JP2020195883A - Ophthalmologic inspection device - Google Patents

Abstract

To obtain thickness information of the tear film of a subject eye and measure the thickness of the tear film by using an OCT device capable of obtaining a tomographic image of an eyeground or an anterior eye part.SOLUTION: Light from a light source is reflected by a scanner 44 and projected onto a cornea. Reflected light from the cornea is detected by a detector such as a photodiode via the scanner 44 to allow a calculation control unit 200 to measure a tear film thickness on the cornea. An OCT unit 100 can project light of a plurality of wavelengths, for example onto the same site on the cornea and detect the amounts of reflected light to obtain a distribution of reflectivities by wavelengths, to thereby allow the calculation control unit 200 to measure the tear film thickness of the projected site.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ophthalmologic examination apparatus, and more particularly to an ophthalmologic examination apparatus capable of measuring the thickness of a tear film.

In recent years, optical coherence tomography (OCT), which forms an image showing the surface morphology and internal morphology of an object to be measured by using a light beam from a laser light source or the like, has attracted attention. For example, in the field of ophthalmology, devices for forming images of the fundus, cornea, etc. have been put into practical use.
Patent Document 1 describes a fundus observation device having a fundus camera unit, an OCT unit, and an arithmetic control device, and capable of acquiring a fundus image and a tomographic image (summary).
Further, Patent Document 2 describes "an ophthalmologic imaging device for acquiring an image of an eye to be inspected using optical coherence tomography (OCT) and an optical unit that can be attached thereto" (paragraph 0001). Has been done.

Further, for example, Patent Document 3 states, "In a system and method for measuring the tear layer structure and measuring the evaporation rate, a broadband light source illuminates the tear layer, and a spectrometer is at least one of the tear layers. Each spectrum of the reflected light from the point is measured. ”(See summary).

Japanese Unexamined Patent Publication No. 2008-73099 JP 2015-160103 International Publication No. 2015-132788

In general, it is difficult to obtain a lacrimal layer tomographic image using a normal OCT device. In principle, it can be obtained, but in the case of a living eye, it is assumed that it is difficult to detect a tear film that is thinner than tissues such as the cornea due to the movement of the eye to be inspected during measurement. The reason is that, for example, although the position of the reference mirror (optical path length of the reference system) does not change, the sample (tear fluid) position (optical path length of the sample system) changes, so that an interference signal is obtained. This is because it becomes difficult to be damaged (washout).

Further, in the prior art, since the thickness of the tear film is thin (for example, less than 10 μm), different devices are usually used for acquiring a tomographic image of anterior segment tissue such as the cornea and for measuring the tear film thickness. However, even in an apparatus in which these are combined, it is necessary to use a measuring instrument in which different optical systems are combined, which complicates the configuration and increases the size of the apparatus.

In view of the above points, an object of the present invention is to obtain information on the thickness of the tear film of the eye to be inspected by using an OCT device capable of acquiring a tomographic image of the fundus or anterior segment of the eye.

According to the solution of the present invention
A light source, a detector, an optical system for projecting measurement light onto an eye to be inspected to obtain a return light of measurement light from the eye to be inspected, an arithmetic control unit, and deflection optics in which the direction of light rays can be controlled by the arithmetic control unit. In an ophthalmic examination apparatus having an element and scanning the eye to be inspected to acquire thickness information of the tear film of the eye to be inspected based on the detection result by the detector via the optical system.
When acquiring the thickness information of the tear film, the incident direction of the measurement light should be perpendicular to the corneal surface of the eye to be inspected in at least one of the X and Y directions, or in the X and Y directions. Provided is an ophthalmologic examination apparatus characterized in that the deflection optical element is arranged so that the intermediate direction is vertical.

According to the present invention, it is possible to obtain information on the thickness of the tear film of the eye to be inspected by using an OCT device capable of acquiring a tomographic image of the fundus or anterior segment of the eye.

The block diagram of the ophthalmologic examination apparatus of this embodiment. The block diagram of the OCT unit. Explanatory drawing about control and adjustment of each part. Explanatory drawing (1) about control and adjustment of each part in each mode. Explanatory drawing (2) about control and adjustment of each part in each mode. Flow of processing executed in this example. The schematic diagram for demonstrating the composition of the composite with the corneal shape measuring instrument by the platide method.

A. Overview

According to the present invention and / or the present embodiment, when the OCT mode is set in an ophthalmologic measuring device such as an OCT device, a known method for acquiring a tomographic image of anterior ocular tissue such as the fundus or cornea. On the other hand, when the tear tomography mode is set, the tear tomographic image can be obtained by blocking the reference light and analyzing the interference signals of the front and back reflections of the tear layer. In this case, since the tear film moves integrally with the eye to be inspected, the difference (layer thickness) from the reference optical path length does not change, so that a signal can be obtained without being affected by the movement of the eye to be inspected. Since the optical path length of the tear film is short (thin), the reflected light on the front and back surfaces can interfere with the measurement light having a short interference distance. For example, the reference light can be blocked by an optical attenuator, or a method of adding a shutter for inserting and removing a light-shielding plate to another part in the reference optical path can also be used. At this time, if the coherent distance is shorter than the tear layer thickness, a filter or the like that limits the wavelength band of the measurement light (extends the coherent distance) may be inserted when the tear tomographic mode is selected.
According to the present invention and / or the present embodiment, in the OCT apparatus for obtaining tomographic images of the fundus and anterior segment, the conventional anterior segment OCT optical system is used without adding a new optical system. The tear film thickness can be obtained.

