Ophthalmic device

Abstract

An ophthalmic apparatus capable of detecting eye position deviation when enlarging a luminance difference of an indicator presented to left and right test eyes in a state of looking from both eyes, regardless of the presence or absence of an oblique position. When a distance from the left and right test eyes to an indicator is an indicator presentation distance, and a distance of a line-of-sight intersection point at which the left and right lines of sight intersect is a vergence distance, the ophthalmic apparatus includes an indicator projection system that presents the indicator, a drive mechanism that adjusts the vergence distance, an observation system that detects anterior eye portion images of the left and right test eyes, and a control section that controls the indicator projection system, the drive mechanism, and the observation system. The control section presents the indicator at an arbitrary indicator presentation distance in a state in which the vergence distance is set to a distance different from the indicator presentation distance, gradually enlarges a luminance difference between the indicator presented to the left test eye and the indicator presented to the right test eye, and detects directions of the left and right lines of sight of the left and right test eyes based on the anterior eye portion images.

Description

Technical Field

[0001] This invention relates to an ophthalmic device. Background Technology

[0002] Previously, there were ophthalmic devices that, starting from confirming the state of the visual target with binocular vision, gradually darkened the field of vision of one of the tested eyes, and estimated the fatigue level of the tested eye based on the moment when the line of sight of the tested eye deviated due to the destruction of fusion, resulting in eye position deviation (line of sight deviation) (for example, see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: Japanese Patent Application Publication No. 2017-169601. Summary of the Invention

[0006] The problem the invention aims to solve

[0007] However, current ophthalmic devices rely on the premise that eye displacement occurs when the visual field of one of the examined eyes is darkened and fusion is disrupted. However, in the absence of subjects with exotropia or esotropia, since fusion is disrupted when viewing from both eyes, the line of sight does not deviate, and therefore eye displacement does not occur. Consequently, eye displacement cannot be detected, making it impossible to presume eye fatigue.

[0008] The present invention was made in view of the above-mentioned problems, and its purpose is to provide an ophthalmic device that can detect eye position deviation when the brightness difference of the visual target indicated to the left and right eyes is amplified in a binocular viewing state, regardless of whether there is strabismus.

[0009] means for solving problems

[0010] To achieve the above objectives, the ophthalmic apparatus of the present invention, wherein, when the distance from the left and right examined eyes to the visual target is used as the visual target prompting distance, the position where the line of sight of the left examined eye and the line of sight of the right examined eye intersect is used as the line of sight intersection point, and the distance from the left and right examined eyes to the line of sight intersection point is used as the convergence distance, comprises: a visual target prompting mechanism that prompts the visual target to the left and right examined eyes and is capable of changing the brightness difference between the visual target prompted to the left examined eye and the visual target prompted to the right examined eye; and a convergence adjustment mechanism that adjusts the convergence distance. The system includes a convergence distance measurement unit, an eye information acquisition unit that acquires eye information of the left and right examined eyes, and a control unit that controls the target prompting mechanism, the convergence adjustment mechanism, and the eye information acquisition unit. The control unit is configured to control the convergence adjustment mechanism to set the convergence distance to a distance different from the target prompting distance, prompt the target at any target prompting distance through the target prompting mechanism, and gradually increase the brightness difference. Based on the eye information acquired by the eye information acquisition unit, the system detects the gaze direction of the left examined eye and the gaze direction of the right examined eye.

[0011] The effects of the invention

[0012] The ophthalmic device of the present invention, configured in this way, can detect eye position deviation when the brightness difference of the visual target indicated to the left and right eyes is amplified in a binocular viewing state, regardless of whether there is strabismus. Attached Figure Description

[0013] Figure 1 This is a perspective view showing the appearance of the ophthalmic device according to the first embodiment.

[0014] Figure 2 This is an explanatory diagram schematically showing the drive mechanism of the measuring head of the ophthalmic device of the first embodiment.

[0015] Figure 3 This is an explanatory diagram showing the convergence distance and the target indication distance.

[0016] Figure 4 This is an explanatory diagram showing the structure of the left measuring optical system of the ophthalmic device of the first embodiment.

[0017] Figure 5 This is a flowchart illustrating the process of eye fatigue estimation treatment implemented by the control unit in the first embodiment. Detailed Implementation

[0018] Hereinafter, based on the first embodiment shown in the accompanying drawings, a method for implementing the ophthalmic device of the present invention will be described.

[0019] The ophthalmic device 1 of the first embodiment has an optical system for measuring the ocular characteristics of an examined eye, and is an ophthalmic device capable of objectively and subjectively measuring the ocular characteristics of an examined eye. That is, the examiner can use the ophthalmic device 1 to perform any objective and subjective examination. Furthermore, in objective examinations, the examined eye is illuminated, and information (ocular characteristics) related to the examined eye is measured based on the detection results of the reflected light. Here, objective examinations include measurements to acquire the ocular characteristics of the examined eye and image acquisition of the examined eye. Objective examinations include objective refractive measurement (refractive measurement), corneal shape measurement (corneal curvature measurement), intraocular pressure measurement, fundus photography, tomographic imaging using optical coherence tomography (OCT), and measurement using OCT, etc. In addition, in subjective examinations, visual targets are presented to the examinee, and information (ocular characteristics) related to the examined eye is measured based on the examinee's response to the presented visual targets, etc. Subjective examinations include examinations for hyperopia, intermediate vision, myopia, contrast, glare, and other subjective refractive measurements and visual field tests.

[0020] Furthermore, the ophthalmic device 1 of the first embodiment is a binocular open type ophthalmic device that can simultaneously measure the ocular characteristics of both eyes while the subject has both eyes open. Additionally, in the ophthalmic device 1 of the first embodiment, ocular characteristics can also be measured eye-by-eye by covering one eye or turning off the fixation target.

[0021] And, as Figure 1 As shown, the ophthalmic device 1 of the first embodiment includes a support base 10, a measuring unit 20, a controller for the examiner 30, a control unit 40, and a controller for the subject (not shown). Hereinafter, from the subject's perspective, the left-right direction is defined as the X direction, the up-down direction (plumb line direction) as the Y direction, and the direction orthogonal to the X and Y directions (depth direction) as the Z direction.

[0022] The support base 10 has a support column 11 erected from the ground and an eye examination table 12 supported by the support column 11. The eye examination table 12 is a table for placing devices or instruments for eye examination, such as the examiner controller 30, or for supporting the posture of the examinee. The eye examination table 12 can also be supported by the support column 11 to a position (height position) that can be adjusted in the Y direction.

[0023] The measuring unit 20 includes an arm 21 and a measuring head 22. One end of the arm 21 is supported by the front end of the support column 11, and the other end extends from the support column 11 toward the anterior side (subject side) along the Z direction, with the measuring head 22 mounted at the front end. Thus, the measuring head 22 is suspended from the support column 11 above the eye examination table 12 via the arm 21. Furthermore, the arm 21 can move relative to the support column 11 in the Y direction. Additionally, the arm 21 can also be configured to move relative to the support column 11 in both the X and Z directions.

[0024] The measuring head 22 is a part that measures the ocular characteristics of the subject's left eye E (left eye EL) and right eye E (right eye ER) respectively. The measuring head 22 has a left eye drive mechanism 23L and a right eye drive mechanism 23R mounted on the front end of the arm 21, a left measuring part 24L located below the left eye drive mechanism 23L, and a right measuring part 24R located below the right eye drive mechanism 23R.

