JP2005245546A - Ophthalmological apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ophthalmological apparatus capable of measuring a cornea thickness without arranging an optical path of a light receiving optical system for measuring the cornea thickness in an inclined direction relative to the optical axis of an anterior ocular segment observing optical system, and to provide the ophthalmological device capable of measuring the cornea thickness while increasing commonly used parts as much as possible. <P>SOLUTION: The ophthalmological apparatus has an observing optical system having an optical axis for observing the anterior ocular segment of an eye to be tested from the front direction, a fixation optical system showing a fixation mark from outside of the light axis of the observing optical system, an irradiating optical system for irradiation with a light beam toward the cornea of the eye to be tested from an optical axis direction symmetrical to the optical axis of the observing optical system across the visual axis of the eye to be tested when fixedly viewing the fixation mark, a light receiving optical system for allowing a light receiving sensor to receive a reflecting image of the front surface of the cornea by irradiation with the optical beam and the reflecting image of the rear surface of the cornea by the sensor from the direction of the optical axis of the observing optical system, and a cornea thickness measuring means for obtaining the cornea thickness based on the output of the light receiving sensor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ophthalmic apparatus used such as an ophthalmic clinic, and relates to an ophthalmic apparatus capable of measuring corneal thickness.

As an ophthalmologic apparatus for measuring the corneal thickness, the visual axis (optical axis) of the eye to be examined is guided on the optical axis of the anterior ocular segment observation optical system for observing the anterior ocular segment of the eye to be examined, and the illumination light beam is emitted from an oblique direction of the eye to be examined. An irradiation optical system for irradiating the cornea is provided, and a light receiving optical system having an optical axis arranged in a direction symmetrical to the optical axis of the irradiation optical system with respect to the optical axis of the anterior ocular segment observation optical system is provided. There is known an apparatus that optically measures the thickness of the cornea by detecting a light beam reflected from the front surface and the back surface of the lens by a light receiving sensor included in a light receiving optical system (see, for example, Patent Document 1).
JP-A-5-146409

  However, in a conventional apparatus capable of measuring the corneal thickness, it is necessary to secure the optical path of the light receiving optical system in an oblique direction with respect to the optical axis of the anterior ocular segment observation optical system. For this reason, for example, if an ophthalmologic apparatus having a measurement optical system for measuring the refractive power and corneal shape of the eye to be examined is added, it may be difficult to secure the optical path of the light receiving optical system. The device configuration becomes complicated.

  In view of the above prior art, the present invention is an ophthalmic apparatus capable of measuring corneal thickness without providing an optical path of a light receiving optical system for measuring corneal thickness in an oblique direction with respect to the optical axis of the anterior ocular segment observation optical system. The technical challenge is to provide It is another object of the present invention to provide an ophthalmologic apparatus capable of measuring the corneal thickness with as many common parts as possible.

(1) An observation optical system having an optical axis for observing the anterior segment of the eye to be examined from the front direction, a fixation optical system for presenting the fixation target from outside the optical axis of the observation optical system, and the fixation target An irradiation optical system that irradiates a light beam toward the eye cornea from an optical axis direction symmetrical to the optical axis of the observation optical system across the visual axis of the eye to be examined when fixed, and the surface of the cornea by irradiation of the light beam A light receiving optical system that causes the light receiving sensor to receive a reflected image and a reflected image of the back side of the cornea from an optical axis direction of the observation optical system; and a corneal thickness measuring unit that calculates a corneal thickness based on an output of the light receiving sensor. It is characterized by.
(2) In the ophthalmologic apparatus according to (1), the observation optical system includes an image sensor that images an anterior segment, and the image sensor also serves as the light receiving sensor.
(3) The ophthalmologic apparatus according to (2) has a measurement optical system for measuring eye refractive power or a corneal shape, and an index projection optical system for projecting an alignment index for aligning the measurement optical system onto the eye to be examined. The fixation optical system also serves as a part of the index projection optical system, and the imaging element of the observation optical system further serves as a detection element that detects the alignment index.
(4) The ophthalmic apparatus according to (1) is a second irradiation optical system that irradiates a light beam toward the eye cornea from an optical axis direction different from the irradiation optical system with respect to the optical axis of the observation optical system. And the corneal thickness measuring means further includes a step of viewing the eye to be inspected based on an output of the light receiving sensor that receives a reflected image on the corneal surface and a reflected image on the back surface of the cornea by irradiation of the light beam of the second irradiation optical system. It is characterized in that a corneal thickness at a part different from the axial part is obtained.

