JP7601643B2 - Ophthalmic device, method for controlling ophthalmic device, and program - Google Patents

Description

This invention relates to an ophthalmic device, a control method for an ophthalmic device, and a program.

Axial length is measured not only to select the power of the intraocular lens (IOL) before cataract surgery, but also to check for axial refractive errors and measure the shape of the eyeball.

Devices capable of measuring axial length include ultrasonic axial length measuring devices that measure axial length by contacting an ultrasonic probe with the cornea, and optical axial length measuring devices that perform optical coherence tomography on the examinee's eye to optically measure axial length in a non-contact manner.

Generally, the axial length measured using an ultrasonic axial length measuring device is used. However, measurement using an ultrasonic axial length measuring device requires skilled technique, and the subject's eye must be anesthetized with eye drops, which places a heavy burden on the subject.

In contrast, measurements using optical axial length measurement devices do not require skilled techniques and can be performed without contact, significantly reducing the burden on the subject. However, measurements cannot be performed on eyes with cataracts, making it difficult to obtain reliable measurement results.

For example, Patent Document 1 discloses an axial length measuring device that includes an ultrasonic axial length measuring means that measures axial length ultrasonically, and a non-contact axial length measuring means that measures axial length optically without contact.

For example, Patent Document 2 discloses a method for measuring the axial length by identifying the position of the corneal apex and the position of the retinal pigment epithelium from an intensity profile in the A-scan direction obtained by performing optical coherence tomography on the subject's eye.

For example, Non-Patent Document 1 discloses a method for converting the optical path length corresponding to the axial length obtained by optical coherence tomography using near-infrared light of 780 nanometers (nm) as the measurement light into the axial length (physical length) measured using an ultrasonic axial length measurement device.

JP 2008-161218 A Special Publication No. 2014-500096

Suheimat M, Verkicharla PK, Mallen EAH, Rozema J, Atchison DA, “Refractive indicators used by the Haag-Street Leinstar to calculate axial biometric dimensions”, Ophthalmic & Physiological Optics 2015, 35:90-96. doi:10.1111/opo. 12182

Axial length is the distance from the corneal apex to the retinal pigment epithelium (RPE) layer. However, in the intensity profile of the interference signal obtained by performing optical coherence tomography, the peak corresponding to the RPE layer may be buried in peaks corresponding to layer regions such as the inner segment-outer segment junction (IS/OS line) and Bruch membrane. In such cases, it may take time to identify the peak corresponding to the RPE layer, or the peak corresponding to the RPE layer may fail to be identified, or the peak corresponding to the RPE layer may be erroneously detected. As a result, the reliability of the axial length measurement results is reduced.

Therefore, it is necessary to quickly and accurately identify the depth position of the desired layer region in the test eye.

The present invention was made in consideration of these circumstances, and one of its objectives is to provide a new technology for quickly and accurately identifying the depth position of a desired layer region in a test eye.

A first aspect of some embodiments is an ophthalmologic device including a layer region identifying unit that identifies a first depth position corresponding to a first layer region in the fundus based on a detection result of interference light obtained by performing an OCT scan on the fundus of a test eye, and a layer region position calculating unit that calculates a second depth position corresponding to a second layer region in the fundus by adding a predetermined offset value to the first depth position.

In a second aspect of some embodiments, in the first aspect, the first layer region is an IS/OS line and the second layer region is a retinal pigment epithelium layer.

In a third aspect of some embodiments, in the first or second aspect, the layer region position calculation unit adds a different offset value to the first depth position depending on the subject's eye.

In a fourth aspect of some embodiments, in the second or third aspect, the layer region identifying unit identifies the first depth position and a third depth position corresponding to the corneal apex based on the detection result of the interference light. The ophthalmic apparatus includes an axial length calculating unit that calculates the axial length of the subject's eye based on the third depth position and the second depth position.

In a fifth aspect of some embodiments, in the fourth aspect, the OCT scan is performed by irradiating the test eye with measurement light having a first wavelength as a measurement wavelength. The ophthalmic device includes a wavelength correction unit that performs wavelength correction on the axial length calculated by the axial length calculation unit to correct the axial length to a second wavelength different from the first wavelength.

A sixth aspect of some embodiments is an ophthalmic device including an axial length calculation unit that calculates an axial length based on a detection result of interference light obtained by performing an OCT scan on a test eye using measurement light having a first wavelength as a measurement wavelength, and a wavelength correction unit that performs wavelength correction on the axial length calculated by the axial length calculation unit to correct the axial length to a second wavelength different from the first wavelength.

In a seventh aspect of some embodiments, in the fifth or sixth aspect, the wavelength correction unit corrects the axial length at the second wavelength by multiplying the axial length calculated by the axial length calculation unit by the ratio of the refractive index of the human eye at the first wavelength to the refractive index of the human eye at the second wavelength.

In an eighth aspect of some embodiments, in any of the fifth to seventh aspects, the second wavelength is 780 nm.

A ninth aspect of some embodiments is any of the fifth to eighth aspects, which includes an axial length conversion unit that converts the axial length corrected by the wavelength correction unit into an axial length obtained using an ultrasonic axial length measurement device.

In a tenth aspect of some embodiments, in the ninth aspect, the axial length conversion unit converts the optical path length as the axial length corrected by the wavelength correction unit into a physical length as the axial length obtained using the ultrasonic axial length measurement device.

An eleventh aspect of some embodiments includes an OCT optical system in any one of the first to tenth aspects that splits light from a light source into measurement light and reference light, irradiates the test eye with the measurement light, and detects the interference light between the return light of the measurement light from the test eye and the reference light that has passed through a reference light path.

A twelfth aspect of some embodiments is a method for controlling an ophthalmologic device, which includes a layer region identifying step for identifying a first depth position corresponding to a first layer region in the fundus based on a detection result of interference light obtained by performing an OCT scan on the fundus of a test eye, and a layer region position calculating step for calculating a second depth position corresponding to a second layer region in the fundus by adding a predetermined offset value to the first depth position.

In some embodiments, in the thirteenth aspect, in the twelfth aspect, the first layer region is an IS/OS line and the second layer region is a retinal pigment epithelium layer.

In a fourteenth aspect of some embodiments, in the twelfth or thirteenth aspect, the layer region identifying step identifies the first depth position and a third depth position corresponding to the corneal apex based on the detection result of the interference light. The control method for an ophthalmic apparatus includes an axial length calculation step of calculating the axial length of the subject's eye based on the third depth position and the second depth position.

In a fifteenth aspect of some embodiments, in the fourteenth aspect, the OCT scan is performed by irradiating the test eye with measurement light having a first wavelength as a measurement wavelength. The control method for an ophthalmic device includes a wavelength correction step of correcting the axial length calculated in the axial length calculation step to a wavelength at a second wavelength different from the first wavelength.

A sixteenth aspect of some embodiments is a method for controlling an ophthalmic device, which includes an axial length calculation step of calculating the axial length based on the detection result of interference light obtained by performing an OCT scan on the subject's eye using measurement light having a first wavelength as a measurement wavelength, and a wavelength correction step of correcting the axial length calculated in the axial length calculation step to a second wavelength different from the first wavelength by performing wavelength correction on the axial length.

A seventeenth aspect of some embodiments, in the fifteenth or sixteenth aspect, includes an axial length conversion step in which the axial length corrected in the wavelength correction step is converted to an axial length obtained using an ultrasonic axial length measurement device.

An 18th aspect of some embodiments is a program that causes a computer to execute each step of the method for controlling an ophthalmic device described in any one of the 12th to 17th aspects.

The configurations according to the above claims can be combined in any way.

The present invention provides a new technology for quickly and accurately identifying the depth position of a desired layer region in a test eye.

1 is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic apparatus according to an embodiment. 1 is a schematic diagram illustrating an example of the configuration of an optical system of an ophthalmic apparatus according to an embodiment. 2 is a schematic diagram illustrating an example of the configuration of a processing system of an ophthalmic apparatus according to an embodiment. FIG. 2 is a schematic diagram illustrating an example of the configuration of a processing system of an ophthalmic apparatus according to an embodiment. FIG. 2 is a schematic diagram illustrating an example of the configuration of a processing system of an ophthalmic apparatus according to an embodiment. FIG. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5A and 5B are schematic diagrams for explaining the operation of the ophthalmologic apparatus according to the embodiment. 5 is a schematic diagram showing a flow of an example of an operation of the ophthalmologic apparatus according to the embodiment. FIG.

Examples of embodiments of an ophthalmic device, a control method for an ophthalmic device, and a program according to the present invention will be described in detail with reference to the drawings. Note that the contents of the documents cited in this specification and any publicly known technology may be incorporated into the following embodiments.

The ophthalmologic apparatus according to the embodiment identifies a depth position corresponding to a first layer region in the fundus based on the detection result of interference light obtained by performing an OCT scan on the subject's eye, and calculates a depth position corresponding to a second layer region in the fundus by adding a predetermined offset value to the identified depth position. For example, the first layer region is the IS/OS line, and the second layer region is the RPE layer.

This makes it possible to accurately identify the representative position on the fundus (retina) side in a short time without failing to identify the representative position on the fundus side. As a result, it is possible to improve the measurement accuracy of the intraocular distance (e.g., axial length) of the test eye identified using the representative position on the fundus side.

The ophthalmic device according to the embodiment is also capable of performing wavelength correction, or wavelength correction and conversion using a predetermined conversion formula, on intraocular distances such as axial length obtained based on the detection results of interference light obtained by performing an OCT scan on the subject's eye. This makes it possible to compare with high accuracy the measurement results of other axial length measurement devices capable of measuring axial length using measurement light of different wavelengths, and the measurement results of ultrasonic axial length measurement devices.