[0025] Here, the left measuring unit 24L and the right measuring unit 24R are a pair, each individually corresponding to the left and right eyes of the subject. Furthermore, the left measuring unit 24L contains a left measuring optical system 25L for measuring the ocular characteristics of the left eye (EL). The right measuring unit 24R contains a right measuring optical system 25R for measuring the ocular characteristics of the right eye (ER). The results measured by the left measuring unit 24L and the right measuring unit 24R are input to the control unit 40.

[0026] Additionally, the left-eye drive mechanism 23L is a mechanism that drives the left measuring unit 24L to move horizontally (X direction), move the plumb bob (Y direction), rotate in the X direction, and rotate in the Y direction. For example... Figure 2 As shown, the left eye drive mechanism 23L includes a left plumb bob drive unit 26L, a left horizontal drive unit 27L, a left Y-axis rotary drive unit 28L, and a left X-axis rotary drive unit 29L. The right eye drive mechanism 23R drives the right measuring unit 24R to move horizontally (X-direction), move the plumb bob (Y-direction), and rotate in the X-direction and Y-direction. The right eye drive mechanism 23R includes a right plumb bob drive unit 26R, a right horizontal drive unit 27R, a right Y-axis rotary drive unit 28R, and a right X-axis rotary drive unit 29R.

[0027] Furthermore, the left eye drive mechanism 23L and the right eye drive mechanism 23R are configured to be symmetrical about the plumb plane located in the middle of them in the X direction. Hereinafter, unless otherwise stated, the left eye drive mechanism 23L and the right eye drive mechanism 23R will be referred to as "drive mechanism 23", the left measuring section 24L and the right measuring section 24R will be referred to as "measuring section 24", the left plumb drive section 26L and the right plumb drive section 26R will be referred to as "plumb drive section 26", the left horizontal drive section 27L and the right horizontal drive section 27R will be referred to as "horizontal drive section 27", the left Y-axis rotary drive section 28L and the right Y-axis rotary drive section 28R will be referred to as "Y-axis rotary drive section 28", and the left X-axis rotary drive section 29L and the right X-axis rotary drive section 29R will be referred to as "X-axis rotary drive section 29".

[0028] A plumb bob drive unit 26 is disposed between the arm 21 and the horizontal drive unit 27, allowing the horizontal drive unit 27 to move relative to the arm 21 in the Y direction (plumb bob direction). The horizontal drive unit 27 is disposed between the plumb bob drive unit 26 and the Y-axis rotary drive unit 28, allowing the Y-axis rotary drive unit 28 to move relative to the plumb bob drive unit 26 in the X and Z directions (horizontal directions). The plumb bob drive unit 26 and the horizontal drive unit 27 are configured to include an actuator that generates driving force, such as a stepper motor, and a transmission mechanism that transmits driving force, such as a gear combination or a rack and pinion. For example, by separately arranging the actuator and transmission mechanism in the X and Z directions, the horizontal drive unit 27 can be easily configured, and horizontal movement can be easily controlled.

[0029] The Y-axis rotation drive unit 28 is disposed between the horizontal drive unit 27 and the X-axis rotation drive unit 29, such that the X-axis rotation drive unit 29 rotates relative to the horizontal drive unit 27 around the Y-axis of eye rotation, which passes through the eye rotation point O of the corresponding examined eye E and extends in the Y direction. The X-axis rotation drive unit 29 is disposed between the Y-axis rotation drive unit 28 and the corresponding measuring unit 24, such that the corresponding measuring unit 24 rotates relative to the Y-axis rotation drive unit 28 around the X-axis of eye rotation, which passes through the eye rotation point O of the corresponding examined eye E and extends in the X direction.

[0030] The Y-axis rotation drive unit 28 and the X-axis rotation drive unit 29 are configured, for example, to have actuators and transmission mechanisms similar to the plumb bob drive unit 26 or the horizontal drive unit 27. The transmission mechanism, which receives the driving force from the actuator, moves along an arc-shaped guide groove. The Y-axis rotation drive unit 28, by aligning the center position of the guide groove with the Y-axis of eye rotation, enables the measuring unit 24 to rotate around the Y-axis of the corresponding eye E. Similarly, the X-axis rotation drive unit 29, by aligning the center position of its guide groove with the X-axis of eye rotation, enables the measuring unit 24 to rotate around the X-axis of the corresponding eye E. In other words, by aligning the center positions of the guide grooves of the Y-axis rotation drive unit 28 and the X-axis rotation drive unit 29 with the eye rotation point O of the corresponding eye E, the measuring unit 24 can rotate around the eye rotation point O in both the left-right direction (rotation direction centered on the Y-direction) and the up-down direction (rotation direction centered on the X-direction).

[0031] Furthermore, the Y-axis rotation drive unit 28 can also support the measuring unit 24 by rotating around its own Y-axis rotation axis, and cooperate with the horizontal drive unit 27 to change and rotate the position supporting the measuring unit 24 via the X-axis rotation drive unit 29, thereby causing the measuring unit 24 to rotate around the Y-axis of the eyeball rotation of the corresponding tested eye E. Additionally, the X-axis rotation drive unit 29 can also support the measuring unit 24 by rotating around its own X-axis rotation axis, and cooperate with the plumb bob drive unit 26 to change and rotate the position supporting the measuring unit 24, thereby causing the measuring unit 24 to rotate around the X-axis of the eyeball rotation of the corresponding tested eye E.

[0032] In this way, the drive mechanism 23 moves the left measuring unit 24L and the right measuring unit 24R individually or in conjunction in the X, Y, and Z directions. The left measuring unit 24L rotates up, down, left, and right around the ocular rotation point O of the left examined eye EL, and the right measuring unit 24R rotates up, down, left, and right around the ocular rotation point O of the right examined eye ER. Thus, the drive mechanism 23 can move the left measuring unit 24L and the right measuring unit 24R relative to their respective examined eyes E to the desired position (posture).

[0033] Furthermore, by adjusting the positions of the left measuring unit 24L and the right measuring unit 24R, the drive mechanism 23 can cause the left eye EL and the right eye ER to diverge (divergence movement) or converge (convergence movement). That is, the drive mechanism 23 (the drive mechanism 23L for the left eye and the drive mechanism 23R for the right eye) becomes a convergence adjustment mechanism for adjusting the convergence distance L1. In addition, as... Figure 3As shown, "convergence distance L1" refers to the distance along the Z direction from the left and right examined eyes EL and ER to the line-of-sight intersection point P1 when observing the left and right examined eyes EL and ER from a top-down perspective. "Line-of-sight intersection point P1" is the position where the line-of-sight direction SL (line of sight) of the left examined eye EL intersects with the line-of-sight direction SR (line of sight) of the right examined eye ER. The convergence distance L1 is set by controlling the angle formed by the line-of-sight direction SL of the left examined eye EL and the line-of-sight direction SR of the right examined eye ER, i.e., the convergence angle θ1.

[0034] Furthermore, in the ophthalmic device 1 of the first embodiment, biasing members 24a are respectively provided in the left measuring unit 24L and the right measuring unit 24R. The left measuring optical system 25L and the right measuring optical system 25R acquire the ocular characteristics of the left and right tested eyes EL and ER respectively through the biasing members 24a. The ophthalmic device 1 adjusts the positions of the left measuring unit 24L and the right measuring unit 24R so that each biasing member 24a is positioned corresponding to the left tested eye EL and the right tested eye ER respectively, thereby enabling the simultaneous acquisition of ocular characteristics when the subject's eyes are open (looking with both eyes). In addition, the ophthalmic device 1 uses the X-axis rotation drive unit 29 to change the rotation posture of the left measuring unit 24L and the right measuring unit 24R around the eyeball rotation X-axis, thereby enabling the acquisition of ocular characteristics when the left and right tested eyes EL and ER are looking down or up. Furthermore, the ophthalmic device 1 uses the Y-axis rotation drive unit 28 to change the rotation posture of the left measurement unit 24L and the right measurement unit 24R around the Y-axis of eye rotation, thereby enabling the acquisition of ocular characteristics when the left and right eyes EL and ER are looking to the left or right.