B. Ophthalmic examination equipment

<Composition>

An exemplary embodiment of the present invention will be described with reference to the drawings. In addition, the description contents of the document cited in this specification and other known techniques can be incorporated into the embodiment.
The ophthalmologic examination apparatus of the present embodiment is based on interference signals on the front and back surfaces of the tear film on the cornea, which are collected by scanning the tear film of the eye to be examined using optical coherence tomography (OCT). Tear fluid thickness distribution information (tear fluid thickness distribution information) can be created. The ophthalmologic examination apparatus of the embodiment can further identify the tear region destruction region based on the tear fluid thickness distribution information (disruption region distribution information). When a distribution of locations where the tear thickness is equal to or less than a predetermined threshold value is created as the tear thickness distribution information, the tear thickness distribution information is (substantially) the same as the distribution information of the fractured region.
In one typical example, the ophthalmologic examination apparatus of the embodiment can acquire the time course of the thickness distribution of the tear fluid based on the time-series tear film thickness distribution information representing the dynamics of the tear fluid. Furthermore, the time course of the distribution of the fractured region can be obtained from the time course of the tear thickness distribution.
The time-series tear layer thickness distribution information, which represents the kinetics of tear fluid, includes a series of distribution information acquired at different times, typically an OCT scan of the anterior segment at a predetermined repetition interval (predetermined repetition frequency). ) Is collected by repeating. The scan pattern at this time is, for example, a raster scan including a plurality of line scans parallel to each other.

The ophthalmologic examination apparatus of the present embodiment includes an optical system, a drive system, a control system, and a data processing system for executing OCT, and is configured to be capable of executing, for example, Fourier domain OCT.
The swept source OCT uses a wavelength sweep light source (wavelength variable light source) and a photodetector (balanced photodiode, etc.) to acquire the spectrum of interference light in a time-divided manner, and Fourier transforms the spectrum to obtain the eye to be examined. It is a method of imaging. The method of OCT is not limited to Fourier domain OCT, and may be time domain OCT or Enface OCT.
The ophthalmologic examination apparatus of the present embodiment may include a modality for imaging the eye and / or other parts (for example, a modality other than OCT). Typical examples thereof include a fundus camera, an SLO (Scanning Laser Ophthalmoscope), a slit lamp microscope, and a microscope for ophthalmic surgery. In addition, the ophthalmologic examination apparatus of the embodiment may include a configuration for measuring the characteristics of the eye and / or other parts, and a configuration for performing the examination.
An exemplary embodiment of an ophthalmic examination device will be described. In this embodiment, an ophthalmologic examination apparatus having a function of acquiring an OCT image will be described.

FIG. 1 shows a configuration diagram of the ophthalmologic examination apparatus of this embodiment.
The ophthalmologic examination device includes an OCT unit 100, an arithmetic control unit 200, a display device 3, an OCT optical system 4, a storage unit 20, an operation unit 50, an objective lens 22, and an anterior ocular lens 23. The ophthalmologic examination apparatus also includes an anterior ocular segment observation system, a fixation target projection system, and other combined observation and measurement systems.
By selecting the normal OCT mode (fundus mode, anterior segment mode), the ophthalmologic examination apparatus 1 obtains a tomographic image of tissues such as the cornea and crystalline lens of the fundus and anterior segment by OCT scan, and also obtains a tear film. By selecting the mode, the interference signals on the front and back surfaces of the tear layer on the cornea are acquired, and the tear thickness distribution information is acquired. It is also possible to identify the tear destruction area and evaluate dry eye.
The ophthalmologic examination device 1 can display a two-dimensional or three-dimensional tomographic image and information obtained from the tomographic image on the display device 3. As an example of the information obtained from the three-dimensional image, in the normal OCT mode, a map showing the shape and thickness (distance) distribution of the eye tissue can be displayed, and in the mode of acquiring the thickness information of the tear film. Has a map showing the distribution of tear thickness, a map showing the distribution of fractured areas, and evaluation results of dry eye type. The display device 3 may be a part of the ophthalmologic examination device 1 or may be an external device connected to the ophthalmologic examination device 1.

The arithmetic control unit 200 controls each part of the ophthalmologic examination apparatus 1. The arithmetic control unit 200 includes a processor. The "processor" includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), a programmable logic device (for example, a SPLD (Simple Program Program)). , FPGA (Field Programmable Gate Array)) and the like. The arithmetic control unit 200 can realize the function according to the embodiment by reading and executing a program stored in a storage circuit or a storage device (storage unit 20, an external device, etc.), for example.
Further, the arithmetic control unit 200 may include a communication device for transmitting / receiving data via a communication line such as a LAN, the Internet, or a dedicated line.
The arithmetic control unit 200 executes control for displaying information on the display device 3. The arithmetic control unit 200 can perform processing (generation, processing, composition, etc.) related to the information displayed on the display device 3. Further, the arithmetic control unit 200 switches between a normal OCT mode (fundus mode, anterior ocular segment mode) and a tear film mode based on an instruction from the operation unit 501 by the measurer to perform control.

In the OCT mode, the OCT unit 100 collects a tomographic image of the fundus of the eye to be inspected (fundus mode) or a tomographic image of the anterior segment of the eye.
The OCT unit 100 collects the tear layer thickness distribution on the cornea by scanning the cornea of the eye to be inspected using OCT in the tear layer mode. In a typical example, the OCT unit 100 collects a layer thickness distribution group (a series of tear film thickness distribution images, time series images) representing the dynamics of the tear film by repeatedly scanning the anterior segment of the eye. Can be done.
In another typical example, the OCT unit 100 can form a single tear film thickness distribution image. At this time, the OCT unit 100 performs one scan. Alternatively, one tear layer thickness distribution image can be formed by adding and averaging a plurality of tear layer thickness information obtained by repeating the scan a predetermined number of times. It should be noted that processing such as addition averaging can also be applied when collecting layer thickness distribution groups.

The OCT unit 100 includes, for example, a configuration for performing measurements using a swept source OCT. This configuration includes an optical system, a drive system, a data acquisition system (DAQ), a control system, a control processing unit (processor), and the like, as in the conventional case. This optical system includes, for example, an interference optical system, an optical scanner (deflection optical element), and a photodetector. The interference optical system divides the light output from the light source into measurement light and reference light, projects the measurement light onto the eye to be inspected, and superimposes the return light of the measurement light from the eye to be inspected on the reference light to interfere with the light. To generate. The optical scanner includes a galvano scanner or the like and deflects the measurement light. The photodetector detects (the spectrum of) the interference light generated by the interference optics. The OCT unit 100 scans a three-dimensional region of the fundus or anterior segment of the eye (three-dimensional scan).