The control method of the ophthalmic device according to the embodiment is a method for controlling the ophthalmic device according to the embodiment. The program according to the embodiment causes a processor (computer) to execute each step of the control method of the ophthalmic device. The recording medium according to the embodiment is a computer-readable non-transitory recording medium (storage medium) on which the program according to the embodiment is recorded.

In this specification, the term "processor" refers to a circuit such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), or a programmable logic device (e.g., an SPLD (Simple Programmable Logic Device), a CPLD (Complex Programmable Logic Device), or an FPGA (Field Programmable Gate Array)). The processor realizes the functions of the embodiment by, for example, reading and executing a program stored in a memory circuit or a storage device.

Below, we will explain a case where the ophthalmic device according to the embodiment is equipped with a measurement optical system including an OCT optical system that performs OCT on the test eye, but the configuration of the ophthalmic device according to the embodiment is not limited to this. For example, the ophthalmic device according to the embodiment may be configured to obtain the detection results of the interference light from an external OCT device.

The ophthalmic device according to some embodiments has not only the function of an OCT device for performing OCT, but also at least one of the functions of a fundus camera, a scanning laser ophthalmoscope, a slit lamp microscope, and a surgical microscope. Furthermore, the ophthalmic device according to some embodiments has a function of measuring the optical characteristics of the subject's eye. Ophthalmic devices having the function of measuring the optical characteristics of the subject's eye include a tonometer, a wavefront analyzer, a specular microscope, and a perimeter. The ophthalmic device according to some embodiments has the function of a laser treatment device used for laser treatment.

In the following embodiment, a detailed description will be given of the case where a spectral domain type OCT technique is used in measurements using OCT. However, the configuration according to the embodiment can also be applied to ophthalmic devices that use other types of OCT (e.g., swept source type).

<Configuration of Optical System>
1 and 2 show examples of the configuration of an optical system of an ophthalmic apparatus according to an embodiment. Fig. 1 shows an example of the overall configuration of an optical system of an ophthalmic apparatus 1000 according to an embodiment. Fig. 2 shows an example of the configuration of an optical system of an OCT unit 100 in Fig. 1.

The ophthalmic device 1000 according to the embodiment includes an optical system for observing the subject's eye E, an optical system for inspecting the subject's eye E, and a dichroic mirror that separates the optical paths of these optical systems by wavelength. An anterior segment observation system 5 is provided as the optical system for observing the subject's eye E. An OCT optical system and a refraction measurement optical system (refractive power measurement optical system) are provided as the optical system for inspecting the subject's eye E.

The ophthalmic device 1000 includes an alignment system 1, a keratometry system 3, a fixation projection system 4, an anterior segment observation system 5, a reflex measurement projection system 6, a reflex measurement light receiving system 7, and an OCT optical system 8. In the following, for example, the anterior segment observation system 5 uses light of 940 nm to 1000 nm, the reflex measurement optical system (reflex measurement projection system 6, reflex measurement light receiving system 7) uses light of 850 nm to 880 nm, and the fixation projection system 4 uses light of 400 nm to 700 nm. In addition, the OCT optical system 8 uses light of 840 nm. In other words, the OCT optical system 8 performs OCT measurement (OCT scan) with a measurement wavelength of 840 nm.

(Alignment system 1)
The alignment system 1 is used for Z alignment and XY alignment of the optical system with respect to the subject's eye E. The Z alignment is alignment in the Z direction (front-back direction, working distance direction) parallel to the optical axis of the anterior segment observation system 5 (e.g., the objective lens 51). The XY alignment is alignment in directions perpendicular to this optical axis (left-right direction (X direction), up-down direction (Y direction)).

The alignment system 1 includes two or more anterior eye cameras 14. The two or more anterior eye cameras 14 capture images of the anterior eye of the subject's eye E from different directions substantially simultaneously, and output the two or more captured images (anterior eye images) to a processing unit 9 described below. The processing unit 9 analyzes the two or more captured images from the two or more anterior eye cameras 14 to identify the three-dimensional position of the subject's eye E (specifically, a characteristic portion of the subject's eye E), and aligns the optical system in the XY and Z directions with respect to the subject's eye E (characteristic portion) based on the identified three-dimensional position.

In the following, the alignment system 1 is assumed to include two anterior eye cameras 14. However, the alignment system 1 may include three or more anterior eye cameras 14. Furthermore, the function of one of the two anterior eye cameras 14 may be realized by an image sensor 59 provided in the anterior eye observation system 5 described below.

(Anterior Eye Observation System 5)
The anterior eye observation system 5 captures a moving image of the anterior eye of the subject's eye E. In the optical system passing through the anterior eye observation system 5, the imaging surface of the imaging element 59 is disposed at a pupil conjugate position (a position optically approximately conjugate with the pupil of the subject's eye E). The anterior eye illumination light source 50 irradiates the anterior eye of the subject's eye E with illumination light (e.g., infrared light). The light reflected by the anterior eye of the subject's eye E passes through the objective lens 51, transmits through the dichroic mirror 52, passes through a hole formed in the aperture (telecentric aperture) 53, passes through the relay lenses 55 and 56, and transmits through the dichroic mirror 76. The dichroic mirror 52 combines (separates) the optical path of the reflex measurement optical system and the optical path of the anterior eye observation system 5. The dichroic mirror 52 is disposed such that the optical path combining surface that combines these optical paths is inclined with respect to the optical axis of the objective lens 51. The light transmitted through the dichroic mirror 76 is imaged on the imaging surface of an image sensor 59 (area sensor) by an imaging lens 58. The image sensor 59 captures images and outputs signals at a predetermined rate. The output (video signal) of the image sensor 59 is input to a processing unit 9 described below. The processing unit 9 displays an anterior eye image E' based on this video signal on a display screen 10a of a display unit 10 described below. The anterior eye image E' is, for example, an infrared moving image.

(Kerato measurement system 3)
The kerato measurement system 3 projects a ring-shaped light beam (infrared light) onto the cornea Cr of the subject's eye E to measure the shape of the cornea Cr. The kerato plate 31 is disposed between the objective lens 51 and the subject's eye E. The kerato plate 31 is provided on the rear side (objective lens 51 side) of the kerato plate 31 with a kerato ring light source 32. The kerato plate 31 is formed with a kerato pattern (transmitting portion) that transmits light from the kerato ring light source 32 along a circumference centered on the optical axis of the objective lens 51. The kerato pattern may be formed in an arc shape (part of the circumference) centered on the optical axis of the objective lens 51. By illuminating the kerato plate 31 with light from the kerato ring light source 32, a ring-shaped light beam (arc-shaped or circumferential measurement pattern) is projected onto the cornea Cr of the subject's eye E. The reflected light (keratinization image) from the cornea Cr of the subject's eye E is detected together with the anterior eye image E' by the imaging element 59. The processing unit 9 performs a known calculation based on this keratinization image to calculate corneal shape parameters that represent the shape of the cornea Cr.

(Reflection measurement projection system 6, reflection measurement light receiving system 7)
The refraction measurement optical system includes a refraction measurement projection system 6 and a refraction measurement light receiving system 7 used for refractive power measurement. The refraction measurement projection system 6 projects a light beam (e.g., a ring-shaped light beam) (infrared light) for refractive power measurement onto the fundus Ef. The refraction measurement light receiving system 7 receives the return light of this light beam from the subject's eye E. The refraction measurement projection system 6 is provided on an optical path branched by an aperture prism 65 provided on the optical path of the refraction measurement light receiving system 7. The hole formed in the aperture prism 65 is arranged at a pupil conjugate position. In the optical system passing through the refraction measurement light receiving system 7, the imaging surface of the imaging element 59 is arranged at a fundus conjugate position (a position optically approximately conjugate with the fundus Ef of the subject's eye E).

In some embodiments, the reflex measurement light source 61 is a superluminescent diode (SLD) light source, which is a high-brightness light source. The reflex measurement light source 61 is movable in the optical axis direction. The reflex measurement light source 61 is arranged at a fundus conjugate position. The light output from the reflex measurement light source 61 passes through the relay lens 62 and enters the conical surface of the conical prism 63. The light that enters the conical surface is deflected and exits from the bottom surface of the conical prism 63. The light that exits from the bottom surface of the conical prism 63 passes through a ring-shaped light-transmitting portion formed in the ring aperture 64. The light that passes through the light-transmitting portion of the ring aperture 64 (ring-shaped light beam) is reflected by a reflecting surface formed around the hole of the hole prism 65, passes through the rotary prism 66, and is reflected by the dichroic mirror 67. The light reflected by the dichroic mirror 67 is reflected by the dichroic mirror 52, passes through the objective lens 51, and is projected onto the subject's eye E. The rotary prism 66 is used to average the light intensity distribution of the ring-shaped light beam on the blood vessels and diseased areas of the fundus Ef and to reduce speckle noise caused by the light source.

The return light of the ring-shaped light beam projected on the fundus Ef passes through the objective lens 51 and is reflected by the dichroic mirror 52 and the dichroic mirror 67. The return light reflected by the dichroic mirror 67 passes through the rotary prism 66, passes through the hole of the aperture prism 65, passes through the relay lens 71, is reflected by the reflecting mirror 72, and passes through the relay lens 73 and the focusing lens 74. The focusing lens 74 can move along the optical axis of the reflex measurement light receiving system 7. The light that passes through the focusing lens 74 is reflected by the reflecting mirror 75, is reflected by the dichroic mirror 76, and is imaged on the imaging surface of the imaging element 59 by the imaging lens 58. The processing unit 9 calculates the refractive power value of the subject's eye E by performing a known calculation based on the output from the imaging element 59. For example, the refractive power value includes a spherical power, a cylindrical power and an astigmatism axis angle, or an equivalent spherical power.