  According to the present invention, the corneal thickness can be measured without providing the optical path of the light receiving optical system for measuring the corneal thickness in an oblique direction with respect to the optical axis of the anterior ocular segment observation optical system. In addition, an ophthalmologic apparatus capable of measuring the corneal thickness can be configured with as many shared parts as possible.

  Embodiments of an ophthalmologic apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is an external view of an ophthalmologic apparatus according to the present invention, and this embodiment is based on an eye refractive power measuring apparatus.

  The measuring apparatus 100 is provided with a base 101, a face support unit 102 attached to the base 101, a movable base 103 provided on the base 101 so as to be movable, and a movable base 103 so as to be movable. A measuring unit 104 that houses the optical system that performs the operation. The measuring unit 104 is moved in the left-right direction (X direction), the up-down direction (Y direction), and the front-back direction (Z direction) with respect to the eye E by an XYZ driving unit 106 provided on the moving table 103. The drive unit 106 includes a slide mechanism, a motor, and the like provided for each of the X, Y, and Z directions. The movable table 103 is moved in the X direction and the Z direction on the base 101 by the operation of the joystick 105, and is moved in the Y direction by the Y drive of the XYZ drive unit 106 by rotating the rotation knob 105a. The moving table 103 is provided with a monitor 107 for displaying various information such as an observation image of the eye E to be examined and measurement results, and a switch unit 108 on which a measurement mode changeover switch and the like are arranged.

  FIG. 2 is a schematic configuration diagram of an optical system and a control system arranged in the measurement unit 104. Reference numeral 1 denotes an infrared light source for measuring eye refractive power, and light from the light source 1 passes through a slit provided in the rotating sector 2 and passes through a projection lens 3, a diaphragm 4, a half mirror 5, and a half mirror 9. The image is projected while being scanned on the fundus of the eye E. Reflected light from the fundus is received by a light receiving unit 8 including a plurality of pairs of light receiving elements via a half mirror 9, a half mirror 5, a light receiving lens 6, and a diaphragm 7. For details on the optical system for measuring eye refractive power, refer to Japanese Patent Application Laid-Open No. 10-108836 by the present applicant. In addition, the cornea reflection image by the light source 1 can also be utilized for alignment in the X direction and the Y direction.

  Reference numeral 14 denotes a visible light source for fixation index projection used for measuring eye refractive power, and the light of the fixation target 15 illuminated by the light source 14 passes through the projection lens 16, the half mirror 13, and the half mirror 9 to be examined. Head to E. Further, as the projection lens 16 moves in the optical axis direction, clouding of the eye E is performed.

  Reference numeral 17 denotes an imaging optical system (anterior ocular segment observation optical system) that images the anterior segment of the eye to be examined. Reference numeral 10 denotes a CCD camera as a two-dimensional imaging device, and light from the anterior segment of the eye to be examined is received by the CCD camera 10 through the half mirror 9, the half mirror 13, the imaging lens 12, and the diaphragm 11. . The optical axis of the imaging optical system 17 is made coaxial with the optical axis L1 by the half mirrors 13 and 9, and the anterior eye portion of the eye to be examined is imaged from the front direction. The diaphragm 11 is at the focal position of the lens 12, and the imaging optical system 17 is configured as a telecentric optical system. The imaging optical system 17 also serves as a detection optical system that detects an alignment index image (an index image of an index projection optical system, which will be described later), and receives a corneal surface reflection image and a corneal back surface reflection image when measuring the corneal thickness. The CCD camera 10 also serves as a light receiving sensor, and also serves as a light receiving optical system. The CCD camera 10 preferably has a high resolution in order to increase the detection accuracy of the index image (corneal reflection image).

