JP2016154910A - Ophthalmic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately perform alignment for measurement of a cornea thickness without regard to a corneal curvature radius.SOLUTION: An ophthalmic apparatus includes: a measurement section that measures a subject's eye; bright spot image acquisition means that acquires a bright spot image on the basis of a return light from the anterior segment of the subject's eye irradiated with a near infrared light; and slit image acquisition means that acquires a slit image of a cornea on the basis of the return light from the subject's eye irradiated with a slit light. In addition, the ophthalmic apparatus includes adjustment means that adjusts the position of the measurement section with respect to the subject's eye by using the bright spot image and the slit image.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an ophthalmic apparatus.

  In order to accurately measure the corneal thickness based on a clear cornea image, it is necessary to accurately align the eye cornea to be examined and the measurement unit.

  In Patent Literature 1, an alignment index is irradiated to the eye to be examined along the optical axis of the measurement unit facing the eye, and the cornea is irradiated by two anterior eye observation illumination light sources provided outside the optical axis. ing. Further, Patent Document 1 discloses that a corneal bright spot image and two anterior ocular illumination light source bright spot images are obtained by imaging these reflected lights with an observation optical system provided on the optical axis of the measurement unit. Yes. Patent Document 1 discloses that alignment is performed using the obtained corneal bright spot image and two anterior eye illumination light source bright spot images.

JP 2000-070224 A

  Here, even if the alignment is performed using the corneal bright spot so that the distance between the eye cornea to be examined and the measurement unit matches the predetermined working distance, the eye to be examined can be referred to by referring to the slit image (scattered image). The distance between the cornea and the measurement unit may not match the predetermined working distance. This is due to the fact that the light receiving position of the light receiving means for the corneal bright spot image differs depending on the radius of curvature of the subject's cornea. That is, depending on the radius of curvature of the cornea, there may be a case where the distance between the eye cornea to be examined and the measurement unit does not match the predetermined working distance only by performing alignment using the corneal bright spot.

The present invention has been made in view of the above situation, and an object of the present invention is to provide an ophthalmologic apparatus that enables accurate alignment for measurement of corneal thickness regardless of the corneal curvature radius.
In addition, the present invention is not limited to the above-described object, and is a function and effect derived from each configuration shown in the embodiment for carrying out the present invention, which is another object of the present invention. It can be positioned as one.

In order to solve the above problems, an ophthalmologic apparatus according to the present invention includes:
A measurement unit for measuring the eye to be examined;
A bright spot image acquisition means for acquiring a bright spot image based on the return light from the eye to be examined irradiated with near infrared light;
Slit image acquisition means for acquiring a slit image of the cornea based on the return light from the eye to be examined irradiated with the slit light;
Adjusting means for adjusting the position of the measuring unit with respect to the eye to be examined using the bright spot image and the slit image;
It is provided with.
The ophthalmic apparatus according to the present invention includes a first alignment light source that emits invisible light having an invisible wavelength,
First imaging means for imaging a bright spot image obtained by irradiating the eye cornea with the invisible light;
A second alignment light source that emits visible light having a visible wavelength;
A second imaging unit that captures a scattered image obtained by irradiating the eye to be examined with the visible light;
The first imaging coordinate position of the first imaging means of the bright spot image is detected, and the measurement with respect to the eye to be examined is performed so that the first imaging coordinate position becomes a predetermined bright spot image coordinate position. First control means for aligning the position of the part;
Detecting a second imaging coordinate position in the second imaging means of the scattered image, calculating an alignment deviation amount in the optical axis direction from a deviation between the second imaging coordinate position and a predetermined scattered image coordinate position; Calculating means for calculating a shift amount of the bright spot image in order to eliminate the alignment shift amount;
Based on the shift amount of the bright spot image, the predetermined bright spot image coordinate position is changed, and the first imaging coordinate position with respect to the eye to be examined is matched with the changed bright spot image coordinate position. And a second control means for aligning the position of the measurement unit.

  ADVANTAGE OF THE INVENTION According to this invention, alignment for the measurement of a corneal thickness can be performed correctly irrespective of a test subject's corneal curvature radius. In addition, since the alignment can be performed accurately, the corneal thickness can be accurately measured regardless of the corneal curvature radius of the subject.