(Fixation Projection System 4)
The OCT optical system 8 described below is provided on an optical path separated by wavelength from the optical path of the reflex measurement optical system by the dichroic mirror 67. The fixation projection system 4 is provided on an optical path branched off from the optical path of the OCT optical system 8 by the dichroic mirror 83.

The fixation projection system 4 presents a fixation target to the subject's eye E. A fixation unit 40 is disposed in the optical path of the fixation projection system 4. The fixation unit 40 is controlled by a processing unit 9, which will be described later, and is movable along the optical path of the fixation projection system 4. The fixation unit 40 includes a liquid crystal panel 41. A relay lens 42 is disposed between the dichroic mirror 83 and the fixation unit 40.

The liquid crystal panel 41, controlled by the processing unit 9, displays a pattern representing a fixation target. By changing the display position of the pattern on the screen of the liquid crystal panel 41, the fixation position of the subject's eye E can be changed. Fixation positions of the subject's eye E include a position for acquiring an image centered on the macular portion of the fundus Ef, a position for acquiring an image centered on the optic disc, and a position for acquiring an image centered on the center of the fundus between the macular portion and the optic disc. The display position of the pattern representing the fixation target can be changed as desired.

Light from the liquid crystal panel 41 passes through the relay lens 42, is transmitted through the dichroic mirror 83, passes through the relay lens 82, is reflected by the reflecting mirror 81, is transmitted through the dichroic mirror 67, and is reflected by the dichroic mirror 52. The light reflected by the dichroic mirror 52 passes through the objective lens 51 and is projected onto the fundus Ef. In some embodiments, the liquid crystal panel 41 and the relay lens 42 can each be moved independently in the optical axis direction.

(OCT optical system 8)
The OCT optical system 8 is an optical system for performing OCT measurement. Based on the result of a reflex measurement performed before the OCT measurement, the position of the focusing lens 87 is adjusted so that the end face of the optical fiber f1 is conjugate with the OCT measurement site and the optical system. The OCT measurement site may be any site of the subject's eye E, such as the fundus Ef or the anterior segment.

The OCT optical system 8 is provided on an optical path that is wavelength-separated from the optical path of the reflex measurement optical system by a dichroic mirror 67. The optical path of the fixation projection system 4 is coupled to the optical path of the OCT optical system 8 by a dichroic mirror 83. This allows the optical axes of the OCT optical system 8 and the fixation projection system 4 to be coaxially coupled.

The OCT optical system 8 includes an OCT unit 100. As shown in FIG. 2, the OCT unit 100 is provided with an optical system for performing OCT measurement (OCT photography, OCT scanning) on the subject's eye E. This optical system has a configuration similar to that of a conventional spectral domain type OCT device. That is, this optical system is configured to split light (low coherence light) from a broadband light source into reference light and measurement light, cause the measurement light that has passed through the subject's eye E (OCT measurement site) to interfere with the reference light that has passed through the reference light path to generate interference light, and detect the spectral components of this interference light. This detection result (detection signal) is sent to the processing unit 9.

The light source unit 101 outputs broadband low-coherence light L0. The low-coherence light L0 has wavelength components in the near-infrared wavelength band (approximately 800 nm to 900 nm) and has a temporal coherence length of approximately several tens of micrometers. In addition, near-infrared light having a central wavelength of approximately 1040 to 1060 nm, for example, a wavelength band that cannot be seen by the human eye, may be used as the low-coherence light L0.

Hereinafter, the light source unit 101 is assumed to output low-coherence light L0 having a wavelength component of 840 nm.

The light source unit 101 is composed of optical output devices such as a super luminescent diode (SLD), an LED, and an SOA (Semiconductor Optical Amplifier).

The low-coherence light L0 output from the light source unit 101 is guided by the optical fiber 102 to the fiber coupler 103 and split into the measurement light LS and the reference light LR.

The reference light LR is guided by the optical fiber 104 and reaches the attenuator (optical attenuator) 105. The attenuator 105 automatically adjusts the amount of light of the reference light LR guided by the optical fiber 104 under the control of the processing unit 9 using a known technique. The reference light LR whose amount of light has been adjusted by the attenuator 105 is guided by the optical fiber 104 and reaches the polarization controller (polarization adjuster) 106. The polarization controller 106 is a device that adjusts the polarization state of the reference light LR guided through the optical fiber 104, for example, by applying external stress to the looped optical fiber 104. Note that the configuration of the polarization controller 106 is not limited to this, and any known technique can be used. The reference light LR whose polarization state has been adjusted by the polarization controller 106 reaches the fiber coupler 109.

The measurement light LS generated by the fiber coupler 103 is guided by the optical fiber f1 to the collimator lens 90 (Figure 1), where it is collimated into a parallel beam. The measurement light LS then passes through the optical path length changer 89, the optical scanner 88, the focusing lens 87, the relay lens 85, and the reflecting mirror 84 to reach the dichroic mirror 83.

In some embodiments, the focusing lens 87 and the optical scanner 88 are housed in a single unit that can move in the optical axis direction. This allows the focusing lens 87 and the optical scanner 88 to move in the optical axis direction while maintaining the optical positional relationship between them. By configuring the focusing lens 87 and the optical scanner 88 to be movable as a unit in this manner, it is possible to adjust the optical system while maintaining the conjugate relationship between the optical scanner 88 and the subject's eye E. Furthermore, with this configuration, by changing the focal length f of the focusing lens 87, it is possible to easily change the magnification relationship between the pupil of the subject's eye E and the optical scanner 88.

In some embodiments, the focusing lens 87 and the optical scanner 88 are moved independently in the optical axis direction within the unit. In some embodiments, the focusing lens 87 and the optical scanner 88 are moved independently or integrally in the optical axis direction under control of the processing unit 9. For example, the pupil of the subject's eye E is positioned at the focal position of the objective lens 51, and the deflection surface of the optical scanner 88 is positioned at the focal position of the focusing lens 87 (when the optical scanner 88 is positioned at the focal position of the focusing lens 87, the pupil conjugate relationship is maintained, and the deflection surface of the optical scanner 88 is positioned at the pupil conjugate position).

The optical path length change unit 89 changes the optical path length of the measurement light LS. By changing the optical path length of the measurement light LS, it is possible to change the difference between the optical path length of the reference light LR and the optical path length of the measurement light LS. For example, the optical path length change unit 89 includes a retroreflector that can move along the optical path of the measurement light LS and the optical path of the return light of the measurement light LS, and changes the optical path length of the measurement light LS by moving the retroreflector.

The optical scanner 88 deflects the measurement light LS one-dimensionally or two-dimensionally.

In some embodiments, the optical scanner 88 includes a first galvanometer mirror and a second galvanometer mirror. The first galvanometer mirror deflects the measurement light LS so as to scan the OCT measurement site in a horizontal direction perpendicular to the optical axis of the OCT optical system 8. The second galvanometer mirror deflects the measurement light LS deflected by the first galvanometer mirror so as to scan the imaging site in a vertical direction perpendicular to the optical axis of the OCT optical system 8. Examples of the scanning mode of the measurement light LS by such an optical scanner 88 include horizontal scan, vertical scan, cross scan, radial scan, circular scan, concentric circle scan, and spiral scan.

In some embodiments, the optical scanner 88 includes a MEMS scanner (MEMS mirror scanner) that two-dimensionally deflects the measurement light LS. The MEMS scanner deflects the measurement light LS so as to scan the OCT measurement site in horizontal and vertical directions perpendicular to the optical axis of the OCT optical system 8.

In addition, the optical scanner 88 may be configured to include a polygon mirror, a rotating mirror, a dowel prism, a double dowel prism, a rotation prism, etc., in addition to the galvanometer mirror and the MEMS scanner.

The measurement light LS that reaches the dichroic mirror 83 is reflected by the dichroic mirror 83, passes through the relay lens 82, and is reflected by the reflecting mirror 81. The measurement light LS reflected by the reflecting mirror 81 is reflected by the dichroic mirror 52, refracted by the objective lens 51, and irradiated onto the OCT measurement site. The measurement light LS is scattered (including reflected) at various depth positions of the OCT measurement site. The backscattered light of the measurement light LS by the OCT measurement site travels in the opposite direction along the same path as the outward path and is guided to the fiber coupler 103, and reaches the fiber coupler 109 via the optical fiber 108.

The fiber coupler 109 causes interference between the backscattered light of the measurement light LS and the reference light LR that has passed through the attenuator 105, etc. The interference light LC thus generated is guided by the optical fiber 110 and emitted from the emission end 111. The interference light LC is then collimated by the collimator lens 112, dispersed (spectrally resolved) by the diffraction grating (spectroscope) 113, and focused by the zoom optical system 114 to be projected onto the light receiving surface of the CCD image sensor 115. Note that although the diffraction grating 113 shown in FIG. 2 is a transmissive type, it is also possible to use other types of spectroscopic elements, such as a reflective diffraction grating.

The CCD image sensor 115 is, for example, a line sensor that has two or more light receiving elements (detection elements) arranged in an array, and detects each spectral component of the dispersed interference light LC and converts it into an electric charge. The CCD image sensor 115 accumulates the electric charge to generate a detection signal, which is then sent to the processing unit 9.

In this embodiment, a Michelson-type interferometer is used, but any type of interferometer, such as a Mach-Zehnder type, can be used as appropriate. Also, instead of the CCD image sensor, other types of image sensors, such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor, can be used.

In addition, in the configuration shown in FIG. 1, the optical path length change unit 89 is configured to change the optical path length of the measurement light LS to change the difference between the optical path length of the measurement light LS and the optical path length of the reference light LR, but the configuration according to the embodiment is not limited to this. For example, the optical path length of the reference light LR may be changed by a known method to change the difference between the optical path length of the measurement light LS and the optical path length of the reference light LR.