  Reference numeral 20 denotes a first index projection optical system that projects a finite index on the eye to be examined. The light source 21 is a near-infrared light source that is visible to the eye to be examined, and two light sources 21 are arranged around the optical axis L1 outside the optical axis L1. The first index projection optical system 20 is arranged such that the projection optical axes intersect at a predetermined angle in the horizontal direction with respect to the optical axis L1. Light from the light source 21 is projected onto the cornea Ec through the spot stop 22. Reference numeral 25 denotes a second index projection optical system that projects an index at infinity onto the eye to be examined. Reference numeral 26 denotes an infrared light source, and two infrared light sources are arranged around the optical axis L1 outside the optical axis L1. The second index projection optical system 25 is arranged such that the projection optical axes intersect with the optical axis in the horizontal direction at a larger angle than the first index projection optical system. Light from the light source 26 is projected onto the cornea Ec via the spot stop 27 and the collimating lens 28.

  Since the index projected by the second index projection optical system 25 is substantially parallel light, the position of the cornea reflection image hardly changes even if the working distance (distance in the Z direction) of the measurement unit 104 with respect to the eye E changes. . On the other hand, since the index projected by the first index projection optical system 20 is divergent light, the position of the corneal reflection image changes when the working distance changes. The alignment state in the Z direction can be detected based on the position of these corneal reflection images (for details, see Japanese Patent Application Laid-Open No. 6-46999 by the present applicant). In addition, since two corneal reflection images by the second index projection optical system 25 are projected left and right around the optical axis L1, by calculating the horizontal center coordinates between these corneal reflection images, The alignment state can be detected. Therefore, by detecting the relative position of the corneal reflection image by the first index projection optical system 20 and the second index projection optical system 25 by the CCD camera 10, the alignment state to the eye to be examined in the XYZ directions can be detected. it can. Thereby, automatic alignment to the eye to be examined can be performed, or alignment can be performed using a predetermined operation unit based on the anterior segment image displayed on the monitor 107.

  A control unit 30 is connected to the CCD camera 10, the light receiving unit 8, the measurement switch 32, the memory 33, and the monitor 107. The control unit 30 has a role of calculating a measurement result based on the outputs of the CCD camera 10 and the light receiving unit 8 and displaying an anterior eye image captured by the CCD camera 10 on the monitor 107. The measurement switch 32 is a switch that outputs a trigger signal for starting measurement. The memory 33 has a role of storing measurement data and the like.

  The measurement of eye refractive power will be briefly described. When the eye refractive power measurement mode is selected by the mode switch of the switch unit 108, the light source 14 and the light source 1 are turned on. The eye to be examined is caused to fixate the fixation target 15 presented from the direction of the optical axis L1 when the light source 14 is turned on. The fixation target 15 is, for example, a landscape chart, and can be distinguished from the light source 21 for alignment. The anterior segment image of the eye to be examined is captured by the CCD camera 10. While observing the anterior segment image and a reticle (not shown) on the monitor 107, the examiner moves the moving table 103 and the measurement unit 104 in the XYZ directions by operating the joystick 105 and the like to roughly align. When the CCD 10 can detect four index images (corneal reflection images) by the first index projection optical system 20 and the second index projection optical system 25, the control unit 30 uses the detection results of these index images as described above. Based on this, the alignment state in each direction of XYZ is obtained, and the measuring unit 104 is moved by the XYZ driving unit 106 to complete the alignment. After the alignment is completed, measurement by the eye refractive power measurement optical system is executed automatically or when the examiner presses the measurement start switch.

  Next, corneal thickness measurement will be described. When the corneal thickness measurement mode is selected by the mode switch, the light source 14 and the light source 1 are turned off. Each alignment light source remains turned on, and either the left or right of the first index projection optical system 20 and the second index projection optical system 25 presents an irradiation optical system and a fixation target for irradiating a light beam for measuring corneal thickness. It is used as a fixation target optical system. For convenience of explanation, in order to distinguish between the left and right first index projection optical systems 20 and the second index projection optical system 25 shown in FIG. 2, in FIG. 3, the left optical system is the first index projection optical system 20a. And the second index projection optical system 25a, and the right optical system as the first index projection optical system 20b and the second index projection optical system 25b. Similarly, each optical member is given a distinguishing symbol.