[0035] The user controller 30 is an information processing device that receives operations from the user and outputs control signals to the control unit 40. The user controller 30 is, for example, a tablet computer or smartphone, separate from the measurement unit 20, and can be carried by the user. Alternatively, the user controller 30 can be a laptop or desktop computer, or a controller specifically designed for the ophthalmic device 1. The user controller 30 can exchange information with the control unit 40 via wireless communication or network communication.

[0036] In addition, such as Figure 1 As shown, the tester controller 30 includes a display unit 31, an operation-side control unit (not shown), and input buttons (not shown). The display unit 31 consists of a touch panel display screen provided on the surface of the tester controller 30, and includes input buttons. The operation-side control unit consists of a microcomputer built into the tester controller 30. Based on the measurement or test results sent from the control unit 40, the operation-side control unit controls the image displayed on the display unit 31. Furthermore, the operation-side control unit outputs control signals corresponding to the operation of the input buttons to the control unit 40.

[0037] The control unit 40 is an information processing device located below the eye examination table 12. Based on control signals sent from the examiner's controller 30, the control unit 40 comprehensively controls each part of the measurement unit 20, including the left measurement optics system 25L and the right measurement optics system 25R. Furthermore, the control unit 40 sends the measurement results of the ocular characteristics (EL and ER) of the left and right examined eyes measured by the left measurement unit 24L and the right measurement unit 24R to the examiner's controller 30.

[0038] In addition, the control unit 40 performs the eye fatigue estimation process described later. In the eye fatigue estimation process, the control unit 40 first controls the target prompting mechanism (the target projection system 42 described later) to individually prompt the target at an arbitrary target prompting distance L2 for the left eye EL and the right eye ER, and allows the left eye EL and the right eye ER to visually confirm the target respectively. At this time, the control unit 40 controls the drive mechanism 23 (the drive mechanism 23L for the left eye and the drive mechanism 23R for the right eye) to adjust the position (orientation) of the left measuring unit 24L and the right measuring unit 24R, setting the convergence angle θ1 to a predetermined angle and the convergence distance L1 to a distance different from the target prompting distance L2. Then, the control unit 40 controls the target prompting mechanism (target projection system 42) to gradually increase the brightness difference (contrast difference) between the brightness of the target prompted to the left eye EL (the contrast of the target relative to the background) and the brightness of the target prompted to the right eye ER (the contrast of the target relative to the background). Furthermore, while amplifying the brightness difference of the visual targets, the control unit 40 detects the gaze direction SL of the left eye EL and the gaze direction SR of the right eye ER based on the eye information (anterior eye image E′) acquired by the eye information acquisition unit (observation system 41 described later). Further, the control unit 40 estimates the fatigue level (eye fatigue) of the left eye EL and the right eye ER based on the gaze direction SL of the left eye EL and the gaze direction SR of the right eye ER.

[0039] In addition, such as Figure 3 As shown, "target cuing distance L2" refers to the distance along the Z-direction from the left eye EL to the target cued to the left eye EL, and the distance along the Z-direction from the right eye ER to the target cued to the right eye ER. Here, the target cuing distance L2 for the left eye EL and the target cuing distance L2 for the right eye ER are set to the same distance. Furthermore, in the first embodiment, the target cuing distance L2 is implemented by the target cuing mechanism, i.e., the target projection system 42. The target cuing distance L2 can be calculated from the power of the target projection system 42 (the force that deflects light using the force of the lens) and expressed as a diopter conversion value.

[0040] That is, the control unit 40 uses the position of the far point, which is in conjunction with the refractive values ​​(equivalent spherical power) of the left and right tested eyes EL and ER, as a reference. It moves the movable lens 42e of the optotype projection system 42 and controls the power of the optotype projection system 42 to display the optotype at any predetermined distance (optotype prompting distance L2). For example, when the optotype prompting distance L2 is set to 50cm, the control unit 40 moves the movable lens 42e according to the position of the far point of the left and right tested eyes EL and ER (for example, assuming the refractive value of the left and right tested eyes EL and ER is -5.0D). The difference in power (2.0D) between displaying the optotype at the far point position (0D) and at a position of 50cm (2.0D) is changed to myopia. This alters the power of the optotype projection system 42 to display the optotype at a position with a refractive value of -7.0D. As a result, the control unit 40 can display the optotype displayed at a position of 50cm for the left and right tested eyes EL and ER through the optotype projection system 42.

[0041] Furthermore, when performing eye fatigue estimation processing, the control unit 40 sets the convergence distance L1, which is set based on the convergence angle θ1, to a distance shorter than the target indication distance L2. The control unit 40 maintains the target indication distance L2 at this time. That is, during eye fatigue estimation processing, the control unit 40 sets the convergence angle θ1 to a value larger than the convergence angle θ2 when both eyes are viewing the indicated target position, causing the left eye EL and right eye ER to converge to view a distance closer than the target indication distance L2, and causing the left eye EL and right eye ER to rotate inward (…). Figure 3 Reference).

[0042] Furthermore, during the implementation of the eye fatigue estimation process, when the control unit 40 detects the line of sight SL of the left eye EL and the line of sight SR of the right eye ER, it detects the focal position (accommodation position) of the left eye EL and the focal position (accommodation position) of the right eye ER based on the eye information (based on the ring image of fundus reflected light) acquired by the eye information acquisition unit (eye refractive power measurement system 43). In addition, the "focal position" is represented by the refractive power of the left eye EL or the right eye ER when observing a predetermined position.

[0043] The following is based on Figure 4 The detailed structure of the left measuring optical system 25L and the right measuring optical system 25R will be described below. Furthermore, the left measuring optical system 25L and the right measuring optical system 25R have the same structure. Therefore, the description of the right measuring optical system 25R will be omitted below, and only the left measuring optical system 25L will be described.

[0044] like Figure 4As shown, the left measurement optics system 25L includes an observation system 41 (eye information acquisition unit), a target projection system 42 (target prompting mechanism), an eye refractive power measurement system 43 (eye information acquisition unit), a Z-alignment system 45, an XY-alignment system 46, and a corneal system 47. Here, the observation system 41 observes the anterior portion of the left examined eye EL and acquires an anterior eye image E′. The target projection system 42 prompts the target at any target prompting position for the left examined eye EL. That is, the target projection system 42 can set the target prompting distance L2 to an arbitrary distance. The eye refractive power measurement system 43 measures the eye refractive power (refractive characteristics) of the left examined eye EL. The Z-alignment system 45 and the XY-alignment system 46 are configured for aligning the left measurement optics system 25L relative to the left examined eye EL. The Z-alignment system 45 generates alignment information along the Z-direction (front-back direction) of the optical axis L of the observation system 41, and the XY-alignment system 46 generates alignment information in the Y-direction and X-direction (up, down, left, and right directions) orthogonal to the optical axis L. The corneal system 47 measures the corneal shape of the left examined eye EL.