The processing unit 9 calculates the refractive power value from the measurement results obtained using the refraction measurement optical system, and based on the calculated refractive power value, moves the refraction measurement light source 61 and the focusing lens 74 in the optical axis direction to a position where the fundus Ef, the refraction measurement light source 61, and the image sensor 59 are conjugate. In some embodiments, the processing unit 9 moves the focusing lens 87 and the optical scanner 88 in the optical axis direction in conjunction with the movement of the focusing lens 74. In some embodiments, the processing unit 9 moves the liquid crystal panel 41 (fixation unit 40) in the optical axis direction in conjunction with the movement of the refraction measurement light source 61 and the focusing lens 74.

In the above embodiment, at least one function of the focusing lenses 74, 87 may be realized by a liquid crystal lens or a liquid lens.

<Processing system configuration>
The configuration of the processing system of the ophthalmic apparatus 1000 will be described. Examples of the functional configuration of the processing system of the ophthalmic apparatus 1000 are shown in Figs. 3 to 5. Fig. 3 shows an example of a functional block diagram of the processing system of the ophthalmic apparatus 1000. Fig. 4 shows an example of a functional block diagram of the OCT optical system 8 in Fig. 3 which is the processing target of the processing unit 9. Fig. 5 shows an example of a functional block diagram of the data processing unit 250 in Fig. 3.

The processing unit 9 controls each part of the ophthalmic device 1000. The processing unit 9 can also execute various types of arithmetic processing. The processing unit 9 includes a processor. The processing unit 9 realizes the functions according to the embodiment, for example, by reading and executing a program stored in a memory circuit or a storage device.

The processing unit 9 includes a control unit 210 and an arithmetic processing unit 220. The ophthalmic device 1000 also includes movement mechanisms 40D, 74D, 87D, 200, a display unit 270, an operation unit 280, and a communication unit 290.

The moving mechanism 200 is a mechanism for moving the head unit housing the optical system in the X, Y, and Z directions. For example, the moving mechanism 200 is provided with an actuator that generates a driving force for moving the head unit, and a transmission mechanism that transmits this driving force. The actuator is, for example, a pulse motor. The transmission mechanism is, for example, a combination of gears or a rack and pinion. The control unit 210 (main control unit 211) controls the moving mechanism 200 by sending a control signal to the actuator.

The moving mechanism 40D is a mechanism for moving the fixation unit 40 in the optical axis direction of the fixation projection system 4 (the optical axis direction of the objective lens 51). For example, like the moving mechanism 200, the moving mechanism 40D is provided with an actuator that generates a driving force for moving the fixation unit 40, and a transmission mechanism that transmits this driving force. The actuator is, for example, a pulse motor. The transmission mechanism is, for example, a combination of gears or a rack and pinion. The control unit 210 (main control unit 211) controls the moving mechanism 40D by sending a control signal to the actuator.

The moving mechanism 74D is a mechanism for moving the focusing lens 74 in the optical axis direction of the reflex measurement light receiving system 7. For example, like the moving mechanism 200, the moving mechanism 74D is provided with an actuator that generates a driving force for moving the focusing lens 74, and a transmission mechanism that transmits this driving force. The actuator is, for example, a pulse motor. The transmission mechanism is, for example, a combination of gears or a rack and pinion. The control unit 210 (main control unit 211) controls the moving mechanism 74D by sending a control signal to the actuator.

The moving mechanism 87D is a mechanism for moving the focusing lens 87 in the optical axis direction of the OCT optical system 8 (the optical axis direction of the objective lens 51). For example, similar to the moving mechanism 200, the moving mechanism 87D is provided with an actuator that generates a driving force for moving the focusing lens 87, and a transmission mechanism that transmits this driving force. The actuator is, for example, a pulse motor. The transmission mechanism is, for example, a combination of gears or a rack and pinion. The control unit 210 (main control unit 211) controls the moving mechanism 87D by sending a control signal to the actuator.

In some embodiments, the control of the moving mechanism 87D includes controlling the movement of the focusing lens 87 in the optical axis direction, controlling the movement of the focusing lens 87 to a focusing reference position corresponding to the imaging region, and controlling the movement within a movement range (focusing range) corresponding to the imaging region. For example, the main control unit 211 controls the moving mechanism 87D by sending a control signal to the actuator, and moves the focusing lens 87 in the optical axis direction.

(Control unit 210)
The control unit 210 includes a processor and controls each unit of the ophthalmic apparatus. The control unit 210 includes a main control unit 211 and a storage unit 212. The storage unit 212 stores in advance computer programs for controlling the ophthalmic apparatus 1000. The computer programs include an alignment system control program, a keratoconjugation system control program, a fixation system control program, an anterior eye observation system control program, a reflex measurement projection system control program, a reflex measurement light receiving system control program, an OCT optical system control program, a calculation processing program, and a user interface program. The main control unit 211 operates according to such computer programs, and the control unit 210 executes control processing.

The main control unit 211 performs various controls of the ophthalmic device as a measurement control unit.

Control of the alignment system 1 includes control of the anterior eye camera 14.

Control of the anterior eye cameras 14 includes adjusting the exposure, gain, and detection rate of each anterior eye camera, and controlling the synchronization of the image capture of the two anterior eye cameras 14. In some embodiments, the two anterior eye cameras 14 are controlled so that the exposure conditions, gain, and detection rate of the two anterior eye cameras are substantially identical.

Control of the keratometry system 3 includes control of the keratin ring light source 32.

The control of the keratinizing light source 32 includes turning the light source on and off, adjusting the light intensity, and adjusting the aperture. This causes the keratinizing light source 32 to be switched on and off, and changes the light intensity. The main control unit 211 causes the calculation processing unit 220 to execute a known calculation on the keratinizing image detected by the image sensor 59. This allows the corneal shape parameters of the test eye E to be found.

Control of the fixation projection system 4 includes control of the liquid crystal panel 41 and movement control of the fixation unit 40.

Control of the liquid crystal panel 41 includes turning the display of the fixation target on and off, switching the fixation target according to the type of examination or measurement, and switching the display position of the fixation target. The main controller 211 controls the moving mechanism 40D by sending a control signal to the actuator, and moves at least the liquid crystal panel 41 in the optical axis direction. This adjusts the position of the liquid crystal panel 41 so that the liquid crystal panel 41 and the fundus Ef are optically conjugate.

Control of the anterior eye observation system 5 includes control of the anterior eye illumination light source 50 and control of the image sensor 59.

The control of the anterior eye illumination light source 50 includes turning the light source on and off, adjusting the light intensity, and adjusting the aperture. This causes the anterior eye illumination light source 50 to be switched on and off, and the light intensity to be changed. The control of the image sensor 59 includes adjusting the exposure, gain, and detection rate of the image sensor 59. The main control unit 211 captures the signal detected by the image sensor 59, and causes the calculation processing unit 220 to perform processing such as forming an image based on the captured signal.

Control of the reflex measurement projection system 6 includes control of the reflex measurement light source 61 and control of the rotary prism 66.

The control of the reflex measurement light source 61 includes turning the light source on and off, adjusting the light intensity, and adjusting the aperture. This causes the reflex measurement light source 61 to be switched on and off, or the light intensity to be changed. For example, the reflex measurement projection system 6 includes a moving mechanism that moves the reflex measurement light source 61 in the optical axis direction. This moving mechanism is provided with an actuator that generates a driving force for moving the moving mechanism, and a transmission mechanism that transmits this driving force, similar to the moving mechanism 200. The main control unit 211 controls the moving mechanism by sending a control signal to the actuator, and moves the reflex measurement light source 61 in the optical axis direction. The control of the rotary prism 66 includes controlling the rotation of the rotary prism 66. For example, a rotating mechanism that rotates the rotary prism 66 is provided, and the main control unit 211 rotates the rotary prism 66 by controlling this rotating mechanism.

The control of the reflex measurement light receiving system 7 includes control to move the reflex measurement light source 61 and the focusing lens 74 in the optical axis direction according to the refractive power of the test eye E, for example, so that the reflex measurement light source 61, the fundus Ef, and the image sensor 59 are optically conjugate. In this case, the main control unit 211 controls the movement mechanism 74D, etc. according to the refractive power of the test eye E to position the reflex measurement light source 61, the fundus Ef, and the image sensor 59 at positions where they are approximately optically conjugate.

Control over the OCT optical system 8 includes control over the optical scanner 88, the optical path length changer 89, and the OCT unit 100. Control over the OCT unit 100 includes control over the light source unit 101, the attenuator 105, the polarization controller 106, the zoom optical system 114, and the CCD image sensor 115.

Control of the optical scanner 88 includes setting a scan mode for scanning the measurement site with a predetermined scan pattern, controlling the scan range, and controlling the scan speed. By controlling the scan range (scan start position and scan end position), it is possible to control the angle range of the deflection plane that deflects the measurement light LS. By controlling the scan speed, it is possible to control the speed at which the angle of the deflection plane is changed. The main control unit 211 controls at least one of the scan mode, scan range, and scan speed by outputting a control signal to the optical scanner 88.

The control of the optical path length changing unit 89 includes control of the optical path length of the measurement light LS. The main control unit 211 outputs a control signal to the optical path length changing unit 89, causing the optical path length changing unit 89 to change the optical path length of the measurement light LS.

The control of the light source unit 101 includes turning the light source on and off, adjusting the light intensity, and adjusting the aperture. The control of the attenuator 105 includes adjusting the light intensity of the reference light LR. The control of the polarization controller 106 includes adjusting the polarization state of the reference light LR. The control of the zoom optical system 114 includes controlling the optical magnification. The control of the CCD image sensor 115 includes adjusting the exposure, gain, and detection rate of the CCD image sensor 115. The main control unit 211 takes in the signal detected by the image sensor 115, and causes the calculation processing unit 220 to execute processing such as forming an image based on the taken-in signal.