  Here, the first index projection optical system 20a and the second index projection optical system 25a on the left side as viewed from the subject are used for corneal thickness measurement. The subject is caused to stare at the light source 21a visible on the left side. The alignment at the time of measuring the corneal thickness is the same as that at the time of measuring the eye refractive power, and the measurement unit 104 is moved based on the four index images of each index projection optical system detected by the CCD camera 10. Made. FIG. 3 shows the alignment completed state when the eye to be examined fixedly looks at the light source 21a.

FIG. 4 is a schematic diagram showing an optical relationship among the eye E, the first index projection optical system 20a, the second index projection optical system 25a, and the imaging optical axis L1 when the alignment is completed. In FIG. 4, N1 is a visual axis when the eye E is fixing the light source 21a. The direction of the optical axis M1 of the first index projection optical system 20a and the direction of the optical axis L1 of the imaging optical system are at an angle θ across the visual axis N1 when the eye E is fixing the light source 21a. They are arranged so as to be almost symmetrical. Point P1 is the intersection of the corneal surface on the visual axis N1, and P2 is the intersection of the visual axis N and the corneal back surface. Here, a reflected image (virtual image) by the cornea surface of the light source 26a observed from the axial direction of the optical axis L1 and a reflected image (virtual image) by the cornea back surface are formed as I ₁ and I ₂ , respectively. Since the imaging optical system 17 is configured as a telecentric optical system, the center of the corneal surface reflection image I1 observed from the direction of the optical axis L1 (the principal ray Ls of regular reflection light on the corneal surface P1) and the corneal back surface reflection image I2 Corneal thickness d can be obtained by detecting the distance H from the center (the principal ray Lr of specularly reflected light at the cornea back surface P2).

  When measuring the corneal thickness, if a trigger signal for starting measurement by the measurement switch 32 is input after completion of alignment (or a trigger signal is automatically issued after completion of alignment is detected), the corneal thickness measurement light source 26a. The other light sources 21a, 21b, and 26b and the anterior ocular segment illumination light source (not shown) are turned off (including the case of dimming). Thereby, noise light other than the measurement of corneal thickness is reduced, and other alignment index images (reflected images) are also disappeared, so that it becomes easy to detect the cornea back surface reflected image I2 having a weak light amount.

The anterior ocular segment image captured by the CCD camera 10 is stored in the memory 33. The control unit 30 extracts the reflection images I ₁ and I ₂ in the image stored in the memory 33 and calculates the corneal thickness d based on the interval H. Hereinafter, a method of obtaining the corneal thickness d based on the interval H will be described with reference to FIG.

In FIG. 5, the corneal curvature center is 0 coordinate, the corneal curvature radius is r ₀ , the intersection of the straight line connecting the corneal curvature center and the corneal surface and the corneal surface is P ₁ (Px, Py), and the corneal curvature center and the fixed viewpoint. Is the intersection of the straight line connecting the corneal surface and the back surface of the cornea, P ₂ , and the intersection of the reflected light from P ₂ and the corneal surface is Q (Qx, Qy), ∠P ₁ OS = θ, ∠P ₁ OQ = α, ∠QOS = Β ₀ , ∠P ₁ P ₂ Q = ∠γ, n is the refractive index in the cornea, and 1 is the refractive index in air.
P ₁ = (r ₀ cos θ, r ₀ sin θ)
Q = (r ₀ cos β ₀ , Py−H)
It becomes. Since w in FIG. 5 is w = Qx−Px,
w = r ₀ cos β ₀ -r ₀ cos θ
It becomes. This time,
β ₀ = sin ⁻¹ {(r ₀ sin θ−H) / r ₀ }
It is. Therefore, the distance v between the coordinates P1 and Q is given by the three square theorem:
v = √ (h ² + w ² )
As required. Also, s and t are
s = v · sin (α / 2)
t = v · cos (α / 2)
It becomes. If c is calculated based on these,
c = t / tan (∠γ)
It becomes. However, ∠γ = α + β ₁ and β ₁ = sin ⁻¹ (β ₀ / n). Therefore, the corneal thickness d can be obtained by obtaining d = c + s from the above formula.