It is explanatory drawing which showed typically the measurement part which concerns on one Embodiment of this invention. It is explanatory drawing of the slit board in embodiment shown in FIG. FIG. 2 is an explanatory diagram of an image captured by the image sensor 28 in the embodiment illustrated in FIG. It is explanatory drawing of an alignment bright spot. FIG. 6 is an explanatory diagram for explaining a corneal scattering image by a slit by the image sensor 50. It is explanatory drawing explaining the image for alignment in case the distance of the optical axis direction in a 1st, 2nd alignment method is very larger than WD. It is explanatory drawing explaining the image for alignment in the case where the distance of the optical axis direction in a 1st, 2nd alignment method is larger than WD. It is explanatory drawing explaining the image for alignment in case the distance of the optical axis direction in a 1st, 2nd alignment method corresponds with WD. It is a flowchart at the time of performing alignment.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows a configuration diagram of an optical system of a measurement unit of an ophthalmologic apparatus according to an embodiment of the present invention. In the present embodiment, the measurement unit corresponds to a unit for measuring the eye to be measured, which measures various data or parameters for knowing the state of the eye to be examined as exemplified by intraocular pressure. In the measurement unit, a nozzle 22 is disposed on the central axis of the plane parallel glass 20 and the objective lens 21 so as to face the cornea Ec of the eye E to be examined. The prism diaphragm 26, the imaging lens 27, and the image sensor 28 are sequentially arranged. These are a light receiving optical path and an alignment detecting optical path of the observation optical system for the eye E.

  The plane-parallel glass 20 and the objective lens 21 are supported by an objective barrel 29, and outside eye illumination light sources 30a and 30b for illuminating the eye E to be examined are arranged on the outside thereof.

  For convenience of explanation, the external illumination light sources 30a and 30b are described in the upper and lower parts of the drawing, but are actually arranged to face the optical axis in a direction perpendicular to the drawing.

  In the reflection direction of the dichroic mirror 25, a relay lens 31, a half mirror 32, a dichroic mirror 44 having characteristics of transmitting near-infrared wavelengths and reflecting visible light wavelengths, an aperture 33, and a light receiving element 34 are disposed. . Note that the position of the aperture 33 is arranged at a position where a cornea reflection image of a measurement light source 37 (to be described later) becomes conjugate when the cornea Ec is deformed, and deformation detection light reception when the cornea Ec is deformed in the visual axis direction together with the light receiving element 34. It is an optical system.

  The relay lens 31 is designed so as to form a cornea reflection image having a size substantially equal to that of the aperture 33 when the cornea Ec is deformed.

  In the incident direction of the half mirror 32, a half mirror 35, a projection lens 36, a measurement light source 37 composed of a near-infrared LED that is an invisible wavelength for both the measurement and the eye E to be measured are arranged. A fixation light source 38 made up of LEDs fixed by the subject is arranged. The measurement light source 37 constitutes a first alignment light source that emits invisible light having an invisible wavelength in the present invention. Moreover, as shown in this embodiment, it is preferable that the said measurement light source 37 in this invention is used together as an intraocular pressure measurement light source for intraocular pressure measurement.

  In the incident direction of the dichroic mirror 44, a projection lens 45, a slit plate 46, and a visible light source 47 for measuring the corneal thickness are arranged.

  The visible light source 47 illuminates the slit plate 46, and the slit plate 46 forms an image on the cornea Ec through the nozzle 22 by the projection lens 45 and the relay lens 31. As shown in FIG. 2, the slit plate 46 has a rectangular aperture that is long in the direction perpendicular to the paper surface. The visible light source 47 constitutes a second alignment light source that emits visible light having a visible wavelength in the present invention. As shown in the present embodiment, the visible light source 47 in the present invention is preferably used in combination as a corneal thickness measurement light source for corneal thickness measurement.