The main control unit 211 also performs processes for writing data to the memory unit 212 and reading data from the memory unit 212.

(Memory unit 212)
The storage unit 212 stores various data. Examples of data stored in the storage unit 212 include objective measurement results (OCT measurement results), image data of OCT images, image data of anterior eye images, subjective test results, and subject eye information. The subject eye information includes information about the subject, such as a patient ID and name, and information about the subject eye, such as left/right eye identification information. The storage unit 212 also stores various programs and data for operating the ophthalmic apparatus.

(Calculation processing unit 220)
The arithmetic processing unit 220 includes a processor and executes various arithmetic processing. A storage unit (e.g., the storage unit 212) not shown in the figure stores computer programs for executing various arithmetic processing in advance. The processor operates according to the computer programs to realize the functions of each unit that executes various arithmetic processing.

As shown in FIG. 3, the calculation processing unit 220 includes an eye refractive power calculation unit 230, an image forming unit 240, and a data processing unit 250. The eye refractive power calculation unit 230 calculates the eye refractive power of the test eye E. The image forming unit 240 forms an OCT image based on the detection result of the interference light LC obtained using the OCT optical system 8. The data processing unit 250 performs various data processing (image processing) and analysis processing on the measurement results (detection result of the interference light LC, etc.) obtained using the optical system provided in the ophthalmic device 1000 and the OCT image formed by the image forming unit 240.

(Eye refractive power calculation unit 230)
The ocular refractive power calculation unit 230 analyzes a ring image (pattern image) obtained by receiving the return light of the ring-shaped light beam (ring-shaped measurement pattern) projected on the fundus Ef by the reflex measurement projection system 6 with the imaging element 59. For example, the ocular refractive power calculation unit 230 obtains the center of gravity of the ring image from the luminance distribution in the image in which the obtained ring image is depicted, obtains the luminance distribution along a plurality of scanning directions extending radially from the center of gravity, and identifies the ring image from the luminance distribution. Next, the ocular refractive power calculation unit 230 obtains an ellipse approximation of the identified ring image, and obtains the spherical power, the cylindrical power, and the cylindrical axis angle by substituting the major axis and minor axis of the ellipse into a known formula. Alternatively, the ocular refractive power calculation unit 230 can obtain parameters of the ocular refractive power based on the deformation and displacement of the ring image relative to the reference pattern.

The eye refractive power calculation unit 230 also calculates the corneal refractive power, the degree of corneal astigmatism, and the corneal astigmatism axis angle based on the keratinizing image acquired by the anterior eye observation system 5. For example, the eye refractive power calculation unit 230 calculates the corneal curvature radius of the principal meridian and the principal meridian of the anterior cornea by analyzing the keratinizing image, and calculates the above parameters based on the corneal curvature radius.

(Image forming unit 240)
The image forming unit 240 forms image data of the OCT image of the test eye E based on the detection signal of the interference light LC obtained by the CCD image sensor 115. That is, the image forming unit 240 forms image data of the test eye E based on the detection result of the interference light LC by the interference optical system. This processing includes filtering, FFT (Fast Fourier Transform), and other processing, as in the conventional spectral domain type OCT. The image data acquired in this manner is a data set including a group of image data formed by imaging the reflection intensity profile in a plurality of A-lines (paths of each measurement light LS in the test eye E).

To improve image quality, multiple data sets collected by repeating the same scan pattern multiple times can be superimposed (averaged).

(Data Processing Unit 250)
The data processing unit 250 performs various data processing (image processing) and analysis processing on the OCT image formed by the image forming unit 240 or the detection signal of the interference light LC obtained by the CCD image sensor 115. For example, the data processing unit 250 executes correction processing such as luminance correction and dispersion correction of the image. In addition, the data processing unit 250 performs various image processing and analysis processing on the image (anterior eye image, etc.) obtained by using the anterior eye observation system 5.

The data processing unit 250 can perform known image processing such as an interpolation process that interpolates pixels between OCT images (tomographic images) formed by the image forming unit 240 to form image data of a three-dimensional image of the fundus Ef or the anterior segment. The image data of the three-dimensional image means image data in which the positions of pixels are defined by a three-dimensional coordinate system. The image data of the three-dimensional image includes image data consisting of three-dimensionally arranged voxels. This image data is called volume data or voxel data. When an image based on the volume data is to be displayed, the data processing unit 250 performs a rendering process (such as volume rendering or MIP (Maximum Intensity Projection)) on the volume data to form image data of a pseudo three-dimensional image as viewed from a specific line of sight. The pseudo three-dimensional image is displayed on a display device such as the display unit 270.

It is also possible to form stack data of multiple tomographic images as image data for a three-dimensional image. Stack data is image data obtained by arranging multiple tomographic images obtained along multiple scan lines in three dimensions based on the positional relationship of the scan lines. In other words, stack data is image data obtained by expressing multiple tomographic images that were originally defined by separate two-dimensional coordinate systems using a single three-dimensional coordinate system (i.e., embedding them in a single three-dimensional space).

The data processing unit 250 can perform various rendering operations on the acquired three-dimensional data set (volume data, stack data, etc.) to form B-mode images (longitudinal and axial images) in any cross section, C-mode images (transverse and horizontal images) in any cross section, projection images, shadowgrams, and the like. Images of any cross section, such as B-mode images and C-mode images, are formed by selecting pixels (voxels) on a specified cross section from the three-dimensional data set. Projection images are formed by projecting the three-dimensional data set in a specified direction (Z direction, depth direction, axial direction). Shadowgrams are formed by projecting a part of the three-dimensional data set (e.g., partial data corresponding to a specific layer) in a specified direction. Images with the front side of the subject's eye as a viewpoint, such as C-mode images, projection images, and shadowgrams, are called en-face images.

The data processing unit 250 can construct B-mode images or frontal images (vessel-enhanced images, angiograms) in which retinal blood vessels and choroidal blood vessels are emphasized based on data (e.g., B-scan image data) collected in a time series by OCT scanning. For example, time-series OCT data can be collected by repeatedly scanning approximately the same area of the subject's eye E.

In some embodiments, the data processor 250 compares time-series B-scan images obtained by B-scanning approximately the same area, and constructs an enhanced image in which the changed area is emphasized by converting pixel values of the changed area in signal intensity into pixel values corresponding to the change. Furthermore, the data processor 250 extracts information of a predetermined thickness in the desired area from the multiple enhanced images constructed, and constructs it as an en-face image to form an OCTA image.

Images generated by the data processing unit 250 (e.g., 3D images, B-mode images, C-mode images, projection images, shadowgrams, OCTA images) are also included in the OCT images.

The data processing unit 250 also identifies a characteristic position corresponding to a characteristic portion of the anterior eye by analyzing each of the two captured images acquired substantially simultaneously by the two anterior eye cameras 14. The characteristic portion of the anterior eye is, for example, the pupil center (pupil centroid). The data processing unit 250 calculates the three-dimensional position of the characteristic portion (i.e., the three-dimensional position of the subject's eye E) by applying known trigonometric methods to the positions of the two anterior eye cameras 14 and the characteristic positions corresponding to the characteristic portions in the two identified captured images. The calculated three-dimensional position can be used to align the optical system with the subject's eye E.

Furthermore, the ophthalmic device 1000 is capable of measuring intraocular distances such as the axial length of the subject eye E by performing an OCT scan on the subject eye E. In the embodiment, the data processing unit 250 realizes the function of an axial length calculation unit.

The data processing unit 250 can calculate the distance between the position corresponding to the corneal apex and the position corresponding to the RPE layer as the axial length based on the detection results of the interference light LC obtained by performing an OCT scan.

Here, in the intensity profile of the interference signal generated by detecting the interference light LC, if the peak corresponding to the RPE layer is close to peaks corresponding to layer regions such as the IS/OS line and Bruch's membrane, and the peak level corresponding to the RPE layer is lower than the peak level corresponding to the IS/OS line, etc., the peak corresponding to the RPE layer will be buried in the peak corresponding to the IS/OS line, etc. This may result in time being required to identify the peak corresponding to the RPE layer, failure to identify the peak corresponding to the RPE layer, or erroneous detection of the peak corresponding to the RPE layer.

First, the data processing unit 250 identifies a depth position corresponding to the IS/OS line or Bruch's membrane (first layer region) based on the detection result of the interference light LC (the intensity profile of the interference light LC). Next, the data processing unit 250 adds a predetermined offset value to the identified depth position to calculate a depth position corresponding to the RPE layer (second layer region) in the fundus. This makes it possible to quickly and reliably identify the depth position corresponding to the RPE layer. As a result, it becomes possible to improve the reliability of intraocular distances such as axial length calculated using the identified RPE layer, compared to when the RPE layer is directly identified.

The data processing unit 250 also identifies the distance corresponding to the axial length, which is the distance between the position corresponding to the corneal apex and the position corresponding to the RPE layer, as the optical path length OPL, and calculates the axial length (physical length) AL according to the relational expression shown in equation (1).

In formula (1), OPL represents the optical path length, AL represents the physical length of the axial length, and n represents the refractive index of the human eye (group index). Here, the refractive index differs for each component of the eye (cornea, lens, etc.), but n represents the refractive index when the eyeball is converted into a single component.

Here, the refractive index n has wavelength dependency. This means that the axial length calculated as the physical length changes depending on the measurement wavelength. For example, if the optical path length when the axial length is measured with the measurement light LS having a measurement wavelength of 840 nm is expressed as OPL ₈₄₀ and the refractive index at 840 nm is expressed as n ₈₄₀ , a relational expression such as formula (2) is obtained. Similarly, for example, if the optical path length when the axial length is measured with the measurement light LS having a measurement wavelength of 780 nm is expressed as OPL ₇₈₀ and the refractive index at 780 nm is expressed as n ₇₈₀ , a relational expression such as formula (3) is obtained.