With the configuration as described above, a simple corneal thickness can be achieved with a simple configuration without including a light receiving element (imaging element) for measuring corneal thickness and a light receiving element for observing and aligning the eye to be examined. Can be measured. Further, in the above-described embodiment, by combining the index projection optical system for eye fixation to be used for measuring the corneal thickness and the index projection optical system for alignment and the index projection optical system for projecting the corneal thickness measurement index, A simpler configuration can be obtained. Since there is little error in the corneal thickness due to the difference in the corneal curvature radius of the eye to be examined, an average value may be used for the corneal curvature radius r ₀ described above. When the corneal curvature radius r ₀ is known, the value may be input.

  In the ophthalmologic apparatus of the above embodiment, the eye refractive power and the corneal thickness can be measured with one ophthalmologic apparatus. In corneal correction surgery, etc., which corrects the refractive error of the eye by changing the curvature of the cornea, information on the corneal thickness is obtained together with the refractive power of the eye to be examined and the corneal shape. In addition, it is convenient that the eye refractive power and corneal thickness can be measured with a single ophthalmic apparatus.

  FIG. 6 is a configuration example in which an index projection system for measuring the corneal shape is provided for the above embodiment. The optical system behind the optical axis L1 is omitted because an optical system similar to that shown in FIG. 2 is disposed. The projection optical system that projects the index onto the eye to be examined includes a first index projection optical system 50, a second index projection optical system 55, and a third index projection optical system 60 in order of increasing distance from the optical axis L1. The first index projection optical system 50 includes a light source 51 and a spot stop 52, and is configured to project an index of finite infrared light onto the eye to be examined. The second index projection optical system 55 includes a near-infrared light source 56 that emits visible near-infrared light, a spot stop 57, and a collimating lens 58, and projects an infinite index onto the eye to be examined by a parallel light flux. The third index projection optical system 60 includes a near-infrared light source 61, a spot stop 62, and a collimating lens 63, which also project an infinite index onto the eye to be examined. Four second index projection optical systems 55 are arranged around the optical axis L1, two of which are projected light in the horizontal direction of the apparatus and the other two in the vertical direction of the apparatus. The axes are arranged so as to intersect with the optical axis L1 at a predetermined angle. The second index projection optical system 55 is used for both corneal shape measurement and alignment, and is used as a fixation optical system when measuring corneal thickness. The third index projection optical system 60 may be arranged on either the left or right side.

  When alignment is performed in the above configuration, the relative position of the corneal reflection image is changed by the first index projection optical system 50 and the second index projection optical system 55 in order to perform alignment so that the eye to be examined is coaxial with the optical axis L1. Is detected by the CCD camera 10 to detect the alignment state. In addition, since the index projected by the second index projection optical system 55 forms four corneal reflection images around the optical axis L1, the corneal shape of the eye to be examined is measured by detecting these positions with the CCD camera 10. To do.

  When measuring the corneal thickness of the eye to be examined, after the alignment is completed with the light source of the second index projection optical system 55 located on the third index projection optical system 60 side fixed to the eye, The light sources 51 and 56 are turned off, and the light source 61 of the third projection optical system 60 is turned on. Thereby, an index for measuring the corneal thickness is projected, and the corneal thickness is measured in the same manner as described above based on the corneal surface reflection image and the corneal back surface reflection image. In this example, the visual axis N2 of the eye to be inspected when the light source 56 of the second index projection optical system 55 is fixed to the eye to be examined is arranged so as to coincide with the projection optical axis. The direction of the optical axis L1 and the optical axis direction of the third index projection optical system 60 are substantially symmetrical with respect to N2.

FIG. 7 shows a modified example in which a third index projection optical system 70 is added to the index projection optical system shown in FIGS. 3 and 4. The index projection / projection optical system 70 includes an infrared ray 71, a spot stop 72, and a collimating lens 73, and projects an index at infinity onto the eye to be examined by a substantially parallel light beam. The projection optical axis M3 is arranged so as to have an angle φ larger than the optical axis M1 of the second index projection optical system 26a with respect to the optical axis L1. For this reason, the light flux by the index projection optical system 70 forms a corneal surface reflection image I ₃ and a corneal back surface reflection image I ₄ at a site different from the second index projection optical system 26a. The reflected images I ₃ and I ₄ are picked up by the CCD camera 10 of the image pickup optical system 17 and the distance between them is detected, whereby the corneal film thicknesses at the corneal surface P3 and the corneal back surface P4 which are different from the visual axis N are obtained. Can be obtained. Further, by setting the third index projection optical system 70 so that the optical axis angle φ is different, the corneal thickness at other parts can be measured.

