Purkinje images Rp1 and Rp2 are easily detected well in the next second Purkinje image detection process (S9).

  Alternatively, the first Purkinje images Ra1 and Ra2 may be captured so as to be included in one image by simultaneously lighting the two ring light sources 11a and 11b. However, the image includes not only the second Purkinje image but also reflected images of other index light beams (for example, the first Purkinje images Ra1, Ra2, etc.). For this reason, when a plurality of second Purkinje images are captured as one image, it is preferable that each second Purkinje image does not overlap with other reflected images.

  After the process of S8, the CPU 101 executes a second Purkinje image detection process (S9). In the present embodiment, in the second Purkinje image detection process (S9), the second Purkinje image is detected based on the imaging signal output from the imaging element 27. More specifically, the detection is performed using the image captured by the process of S8. In the present embodiment, information on the position and shape of each of the second Purkinje images Rp1 and Rp2 (for example, coordinate data of each part of the image) is acquired as a result (detection result) of S9. Specifically, for example, the detection result is acquired by storing the detection result in the RAM 102.

  Various processes can be used as the process of S9. For example, similarly to the process of S6 described above, in the process of S9, detection may be performed based on luminance information in the anterior segment image. The second Purkinje images Rp1 and Rp2 have a width in the meridian direction. Therefore, for example, in the luminance distribution on the meridian of the cornea in the image, the positions of the first Purkinje images Ra1 and Ra2 may be detected from an area in which luminance values equal to or higher than a predetermined threshold are continuously included. However, the image acquired by the process of S8 includes at least the first Purkinje image. In general, the first Purkinje image is brighter and clearer than the second Purkinje image. Therefore, for example, the second Purkinje images Rp1 and Rp2 may be detected from a region including a peak with low luminance with respect to a region including the first Purkinje images Ra1 and Ra2 in the luminance distribution on the meridian. In general, the second Purkinje image is generated on the inner side (near the optical axis) than the first Purkinje image. Therefore, in the luminance distribution on the meridian, the optical axis is compared with the region including the first Purkinje images Ra1 and Ra2. The second Purkinje images Rp1 and Rp2 may be detected from a region including a peak generated near L1. Since the second Purkinje images Rp1 and Rp2 also have a width in the meridian direction, a detailed position or the like may be detected based on the distribution shape. For example, the position of the distribution peak (maximum value or maximum value), the center position, and the like may be detected as the positions of the second Purkinje images Rp1, Rp2.

  Next, the CPU 101 executes anterior eye part information acquisition processing (S10). In the anterior ocular segment information acquisition process (S10) of this embodiment, at least information on the posterior cornea based on the detection results of the second Purkinje images Rp1 and Rp2 is acquired as anterior segment information.

  Here, an example of the anterior segment information acquisition process will be described with reference to FIG. In the anterior ocular segment information acquisition process (S10) of the present embodiment, first, the CPU 101 calculates the curvature radius r1 of the corneal front surface Ec1 (S21). For example, the radius of curvature r1 of the corneal front surface Ec1 can be obtained based on the first Purkinje images Ra1 and Ra2 detected by the process of S6. Specifically, the corneal curvature radius r1 is set to the image height of the first Purkinje images Ra1 and Ra2 (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 the corneal center). ) To the first Purkinje images Ra1 and Ra2). For a specific method, for example, refer to Japanese Patent Application Laid-Open No. 2003-111727 by the present applicant.

  In the present embodiment, since the first Purkinje images Ra1 and Ra2 are ring-shaped, it is possible to obtain a radius of curvature r1 in the arbitrary meridian direction of the cornea Ec. For this reason, as shown in this embodiment, the curvature radius r1 with respect to several meridian directions can be obtained.

  Moreover, in this embodiment, since several 1st Purkinje image Ra1, Ra2 from which a diameter differs is detected, a curvature radius can each be obtained from the detection result of each 1st Purkinje image Ra1, Ra2.

  Next, the CPU 101 calculates the curvature radius r2 of the corneal rear surface Ec2. The curvature radius r2 of the corneal rear surface Ec2 can be obtained by using, for example, the detection result of the second Purkinje images Rp1 and Rp2 by the processing of S9 and the curvature radius r1 of the corneal front surface Ec1 obtained by the processing of S21.