This means that the axial length measured using measurement light LS with a measurement wavelength of 840 nm is different from the axial length measured using measurement light LS with a measurement wavelength of 780 nm.

Therefore, in the embodiment, wavelength correction is performed on the axial length measured using measurement light LS with a measurement wavelength of 840 nm. This makes it possible to calculate the axial length at a wavelength other than 840 nm (e.g., 780 nm) (axial length measured using measurement light LS with other wavelength components).

More precisely, the axial length measurement value obtained by the non-contact axial length measurement device according to the embodiment is different from the axial length measurement value obtained by the ultrasonic axial length measurement device.

Therefore, in the embodiment, the measurement value of the axial length measured using measurement light LS with a measurement wavelength of 840 nm can be converted to the measurement value of the axial length obtained by an ultrasonic axial length measurement device.

As shown in FIG. 5, such a data processing unit 250 includes a layer region identification unit 251, a layer region position calculation unit 252, an axial length calculation unit 253, a wavelength correction unit 254, and an axial length conversion unit 255.

(Layer area identification unit 251)
The layer region specifying part 251 specifies a depth position corresponding to a predetermined part of the subject's eye E based on the detection result of the interference light LC acquired by the OCT unit 100. Examples of a predetermined layer region in the fundus Ef include the IS/OS line and Bruch's membrane.

In the embodiment, the layer region identification unit 251 identifies a depth position corresponding to the corneal apex in the anterior segment (cornea Cr) and a depth position corresponding to the IS/OS line in the fundus Ef.

(Layer region position calculation unit 252)
The layer region position calculation unit 252 adds a predetermined offset value to the depth position specified by the layer region specification unit 251, thereby determining whether the layer region of the subject's eye E is different from the region specified by the layer region specification unit 251. An example of the other portion is the RPE layer.

Figure 6 shows an explanatory diagram of the operation of the layer region position calculation unit 252 according to the embodiment. Figure 6 shows a schematic diagram of an example of an OCT image (tomographic image) of the fundus Ef.

As described above, it is assumed that the layer region identification unit 251 has identified the depth position corresponding to the IS/OS line. The layer region position calculation unit 252 calculates a depth position corresponding to another layer region different from the IS/OS line based on the IS/OS line by adding an offset value dt to the depth position corresponding to the IS/OS line. Therefore, the layer region position calculation unit 252 can calculate the depth position corresponding to the RPE layer by adding an offset value dt to the depth position corresponding to the IS/OS line.

Examples of the offset value dt include a constant, a variable that varies depending on the subject or the eye being examined, etc.

When the offset value dt is a constant, the offset value dt is determined based on normative data obtained in advance by measuring multiple test eyes. For example, the offset value dt is determined by averaging the measurement values for multiple test eyes.

When the offset value dt is variable, the offset value dt can be determined according to information about the subject. The offset value dt can also be determined according to information about the subject's eye E. The information about the subject's eye E includes the intraocular distance (e.g., the distance between specific layer regions in the fundus Ef). In some embodiments, the offset value dt is determined according to the distance between the depth position corresponding to the IS/OS line of the subject's eye E and the depth position corresponding to Bruch's membrane.

(Ecular axis length calculation unit 253)
The axial length calculation part 253 is configured to calculate a depth position (first depth position) of the layer region specified by the layer region specification part 251 and a depth position of another layer different from the layer region calculated by the layer region position calculation part 252. The distance to the depth position (second depth position) of the region is calculated as the axial length (optical path length). When the axial length is calculated as a physical length, the axial length calculation unit 253 calculates the distance from the depth position (second depth position) of the region as the axial length (optical path length) using the formula (1) The physical length of the eye's axial length is calculated according to the following:

Figure 7 shows an explanatory diagram of the operation of the axial length calculation unit 253 according to the embodiment. Figure 7 shows a schematic diagram of an example of an intensity profile of an interference signal obtained by performing an OCT scan on the anterior segment, and an example of an intensity profile of an interference signal obtained by performing an OCT scan on the fundus Ef. In Figure 7, parts that are the same as those in Figure 1 or Figure 6 are given the same reference numerals, and descriptions thereof will be omitted as appropriate.

For example, it is assumed that the alignment between the subject eye E and the optical system shown in FIG. 1 has been completed using the alignment system 1 and the moving mechanism 200 so that the optical axis of the OCT optical system 8 coincides with the center of the pupil of the subject eye E. After the alignment is completed, the layer region identifying unit 251 searches for a peak in the intensity profile of the interference signal obtained by performing an OCT scan on the anterior segment, and identifies the position of the identified peak as the depth position za corresponding to the corneal apex.

Next, the layer region identification unit 251 searches for a peak in the intensity profile of the interference signal obtained by performing an OCT scan on the fundus Ef after the alignment is completed, and identifies the position of the peak corresponding to the IS/OS line (or Bruch's membrane) as the depth position zf. The layer region position calculation unit 252 calculates the depth position (zf+dt) corresponding to the RPE layer by adding an offset value dt to the depth position zf corresponding to the IS/OS line.

Here, when the peak corresponding to the RPE layer in the intensity profile of the interference signal is close to a peak corresponding to another layer region, and the peak level corresponding to the RPE layer is lower than the peak level corresponding to the other layer region, it becomes difficult to identify the peak corresponding to the RPE layer. In response to this, in the embodiment, a depth position corresponding to the IS/OS line (or Bruch's membrane), where the peak is easy to identify, is identified, and an offset value is added to the identified depth position. This makes it possible to accurately identify the representative position on the fundus Ef side in a short time without failing to identify the representative position on the fundus Ef side.

The axial length calculation unit 253 calculates the distance between the depth position za corresponding to the corneal apex identified by the layer region identification unit 251 and the depth position (zf+dt) corresponding to the RPE layer calculated by the layer region position calculation unit 252 as the axial length AL0 (optical path length).

As described above, the representative position on the fundus Ef side is accurately identified in a short time without failing to be identified, thereby improving the measurement accuracy of the axial length of the test eye E.

In some embodiments, a single OCT scan is used to obtain an intensity spectrum of the interference signal ranging from the anterior segment to the fundus Ef, and the depth position corresponding to the corneal apex and the depth position corresponding to the IS/OS line are identified from the obtained intensity spectrum.

In some embodiments, the layer region identifying unit 251 identifies the depth position of a layer region of the fundus Ef other than the IS/OS line (or Bruch's membrane), and the layer region position calculating unit 252 calculates the depth position of the RPE layer by adding an offset value to the identified depth position.

(Wavelength correction unit 254)
The wavelength correction unit 254 performs wavelength correction on the axial length calculated by the axial length calculation unit 253 as shown in Equation (4), thereby correcting the wavelength ( For example, the axial length is corrected to the axial length obtained using a measurement light having a measurement wavelength of 780 nm.

Here, it is assumed that the axial length (optical path length) OPL _{840 has been calculated by the axial length calculation unit 253. At this time, the wavelength correction unit 254 multiplies the axial length (optical path length) OPL 840} by the ratio of the refractive index of the human eye at 840 nm (n ₈₄₀ ) to the refractive index of the human eye at 780 nm (n ₇₈₀ ). This corrects the axial length (optical path length) OPL ₈₄₀ to the axial length (optical path length) OPL ₇₈₀ obtained using measurement light having a wavelength component of 780 nm.

(Ecular axis length conversion unit 255)
The axial length conversion section 255 converts the axial length that has been wavelength-corrected by the wavelength correction section 254 into an axial length (physical length) obtained using an ultrasonic axial length measurement device.

For example, the axial length conversion unit 255 converts the axial length (optical path length) that has been wavelength-corrected by the wavelength correction unit 254 into the axial length (physical length) obtained using an ultrasonic axial length measurement device according to formula (5). For example, Non-Patent Document 1 discloses formula (5) as a formula for converting the optical path length obtained by a non-contact axial length measurement device into the axial length measured using an ultrasonic axial length measurement device.

Here, it is assumed that the axial length (optical path length) OPL ₇₈₀ is calculated by the wavelength correction unit 254. At this time, the axial length conversion unit 255 calculates the axial length (physical length) AL1 by substituting the axial length (optical path length) OPL ₇₈₀ calculated by the wavelength correction unit 254 into equation (5).

In some embodiments, the axial length conversion unit 255 calculates the axial length (physical length) AL1 by directly substituting the axial length (optical path length) OPL ₈₄₀ calculated by the axial length calculation unit 253 into equation (6) without performing wavelength correction according to equation (4) by the wavelength correction unit 254.

In some embodiments, the main controller 211 controls the display unit 270 described below to display the axial length (optical path length) calculated by the axial length calculator 253 and the axial length (optical path length) corrected by the wavelength corrector 254 on the same screen. In some embodiments, the main controller 211 controls the display unit 270 described below to display the axial length (physical length) obtained by converting the axial length (optical path length) calculated by the axial length calculator 253 according to formula (2) and the axial length (physical length) obtained by converting the axial length (optical path length) corrected by the wavelength corrector 254 according to formula (3) on the same screen.

In some embodiments, the main control unit 211 controls the display unit 270 described below to display at least two of the axial length (physical length) calculated by the axial length calculation unit 253 and converted according to formula (2), the axial length (physical length) corrected by the wavelength correction unit 254 and converted according to formula (3), and the axial length (physical length) calculated by the axial length conversion unit 255 on the same screen.

According to the embodiment, it becomes possible to compare with high accuracy the measurement results of other axial length measurement devices that measure axial length using measurement light of different wavelengths, and with the measurement results of ultrasonic axial length measurement devices.

(Display section 270, operation section 280)
The display unit 270 serves as a user interface unit and displays information under the control of the control unit 210. The display unit 270 includes the display unit 10 shown in FIG.