  In the obliquely downward direction of the eye E, a filter 48, an imaging lens 49, and an image sensor 50 that transmit light in the corneal scattering image wavelength range by the visible light source 47 having a visible wavelength of, for example, about 500 nm are disposed. The corneal thickness measurement optical system is configured, and the observation optical system optical axis and the corneal thickness measurement optical system optical axis intersect at the corneal apex of the eye cornea Ec to be examined. In addition, the slit plate 46, the cornea Ec, and the image sensor 50 are in a conjugate relationship.

A piston 40 is fitted into a cylinder 39 constituting a part of the air chamber 23, and the piston 40 is driven by a solenoid 42. A pressure sensor 43 for monitoring the internal pressure is disposed in the air chamber 23.
Moreover, the control part 41 is provided and controls the whole apparatus, especially each element of the measurement part shown by FIG.

The light source for fixation 38 is turned on, and the measurement start switch 6 is pressed in a state where the eye E is fixed with the light source 38. In the measurement, when the alignment is completed, the visible light source 47 is turned on, and the cornea Ec is irradiated with slit light. A scattered image (slit image) obtained from the slit light scattered by the cornea Ec is captured by the image sensor 50, and corneal thickness measurement is performed based on the captured scattered image. Here, the image sensor 50 functions as a slit image acquisition means in the present invention. A corneal scattering image S imaged by the image sensor 50 is shown in FIG.
When the corneal thickness measurement is completed, the intraocular pressure measurement is subsequently performed.

  Regarding the alignment operation, a case where the radius of curvature of the eye cornea to be examined is smaller than the radius of curvature of the cornea used as a design value by the measurement unit will be described according to the flowchart of FIG.

The examiner inputs the ID (identifier) of the subject in advance (Step 1).
When the measurement switch 6 is pushed by the examiner (Step 2), the control unit 41 performs the following control.
When the measurement start switch 6 is pressed, the measurement light source 37 as the first alignment light source is turned on (Step 3).

  The light beam from the measurement light source 37 is converted into parallel light by the projection lens 36, reflected by the half mirror 32, temporarily formed in the nozzle 22 by the relay lens 31, and irradiated on the cornea Ec of the eye E to be examined.

  That is, Step 3 in the flowchart of FIG. 9 turns on the measurement light source 37 that emits measurement light having a near-infrared wavelength, which is an invisible wavelength, and thereafter the bright spot image obtained from the invisible light emitted by the measurement light source 37. Perform alignment using.

  More specifically, as shown in FIG. 3, during alignment, the corneal bright spot imaged by the cornea Ec is divided by the prism diaphragm 26 and illuminated by the external illumination light sources 30 a and 30 b and the external illumination. Along with the bright spot images 30a ′ and 30b ′ of the light sources 30a and 30b, the image pickup device 28 takes images as index images T1 and T2. The imaging device 28 captures a bright spot image obtained from or based on the return light from the eye to be examined, which is obtained by irradiating the eye cornea with the near-infrared light that is invisible light in the present invention. A first imaging unit or a bright spot image acquisition unit is configured.

  The alignment operation is executed using the index images T1 and T2 imaged by the image sensor 28. For example, at the stage where the alignment operation is not performed, as shown in FIG. 3, the so-called working distance (WD) in the direction of the nozzle center axis, the coordinates of the nozzle center axis (imaging optical axis), and the coordinates of the cornea center are Both are off.

  The controller 41 calculates coordinates T1 (x1, y1) and T2 (x2, y2) and center coordinates T (xt, yt) of the two index images during alignment.

  Here, an alignment operation using the index images T1 and T2 will be described with reference to FIG. In FIG. 4, the center of the cornea is indicated by an intersection C (x0, y0) between the x coordinate and the y coordinate.

  If the central axis of the nozzle and the corneal center are displaced in the vertical direction, y1 and y2 coincide as shown in FIG. 4A, and x0 and xt coincide with the corneal center C (x0, y0). Since the directions y0 and yt are different, the measurement unit is moved in the vertical direction by a driving means (not shown) and controlled so as to have the same coordinates.