The arithmetic control unit 200 forms a 3D image based on the 3D data set collected by the 3D scan. This process includes, for example, noise removal (noise reduction), filter processing, FFT (Fast Fourier Transform), and the like, as in the conventional OCT technique. Each 3D image is constructed as, for example, stack data or volume data. When the 3D region of the anterior segment is repeatedly scanned, the arithmetic control unit 200 applies the same processing to each of the series of 3D data sets collected by this repeated scan to obtain a series of 3D images ( A three-dimensional image group, a time-series image) is formed.

The arithmetic control unit 200 renders a three-dimensional image to produce a B-mode image (vertical section image, axial section image), C-mode image (cross-section image, horizontal section image), projection image, shadowgram, and the like. Can be formed. An image of an arbitrary cross section such as a B mode image or a C mode image is formed by selecting pixels (pixels, voxels) on a designated cross section from a three-dimensional image. The projection image is formed by projecting a three-dimensional image in a predetermined direction (Z direction, depth direction, A scan direction). The shadow gram is formed by projecting a part of a three-dimensional image (for example, partial data corresponding to a specific layer) in a predetermined direction.
The arithmetic control unit 200 collects one or more tear layer thickness information on the cornea to be inspected by the OCT unit 100. In addition, the tear film thickness distribution may be collected by scanning in two dimensions. In addition, the time-series layer thickness distribution may be collected. The arithmetic control unit 200 can collect the (time-series) tear layer thickness distribution representing the dynamics of tears on the cornea by repeatedly photographing the eye to be inspected by the OCT unit 100.

Various information is stored in the storage unit 20.
The operation unit 50 is used for the user to input an instruction to the ophthalmologic examination device 1. The operation unit 50 may include a known operation device used in an ophthalmic apparatus or a computer. For example, the operation unit 50 may include a mouse, a touch pad, a trackball, a keyboard, a pen tablet, an operation panel, a joystick, a button, a switch, and the like. Further, the operation unit 50 may include a touch panel. In this case, the arithmetic control unit 200 can display the GUI for operating the ophthalmologic examination device 1 on the touch panel.

<OCT unit>

FIG. 2 shows a configuration diagram of the OCT unit.
The OCT unit 100 includes an optical system, a drive system, a control system, and a processing system for executing imaging. For example, the OCT unit 100 includes a wavelength sweep light source 101 and a photodiode 125. The OCT optical system 4 includes a scanner 44 composed of a galvano mirror or the like, a focusing lens 43, an auxiliary focusing lens 47, and the like. An appropriate detector can be used for the photodiode 125.

An example of the configuration of the OCT unit 100 will be described below with reference to the drawings. The OCT unit 100 is provided with an optical system for acquiring an OCT image of the eye E to be inspected. This optical system divides the low coherence light into the reference light LS and the measurement light LR, and causes the measurement light LS reflected on the test surface to interfere with the reference light LR passing through the reference optical path to generate interference light. It is configured to detect the spectral components of the interfering light. This detection result (detection signal) is sent to the arithmetic control unit 200.
In the swept source type OCT apparatus, a wavelength sweep light source is used as a light source. In general, for the configuration of the OCT unit 100, a known technique depending on the type of optical coherence tomography can be arbitrarily applied.

The coherence light L0 output from the wavelength sweep light source 101 is guided by the optical fiber 102 to the fiber coupler 105 via the polarization controller 103 and the optical fiber 104, and is divided into the measurement light LS and the reference light LR.
The reference optical LR is emitted by the optical fiber 110, becomes a parallel light beam by the collimator 111, passes through the optical path length correction member 112, the dispersion compensation member 113, and the corner cube 114 for optical path length correction, and then passes through the optical fiber 117 and the polarization by the collimator 116. It reaches the optical attenuator (attenuator) 120 via the controller 118 and the optical fiber 119. The optical attenuator 105 automatically adjusts or shields the light amount of the reference light LR guided to the optical fiber 104 under the control of the arithmetic control unit 200 by using a known technique. The reference light LR whose light amount is adjusted by the attenuator 120 is guided by the optical fiber 121 and reaches the fiber coupler 122.

The measurement light LS branched by the fiber coupler 105 is guided by the optical fiber 127 and is converted into a parallel luminous flux by the collimator lens unit 40. Further, the measurement light LS reaches the dichroic mirror 46 via the optical path length changing unit 41, the dispersion compensation member 42, the focusing lens 43, the compensation focusing lens 47, the scanner 44, and the relay lens 45. Then, the measurement light LS is reflected by the dichroic mirror 46, refracted by the objective lens 22, and irradiated to, for example, the fundus Ef. The measurement light LS is scattered (including reflection) at various depth positions of the fundus Ef. The backscattered light (return light) of the measurement light LS measured by the fundus Ef travels in the same direction as the outward path in the opposite direction, is guided to the fiber coupler 105, and reaches the fiber coupler 122 via the optical fiber 128.

The fiber coupler 122 interferes with the backscattered light of the measurement light LS and the reference light LR via the optical fiber 104. The interference light LC generated thereby is guided by the optical fibers 123 and 124 and projected onto the light receiving surface of the photodiode 125.
The photodiode 125 accumulates this electric charge to generate a detection signal, and sends the detection signal to the DAT (Data Acquisition System) 130. The DATA 130 samples the detection signal based on the clock KC from the light source unit 101, and sends the result to the arithmetic control unit 200.
In addition to this embodiment, as the interferometer, for example, an interferometer of any type such as a Michelson type interferometer Mach-Zehnder type can be appropriately adopted.

<Measurement mode>

FIG. 3 shows an explanatory diagram of control / adjustment of each part.
Further, FIGS. 4 and 5 show explanatory views (1) and (2) for controlling and adjusting each part in each mode.

The measurement modes are as follows.
(1) OCT mode (fundus mode)
(2) OCT mode (anterior segment mode)
(3) Tear layer mode

The arithmetic control unit 200 switches the measurement mode and controls based on the instruction of the operation unit 50 by the measurer.
In each mode, the arithmetic control unit 200 retracts / removes / inserts / attaches (removes / inserts) the anterior segment lens 23, dims / shades the attenuator 1200, and retracts the auxiliary focusing lens 47, as shown in FIG. / Controls insertion (removal / insertion). Further, in each mode, as shown in FIGS. 4 and 5, the focusing lens 43 is manually controlled and adjusted to move (diopter) / fixed by the manual or arithmetic control unit 200, and the focusing position (fiber 127). Control and adjust the fundus / anterior segment / corneal surface (tear layer).