The operation unit 280 is used as a user interface unit to operate the ophthalmic device. The operation unit 280 includes various hardware keys (joystick, buttons, switches, etc.) provided on the ophthalmic device. The operation unit 280 may also include various software keys (buttons, icons, menus, etc.) displayed on the touch panel display screen 10a.

At least a portion of the display unit 270 and the operation unit 280 may be configured as an integrated unit. A typical example of this is a touch panel type display screen 10a.

(Communication unit 290)
The communication unit 290 has a function for communicating with an external device (not shown). The communication unit 290 has a communication interface according to the connection form with the external device. An example of the external device is a spectacle lens measuring device for measuring the optical characteristics of a lens. The spectacle lens measuring device measures the degree of the spectacle lens worn by the subject, and inputs the measurement data to the ophthalmic device 1000. The external device may be any ophthalmic device, a device (reader) that reads information from a recording medium, or a device (writer) that writes information to a recording medium. Furthermore, the external device may be a hospital information system (HIS) server, a DICOM (Digital Imaging and Communication in Medicine) server, a doctor's terminal, a mobile terminal, a personal terminal, a cloud server, or the like. The communication unit 290 may be provided in, for example, the processing unit 9.

The IS/OS line or Bruch's membrane is an example of a "first layer region" according to an embodiment. The RPE layer is an example of a "second layer region" according to an embodiment. 840 nm is an example of a "first wavelength" according to an embodiment. 780 nm is an example of a "second wavelength" according to an embodiment.

<Example of operation>
The operation of the ophthalmologic apparatus 1000 according to the embodiment will be described.

Figure 8 shows an example of the operation of the ophthalmic device 1000. Figure 8 shows a flow diagram of an example of the operation of the ophthalmic device 1000. The memory unit 212 stores a computer program for realizing the processing shown in Figure 8. The main control unit 211 operates according to this computer program to execute the processing shown in Figure 8.

(S1: Alignment)
With the subject's face fixed on a face receiving portion (not shown), the examiner performs a predetermined operation on the operation portion 280, whereby the ophthalmologic apparatus 1000 performs alignment.

Specifically, the main controller 211 controls the two anterior eye cameras 14 to start photographing the anterior eye of the subject's eye E. When the two photographed images (anterior eye images) are acquired by the two anterior eye cameras 14, the main controller 211 controls the data processor 250 to analyze each of the two photographed images to identify a characteristic position corresponding to the pupil center, and calculates the three-dimensional position of the pupil center (subject's eye E) by applying a known trigonometric method to the positions of the two anterior eye cameras 14 and the characteristic positions in the identified two photographed images. The main controller 211 performs alignment of the optical system with respect to the subject's eye E by controlling the moving mechanism 200 based on the calculated three-dimensional position of the subject's eye E. Specifically, the main controller 211 controls the moving mechanism 200 based on the calculated three-dimensional position so as to align the optical axis of the OCT optical system 8 (optical axis of the objective lens 51) with the axis of the subject's eye E, and so that the distance of the optical system (objective lens 51) with respect to the subject's eye E is a predetermined working distance. Here, the working distance is a preset value, also called the working distance, and refers to the distance between the subject's eye E and the optical system during examination using the optical system.

In addition, when the anterior eye camera 14 captures video of the anterior eye from different directions in parallel, the main control unit 211 can perform tracking of the optical system in response to the movement of the subject eye E, for example, by performing the following processes (1) and (2).
(1) The data processing unit 250 sequentially analyzes two frames obtained substantially simultaneously in moving image capture by the two anterior eye cameras 14, thereby sequentially determining the three-dimensional position of the subject's eye E.
(2) The main control unit 211 sequentially controls the moving mechanism 200 based on the three-dimensional position of the subject's eye E sequentially obtained by the data processing unit 250, thereby causing the position of the optical system to follow the movement of the subject's eye E.

The main control unit 211 also moves the reflex measurement light source 61, the focusing lens 74, and the liquid crystal panel 41 along their respective optical axes to their origin positions (e.g., a position equivalent to 0D (diopter)).

(S2: Fundus OCT scan)
Next, the main controller 211 controls the OCT optical system 8 and the like to perform an OCT scan of the fundus Ef.

Specifically, the main controller 211 controls the moving mechanism 87D to move the focusing lens 87 in the optical axis direction so that the focal position of the measurement light LS is set on the fundus Ef. Next, the main controller 211 adjusts the light source unit 101, the attenuator 105, the polarization controller 106, the zoom optical system 114, the CCD image sensor 115, and the optical path length change unit 89. Next, the main controller 211 displays a pattern indicating a fixation target on the liquid crystal panel 41 at a display position corresponding to the desired fixation position. This allows the subject's eye E to gaze at the desired fixation position. The main controller 211 controls the optical scanner 88 to perform a scan with the measurement light LS over a predetermined scan range on the fundus Ef. The detection result of the interference light LC obtained by scanning the measurement light LS is sent to the image forming unit 240.

(S3: Anterior segment OCT scan)
Next, the main controller 211 controls the OCT optical system 8 and the like to perform an OCT scan on the anterior segment.

Specifically, the main controller 211 controls the moving mechanism 87D to move the focusing lens 87 in the optical axis direction so that the focal position of the measurement light LS is set on the anterior segment. Next, the main controller 211 adjusts the light source unit 101, the attenuator 105, the polarization controller 106, the zoom optical system 114, the CCD image sensor 115, and the optical path length changer 89. Next, the main controller 211 causes the liquid crystal panel 41 to display a pattern showing a fixation target at a display position corresponding to the desired fixation position. The main controller 211 controls the optical scanner 88 to perform a scan with the measurement light LS over a predetermined scan range in the anterior segment. The detection result of the interference light LC obtained by scanning the measurement light LS is sent to the image forming unit 240.

(S4: Identify IS/OS line)
Next, the main control unit 211 controls the layer region identification unit 251 to analyze the detection results of the interference light LC at the fundus Ef acquired in step S2 (or the OCT image of the fundus Ef) and identify the depth position corresponding to the IS/OS line.

The main controller 211 also controls the layer region identification unit 251 to analyze the detection result of the interference light LC in the anterior segment (or the OCT image of the anterior segment) acquired in step S3, and to identify the depth position corresponding to the corneal apex.

(S5: Add offset value)
Next, the main controller 211 controls the layer region position calculator 252 to add a predetermined offset value to the depth position of the IS/OS line identified in step S4, thereby identifying the depth position corresponding to the RPE layer.

(S6: Calculate axial length)
Next, the main controller 211 controls the axial length calculator 253 to calculate the distance between the depth position corresponding to the corneal apex identified in step S2 and the depth position corresponding to the RPE layer calculated in step S3 as the axial length (optical path length) OPL ₈₄₀ .

(S7: Wavelength correction)
Next, the main controller 211 controls the wavelength corrector 254 to perform wavelength correction on the axial length OPL ₈₄₀ calculated in step S6 according to equation (4), thereby correcting the axial length OPL 840 to the axial length OPL ₇₈₀ at 780 nm.

(S8: Convert axial length)
Next, the main controller 211 controls the axial length converter 255 to convert the axial length OPL ₇₈₀ corrected in step S7 into equation (5) to convert it into the axial length AL1 measured using the ultrasonic axial length measurement device.

In some embodiments, the main control unit 211 displays at least two of the calculation results of steps S6 to S8 on the same screen of the display unit 270. This makes it easy to compare the calculation results of steps S6 to S8.

This completes the operation of the ophthalmic device 1000 (end).

In the flow shown in FIG. 8, step S8 may convert the axial length OPL ₈₄₀ calculated in step S6 into the equation (6) to the axial length AL1 measured using an ultrasonic axial length measurement device.

[Action]
An ophthalmic apparatus, a control method for the ophthalmic apparatus, and a program according to an embodiment will be described.

The ophthalmic device (1000) according to the embodiment includes a layer region identification unit (251) and a layer region position calculation unit (252). The layer region identification unit identifies a first depth position (zf) corresponding to a first layer region in the fundus based on the detection result of interference light obtained by performing an OCT scan on the fundus (Ef) of the subject eye (E). The layer region position calculation unit calculates a second depth position (zf+dt) corresponding to a second layer region in the fundus by adding a predetermined offset value (dt) to the first depth position.

According to this aspect, even if it takes a long time to identify the second layer region, or if the identification fails or is erroneously detected, for example, because the intensity peak of the interference light (interference signal) corresponding to the second layer region is close to the intensity peak of the interference light corresponding to another layer region, it is possible to accurately identify the depth position of the second layer region in a short time.

In some embodiments, the first layer region is the IS/OS line and the second layer region is the retinal pigment epithelium layer.

According to this aspect, even if it takes a long time to identify the retinal pigment epithelium layer, or if identification fails or there is a false detection, it is possible to accurately identify the depth position of the retinal pigment epithelium layer in a short time.

In some embodiments, the layer region position calculation unit adds a different offset value to the first depth position depending on the test eye.

According to this aspect, the offset value is changed depending on the subject's eye, so that the depth position of the second layer region can be identified more accurately.

In some embodiments, the layer region identifying unit identifies the first depth position and a third depth position (za) corresponding to the corneal apex based on the detection result of the interference light. The ophthalmic apparatus includes an axial length calculating unit (253) that calculates the axial length of the subject's eye based on the third depth position and the second depth position.

According to this aspect, even if it takes a long time to identify the second layer region, or if identification fails or there is a false detection, the depth position of the second layer region can be identified accurately in a short time, making it possible to calculate the axial length with higher accuracy.

In some embodiments, the OCT scan is performed by irradiating the test eye with measurement light (LS) having a first wavelength (840 nm) as a measurement wavelength. The ophthalmic device includes a wavelength correction unit (254) that performs wavelength correction on the axial length calculated by the axial length calculation unit to correct the axial length to a second wavelength (780 nm) different from the first wavelength.