  Here, with reference to FIG. 5, how to obtain the radius of curvature r2 of the corneal posterior surface Ec2 will be described as an example. Here, for convenience of explanation, a concept in the case of paraxial approximation is shown. In FIG. 5, under the condition that the optical axis L1 passes through the center of the cornea, a rear reflection image f2 is formed on the corneal rear surface Ec2 by the object f1. In FIG. 5, the arrow tip of the object f1 indicates the position of the light source 11 (the first ring light source 11a or the second ring light source 11b). Therefore, the object height h1 indicates the distance from the optical axis L1 to the light source 11. On the other hand, the arrow tip of the rear reflection image f2 indicates the position of the ring image formed by the light source 11 located at the arrow tip of the object f1. That is, the image height h2 of the rear surface reflection image f2 indicates the distance from the ring image formed on the corneal rear surface Ec2 to the optical axis L1.

  In FIG. 5, D1 indicates the distance from the object f1 to the corneal front surface Ec1. D2 indicates the distance from the object f1 to the rear reflection image f2. d is the corneal thickness at the reference position of the cornea (an example of corneal thickness information). Here, d is the corneal thickness at the center of the cornea, and indicates the corneal thickness at the position where the optical axis L1 passes. In the present embodiment, the distance D1 is set to a fixed value as a result of the optical system alignment process (S1). For the corneal thickness d, for example, a value obtained by a 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.

  Here, the image height h2 can be expressed using the following equation (1), for example. In the following, the image height h2 with respect to the object height h1 = 1 is shown.

  However, n shows a corneal refractive index. β is a correction coefficient for the magnification (or size) of the image. More specifically, the effect of refraction by the cornea is corrected by β. About D2 and (beta), it can represent by the following formula | equation (2) and (3), for example.

  For the image height h2, for example, a measurement value based on the result of the second Purkinje image detection process (S9) is used. For this reason, the value of the curvature radius r2 of the corneal posterior surface Ec2 can be obtained from the equation (1).

  Although the paraxial approximation is shown here, it is of course possible to correct or change the above equation according to the actual device design.

  In the process of S22, the curvature r2 of the corneal rear surface may be obtained by a method other than the calculation by the CPU 101. For example, even if the CPU 101 obtains the curvature radius r2 of the corneal posterior surface Ec2 using a table in which parameters related to the cornea (for example, corneal thickness information, anterior curvature information) are associated with the curvature radius r1 of the corneal posterior surface Ec2. Good. As one method, a table in which the curvature radius r2 of the corneal rear surface Ec2 is stored with respect to the values of the curvature radius r1 of the corneal front surface Ec1 and the reference corneal thickness d is provided in a storage device such as the storage device 105 in advance. The radius of curvature r2 in the table may be a value obtained by using the above formula, for example. In this case, the curvature radius r2 of the corneal posterior surface Ec2 is obtained as a result of the CPU 101 referring to the curvature radius r1 of the corneal front surface Ec1 and the reference corneal thickness d obtained by the processing of S21 or the like. .

  Returning to the flowchart of FIG. Next, the CPU 101 acquires corneal thickness information (S23). As the corneal thickness information, for example, information indicating the corneal thickness distribution in a specific meridian direction may be acquired. The thickness distribution of the cornea in one meridian direction can be determined using, for example, the radii of curvature r1 and r2 of the anterior corneal surface Ec1 and the posterior corneal surface Ec2 in one meridian direction and the value of the reference corneal thickness d. In the process of S23, information indicating the thickness distribution of the entire cornea may be acquired based on the thickness distribution of the entire cornea in a plurality of meridian directions.

  Next, in this embodiment, CPU101 calculates | requires the corneal refractive power based on a corneal front curve and a back curve (S24). The corneal refractive power can be expressed, for example, in the form of the power of the cornea Ec (P (θ)) or {spherical power (S), surface power (C), astigmatic axis angle (A)}. In the present embodiment, 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). Get the combined value with each value). In the present embodiment, a synthesized value synthesized using the power vector method is obtained. In general, the power P (θ) can be expressed by the following equation (4).