[0045] The observation system 41 includes an objective lens 41a, a first dichroic filter 41b, a first semi-reflective mirror 41c, a first relay lens 41d, a second dichroic filter 41e, a first imaging lens 41f, and an imaging element (CCD) 41g.

[0046] In the observation system 41, a light beam reflected from the anterior portion of the left examined eye EL passes through the objective lens 41a and is imaged onto the imaging element 41g by the first imaging lens 41f. Thus, an anterior eye image E′ is formed on the imaging element 41g by projecting (illuminating) the corneal ring beam (described later), the beam from the first aligned light source 45a, and the beam from the second aligned light source 46a (spot image Br). The imaging element 41g captures the anterior eye image E′, acquiring the image signal of the anterior eye image E′. The control unit 40 displays the anterior eye image E′, etc., based on the image signal output from the imaging element 41g, on the display unit 31 of the examiner's controller 30. Furthermore, the control unit 40 detects the gaze direction SL of the left examined eye EL based on the anterior eye image E′.

[0047] A corneal system 47 is disposed in front of the objective lens 41a. The corneal system 47 includes a corneal plate 47a and a corneal ring light source 47b. The corneal plate 47a is a plate with concentric slits about the optical axis L of the observation system 41 and is disposed near the objective lens 41a. The corneal ring light source 47b is disposed corresponding to the slits of the corneal plate 47a.

[0048] In the corneal system 47, a light beam from the illuminated corneal ring light source 47b passes through the slit of the corneal plate 47a, thereby projecting (projecting) the corneal ring beam (a ring-shaped target for corneal curvature measurement) used for corneal shape determination onto the cornea Ec of the left examined eye EL. The corneal ring beam is reflected at the cornea Ec of the left examined eye EL, and is thus imaged on the imaging element 41g by the observation system 41. The imaging element 41g detects (receives) the image of the ring-shaped corneal ring beam. The control unit 40 displays the image of the corneal ring beam detected by the imaging element 41g on the display unit 31. Furthermore, based on the image signal detected by the imaging element 41g, the control unit 40 determines the corneal shape (radius of curvature) of the left examined eye EL using a known method.

[0049] A Z-alignment system 45 is provided behind the corneal system 47 (corneal plate 47a). The Z-alignment system 45 has a pair of first alignment light sources 45a and a pair of first projection lenses 45b.

[0050] In the Z alignment system 45, the light beams from each of the first alignment light sources 45a are transformed into parallel light beams by each of the first projection lenses 45b, and the parallel light beams are projected onto the cornea Ec of the left eye EL through the alignment aperture provided in the corneal plate 47a.

[0051] The control unit 40 or the examiner aligns the image along the optical axis L (Z-direction, front-back direction) of the observation system 41 by moving the left measuring unit 22L (or the right measuring unit 22R) in the front-back direction, based on the light spot (light spot image Br) projected onto the cornea Ec. Furthermore, during Z-direction (front-back direction) alignment, the control unit 40 or the examiner adjusts the position of the left measuring unit 22L (or the right measuring unit 22R) so that the ratio of the distance between the two point images from the first alignment light source 45a on the imaging element 41g to the diameter of the corneal ring image converges within a specified range.

[0052] Additionally, an XY alignment system (parallel optical system) 46 is provided in the observation system 41. The XY alignment system 46 has a second alignment light source 46a and a second projection lens 46b. Furthermore, the XY alignment system 46 shares a first semi-reflective mirror 41c, a first dichroic filter 41b, and an objective lens 41a with the observation system 41.

[0053] In the XY alignment system 46, the light beam from the second alignment light source (point light source) 46a is converted into a parallel beam by the objective lens 41a and projected onto the cornea Ec of the left eye EL being examined. The parallel beam projected from the XY alignment system 46 onto the cornea Ec of the left eye EL being examined forms an alignment light spot at approximately the midpoint between the corneal apex and the center of curvature of the cornea Ec.

[0054] The control unit 40 or the examiner aligns the light spot (light spot image Br) projected onto the corneal Ec by moving the left measuring unit 22L (or the right measuring unit 22R) in the up-down or left-right direction, based on the light spot (light spot image Br) projected onto the corneal Ec.

[0055] The target projection system 42 includes a display 42a (first display), a first rotating prism 42b, a second rotating prism 42c, a second imaging lens 42d, a moving lens 42e, a second relay lens 42f, a first field lens 42g, a first reflecting mirror 42h, and a third dichroic filter 42i. Furthermore, the target projection system 42 shares the first dichroic filter 41b and the objective lens 41a with the observation system 41.

[0056] The display 42a displays various types of visual targets, including fixed or dot-shaped visual targets used as fixed lines of sight during objective examinations or when fogging is applied to the left eye (EL) being examined, and subjective examination targets used for subjectively examining the ocular characteristics (visual acuity or correction power (for hyperopia, myopia, etc.)) of the left eye (EL). Furthermore, the visual targets displayed on the display 42a are not particularly limited as long as they are used for eye examinations; for example, Randall's ring, Snellen's target, and E-target are preferred. Additionally, the visual targets can be still images or moving images.

[0057] Furthermore, the display 42a can use an EL (electroluminescent) or liquid crystal display (LCD) to display targets with desired shapes, forms, and contrast (brightness). That is, the display 42a can be controlled by the control unit 40 to display any target, and the brightness (contrast of the target relative to the background) of the displayed target can be changed arbitrarily.

[0058] The first rotating prism 42b and the second rotating prism 42c are used to adjust the prism power and prism base orientation during oblique inspection, and are rotated independently by a stepper motor or the like. If the first rotating prism 42b and the second rotating prism 42c rotate in opposite directions, the prism power will change continuously; if they rotate together in the same direction, the prism base orientation will change continuously.

[0059] The movable lens 42e is driven forward and backward along the optical axis of the optotype projection system 42 by a drive motor (not shown) controlled by the control unit 40. The control unit 40 can shift the refractive index towards the negative side by moving the movable lens 42e to the left eye EL side. Furthermore, the control unit 40 can shift the refractive index towards the positive side (hyperopic direction) by moving the movable lens 42e away from the left eye EL. Therefore, the optotype projection system 42 changes the prompting position of the optotype displayed on the display 42a by driving the movable lens 42e forward and backward, thereby enabling the optotype to be prompted at any position for the left eye EL. That is, the ophthalmic device 1 of the first embodiment can set the optotype prompting distance L2 from the left eye EL to the optotype prompting position to an arbitrary distance.

[0060] Furthermore, the ophthalmic device 1 of the first embodiment includes a left measurement optics system 25L for measuring the ocular characteristics of the left eye (EL) and a right measurement optics system 25R for measuring the ocular characteristics of the right eye (ER). Thus, the ophthalmic device 1 includes a display 42a (first display) corresponding to the left eye (EL) and a display 42a (second display, see reference 42R) corresponding to the right eye (ER). Figure 3 (Two monitors)

[0061] Therefore, the ophthalmic device 1 can individually display visual targets for the left eye (EL) and the right eye (ER), and can set the visual target display distance L2 to an arbitrary distance. In addition, the ophthalmic device 1 can make the brightness of the visual target displayed for the left eye (EL) different from the brightness of the visual target displayed for the right eye (ER), thereby changing (amplifying) the brightness difference between the left and right visual targets.