This aspect makes it possible to compare axial length measurements obtained at different measurement wavelengths, regardless of the wavelength dependence of the axial length measurements.

The ophthalmic device (1000) according to the embodiment includes an axial length calculation unit (253) and a wavelength correction unit (254). The axial length calculation unit calculates the axial length based on the detection result of interference light obtained by performing an OCT scan on the test eye (E) using measurement light (LS) having a first wavelength (840 nm) as a measurement wavelength. The wavelength correction unit performs wavelength correction on the axial length calculated by the axial length calculation unit, thereby correcting the axial length to a second wavelength (780 nm) different from the first wavelength.

This aspect makes it possible to compare axial length measurements obtained at different measurement wavelengths, regardless of the wavelength dependence of the axial length measurements.

In some embodiments, the wavelength correction unit corrects the axial length at the second wavelength by multiplying the axial length calculated by the axial length calculation unit by a ratio of the refractive index of the human eye at the first wavelength (n ₈₄₀ ) to the refractive index of the human eye at the second wavelength (n ₇₈₀ ).

This aspect makes it possible to correct the axial length to that obtained at the desired measurement wavelength through simple processing.

In some embodiments, the second wavelength component is 780 nm.

This aspect makes it possible to compare the measured axial length with that obtained using a non-contact axial length measuring device that uses a measurement wavelength of 780 nm.

Some embodiments include an axial length conversion unit (255) that converts the axial length corrected by the wavelength correction unit into an axial length obtained using an ultrasonic axial length measurement device.

This aspect makes it possible to compare the axial length measurement obtained by the ophthalmic device with the measurement results of the ultrasonic axial length measurement device with high accuracy.

In some embodiments, the axial length conversion unit converts the optical path length as the axial length corrected by the wavelength correction unit into a physical length as the axial length obtained using an ultrasonic axial length measurement device.

According to this aspect, it is possible to convert the measurement of axial length obtained using an ultrasonic axial length measurement device with simple processing.

Some embodiments include an OCT optical system (8) that splits light (L0) from a light source (light source unit 101) into measurement light (LS) and reference light (LR), irradiates the test eye with the measurement light, and detects interference light (LC) between the return light of the measurement light from the test eye and the reference light that has passed through the reference light path.

According to this aspect, it is possible to provide an ophthalmic device that can perform OCT on the subject's eye and accurately identify the depth position of the second layer region in the fundus in a short period of time.

The control method for the ophthalmic device (1000) according to the embodiment includes a layer region identification step and a layer region position calculation step. The layer region identification step identifies a first depth position (zf) corresponding to a first layer region in the fundus based on the detection result of interference light (LC) obtained by performing an OCT scan on the fundus (Ef) of the subject eye (E). The layer region position calculation step calculates a second depth position (zf+dt) corresponding to a second layer region in the fundus by adding a predetermined offset value (dt) to the first depth position.

According to this aspect, even if it takes a long time to identify the second layer region, or if the identification fails or is erroneously detected, for example, because the intensity peak of the interference light (interference signal) corresponding to the second layer region is close to the intensity peak of the interference light corresponding to another layer region, it is possible to accurately identify the depth position of the second layer region in a short time.

In some embodiments, the first layer region is the IS/OS line and the second layer region is the retinal pigment epithelium layer.

According to this aspect, even if it takes a long time to identify the retinal pigment epithelium layer, or if identification fails or there is a false detection, it is possible to accurately identify the depth position of the retinal pigment epithelium layer in a short time.

In some embodiments, the layer region identifying step identifies a first depth position and a third depth position (za) corresponding to the corneal apex based on the detection result of the interference light. The control method for an ophthalmic apparatus includes an axial length calculating step of calculating the axial length of the subject's eye based on the third depth position and the second depth position.

According to this aspect, even if it takes a long time to identify the second layer region, or if identification fails or there is a false detection, the depth position of the second layer region can be accurately identified in a short time, making it possible to calculate the axial length with higher accuracy.

In some embodiments, the OCT scan is performed by irradiating the test eye with measurement light having a first wavelength (840 nm) as the measurement wavelength. The control method for the ophthalmic device includes a wavelength correction step of correcting the axial length calculated in the axial length calculation step to a wavelength at a second wavelength (780 nm) different from the first wavelength.

This aspect makes it possible to compare axial length measurements obtained at different measurement wavelengths, regardless of the wavelength dependence of the axial length measurements.

The control method for the ophthalmic device (1000) according to the embodiment includes an axial length calculation step and a wavelength correction step. The axial length calculation step calculates the axial length based on the detection result of interference light obtained by performing an OCT scan on the subject's eye (E) using measurement light (LS) having a first wavelength (840 nm) as a measurement wavelength. The wavelength correction step performs wavelength correction on the axial length calculated in the axial length calculation step, thereby correcting the axial length to a second wavelength (780 nm) different from the first wavelength.

This aspect makes it possible to compare axial length measurements obtained at different measurement wavelengths, regardless of the wavelength dependence of the axial length measurements.

Some embodiments include an axial length conversion step in which the axial length corrected in the wavelength correction step is converted to an axial length obtained using an ultrasonic axial length measurement device.

This aspect makes it possible to compare the axial length measurement obtained by the ophthalmic device with the measurement results of the ultrasonic axial length measurement device with high accuracy.

The program according to the embodiment causes a computer to execute each step of the control method for an ophthalmic device described above.

According to this aspect, it is possible to provide a program that can accurately identify the depth position of the second layer region in a short time even when it takes a long time to identify the second layer region, or when identification fails or there is a false detection, for example, when the intensity peak of the interference light (interference signal) corresponding to the second layer region is close to the intensity peak of the interference light corresponding to another layer region.

＜Other＞
The embodiment described above is merely one example for carrying out the present invention. Anyone who wishes to carry out the present invention may make any modifications, omissions, additions, etc. within the scope of the gist of the present invention.

Reference Signs List 1 Alignment system 3 Keratometry system 4 Fixation projection system 5 Anterior segment observation system 6 Refractive measurement projection system 7 Refractive measurement light receiving system 8 OCT optical system 9 Processing unit 51 Objective lens 88 Optical scanner 210 Control unit 211 Main control unit 250 Data processing unit 251 Layer region identification unit 252 Layer region position calculation unit 253 Axial length calculation unit 254 Wavelength correction unit 255 Axial length conversion unit 1000 Ophthalmic device

Claims (14)

a layer region specifying unit that specifies a first depth position corresponding to an IS/OS line or a Bruch's membrane in the fundus based on a detection result of interference light obtained by performing an OCT scan on the fundus of the test eye;
a layer region position calculation unit that calculates a second depth position corresponding to a retinal pigment epithelium layer of the fundus by adding a predetermined offset value to the first depth position;
13. An ophthalmic device comprising: The ophthalmic apparatus according to claim 1 , wherein the layer region position calculation unit adds a different offset value to the first depth position depending on the subject's eye. the layer region specifying unit specifies the first depth position and a third depth position corresponding to a corneal apex based on a detection result of the interference light,
The ophthalmologic apparatus according to claim 1 or 2, further comprising an axial length calculation unit that calculates an axial length of the subject's eye based on the third depth position and the second depth position. The OCT scan is performed by irradiating the test eye with measurement light having a first wavelength as a measurement wavelength,
The ophthalmic apparatus according to claim 3 , further comprising a wavelength correction unit that performs wavelength correction on the axial length calculated by the axial length calculation unit to correct the axial length to a second wavelength different from the first wavelength. The ophthalmic device according to claim 4, wherein the wavelength correction unit corrects the axial length at the second wavelength by multiplying the axial length calculated by the axial length calculation unit by a ratio of the refractive index of the human eye at the first wavelength to the refractive index of the human eye at the second wavelength . The ophthalmic apparatus according to claim 4 or 5 , wherein the second wavelength is 780 nm. The ophthalmic device according to any one of claims 4 to 6 , further comprising an axial length conversion unit that converts the axial length corrected by the wavelength correction unit into an axial length obtained using an ultrasonic axial length measurement device. The ophthalmic apparatus according to claim 7 , wherein the axial length conversion unit converts the optical path length as the axial length corrected by the wavelength correction unit into a physical length as the axial length obtained by using the ultrasonic axial length measurement device. The ophthalmic device according to any one of claims 1 to 8, further comprising an OCT optical system that splits light from a light source into measurement light and reference light, irradiates the measurement light onto the subject's eye, and detects the interference light between return light of the measurement light from the subject's eye and the reference light that has passed through a reference light path . a layer region identifying step of identifying a first depth position corresponding to the IS/OS line or Bruch's membrane in the fundus based on a detection result of interference light obtained by performing an OCT scan on the fundus of the test eye;
a layer region position calculation step of calculating a second depth position corresponding to a retinal pigment epithelium layer in the fundus by adding a predetermined offset value to the first depth position;
A method for controlling an ophthalmic device, comprising: the layer region specifying step includes specifying the first depth position and a third depth position corresponding to a corneal apex based on a detection result of the interference light;
The control method for an ophthalmologic apparatus according to claim 10, further comprising: an axial length calculating step of calculating an axial length of the subject's eye based on the third depth position and the second depth position. The OCT scan is performed by irradiating the test eye with measurement light having a first wavelength as a measurement wavelength,
The method for controlling an ophthalmic apparatus according to claim 11, further comprising a wavelength correction step of performing wavelength correction on the axial length calculated in the axial length calculation step to correct the axial length to a second wavelength different from the first wavelength. 13. The method of controlling an ophthalmic apparatus according to claim 12 , further comprising an axial length conversion step of converting the axial length corrected in the wavelength correction step into an axial length obtained using an ultrasonic axial length measurement device. A program for causing a computer to execute each step of the method for controlling an ophthalmic apparatus according to any one of claims 10 to 13 .

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