The arithmetic control unit 200 controls the focusing lens 43, the auxiliary focusing lens 47, the wavelength sweep light source 101, and the galvanometer mirror 44, detects a signal from the photodiode 125, and collects tomographic information.
In the OCT mode, the OCT unit 100 selectively emits light having a specific wavelength in, for example, a near-infrared wavelength range from the wavelength sweep light source 101. The light from the wavelength sweep light source 101 is branched into the measurement light LS and the reference light LR by the fiber coupler 105. The measurement light LS is deflected by the galvanometer mirror 44 and irradiates the eye to be inspected. On the other hand, the reference light LR is guided to the reference optical path. The measurement light LS light reflected from the eye to be inspected is combined with the reference light LR that has passed through the reference optical path by the fiber coupler 122 via the galvano mirror 44, and the interference signal obtained is detected by the photodiode 125, and the arithmetic control unit 200 detects it. , A tomographic image of the scanned structure is obtained by processing such as Fourier transform, and a three-dimensional tomographic layer can be obtained by scanning the measurement light LS two-dimensionally on the test surface with the scanner 44.

On the other hand, in the tear film mode, since the tear film is thin, it is greatly affected by the change in the measured optical path length due to the movement of the eye to be inspected such as fixation tremor, and it is difficult to acquire a cross-sectional image by normal OCT measurement. is assumed. Therefore, it is possible to obtain a tear film cross-sectional image by detecting and analyzing an interference signal due to an optical path length difference between the measurement light reflected on the front surface of the tear solution and the measurement light reflected on the back surface. Since the front and back surfaces of the tear film move together with the eye to be examined, only one optical path length does not change.

When measuring the tear film thickness, the measurement light LS branched by the fiber coupler 105 reaches the tear film of the eye E to be inspected as described above, and a part of the measurement light LS is reflected on the surface of the tear film layer. A part of the measurement light LS transmitted through the surface of the tear film is reflected by the back surface of the tear film. If the tear film thickness is shorter than the interferable distance of the measured light, the light reflected on the front and back surfaces of the tear film interferes and returns to the OCT unit 100, which is detected by the photodiode 125 as an interference signal. In the tear film mode, the arithmetic control unit 200 controls the attenuator 120 in a light-shielded state. At this time, the reference light LR branched by the photocoupler 105 is shielded by the attenuator 120 in the reference optical path to the photocoupler 122. Does not reach. The interference signal detected by the photodiode 125 undergoes a process such as Fourier transform in the arithmetic control unit 200 to obtain a tear film tomographic image. Further, the OCT unit 100 scans the luminous flux on the cornea with the scanner 44, and the arithmetic control unit 200 can obtain the tear film thickness at a plurality of sites on the cornea.

The optical system from the light source 101 to the photodiode 125 is housed in a housing, and is integrated in the front-rear direction (Z direction) along the optical axis of the objective lens 22 and in the plane orthogonal to the vertical direction (Y direction), left and right. It is possible to move in the direction (X direction). The movement may be performed manually by the measurer or driven by a motor or the like.
When measuring the tear film thickness, the apex of the cornea of the eye to be inspected coincides with the optical axis of the objective lens 22 (X, Y directions), and the distance from the objective lens 22 to the center of curvature of the cornea is the default distance (Z direction). ) Align. A known method is used as a method for detecting the alignment state. When the alignment states of X, Y and Z are within the allowable range, the alignment is completed. Further, the focusing lens 43 is moved so that the end face on the ejection side of the optical fiber 127 arranges the cornea to be inspected in a conjugated manner. If necessary, the auxiliary focusing lens 47 may be inserted. The attenuator 120 inserts a shutter or the like so as to block the reference light LR.

The arithmetic control unit 200 may be controlled to retract the auxiliary focusing lens 47 in the OCT mode and insert the auxiliary focusing lens 47 in the tear film mode, or vice versa. You may.
Further, in general OCT, when photographing the anterior segment based on the fundus type, the anterior segment lens 23 is attached in front of the objective lens. However, as a configuration, it is also possible to attach a "fundus lens" to the anterior segment-based OCT device at the time of fundus photography.

The arithmetic control unit 200 emits a trigger signal to start measurement (auto start). Alternatively, the measurement may be started by pressing the measurement switch by the operator (manual start).

When the measurement is started, the wavelength sweep light source 101 irradiates the measurement light swept at a predetermined sweep width and frequency, detects the interference signal due to the reflected light on the front and back of the tear layer with the photodiode 125, and the arithmetic control unit 200 detects the interference signal. A tear film tomographic image is obtained by an operation such as Fourier transform. The arithmetic control unit 200 can obtain a two-dimensional thickness distribution of the tear film by scanning the measurement light LS on the cornea with the scanner 44.

When observing the time-series change of the tear film continuously, the first measurement (any one measurement) is performed by the above method, and this is repeated at intervals to time the thickness distribution of the tear film. It is possible to observe various changes.

By measuring the tear film thickness at each site on the cornea, creating a pseudo-color thickness map in which the thickness is converted into a color, and displaying it on the screen, the thickness distribution of the tear film can be shown. By displaying the thickness map at each time side by side on the screen, it is possible to confirm the change over time. By switching the image for each hour to the same part on the screen and displaying it, it can be presented as a pseudo moving image. The portion less than the specified thickness may be emphasized and displayed, or the area of the portion may be obtained and displayed.

(Corneal curvature error correction)
In order to efficiently detect the reflected light of the measurement light incident on the tear film, it is desirable that the light beam is vertically incident on each part of the tear film. In this case, it is necessary to align the scanner 44 via the objective lens 22 so as to be conjugate with the position of the center of curvature of the cornea of the eye to be inspected. In addition, in order to acquire tear film thickness data with good resolution, it is necessary to irradiate the tear fluid surface with a light flux to be focused. It is configured as an average corneal radius of curvature (eg r7.7 mm). Alignment in the anteroposterior direction (Z direction) is performed on the apex of the cornea or the Purkinje image of the projected alignment index. The Pulkinje image is at the focal point of the corneal reflex (1/2 of the radius of curvature of the cornea from the apex of the cornea). Therefore, when the radius of curvature of the cornea is r7.7 mm, the center position of the curvature of the cornea may be aligned 7.7 mm behind the apex position of the cornea and 3.85 mm behind the Pulkinje image. If it is a device that moves the measuring part by driving with a motor, it counts the pulse of the stepping motor, and if it is manual, it controls the amount of movement from the corneal apex (or Pulkinje image position) by adding an encoder etc. Can be done.