  Similarly, when they are shifted in the left-right direction, y1 and y2 match as shown in FIG. 4B, and this time x0 and xt are different, so the measurement unit is moved in the left-right direction and controlled so as to have the same coordinates. . In the above operation, the control unit 41 detects the first imaging coordinate position, which is the coordinates of the bright spot image (index image) on the imaging device 28, and the bright spot image in which the first imaging coordinate position is predetermined. This is executed in a module that functions as a first control unit that adjusts the position of the measurement unit with respect to the eye to be coordinated (the position of the index image when the cornea center is at the correct position).

  Further, when the cornea center is displaced in the working distance direction in the nozzle center axis direction, the center of gravity position coincides with the cornea center as shown in FIG. 4C, but x1 and x2, and y1 and y2 are different. Therefore, the measurement unit is moved in the direction of the nozzle center axis so that y1 and y2 in the y coordinate are matched.

  First, the control unit 41 aligns the center of the cornea in the x and y directions (in a plane perpendicular to the measurement optical axis) by the first control means (Step 4). The bright spot image at that time is in a point-symmetrical position around the optical axis as shown in FIG. The distance between the eye to be examined and the measurement unit is in a state of being separated from a predetermined working distance (WD) designed as shown in FIG. FIG. 6C shows an image picked up by the image pickup device arranged in the corneal thickness measurement optical system that receives the corneal scattering image, and the center cross indicates the position where the slit image is located when the alignment is completed. It is.

  In the state where the image shown in the figure is obtained, the distance to the center of the cornea in the z direction (the optical axis direction of the measurement unit) is far away, so if the slit light is emitted, the cross and the slit image The position shift (Δz) is a large position (actually, slit light is not emitted in this step).

  Next, the control part 41 transfers a flowchart to Step6. Bring the measurement part closer to the eye to be examined and match the y coordinates of the two bright spot images. This state is shown in FIG.

  When the first alignment is completed, as shown in FIG. 4D, the two index images are arranged at equal intervals from the corneal center on the x axis, and the center coordinate T (xt, yt) and the corneal center C (x0, matches y0).

  However, since the corneal curvature radius of the eye to be examined does not coincide with the corneal curvature radius assumed by the apparatus, the distance between the eye to be examined and the measurement unit is a predetermined working distance as shown in FIG. Absent.

  In step 7 of the flowchart, the control unit 41 causes the visible light source 47 to emit the slit light that is visible light once. A slit image as shown in FIG. 7C is projected onto the image sensor of the corneal thickness measurement light receiving system, and the image is taken where the imaging position does not coincide with the cross position. The cross position is, for example, the center position of the image sensor 50. The cross position is a corneal curvature radius assumed as the corneal curvature radius, and is a position where a slit image is formed when the distance between the eye to be examined and the measurement unit is equal to the working distance. Here, since the clear slit image can be obtained as the distance between the eye to be examined and the measurement part becomes equal to the working distance, the slit image is unclear when the distance between the eye to be examined and the measurement part is not equal to the working distance. Therefore, it is difficult to accurately determine the corneal thickness. Therefore, it is necessary to make the distance between the eye to be examined and the measurement unit equal to the working distance. “Equal” is a concept including a completely equal state and a substantially equal state.

The control unit 41 calculates the deviation Δz of the slit position from the cross position at this time (Step 8). The relationship between this Δz and the shift amount ΔD (= y1−y2) of the near-infrared bright spot image that indicates how much the measurement unit is moved in which direction in order for the slit position to coincide with the cross position, It is stored in the first storage means 51 as a table. Therefore, based on the calculated Δz, the shift amount ΔD is determined with reference to the table (Step 9). From the above calculation of Δz, ΔD is determined by detecting the coordinate position (second imaging coordinate position) of the slit image obtained on the image sensor 50 in the control unit 41, and this coordinate position and a predetermined scattered image coordinate. The amount of misalignment in the optical axis direction (shift amount ΔD) is calculated from the shift from the position of the cross, which is the position, and the shift amount of the bright spot image is calculated based on the table so as to eliminate the misalignment amount. It is executed in a module that functions as calculation means. According to the above steps, the position adjustment using the corneal slit image is performed after the position adjustment between the measurement unit using the bright spot image and the eye to be examined. The adjustment of the position, which is the alignment of the measurement unit with respect to the eye to be examined, is executed by the module area that functions as an adjustment unit in the control unit 41. Note that the alignment deviation amount in the optical axis direction is caused by the fact that the eye's corneal curvature radius is different from the assumed corneal curvature radius, so that the subject's corneal curvature radius can be calculated from the deviation amount. . For example, the control means 41 may calculate the corneal curvature radius of the subject based on the alignment deviation amount ΔD in the optical axis direction.
When y1 <y2, the image shown in FIG. 8B is obtained, and ΔD is ΔD <0.