  The values of S, C, and A are, for example, the 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 is approximated by an ellipse, and the strong main meridian and the weak main meridian It can be determined from the shaft angle or the like. Therefore, the power P2 and the like on the corneal rear surface Ec2 can be obtained based on the detection results of the second Purkinje images Rp1 and Rp2 formed on the corneal rear surface Ec2. Further, the power P1 and the like at the corneal front surface Ec1 can be obtained based on the detection results of the first Purkinje images Ra1 and Ra2 formed on the corneal front surface Ec1.

  The power P (θ) can be converted as follows.

Here, the values of J45, J180, and M calculated for the power P1 are represented by J145.
, J1180, M1, and the values of J45, J180, M calculated for the power P2 are denoted as J245, J2180, M2, respectively. J45, J180 for the combined power value Pmix (θ)
The value of M can be expressed by the following equation.

  By substituting the result of equation (6) into equation (5), the combined value of each value of power (refractive power value), spherical power (S), gazing power (C), and astigmatic axis angle (A). Is obtained. The calculation of the composite value is not limited to the above method. For example, a combined value such as power may be obtained by ray tracing.

  In the present embodiment picture, the process of S24 is performed, and the corneal information acquisition process ends. As a result, the process of the flowchart of FIG.

  As described above, in the present embodiment, information on the corneal posterior surface Ec (for example, the curvature radius r2 of the corneal posterior surface Ec2, the corneal thickness distribution information, the power of the cornea Ec, etc.) Obtained by the CPU 101 based on the result of the detection process (S9). Therefore, the ophthalmologic measurement apparatus 1 according to the present embodiment can acquire information related to the corneal posterior surface Ec without necessarily requiring an apparatus for performing cross-sectional imaging of the anterior segment such as the anterior segment OCT apparatus or the Scheimpflug camera.

  In addition, when information on the corneal rear surface is acquired from a cross-sectional image captured by an anterior segment OCT apparatus, a Scheimpflug camera, or the like, an edge (boundary) of a corneal cross-section in the image is detected. For example, the position of the edge of the rear cornea in the image is specified as the position of the rear cornea. However, in general, it is difficult to accurately specify the position of the edge of an object by image processing. This is because the edge detection position changes even when the same object is imaged in accordance with imaging conditions such as the amount of illumination light. In particular, in the cross-sectional image of the eye to be inspected, an error corresponding to the optical characteristics of the anterior segment (for example, light transmittance in the cornea) occurs between the actual posterior corneal surface and the edge detection position in the image. It is thought that it will end.

  On the other hand, in this embodiment, the case where the detection of the posterior surface of the cornea is performed based on the distribution shape of the luminance distribution in each meridian direction in the image obtained by capturing the second Purkinje image is shown as an example. Although the distribution shape depends on the amount of illumination light and the optical characteristics of the anterior segment, for example, the position of the distribution peak (maximum value), the median value of the curve including the peak, etc. are affected by these conditions. It is hard to receive. Therefore, in the said embodiment, the ophthalmologic measurement apparatus 1 can acquire the information regarding the back cornea surface Ec more correctly with respect to the system which acquires the information regarding the cornea back surface from a cross-sectional image.

  In addition, when calculating | requiring the curvature of a corneal rear surface, 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 a cornea is obtained as information regarding the cornea back surface Ec. In contrast to the case where the composite power is obtained from the cross-sectional image, the ophthalmic measurement apparatus 1 can obtain accurate power. 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.

  By the way, it is difficult for the second Purkinje images Rp1 and Rp2 to form clear images. On the other hand, in the present embodiment, in the second Purkinje image capturing mode in which the anterior segment image in which the second Purkinje image detection process is performed is acquired, the index light beam is projected at least with respect to the first Purkinje image capturing mode. The CPU 101 increases the light amount of the light source 11 or the gain of the light receiving element 27. As a result, image data including clear second Purkinje images Rp1 and Rp2 are easily obtained in the second Purkinje image imaging mode. Therefore, in the second Purkinje image detection process (S9), detection of the second Purkinje images Rp1 and Rp2 is likely to be performed satisfactorily.