[0062] In the first embodiment, the ocular refractive power measurement system 43 has the function of projecting a predetermined measurement pattern onto the fundus Ef of the left examined eye EL and the function of detecting the image of the measurement pattern projected onto the fundus Ef. That is, the ocular refractive power measurement system 43 has an annular beam projection system 43A that projects an annular measurement pattern onto the fundus Ef of the left examined eye EL and an annular beam receiving system 43B that detects (receives) the reflected light from the annular measurement pattern from the fundus Ef. Furthermore, the ocular refractive power measurement system 43 is not limited to the structure of the first embodiment as long as it is a measurement system that projects a measurement beam onto the fundus Ef of the left examined eye EL and obtains the measurement beam reflected on the fundus Ef as a measurement annular image Ri. As another example of the structure of the ocular refractive power measurement system 43, the structure can be described as follows: a point light is projected as a measurement beam onto the fundus Ef, and the measurement beam reflected at the fundus Ef (its reflected beam) passes through an annular slit or lens to become an annular beam, and a measurement annular image Ri is acquired.

[0063] The annular beam projection system 43A includes a refractive light source unit 43a, a third relay lens 43b, a pupil annular aperture 43c, a second field lens 43d, an aperture prism 43e, and a third rotating prism 43f. Furthermore, the annular beam projection system 43A shares a third dichroic filter 42i with the optotype projection system 42, and shares a first dichroic filter 41b and an objective lens 41a with the observation system 41. The refractive light source unit 43a includes, for example, a refractive power measurement light source 43g using an LED, a collimating lens 43h, a conical prism 43i, and an annular pattern forming plate 43j. The refractive light source unit 43a is controlled by a control unit 40 and moves integrally along the optical axis of the ocular refractive power measurement system 43.

[0064] The annular beam receiving system 43B includes an aperture 43p of an open-aperture prism 43e, a third field mirror 43q, a second reflecting mirror 43r, a fourth relay lens 43s, a focusing lens 43t, and a third reflecting mirror 43u. The annular beam receiving system 43B shares an objective lens 41a, a first dichroic filter 41b, a second dichroic filter 41e, a first imaging lens 41f, and an imaging element 41g with the observation system 41. Furthermore, the annular beam receiving system 43B shares a third dichroic filter 42i with the target projection system 42, and shares a third rotating prism 43f and an open-aperture prism 43e with the annular beam projection system 43A.

[0065] When measuring the refractive power of the left eye (EL) using the ocular refractive power measurement system 43, firstly, the control unit 40 illuminates the refractive measurement light source 43g. Then, the control unit 40 moves the refractive light source unit 43a of the annular beam projection system 43A and the focusing lens 43t of the annular beam receiving system 43B in the optical axis direction. Then, in the annular beam projection system 43A, the refractive light source unit 43a emits an annular measurement pattern, which travels through the third relay lens 43b, the pupil annular aperture 43c, and the second field lens 43d to the aperture prism 43e, is reflected at its reflecting surface 43v, and is guided to the third dichroic filter 42i through the third rotating prism 43f. The annular beam projection system 43A guides the measurement pattern to the objective lens 41a via the third dichroic filter 42i and the first dichroic filter 41b, thereby projecting the annular measurement pattern onto the fundus Ef of the left eye EL being examined.

[0066] The annular beam receiving system 43B uses the objective lens 41a to focus light onto the annular measurement pattern formed on the fundus Ef, which then travels through the first dichroic filter 41b, the third dichroic filter 42i, and the third rotating prism 43f to the aperture 43p of the aperture prism 43E. Next, the annular beam receiving system 43B causes the measurement pattern to pass through the third field lens 43q, the second reflecting mirror 43r, the fourth relay lens 43s, the focusing lens 43t, the third reflecting mirror 43u, the second dichroic filter 41e, and the first imaging lens 41f, thereby forming an image on the imaging element 41g. The imaging element 41g detects the image of the annular measurement pattern, and the control unit 40 displays the image of the measurement pattern detected by the imaging element 41g on the display unit 31. Then, based on the image signal from the imaging element 41g, the control unit 40 measures the spherical power, cylindrical power, and axial angle of the eye's refractive power using known methods.

[0067] Furthermore, the structures of the eye refractive power measurement system 43, the Z alignment system 45, the XY alignment system 46, and the corneal system 47, as well as the measurement principles of eye refractive power (refractive error), subjective examination, and corneal shape (corneal curvature), are well known, so detailed descriptions are omitted.

[0068] The following is based on Figure 5 The flowchart shown illustrates the processing sequence of the eye fatigue estimation process performed by the control unit 40 in the first embodiment.

[0069] In step S1, the control unit 40 measures the ocular refractive power of the left eye EL and the right eye ER, and proceeds to step S2. Specifically, the control unit 40 first aligns the left measuring unit 24L relative to the left eye EL and the right measuring unit 24R relative to the right eye ER. Then, the control unit 40 measures the ocular refractive power of the left and right eyes EL and ER respectively. The ocular refractive power of the left and right eyes EL and ER is detected based on the ring image generated by the fundus reflected light obtained using the ocular refractive power measurement system 43.

[0070] In step S2, after measuring the refractive power of both eyes in step S1, the control unit 40 displays arbitrary targets on the display 42a of the target projection system 42 of the left measuring optics system 25L and the display 42a of the target projection system 42 of the right measuring optics system 25R, and proceeds to step S3. That is, in step S2, the control unit 40 controls the target projection system 42 to prompt targets for the left eye (EL) and the right eye (ER). Furthermore, the targets displayed at this time can be arbitrarily set, but targets that are easy for the examinee to fixate on are preferred, such as Siemens star charts or stars with clearly defined centers. Additionally, the targets can be displayed, for example, in white on a black background or in black on a white background. Furthermore, the control unit 40 can display targets using a color that is easy to fixate on against any background color.

[0071] At this time, the control unit 40 controls the target projection system 42 to set the target prompting distance L2 to a predetermined distance (e.g., 50 cm) that can be set arbitrarily in both the left and right eyes. Furthermore, the target prompting distance L2 is the same for both the left and right eyes being examined (EL and ER). Thus, each target projection system 42 corresponding to the left and right eyes being examined (EL and ER) prompts the target at the predetermined target prompting distance L2.

[0072] Additionally, at this time, the control unit 40 controls the left eye drive mechanism 23L and the right eye drive mechanism 23R, and adjusts the position (or orientation) of the left measuring unit 24L and the right measuring unit 24R through the Y-axis rotary drive unit 28. This adjusts the horizontal position in conjunction with the interpupillary distance adjustment of the left and right tested eyes EL and ER, and sets the convergence angle θ1 to a pre-set predetermined angle, thereby setting the convergence distance L1 to a distance different from the target indication distance L2 (e.g., 40 cm). That is, the angle rotated by the Y-axis rotary drive unit 28 is determined by the convergence distance L1. As a result, when the convergence distance L1 is set to a distance different from the target indication distance L2 (in the first embodiment, the convergence distance L1 is set to a distance shorter than the target indication distance L2), the control unit 40 indicates the target to the left and right tested eyes EL and ER at any target indication distance L2. Furthermore, in the first embodiment, the convergence distance L1 and the target indication distance L2 are pre-set to predetermined distances.

[0073] Furthermore, in the ophthalmic device 1 of the first embodiment, when the visual target is prompted, the control unit 40 displays the anterior eye images E′ of the left examined eye EL and the right examined eye ER acquired by the observation system 41 on the display unit 31 of the examiner's controller 30. In addition, the anterior eye image E′ is also continuously displayed during the implementation of eye fatigue estimation processing.