The control unit 41 causes the second storage means 52 to store ΔD obtained in association with the subject's ID (Step 10).
Then, the measurement unit is moved in the z direction according to the obtained ΔD (Step 11), and the alignment operation is completed. The eye to be examined is changed so as to coincide with the bright spot image coordinate position after the predetermined bright spot image coordinate position is changed based on the shift amount of the bright spot image and the first imaging coordinate position is changed. The operation of aligning the position of the measuring unit with respect to is performed in a module that functions as the second control means of the control unit 41 in the present invention.

After that, the alignment in the z direction with the alignment bright spot, which is near infrared light, is done by aligning the barycentric position of the bright spot with x0, y0, and the y coordinate does not match y1 and y2, but the y coordinate by ΔD Will be adjusted to the shifted position.
When the alignment operation is completed, slit light is emitted to measure the corneal thickness (Step 12).

After the measurement, the alignment bright spot is detected. If the bright spot is shifted, the center of gravity of the bright spot coordinate is matched to x0, y0, and the alignment is performed so that the y coordinate is ΔD. The second measurement of corneal thickness is performed (Steps 11 to 13). Steps 11 to 13 are performed a predetermined number of times, and the corneal thickness measurement is terminated (Step 14).
Note that ΔD> 0 when the corneal curvature radius of the eye to be examined is large.

  If it matches the corneal curvature radius assumed by the device, alignment with the alignment bright spot of near infrared light (Steps 4 and 6) as shown in FIG. The distance to the part is d = WD, which coincides with the working distance, and the obtained image is as shown in FIG. When the visible slit light is irradiated in Step 7 and ΔZ is calculated (Step 8), the slit imaged by the imaging device of the corneal thickness measurement optical system matches the cross as shown in Fig. 8 (c). = 0. At this time, since ΔD stored in the storage means is ΔD = 0, the center of gravity of the two bright spots coincides with x0, y0 and y1 = y2 when realignment is performed thereafter. .

In addition, as in Step 5, by adding a step for determining whether or not ΔD is already recorded in association with the ID of the subject, visible light is used for alignment when measuring the recorded subject. There is no need to irradiate slit light. In this case, the alignment operation can be performed by using ΔD associated with the ID.
When the corneal thickness measurement is completed by the above operation, the intraocular pressure measurement is performed.

  The control unit 41 drives the solenoid 42, and the air in the air chamber 23 is compressed by the piston 40 pushed up by the solenoid 42 and ejected from the nozzle 22 toward the cornea Ec of the eye E as pulsed air. The light beam projected from the measurement light source 37 through the nozzle is successively monitored by the light receiving element 34 as described above.

  The pressure signal detected by the pressure sensor 43 in the air chamber 23 and the light reception signal from the light receiving element 34 are output to the control unit 41, and the control unit 41 calculates the intraocular pressure value from the peak value of the light reception signal and the pressure signal at that time. .

  According to the present invention, since the alignment is performed by the corneal bright spot image, the structure is not complicated. In addition, since precise alignment in the optical axis direction is performed using the scattered image from the second alignment light source, the working distance between the subject's eye and the measurement unit can be made constant irrespective of the corneal curvature radius of the subject. Can be done accurately. Furthermore, since the bright spot position for alignment is changed according to the corneal curvature radius of the subject, the visible light irradiated to the subject at the time of alignment only needs to be applied once, so that the burden on the subject can be reduced.

Furthermore, according to the present invention, since the first alignment light source is also used as the intraocular pressure measurement light source, a new light source is not necessary. In addition, the intraocular pressure can be measured with high accuracy.
Further, since the second alignment light source is also used as a corneal thickness measurement light source, a new light source is unnecessary. In addition, the corneal thickness can be measured with high accuracy.