  In the eye E, the iris is a region having a complicated luminance change. For this reason, if the second Purkinje images Rp1, Rp2 are formed overlapping the iris, it may be difficult to detect the second Purkinje images Rp1, Rp2. On the other hand, in the present embodiment, the amount of visible light emitted from the fixation target presenting optical system 50 to the eye E in the second Purkinje image capturing mode is determined by the CPU 101 at least with respect to the first Purkinje image capturing mode. Reduced. Thereby, in the second Purkinje image capturing mode, miosis due to glare is reduced. As a result, the formation of the second Purkinje images Rp1 and Rp2 at a position overlapping the iris is suppressed. Therefore, in the ophthalmologic measurement apparatus 1 of the present embodiment, the second Purkinje images Rp1 and Rp2 are easily detected satisfactorily.

  In the present embodiment, fixation for imaging an anterior segment image including the second Purkinje images Rp1 and Rp2 is performed using a fixation target disposed at a far point of the eye E. Thereby, an anterior ocular segment image can be taken in a state where miosis due to adjustment is reduced. As a result, the second Purkinje images Rp1 and Rp2 are prevented from being formed at positions overlapping with the iris, and the second Purkinje images Rp1 and Rp2 are easily detected favorably in the ophthalmologic measurement apparatus 1.

  As mentioned above, although demonstrated based on embodiment, this invention is not limited to the said embodiment, A various deformation | transformation is possible.

  For example, in general, as the Purkinje image formed by reflecting the light beam projected by the eye E to be examined by the anterior eye part, in addition to the first and second Purkinje images described in the above embodiment, a third And the fourth Purkinje image is known. Each of the third Purkinje image and the fourth Purkinje image is formed by the light beams reflected on the front surface of the crystalline lens and the rear surface of the crystalline lens. Here, since the amount of light reflected from the back surface of the crystalline lens is small compared to the light reflected from the back surface of the cornea, the fourth Purkinje image is unlikely to be a problem when detecting the second Purkinje image from the anterior segment image. . On the other hand, the light reflected on the front surface of the crystalline lens is more than the light reflected on the rear surface of the crystalline lens. As a result, a third Purkinje image having the same brightness as the second Purkinje image may occur.

  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 (optical axis center) of the cornea. 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, for example, each of 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 arranged asymmetrically with respect to the meridian of the cornea.

  In FIG. 6, as an example, an anterior segment image captured in a mode in which only the upper half of the light source 11 (here, the first ring light source 11 a) is turned on is shown. Since the second Purkinje image is an upright reflection image, the second Purkinje image Rp is generated in the upper half of the cornea Ec in the example of FIG. On the other hand, the third Purkinje image Rq1 is an inverted reflection image. For this reason, in the example of FIG. 6, the third Purkinje image Rq1 is generated in the lower half of the cornea Ec. In this case, in order to detect the second Purkinje image Rp from the erect reflection image, for example, the detection range of the second Purkinje image Rp in the image is a range in which the erect reflection image is generated (in this example, a corneal portion or an image). Upper half). As a result, the possibility that the CPU 101 erroneously detects the third Purkinje image as the second Purkinje image can be reduced.

  Further, not only the kerato projection optical system 10 but also the alignment projection optical system 30 may be used as a projection light optical system for a target luminous flux for forming a Purkinje image. In the above-described embodiment, when the alignment projection optical system 30 is also used as a projection light beam projection optical system, the anterior segment image may be captured by sequentially turning on each light source one by one. In addition, a state in which the light source 11a and the light source 31 are turned on and a state in which the light source 11b is turned on so that two adjacent light sources (for example, the light source 11a and the light source 11b and the light source 11b and the light source 31) are not turned on simultaneously. Alternatively, the images may be switched alternately. Thereby, it is suppressed that the Purkinje image (the 1st Purkinje image and the 2nd Purkinje image) formed by each light source overlaps with the Purkinje image by other light sources. As a result, each Purkinje image is detected well in the apparatus.

  In the above embodiment, the case where the corneal thickness at the center of the cornea is used as the corneal thickness at the reference position of the cornea is not necessarily limited to this, and the corneal thickness at the reference position is The corneal thickness in a region away from the center of the cornea may be used.