[0074] In step S3, after the visual aids provided in step S2, the control unit 40 detects the gaze direction SL, which serves as the reference for the left examined eye EL, and the gaze direction SR, which serves as the reference for the right examined eye ER, and proceeds to step S4. Here, "the gaze directions SL and SR, which serve as the references" refer to the gaze directions when there is no brightness difference between the visual aids provided for the left and right examined eyes EL and ER (before the brightness difference is amplified). The gaze directions SL and SR are detected based on the anterior eye images E′ of the left examined eye EL and the right examined eye ER acquired by the observation system 41. Therefore, the observation system 41 is equivalent to an eye information acquisition unit that acquires eye information for detecting the gaze direction SL of the left examined eye EL and the gaze direction SR of the right examined eye ER.

[0075] Furthermore, in the ophthalmic device 1 of the first embodiment, when the control unit 40 detects the gaze direction SL and SR, it not only displays the anterior eye images E′ of the left examined eye EL and the right examined eye ER acquired by the observation system 41, but also displays the detection results of the gaze direction SL and SR, which serve as the reference for the left examined eye EL and the right examined eye ER, on the display unit 31 of the examiner's controller 30.

[0076] Furthermore, to detect the gaze directions SL and SR, the control unit 40 first determines the two-dimensional position of the pupil center of the left and right examined eyes EL and ER based on the anterior eye images E′ and magnification. Then, the control unit 40 determines the two-dimensional position, i.e., the reference position, of the light spot (light spot image Br) depicted by the XY alignment system 46 based on the anterior eye images E′ and magnification. Then, the control unit 40 determines the gaze directions SL and SR based on the reference position and the pupil center position. The method for determining the gaze directions SL and SR is not limited to the above method; other known methods can be used.

[0077] Furthermore, when the gaze directions SL and SR are detected, if the difference between the convergence distance calculated from the convergence angle obtained through the detected gaze directions SL and SR and the convergence distance L1 set by the control drive mechanism 23 is large, or if the subject reports that the target appears double, it can be assumed that the subject is not being viewed with both eyes. Therefore, the examiner or control unit 40 will urge the subject to direct their gaze towards the target, thereby re-detecting the gaze directions SL and SR used as a reference in step S3. If the above phenomenon does not improve even after re-detecting the gaze directions SL and SR, the control unit 40 can temporarily suspend the eye fatigue estimation process, and then resume the eye fatigue estimation process after prompting the target with the target prompt distance L2 and convergence distance L1 equal.

[0078] In step S4, after detecting the viewing directions SL and SR as a reference in step S3, the control unit 40 controls the left and right displays 42a to increase the brightness difference (contrast difference) between the target brightness (target contrast relative to background) presented to the left eye EL and the target brightness (target contrast relative to background) presented to the right eye ER, proceeding to step S5. At this time, the control unit 40 continuously or periodically reduces the brightness (target contrast relative to background) of the target presented to the non-dominant eye (e.g., the target presented to the right eye ER) over time, while maintaining the brightness (target contrast relative to background) of the target presented to the dominant eye (e.g., the target presented to the left eye EL). As a result, the brightness difference (contrast difference) of the targets continuously or periodically increases over time, making it increasingly difficult for the non-dominant eye to see the targets. Furthermore, the control unit 40 controls the light source of the displays 42a to reduce the brightness of the targets presented to the non-dominant eye by changing the color of the targets to a color closer to the background. Furthermore, the amount of brightness reduction and the method of reducing brightness can be arbitrarily set. For example, the control unit 40 can divide the amount of hue change of the target from before the brightness change until the colors of the target and the background become the same into multiple stages, and reduce one stage each time in processing step S3, or it can continuously change the hue of the target at a certain ratio until the colors of the target and the background become the same.

[0079] In step S5, after the brightness difference of the expanded target in step S4, the control unit 40 detects the line-of-sight direction SL of the left eye EL and the line-of-sight direction SR of the right eye ER, and proceeds to step S6. Furthermore, the detection methods for line-of-sight directions SL and SR are the same as in step S3.

[0080] In step S6, following the detection of the line of sight in step S5, the focal position (refractive value of the eye at a specified observation position) of the left examined eye EL and the focal position (refractive value of the eye at a specified observation position) of the right examined eye ER are detected, and the process proceeds to step S7. Here, the focal position is detected based on the ring image generated by the fundus reflected light obtained using the ocular refractive power measurement system 43. That is, the control unit 40 calculates the focal position (accommodation position) on the visual axis based on the refractive power of the left examined eye EL or the right examined eye ER, respectively. Therefore, the ocular refractive power measurement system 43 is equivalent to an eye information acquisition unit that acquires eye information for detecting the focal position of the left examined eye EL and the focal position of the right examined eye ER.

[0081] In step S7, after detecting the focal position in step S6, based on the gaze direction SL of the left examined eye EL (as a reference) and the gaze direction SR of the right examined eye ER (as a reference) detected in step S3, the gaze direction SL of the left examined eye EL and the gaze direction SR of the right examined eye ER (as a reference) detected in step S5, and the focal positions of the left and right examined eyes EL and ER detected in step S6, it is determined whether there is a change in the gaze direction SL and SR. If yes (there is a change in gaze direction), proceed to step S8. If no (there is no change in gaze direction), return to step S4.

[0082] Furthermore, for example, the presence or absence of a change in the gaze direction SL, SR is determined based on whether the gaze direction SL, SR detected in step S5 deviates from the average angle of the reference gaze direction SL, SR detected in step S3 by a predetermined amount (e.g., ±0.5°). That is, when the gaze direction SL, SR deviates from the average angle of the reference gaze direction SL, SR by a predetermined amount, the control unit 40 determines that "there is a change in gaze direction". In addition, if the focal position of the left eye EL and the right eye ER deviates from the target indication distance L2 by, for example, ±1.0D or more in diopter conversion, it is possible that the left and right eyes EL and ER have not been able to continuously observe the fixation target. Therefore, in this case, the examiner or the control unit 40 urges the examinee to pay attention to continuously observing the fixation target and repeats the gaze direction SL, SR detection in step S5.

[0083] Therefore, the control unit 40 repeatedly executes the processing from step S4 to step S7 until it determines in step S7 that "there is a change in the gaze direction". Thus, the brightness difference between the visual target presented to the left eye EL and the visual target presented to the right eye ER will continuously increase over time until the gaze directions SL and SR change. Meanwhile, the detection results of the anterior eye images E′ and gaze directions SL and SR for the left and right eyes EL and ER are continuously displayed. Therefore, the detection results of the anterior eye images E′ and gaze directions SL and SR for the left and right eyes EL and ER are displayed on the display unit 31 simultaneously with the increase in the brightness difference of the visual targets, allowing the examiner to monitor the status of the left and right eyes EL and ER in real time.

[0084] In step S8, after determining a change in gaze direction in step S7, the control unit 40 determines the brightness difference between the visual target indicated to the left eye EL and the visual target indicated to the right eye ER at the moment the gaze direction change was determined in step S7 (the brightness difference when the gaze directions SL and SR begin to change, hereinafter referred to as the "brightness difference at the start of the gaze change"), and proceeds to step S9. Furthermore, the "brightness difference at the start of the gaze change" can be represented by the brightness of the visual target whose brightness has been reduced (the visual target indicated to the non-dominant eye) at the moment the gaze directions SL and SR begin to change.

[0085] In step S9, after determining the brightness difference at the start of the line of sight change in step S8, the control unit 40 displays the information of the brightness difference at the start of the line of sight change determined in step S8 on the display unit 31 (output) of the detector controller 30, and proceeds to step S10.