  A configuration in which the visual axis N of the eye to be examined is guided to the optical axis L1 using the fixation target 15 at the center of the optical axis L1, and a plurality of the second index projection optical system 26a and the third index projection projection optical system 70 are provided. Then, the corneal thickness of the corneal region other than on the visual axis N can be measured at a plurality of locations, and the distribution of corneal thickness can be easily obtained.

  In the above embodiment, the CCD camera 10 of the imaging optical system 17 also serves as a light receiving sensor for receiving a corneal surface reflection image and a corneal back surface reflection image for measuring the corneal thickness, but a dedicated light receiving sensor is provided. Also good. In this case, a beam splitter is provided between the diaphragm 11 and the CCD camera 10, and a light receiving sensor for receiving the cornea surface reflection image and the cornea back surface reflection image is provided in the reflection direction. When a one-dimensional line sensor is used as the light receiving sensor, a corneal reflection image can be easily detected by arranging a cylindrical lens having a cylindrical axis perpendicular to the detection direction in the optical path.

1 is an external view of an ophthalmologic apparatus according to the present invention. It is a schematic block diagram of the optical system and control system which are arrange | positioned at a measurement part. It is a figure which shows the alignment completion state when a to-be-tested eye stares at the light source 21a of a 1st parameter | index projection optical system. It is the schematic which shows the optical relationship of the to-be-tested eye E, the 1st parameter | index projection optical system, the 2nd parameter | index projection optical system, and the imaging optical axis L1 when alignment is completed. It is a figure explaining the method of calculating | requiring a corneal thickness. It is a configuration example provided with an index projection system for corneal shape measurement. It is an example of a configuration in which the corneal thickness of a part different from the visual axis part of the eye to be examined can be measured simultaneously.

Explanation of symbols

10 CCD camera 20 First index projection optical system 21a Light source 25, 25a Second index projection optical system 33 Memory 50 First index projection optical system 55 Second index projection optical system 60 Third index projection optical system 70 Third index projection optical System L1 Imaging optical axis N1 Visual axis

Claims (4)

An observation optical system having an optical axis for observing the anterior segment of the eye to be examined from the front direction, a fixation optical system for presenting the fixation target from outside the optical axis of the observation optical system, and the fixation target An irradiation optical system that irradiates a light beam toward the eye cornea from an optical axis direction symmetrical to the optical axis of the observation optical system across the visual axis of the subject eye, and a reflection image of the cornea surface by irradiation of the light beam A light-receiving optical system that causes a light-receiving sensor to receive a reflected image of the back surface of the cornea from an optical axis direction of the observation optical system; Ophthalmic equipment. The ophthalmologic apparatus according to claim 1, wherein the observation optical system includes an image sensor that captures an anterior segment, and the image sensor also serves as the light receiving sensor. The ophthalmologic apparatus according to claim 2 includes a measurement optical system for measuring eye refractive power, a corneal shape, and the like, and an index projection optical system for projecting an alignment index for aligning the measurement optical system onto the eye to be examined. An ophthalmologic apparatus, wherein an optical system also serves as a part of the index projection optical system, and an imaging element of the observation optical system further serves as a detection element that detects the alignment index. The ophthalmologic apparatus according to claim 1 includes a second irradiation optical system that irradiates a light beam from the direction of the optical axis different from the irradiation optical system with respect to the optical axis of the observation optical system toward the eye cornea. The corneal thickness measurement means further includes a visual axis portion of the eye to be inspected based on an output of the light receiving sensor that receives a reflection image of the corneal surface and a reflection image of the back surface of the cornea by irradiation of the light beam of the second irradiation optical system. An ophthalmologic apparatus characterized by obtaining corneal thickness at different sites.

Images