  In the above embodiment, when the first Purkinje images Ra1 and Ra2 and the second Purkinje images Rp1 and Rp2 are imaged, the anterior segment illumination (for example, the light source 31) may be turned off. That is, it is only necessary to capture an image that can detect information about the position and shape of each Purkinje image. For example, it is not necessary to capture an image that can confirm each part of the anterior segment, such as the position and shape of the pupil. .

  In the above embodiment, the case where the second Purkinje images Rp1 and Rp2 are detected from one image obtained by imaging the anterior segment has been described. However, it is not necessarily limited to this. For example, in the second Purkinje image capturing mode, a plurality of images having the same pattern index position may be captured, and an added image of these images may be generated by the CPU 101. Thereafter, the second Purkinje image Rp1, Rp2 detection process (for example, the process of S9) 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 images Rp1 and Rp2 can be easily detected. Note that the first Purkinje images Ra1 and Ra2 may also be detected from the added image. However, the second Purkinje image is picked up so that the number of picked-up images (number of picked-up images) of the second Purkinje images Rp1, Rp2 is larger than the number of picked-up images of the first Purkinje images Ra1, Ra2. It is preferable that the number of added sheets is set in the mode setting process (S7).

  Moreover, although the said embodiment demonstrated the case where imaging conditions differ between 1st Purkinje imaging mode and 2nd Purkinje imaging mode, a 1st Purkinje image and a 2nd Purkinje image are imaged on the same conditions. Also good. Further, for example, the second Purkinje image and the first Purkinje image may be detected from the same image.

  In the above-described embodiment, the case where the image analysis process is performed by the CPU 101 is described as an example of the Purkinje image detection process in the processes of S6 and S9. However, the present invention is not necessarily limited thereto. For example, at least one of the processes of S6 and S9 is performed by the Purkinje image input via the operation unit 80 by the examiner who has confirmed the anterior segment image (the image captured in the process of S8) displayed on the monitor 70 or the like. The Purkinje image may be detected based on position information on the image.

  In each of the above embodiments, the case where the ophthalmic measurement apparatus 1 acquires information related to the posterior surface of the cornea has been described. However, the present invention is not necessarily limited thereto. Data) can be transferred to a general-purpose computer (for example, a personal computer), and information related to the corneal surface can be obtained by analysis processing executed by the computer. For example, when information about the posterior cornea is acquired using the image data of the second Purkinje image and the image data of the first Purkinje image, a hard disk storing a program for obtaining information about the posterior cornea by a computer For example, an analysis program for causing the processor of the computer to execute the processes of S6, S9, and S10 in FIG. 3 may be prepared. Also in this case, as with the ophthalmologic measurement apparatus 1 of the above embodiment, information related to the corneal posterior surface is obtained.

10 kerato projection optical system 20 imaging optical system 27 imaging device 40 second measurement optical system Ra1, Ra2 first Purkinje image Rp1, Rp2 second Purkinje image

Claims (4)

A projection optical system that projects a pattern index toward the cornea of the eye to be examined, a first Purkinje image that is an index image formed by reflecting the pattern index on the front of the cornea of the eye to be examined, and the pattern index An imaging optical system that captures an image of a second Purkinje image, which is an index image formed by being reflected by the corneal posterior surface of the eye to be examined;
A corneal thickness measurement unit that is separate from the photographing optical system and measures the corneal thickness at a reference position;
Detection means for performing detection processing of the first Purkinje image and the second Purkinje image based on an imaging signal output from the imaging device;
The detection result of the second Purkinje image in consideration of the information on the front surface of the cornea of the eye to be acquired acquired based on the detection result of the first Purkinje image and the corneal thickness information acquired by the corneal thickness measurement unit An ophthalmologic measurement apparatus comprising: a rear surface information acquisition unit that acquires information related to the rear surface of the cornea of the eye to be examined.   The ophthalmologic measurement apparatus according to claim 1, wherein the corneal thickness measuring unit measures a corneal thickness at a central portion of the cornea.   The ophthalmologic measurement apparatus according to claim 1, wherein the corneal thickness measurement unit optically measures the corneal thickness.   The posterior surface information acquisition unit acquires at least one of a corneal thickness distribution of the eye to be examined, a corneal power, and a curvature radius of the corneal rear surface as information on the corneal posterior surface. The ophthalmic measuring device described.

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