However, in reality, the radius of curvature of the cornea varies from person to person, and is distributed in the range of about r6 mm to 9 mm. Furthermore, it may deviate from the spherical surface such as corneal astigmatism and keratoconus. If the cornea is an ideal r7.7 sphere, the Z alignment signal completes the alignment so that the apex of the cornea and the aperture are conjugate, and the radius of curvature of the cornea deviates from 7.7 mm, the measurement light is tears. Since it cannot be incident perpendicular to the layer, the detected signal strength is reduced and the measured value contains an error. Here, it is desirable to measure the radius of curvature of the cornea by the following method and optimize the alignment.

The scanner 44 may be composed of, for example, an X scanner and a Y scanner. In this case, since the X scanner and the Y scanner are arranged at physically different positions, arranging the measured luminous flux so as to be vertically incident on the cornea on both sides is expected to complicate the structure. Therefore, when acquiring the thickness information of the tear film, the incident direction of the measurement light is conjugate with the corneal curvature center of the eye to be examined (Y scanner is not conjugate), and Y scanner is corneal curvature. Alignment can be performed so that it is conjugate to the center (the X scanner is not conjugate), or the intermediate position between the X and Y scanners is conjugate to the center of curvature of the cornea (both are not conjugate). Conceivable.

(Platide method)
In the ophthalmologic examination apparatus, a plated plate having a plurality of concentric translucent portions is arranged on a light-shielding plate around the objective lens 22. The plated plate is illuminated by a light source (near-infrared LED, etc.) arranged on the back surface (the surface opposite to the eye to be inspected), and becomes a concentric light source to illuminate the cornea to be inspected. The ring image due to the reflection by the cornea is reflected by the croic mirror through the objective lens 22 and captured by the anterior segment observation camera. Since the corneal reflex ring image is deformed by the influence of the corneal shape, the corneal shape is obtained by a known method from the change in the size and shape of the ring image.

(OCT method)
The shape of the corneal surface is obtained from the anterior segment tomographic image obtained by the anterior segment scan by OCT. Scanning methods include radiation scan and raster scan.
Based on the corneal surface shape obtained by these methods, it is possible to obtain the radius of curvature of the cornea.

<Other configurations of ophthalmic examination equipment>

Further, FIG. 7 shows a schematic view for explaining the configuration of the composite with the corneal shape measuring instrument by the placido method.
A plated plate having a ring pattern for measuring the shape of the cornea is arranged around the objective lens, and is illuminated by a light source (not shown) arranged on the back surface (the surface opposite to the eye to be inspected). The luminous flux transmitted through the ring pattern irradiates the cornea, producing a corneal reflex image. This reflected image is reflected by a dichroic mirror via an objective lens and captured by an anterior segment observation camera. The deformation of the imaged corneal reflex ring makes it possible to obtain the corneal shape (curvature) by a known method.

On the other hand, the measurement light from the OCT unit 100 reaches the scanner 44. The scanner 44 is composed of a galvano mirror or the like and can change the angle of the measurement light. It is two-dimensional by combining two galvano mirrors that deflect in the paper surface (y-axis) and in the plane orthogonal to the paper surface (X-axis). Allows in-plane scanning. The measurement light deflected to an arbitrary angle by the scanner 44 is transmitted through the dichroic mirror, refracted by the objective lens, and irradiated to the cornea to be inspected. Based on the measured corneal curvature, the positions of the centers of curvature of the scanner and the cornea to be inspected are arranged so as to be substantially conjugate, so that the light beam deflected by the scanner is incident along the normal line of the cornea.
However, as described above, when the scanner is composed of two galvano mirrors, the structure is complicated in order to simultaneously conjugate both galvano mirrors and the center of curvature of the cornea. One of them should be arranged so as to be conjugate with the center of curvature of the cornea, or the point between both galvanometers, ideally the midpoint, should be arranged so as to be conjugate with the center of curvature of the cornea.
Light rays incident along the normal line of the cornea (perpendicular to the surface of the cornea) are specularly reflected on the front and back surfaces of the tear film and returned to the scanner via the objective lens. The measurement light that has passed through the scanner is detected by the photodiode in the OCT unit 100. Here, the injection side end of the optical fiber 127 and the corneal surface of the eye E to be inspected are arranged in conjugation.

<Additional configuration of arithmetic control unit>

The arithmetic control unit 200 can perform various data processing, image processing, image analysis, and the like. The arithmetic control unit 200 can include, for example, a segmentation processing unit, a distribution information acquisition unit, and a destruction region identification unit.

The segmentation processing unit applies the segmentation to the three-dimensional image collected by the OCT unit 100. Segmentation is used to determine a particular organization or organizational boundary. This identifies the fundus and corneal tissue.
When a time-series image is obtained, the segmentation processing unit applies segmentation to each of the plurality of three-dimensional images included in the time-series image. Here, the plurality of images to be segmented may be a part or all of a series of three-dimensional images constituting the time series image. As an example of analyzing only a part of the image group, the image acquired during the blinking may be specified in advance, and only the images other than that (them) may be segmented.

The thickness at each measurement point is calculated, for example, by counting the number of pixels corresponding to the tear film along a predetermined measurement direction, and the distance (unit) corresponding to the number of pixels and the pixel pitch obtained by the process. Includes processing to multiply distance) with.
Here, the direction for counting the number of pixels (the measurement direction) is arbitrary, and for example, the A-line direction in the OCT scan or the normal direction at each position on the corneal surface can be applied as the measurement direction. The process of specifying the normal direction at each position of the corneal surface includes, for example, approximating the curved surface of the corneal surface, specifying the tangent plane at each position, and specifying the normal of each tangent plane.