[0086] In step S10, after displaying the brightness difference information in step S9, the control unit 40 estimates eye fatigue in the left and right tested eyes (EL and ER) based on the brightness difference information at the start of the gaze direction change determined in step S8, and then proceeds to the end. Furthermore, the control unit 40 displays the estimated eye fatigue result on the display unit 31 of the tester's controller 30. Additionally, for example, by comparing the brightness of the visual target indicated to the non-dominant eye when a gaze direction change (SL or SR) occurs, the control unit 40 can estimate the possibility of eye fatigue if the brightness of the visual target indicated to the non-dominant eye at the start of the gaze direction change (SL or SR) is lower than that brightness. Furthermore, the control unit 40 can estimate current eye fatigue based on comparisons with past brightness differences when the gaze direction changes (SL or SR) in the left and right tested eyes (EL and ER).

[0087] The effects of the ophthalmic device 1 in the first embodiment will be explained below.

[0088] When estimating eye fatigue in the left eye (EL) or the right eye (ER) under examination, the ophthalmic device 1 of the first embodiment performs the following... Figure 5 The eye fatigue estimation process is shown below. Specifically, the control unit 40 measures the refractive power of the left eye (EL) and the right eye (ER) (step S1). Then, for each eye (EL) and eye (ER), a visual target is provided at an arbitrary distance L2 (step S2). At this time, the control unit 40 controls the drive mechanisms 23 (drive mechanism 23L for the left eye and drive mechanism 23R for the right eye) to adjust the positions (orientations) of the left measuring unit 24L and the right measuring unit 24R. The horizontal position is adjusted in conjunction with the interpupillary distance of the left and right eyes (EL and ER) to make the convergence angle θ1 a predetermined angle, and the convergence distance L1 is set to a distance different from the visual target distance L2.

[0089] Specifically, in the first embodiment, the control unit 40 sets the convergence distance L1 to 40 cm and the target cuing distance L2 to 50 cm. That is, the control unit 40 sets the convergence distance L1 to be shorter than the target cuing distance L2. As a result, the left eye EL and the right eye ER undergo convergence movement so that the line of sight is directed towards a position different from the position where the target is cued, which in the first embodiment is a position closer to the target cuing position.

[0090] Then, based on the anterior eye image E′ acquired by the observation system 41, the control unit 40 detects the reference gaze direction SL of the left eye EL and the reference gaze direction SR of the right eye ER (step S3).

[0091] Then, the control unit 40 increases the brightness difference between the left and right visual targets by using the visual target cues distance L2. Specifically, the control unit 40 continuously or intermittently decreases the brightness of either the visual target cues given to the left eye EL or the visual target cues given to the right eye ER (for example, if the right eye is the non-dominant eye, then the visual target cues given to the right eye ER) over time, while fixing the brightness of the other visual target (for example, if the left eye is the dominant eye, then the visual target cues given to the left eye EL) (step S4). As a result, the brightness difference between the left and right visual targets increases over time, and the visual target with decreasing brightness (for example, the visual target cues given to the right eye ER) continuously or intermittently dims over time.

[0092] Next, the control unit 40, based on the anterior eye image E′, again detects the gaze direction SL of the left examined eye EL and the gaze direction SR of the right examined eye ER (step S5). Furthermore, while detecting the gaze directions SL and SR, the control unit 40 also detects the focal positions of the left examined eye EL and the right examined eye ER based on the annular image acquired by the ocular refractive power measurement system 43 (step S6). Afterward, the control unit 40 determines whether there are changes in the gaze directions SL and SR based on the gaze directions SL and SR and focal positions of the left and right examined eyes EL and ER detected before and after the increase in the brightness difference of the target (step S7).

[0093] Here, when the brightness (contrast of the target relative to the background) of the target presented to the left eye EL and the brightness (contrast of the target relative to the background) of the target presented to the right eye ER are the same, and the brightness difference (contrast difference) between the left and right targets is 0 (including almost 0), the fusion of images that the subject recognizes by visually viewing the target from the left and right eyes EL and ER respectively is established, and the gaze directions SL and SR remain unchanged.

[0094] Furthermore, if the brightness of the visual target presented to the non-dominant eye (e.g., the right ER) decreases over time (the contrast of the visual target relative to the background decreases), and the brightness difference between the left and right visual targets continues to widen, the visual target will gradually become invisible in the non-dominant eye. At this point, when the brightness difference between the left and right visual targets is within a certain range, because the subject will want to recognize the images of the visual targets viewed separately by the left and right EL and ER as a single image, the convergence state of the left and right EL and ER is maintained, and fusion is achieved.

[0095] On the other hand, if the brightness difference between the left and right visual targets continues to widen beyond a certain range, the examinee will be unable to visually confirm the targets using the non-dominant eye, resulting in a state where convergence is not maintained. Consequently, fusion is disrupted, and the eye positions of the left and right examined eyes (EL and ER) become those of a state where fusion is absent, causing changes in the visual directions (SL and SR). Furthermore, "eye position" refers to the direction in which the left and right examined eyes (EL and ER) are facing, which in this case aligns with the visual directions (SL and SR).

[0096] In contrast, in the ophthalmic device 1 of the first embodiment, when the visual target is initially presented, the convergence distance L1 is set to a distance different from the visual target presentation distance L2 (the convergence distance L1 is set to a distance shorter than the visual target presentation distance L2). As a result, the left and right examined eyes EL and ER will converge, so that the line of sight is directed towards a position closer to the visual target presentation position, resulting in an eye position that is more inwardly rotated than when the convergence distance L1 and the visual target presentation distance L2 are the same (the eye position when looking at the actual visual target presented at the visual target presentation distance L2, with a convergence angle θ2).

[0097] Thus, for example, when the non-dominant eye (the eye being examined where the target brightness is reduced) is in exotropia or orthotropia, during fusion removal, it will rotate outward from the convergent state, more outward than when the target cues are confirmed using binocular vision to indicate distance L2.

[0098] Furthermore, when the eye being examined corresponds to the target with reduced brightness is in esotropia, the eye position of this eye, even with fusion removal, becomes more inwardly rotated than in orthotropia. Therefore, even with fusion removal, the eye position is unlikely to change significantly. In this case, when the eye being examined is determined to be in esotropia, the control unit 40 sets the convergence distance L1 to a distance longer than the target indication distance L2 and prompts the target again, while increasing the brightness difference of the target and re-measuring the changes in the line-of-sight directions SL and SR. Alternatively, if the eye being examined is known to be in esotropia beforehand, the control unit 40 sets the convergence distance L1 to a distance longer than the target indication distance L2 and prompts the target, while increasing the brightness difference of the target and measuring the changes in the line-of-sight directions SL and SR. Thus, when fusion removal is performed, the line-of-sight directions SL and SR are on the myopic side, meaning that the left and right eyes EL and ER rotate inward from a divergent state, more inwardly than when visually viewing the target indication distance L2.

[0099] In this way, even if the examinee does not have strabismus, that is, regardless of whether the examinee has strabismus, the ophthalmic device 1 of the first embodiment can amplify the brightness difference of the visual targets of the left and right examinee eyes EL and ER from the state of binocular vision, and when the eye position becomes the state of fusion removal, the left and right examinee eyes EL and ER will shift.

[0100] Furthermore, in the ophthalmic device 1 of the first embodiment, when a visual target is prompted by the visual target prompting mechanism, the control unit 40 sets the convergence distance L1 to be shorter than the visual target prompting distance L2. Therefore, the left and right examined eyes EL and ER will converge so that the line of sight is directed to a position closer than the position of the prompted visual target, resulting in a state where the eye position is more inwardly rotated than when visually viewing the actual visual target prompted at the visual target prompting distance L2.