Further, by having the alignment deviation amount in the optical axis direction and the coordinate position to be changed in a table, the calculation processing time can be shortened and the alignment time can be shortened.
In addition, by having a second storage means for storing the changed coordinate position in association with the ID of the subject, the cornea bright spot image to be changed when the subject with the same ID performs the second measurement. Since the coordinate position is known, there is no need to irradiate visible alignment light.
Further, since the misalignment amount in the optical axis direction is caused by the difference between the corneal curvature radius of the eye and the assumed corneal curvature radius, the subject's corneal curvature radius can be calculated from the misalignment amount. . Therefore, the ophthalmologic apparatus according to the present invention can be used not only for precise alignment but also as a corneal curvature radius measuring device.

(Other examples)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.
The disclosed technology is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present embodiment.

E: eye to be examined, 26: prism diaphragm, 28: imaging device, 37: measurement light source, 41: control unit, 46: slit plate, 47: visible light source, 50: imaging unit, 51: first storage unit, 52 : Second storage means

Claims (9)

A measurement unit for measuring the eye to be examined;
A bright spot image acquisition means for acquiring a bright spot image based on the return light from the eye to be examined irradiated with near infrared light;
Slit image acquisition means for acquiring a slit image of the cornea based on the return light from the eye to be examined irradiated with the slit light;
Adjusting means for adjusting the position of the measuring unit with respect to the eye to be examined using the bright spot image and the slit image;
An ophthalmologic apparatus characterized by comprising:   The ophthalmologic apparatus according to claim 1, wherein the adjustment unit performs the adjustment using the slit image after performing the adjustment using the bright spot image. Comprising light receiving means for receiving return light from the eye to be examined;
3. The ophthalmologic apparatus according to claim 1, wherein the adjustment unit performs the adjustment based on a difference between an imaging position of the slit image in the light receiving unit and a predetermined position of the light receiving unit. . A first alignment light source that emits invisible light having an invisible wavelength;
First imaging means for imaging a bright spot image obtained by irradiating the eye cornea with the invisible light;
A second alignment light source that emits visible light having a visible wavelength;
A second imaging unit that captures a scattered image obtained by irradiating the eye to be examined with the visible light;
The first imaging coordinate position of the first imaging means of the bright spot image is detected, and the measurement with respect to the eye to be examined is performed so that the first imaging coordinate position becomes a predetermined bright spot image coordinate position. First control means for aligning the position of the part;
Detecting a second imaging coordinate position in the second imaging means of the scattered image, calculating an alignment deviation amount in the optical axis direction from a deviation between the second imaging coordinate position and a predetermined scattered image coordinate position; Calculating means for calculating a shift amount of the bright spot image in order to eliminate the alignment shift amount;
Based on the shift amount of the bright spot image, the predetermined bright spot image coordinate position is changed, and the first imaging coordinate position with respect to the eye to be examined is matched with the changed bright spot image coordinate position. An ophthalmologic apparatus comprising: a second control unit that aligns the position of the measurement unit.   The ophthalmologic apparatus according to claim 4, wherein the first alignment light source is an intraocular pressure measurement light source.   The ophthalmologic apparatus according to claim 4, wherein the second alignment light source is a corneal thickness measurement light source. A first storage unit that stores a relationship between the amount of misalignment in the optical axis direction and the amount of shift of the bright spot image as a table;
The ophthalmologic apparatus according to claim 4, wherein the calculation unit calculates a shift amount of the bright spot image based on the table. A second storage means for storing the bright spot shift amount in association with the subject's ID;
The second control unit uses the shift amount of the bright spot image stored in the second storage unit when obtaining the changed bright spot image coordinate position based on the shift amount of the bright spot image. The ophthalmologic apparatus according to any one of claims 4 to 7, wherein the ophthalmic apparatus is characterized.   The ophthalmologic apparatus according to claim 4, wherein a corneal curvature radius of the subject is calculated from the amount of misalignment in the optical axis direction.

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