The distribution information acquisition unit can also apply a process (flattening) for flattening a specified predetermined region (for example, the surface of the cornea) to a three-dimensional image. By performing flattening, it becomes easy to calculate the thickness. Further, by displaying the flattened image, the thickness distribution can be easily grasped.
The distribution information acquisition unit can also acquire and identify the tear region destruction region based on the tear thickness distribution information. The disrupted region is, for example, a region where the tear film is disrupted (a region where the fluid layer region is not detected or a region that is extremely thin).
In a typical example, the distribution information acquisition unit can specify a portion where the thickness of the tear film region is equal to or less than a predetermined threshold value as a region where the fluid layer is destroyed.

When two or more types of distribution information (tear thickness distribution information, fracture area distribution information, etc.) are obtained from two or more types of images (image groups) related to the same eye to be inspected, these distribution information are compared or combined. It is possible. For example, the difference between at least a part of the first distribution information created from the OCT image and at least a part of the second distribution information obtained from the front image can be obtained. In addition, at least a part of the first distribution information and at least a part of the second distribution information can be combined. In addition, other distribution information can be used to interpolate or refine one distribution information.

<Front image acquisition unit>

The ophthalmologic examination apparatus of the present embodiment may further include a front image acquisition unit.
The front image acquisition unit acquires a front image of the anterior segment of the eye (cornea, etc.). The process for acquiring the front image is optional. In the first example, the front image acquisition unit may include a configuration for photographing the anterior eye portion.
In the second example, the front image acquisition unit may include a configuration for acquiring a front image of the anterior eye portion of the eye to be inspected from an external device. For example, the front image acquisition unit may include a communication device for transmitting / receiving data via a communication line such as a LAN, the Internet, or a dedicated line. In this case, the front image acquisition unit can acquire, for example, the front image of the anterior segment of the eye to be inspected stored in the electronic medical record system or the image archiving system, using the patient ID, DICOM tag, or the like as a search query. ..

In the third example, the front image acquisition unit can form a front image from the three-dimensional image collected by the OCT unit 100. Examples of such a front image include a C-mode image, a projection image, and a shadow gram.
Registration can be performed between the OCT image collected by the OCT unit 100 and the front image acquired by the front image acquisition unit. Registration is performed, for example, by detecting a characteristic site (corneal apex, pupil, pupil center, pupil center of gravity, iris, iris center, iris center of gravity, etc.) from both images, and using both images as a reference. It can be done through the process of alignment.

Similarly, various maps such as a tear thickness distribution map, a fractured area distribution map, and an evaluation result distribution map can be registered with the front image acquired by the front image acquisition unit. This registration is performed using, for example, the result of registration between the three-dimensional image on which the map is based and the front image.

C. flowchart

Some examples of actions that an exemplary ophthalmic examination device can perform will be described.
FIG. 6 shows the flow of processing executed in this example. It is assumed that preparatory processing such as input of the patient ID and the like, alignment of the optical system with respect to the eye to be inspected, focus adjustment of the optical system, OCT optical path length adjustment, setting of the OCT scan range, etc. has already been performed.

(S1: Perform OCT scan of the anterior segment of the eye)
First, when the tear film mode for measuring the tear film thickness is selected, each part is controlled and adjusted as described above, and the reference light LR is blocked by the attenuator 120. In this state, the OCT unit 100 collects the tear film thickness distribution on the cornea by performing an OCT scan of the anterior segment of the eye to be inspected. At this time, the OCT unit 100 may collect a distribution information group (time-series distribution information) representing the dynamics of tears on the cornea by repeatedly performing an OCT scan.
The display control unit 11 can display the tear film thickness distribution based on the collected distribution information on the display device 3.
When the time-series distribution information is collected, one or more distribution information included in the time-series distribution information can be rendered, and the one or more rendering information obtained thereby can be displayed on the display device 3. When displaying a plurality of rendering information, it is possible to arrange them in chronological order. It is also possible to switch and display a plurality of rendering information in chronological order.

Further, when the time-series distribution information is collected, the blink information can be specified from a series of information constituting the time-series information image. Further, the last blink information or the next information in the series of blink information can be set as the distribution information at the start of eyelid opening (the above-mentioned reference information).

(S3: Create tear thickness distribution information)
Subsequently, the distribution information acquisition unit 42 creates tear thickness distribution information based on the obtained results.
When the time-series distribution information is collected, the distribution information acquisition unit 42 creates tear thickness distribution information for each of the plurality of distribution information included in the time-series distribution information. As a result, a plurality of tear thickness distribution information corresponding to the plurality of distribution information included in the time series distribution information can be obtained. The plurality of tear thickness distribution information represents the time course of the tear thickness distribution, that is, the dynamics of the tear fluid.
(S4: Acquire a front image of the anterior segment of the eye)
Next, the front image acquisition unit 60 of the anterior segment of the eye, for example, by photographing the anterior segment of the eye, accessing an electronic medical record system or the like, or rendering the image collected in step S1. Get the front image.
The timing of acquiring the front image may be arbitrary. For example, the front image of the anterior segment can be acquired by accessing the electronic medical record system or the like or by photographing the anterior segment before or after step S1. Alternatively, the front image of the anterior segment can be acquired by rendering the three-dimensional image collected in step S1 at an arbitrary timing after step S1.

(S5: Display a composite image of the tear thickness distribution image and the front image)
Subsequently, the display control unit 11 (and the data processing unit 40) forms an image (tear thickness distribution image) based on the tear solution thickness distribution information created in step S3, and the tear solution thickness distribution image and the step. The front image acquired in S4 is combined and displayed on the display device 3. The tear thickness distribution image is, for example, a pseudo color map in which the thickness value of each point represented by the tear thickness distribution information is expressed in pseudo color.
In one example, the composite display of the tear thickness distribution image and the front image includes image processing for synthesizing the tear thickness distribution image and the front image, and control for displaying the composite image formed by the image processing. In another example, the composite display includes a control for displaying the tear thickness distribution image and the front image in an overlapping manner by using a layer display function or the like. A display image obtained by superimposing two (or more) images under display control in this way is also an example of a composite image. In the composite display, registration between the tear thickness distribution image and the front image can be performed. This registration is performed, for example, through the registration of the image on which the tear thickness distribution image is based and the front image.
When the time-series images are collected, a composite image of the tear thickness distribution image and the front image based on one or more images included in the time-series images can be displayed on the display device 3. When displaying a plurality of composite images, it is possible to arrange them in chronological order. It is also possible to switch and display a plurality of composite images in chronological order.

D. Addendum

According to such an embodiment, the structure and dynamics of the tear film can be grasped by using a high-resolution modality called OCT. Therefore, it is possible to perform the examination with higher accuracy, higher accuracy, and non-invasiveness than the conventional examination using the fluorescence contrast image.
In the embodiment, the ophthalmologic examination apparatus may further include a front image acquisition unit and a display control unit. The front image acquisition unit can acquire a front image of the cornea. The display control unit can display a composite image of the tear thickness distribution image and the front image based on the distribution information acquired by the distribution information acquisition unit on the display means.

According to such an embodiment, it is possible to easily grasp how the tear fluid is distributed on the cornea.
According to such an embodiment, it is possible to identify the fractured region of the tear film using a high-resolution modality called OCT. Therefore, it is possible to perform the inspection with higher accuracy and higher accuracy than before.
The actions and effects of the embodiments are not limited to these, and the actions and effects provided by each of the items described as the embodiments and the actions and effects provided by the combination of a plurality of items should be considered.

<Modification example>
The configuration described above is only an example for preferably carrying out the present invention. Therefore, any modification (omission, substitution, addition, etc.) within the scope of the gist of the present invention can be appropriately applied.
For example, in an embodiment having an OCT function (OCT unit 100 or the like) such as the ophthalmologic examination device 1, a (three-dimensional) OCT scan of the anterior segment of the eye is started in response to an eyelid opening or a blink of an eye. Can be configured in.
For the detection of eyelid opening and blinking, for example, a processor for determining the blinking state / eyelid opening state by analyzing the anterior segment imaging unit such as the front image acquisition unit 60 and the anterior segment image acquired thereby ( It is realized by the data processing unit 40 etc.).

Alternatively, a projection unit that projects a light beam from the first direction onto the cornea, a light receiving unit that receives the corneal reflex light of this light flux in the second direction, and a blinking state / eyelid state based on the light receiving state of the cornea by the light receiving unit. It is realized by a processor (calculation control unit 200, data processing unit 40, etc.) that determines.
The control processor (calculation control unit 200 or the like) controls the OCT collecting unit according to the blinking state / eyelid opening state obtained by such a method. In the first example, when the transition from the blinking state to the open eyelid state is detected, the control processor starts the (three-dimensional) OCT scan and performs the (three-dimensional) OCT scan for a predetermined time or a predetermined number of repetitions. It can be performed.

In the second example, when the eyelid state shifts to the blinking state, or when a predetermined time elapses after shifting to the blinking state, the control processor starts a (three-dimensional) OCT scan and determines. A (three-dimensional) OCT scan can be performed for a period of time or a predetermined number of iterations.
In a third example, the control processor transitions from the eyelid state to the eyelid state when a transition from the eyelid state to the eyelid state is detected after initiating a repetitive (three-dimensional) OCT scan. When a predetermined time elapses after shifting to the blinking state, the capture of the (three-dimensional) data set repeatedly collected by OCT can be started or the data processing can be started.
The following configuration can be applied to an embodiment having an OCT function (OCT unit 100 or the like) and an anterior segment imaging function (front image acquisition unit or the like) such as the ophthalmic examination apparatus 1.
First, the control processor (calculation control unit 200, etc.) acquires the anterior segment image (repeatedly). The analysis processor (data processing unit 40, etc.) evaluates the state and dynamics of the tear fluid by analyzing the acquired front image (sequentially). The control processor executes a (three-dimensional) OCT scan based on the evaluation result.

For example, the analysis processor analyzes the front image to determine the position where the tear state is characteristic (the position of the fracture area, the position of the characteristic fracture area, the position where the destruction is rapidly progressing, and the destruction area are dense. It is possible to specify the part that exists in. The control processor can set the scan range to include the specified position and cause a (three-dimensional) OCT scan on this scan range.
When the position where the tear condition is characteristic changes over time, the control processor can repeatedly perform the setting of the scan range and the (three-dimensional) OCT scan according to the change in the position.

Furthermore, by using a light source capable of sweeping a wider wavelength in the visible region as the light source, it is possible to obtain a more detailed tomographic image of the tear film. In this case, it is also possible to distinguish between the oil layer and the water layer constituting the tear film.
In addition to the fiber optical system, a bulk (using a prism or a mirror) optical system may be used.

A configuration example of the present invention and / or the present embodiment is shown below.
[Configuration Example 1]
To obtain an interference signal between the return light of the measurement light from the eye to be inspected and the reference light by dividing the light from the light source into the measurement light and the reference light by the light source, the detector, and optical coherence stromography (OCT). Optical system, an arithmetic control unit that forms a tomographic image based on the detection result by the detector via the optical system, and a deflection optical element whose light ray direction can be controlled by the arithmetic control unit. In an ophthalmologic examination device that obtains a tomographic image of the eye to be examined by scanning the eye examination.
An ophthalmologic examination apparatus having a first mode of acquiring a tomographic image of the fundus or anterior segment of the eye to be inspected and a second mode of acquiring information on the thickness of the tear film of the eye to be inspected.

[Configuration Example 2]
It is an ophthalmic examination device
To obtain an interference signal between the return light of the measurement light from the eye to be inspected and the reference light by dividing the light from the light source into the measurement light and the reference light by the light source, the detector, and optical coherence stromography (OCT). OCT unit and
An arithmetic control unit that forms a tomographic image based on the detection result by the OCT unit via the optical system,
An optical system having a deflection optical element whose light ray direction can be controlled by the arithmetic control unit, guiding the measurement light from the OCT unit to the eye to be inspected, and guiding the return light of the measurement light from the eye to be inspected to the OCT unit. ,
With
The arithmetic control unit sets a mode of a first mode for acquiring a tomographic image of the fundus or anterior segment of the eye to be inspected, or a second mode for acquiring information on the thickness of the tear film of the eye to be inspected. According to this, the OCT unit and the optical system are controlled.
When the first mode is set, the arithmetic control unit controls the deflection optical element, scans the fundus or anterior segment of the eye to be inspected by the OCT unit, and acquires a tomographic image of the fundus or anterior segment. And
When the second mode is set, the arithmetic control unit controls the deflection optical element, and the OCT unit acquires the thickness information of the tear film of the eye to be inspected.
Ophthalmic examination equipment.

[Configuration Example 3]
The ophthalmologic examination apparatus according to the configuration example 1 or 2.
At the time of acquisition of the thickness information of the tear film in the second mode,
The arithmetic control unit blocks the optical path of the reference light of the optical system.
The OCT unit is an ophthalmologic examination apparatus characterized in that it acquires an interference signal between the reflected light on the front surface and the reflected light on the back surface of the tear film of the eye to be inspected among the measured lights.

[Configuration Example 4]
The ophthalmologic examination apparatus according to any one of Configuration Examples 1 to 3.
When acquiring the thickness information of the tear film in the second mode, the incident direction of the measurement light is perpendicular to the corneal surface of the eye to be inspected in at least one of the X direction and the Y direction, or An ophthalmologic examination apparatus characterized in that the deflection optical element is arranged so that the intermediate direction between the X direction and the Y direction is vertical.

[Configuration Example 5]
The ophthalmologic examination apparatus according to any one of Configuration Examples 1 to 4.
An ophthalmologic examination apparatus, characterized in that, when acquiring the thickness information of the tear film in the second mode, the measured luminous flux is focused so as to be focused on the corneal surface or in the vicinity of the corneal surface.

[Configuration Example 6]
The ophthalmologic examination apparatus according to any one of Configuration Examples 1 to 5.
The deflection optical element is composed of two galvanometer mirrors.
At the time of acquisition of the thickness information of the tear film in the second mode, at least one of the two galvanometers is arranged so as to be conjugate with the center of curvature of the cornea, or any between the two galvanometers. An ophthalmologic examination apparatus characterized in that the points or intermediate points of the above points are arranged so as to be conjugate with the center of curvature of the cornea.

[Configuration Example 7]
The ophthalmologic examination apparatus according to any one of Configuration Examples 1 to 6.
The optical system has an auxiliary focusing lens between the OCT unit and the deflection optical element.
The arithmetic control unit
In the first mode, the auxiliary focusing lens is retracted, and in the second mode, the auxiliary focusing lens is controlled to be inserted.
Or
In the first mode, the auxiliary focusing lens is inserted, and in the second mode, the auxiliary focusing lens is controlled to be retracted.
An ophthalmic examination device characterized by this.

[Configuration Example 8]
The ophthalmologic examination apparatus according to any one of Configuration Examples 1 to 7.
A lens that can be inserted and removed on the optical axis between the deflection optical element and the eye to be inspected is further provided.
The arithmetic control unit
In the first mode, when acquiring a tomographic image of the fundus and when acquiring a tomographic image of the anterior segment of the eye, the removable lens can be retracted or removed, and inserted or attached. When acquiring the thickness information of the tear film in the second mode, the ophthalmologic examination apparatus is characterized in that the removable lens is either inserted or retracted, as in the case of acquiring a tomographic image of the fundus. ..

[Configuration Example 9]
The ophthalmologic examination apparatus according to any one of Configuration Examples 1 to 8.
The arithmetic control unit acquires the distribution information of the thickness of the tear film by scanning the measured luminous flux on the cornea two-dimensionally using the deflection optical element, and displays it on the display unit and / or the storage unit. An ophthalmic examination device characterized by memorizing in.

[Configuration Example 10]
The ophthalmologic examination apparatus according to the configuration example 9.
A front image acquisition unit for acquiring a front image of the cornea is further provided.
The arithmetic control unit displays a composite image of the acquired tear layer thickness distribution image and the front image acquired by the front image acquisition unit on the display unit and / or stores it in the storage unit. A featured ophthalmic examination device.

1 Ophthalmic examination device 3 Display device 20 Storage unit 100 OCT unit 200 Calculation control unit 50 Operation unit

Claims (5)

A light source, a detector, an optical system for projecting measurement light onto an eye to be inspected to obtain a return light of measurement light from the eye to be inspected, an arithmetic control unit, and deflection optics in which the direction of light rays can be controlled by the arithmetic control unit. In an ophthalmic examination apparatus having an element and scanning the eye to be inspected to acquire thickness information of the tear film of the eye to be inspected based on the detection result by the detector via the optical system.
When acquiring the thickness information of the tear film, the incident direction of the measurement light should be perpendicular to the corneal surface of the eye to be inspected in at least one of the X and Y directions, or in the X and Y directions. An ophthalmologic examination apparatus characterized in that the deflection optical element is arranged so that the intermediate direction is vertical.
The ophthalmologic examination apparatus according to claim 1.
An ophthalmologic examination apparatus characterized in that when the thickness information of the tear film is acquired, the measured luminous flux is focused so as to be focused on the corneal surface or in the vicinity of the corneal surface.
The ophthalmologic examination apparatus according to claim 1 or 2.
The deflection optical element is composed of two galvanometer mirrors.
At the time of acquisition of the thickness information of the tear film, at least one of the two galvanometers is arranged so as to be conjugate with the center of curvature of the cornea, or an arbitrary point or an intermediate point between both galvanometers. An ophthalmologic examination device characterized in that is arranged so as to be conjugate with the center of curvature of the cornea.
The ophthalmologic examination apparatus according to any one of claims 1 to 3.
The arithmetic control unit acquires the distribution information of the thickness of the tear film by scanning the measured luminous flux on the cornea two-dimensionally using the deflection optical element, and displays it on the display unit and / or the storage unit. An ophthalmic examination device characterized by memorizing in.
The ophthalmologic examination apparatus according to claim 4.
A front image acquisition unit for acquiring a front image of the cornea is further provided.
The arithmetic control unit displays a composite image of the acquired tear layer thickness distribution image and the front image acquired by the front image acquisition unit on the display unit and / or stores it in the storage unit. A featured ophthalmic examination device.

Images