[0101] Here, it is generally believed that more people have exotropia compared to those with normal eye alignment (orthotropia). Therefore, it can be envisioned that by causing the left and right eyes (EL, ER) to converge, so that the line of sight is directed closer to the indicated position of the visual target, the significant changes in the line of sight (SL, SR) can be increased when the eye position is in a state of fusion removal. This would make it easier to estimate eye fatigue.

[0102] Furthermore, the convergence distance L1 can be set to a distance different from the target cues distance L2. Therefore, the control unit 40 can, for example, set the convergence distance L1 to 40 cm, or, for the eye being examined with its esotropia known in advance, set the target cues distance L2 to 30 cm, and set the convergence distance L1 to a distance longer than the target cues distance L2. In this case, the left and right eyes EL and ER of the examined eye diverge, so that the line of sight is directed to a position farther than the target cues position, resulting in a state where the eye position is more outwardly rotated than when the target is actually cuesed at the target cues distance L2 and the eye is looking at it.

[0103] Even in this case, when the left and right examined eyes EL and ER are in the state of fusion removal, the line of sight SL and SR are prone to change, which can cause eye position deviation.

[0104] Furthermore, when it is determined that the gaze direction SL and SR have changed, that is, when eye position shift occurs, the control unit 40 determines the brightness difference between the left and right visual targets at the moment the gaze direction change is determined (brightness difference at the start of the gaze change) (step S8). Further, the control unit 40 displays the brightness difference information at the start of the gaze change on the display unit 31 (step S9), and based on the brightness difference information at the start of the gaze change, estimates eye fatigue in the left and right examined eyes EL and ER (step S10). Additionally, the control unit 40 displays the estimated eye fatigue result on the display unit 31.

[0105] That is, in the ophthalmic device 1 of the first embodiment, the control unit 40 estimates the fatigue of the left and right eyes EL and ER based on the line of sight SL of the left eye EL and the line of sight SR of the right eye ER, so that eye fatigue can be estimated appropriately.

[0106] In addition, in the ophthalmic device 1 of the first embodiment, the control unit 40 displays the estimated result of eye fatigue on the display unit 31, so the examiner can visually confirm the display unit 31 and thus easily grasp the fatigue level of the left and right examined eyes EL and ER.

[0107] Furthermore, in the ophthalmic device 1 of the first embodiment, two optotype projection systems 42 are provided, each corresponding to the left and right eyes (EL and ER) being examined. One optotype projection system 42 has a display 42a that displays the optotype to the left eye (EL) and allows for arbitrary adjustment of the optotype's brightness, while the other optotype projection system 42 has a display that displays the optotype to the right eye (ER) and allows for arbitrary adjustment of the optotype's brightness. Therefore, the optotype projection systems 42 can precisely adjust the brightness of the optotype displayed to the left eye (EL) and the brightness of the optotype displayed to the right eye (ER), respectively, and the control unit 40 can appropriately increase the brightness difference between the left and right optotypes.

[0108] Furthermore, in the ophthalmic device 1 of the first embodiment, when the control unit 40 detects the line-of-sight directions SL and SR of the left and right examined eyes EL and ER, it also detects the focal position of the left examined eye EL and the focal position of the right examined eye ER. Here, the control unit 40 can determine the position (distance) at which the left examined eye EL and the right examined eye ER are looking based on the detection results of the focal position. Therefore, by detecting the focal positions of the left and right examined eyes EL and ER, the control unit 40 can determine whether the visual target is being observed correctly based on the determination results of the focal position when judging whether there is a change in the line-of-sight directions SL and SR, thereby improving the accuracy of judging whether there is a change in the line-of-sight directions SL and SR.

[0109] Furthermore, in the ophthalmic device 1 of the first embodiment, as the brightness difference of the visual targets gradually increases, the control unit 40 simultaneously displays the anterior eye images E′ of the left examined eye EL and the right examined eye ER, acquired by the observation system 41, and the increase in the brightness difference (contrast difference) between the left and right visual targets on the display unit 31. Here, the anterior eye images E′ of the left and right examined eyes EL and ER are eye information used for detecting the gaze directions SL and SR. Thus, by visually confirming the display unit 31, the examiner can monitor the movement of the left and right examined eyes EL and ER during the period of increasing brightness difference of the visual targets, and the examiner can also determine whether there is a change in the gaze directions SL and SR.

[0110] The ophthalmic device of the present invention has been described above based on the first embodiment, but the specific structure is not limited to this embodiment. As long as it does not depart from the spirit of the invention of each claim, design changes or additions are allowed.

[0111] That is, in the ophthalmic device 1 of the first embodiment, an example is shown where the convergence distance L1 and the target cues distance L2 are determined in advance. However, when the control unit 40 performs eye fatigue estimation processing, it first detects the eye position of the left examined eye EL and the eye position of the right examined eye ER, respectively. Furthermore, the control unit 40 can set the convergence distance L1 and the target cues distance L2 based on the eye positions of the left examined eye EL and the right examined eye ER. In other words, the control unit 40 can adjust the convergence distance L1 and the target cues distance L2 according to the eye positions of the left and right examined eyes EL and ER.

[0112] Furthermore, the eye position being tested at this time can be, for example, the eye position during fusion removal (the eye position during fusion removal while maintaining binocular fixation), or the eye position when visually confirming the state of the target while the convergence distance L1 and the target cue distance L2 are consistent. The eye position during fusion removal is comfortable because the tested eye does not need to observe the target (object) and therefore does not require convergence. Additionally, eye position can be tested through occlusion tests or occlusion-unocclusion tests. Here, the occlusion test evaluates the change in eye position of the other eye while the test subject is looking at the target with both eyes and one eye is covered. The occlusion-unocclusion test evaluates the change in eye position of the covered test eye when the occlusion is removed from a monocular occlusion state.

[0113] Therefore, the control unit 40 can set the convergence distance L1 and the target cues distance L2 to appropriate distances based on the eye positions of the left and right examined eyes (EL and ER). Thus, when the eye position is in a state where fusion is removed, the ophthalmic device 1 of the first embodiment will cause sufficient eye position shift, thereby improving the accuracy of eye fatigue estimation.

[0114] In addition, in the first embodiment, an example of a target prompting mechanism is shown, which has two target projection systems 42 corresponding to the left and right eyes EL and ER, respectively. Each target projection system 42 can display any target and has a display 42a with adjustable brightness. However, the structure of the target prompting mechanism is not limited to this. For example, the target prompting mechanism may have a liquid crystal shutter disposed between the target and the left and right eyes EL and ER, and the brightness difference of the target prompted to the left and right eyes EL and ER can be increased by changing the transmittance of the liquid crystal shutter. That is, the target prompting mechanism can change not only the brightness of the target itself (the contrast of the target relative to the background), but also the brightness difference between the left and right targets by changing the amount of light incident on the left and right eyes EL and ER, respectively.

[0115] Furthermore, if the optotype projection system 42 can provide optotype prompts to the left and right eyes EL and ER at any optotype prompt distance L2, and has a mechanism that changes the brightness (contrast) of the optotype only for one eye, then it is not necessary to set them separately for the left and right eyes.

[0116] Furthermore, in the ophthalmic device 1 of the first embodiment, an example is shown in which the focal positions of the left and right examined eyes EL and ER are detected when determining whether there is a change in the line of sight direction SL or SR. However, since the focal position is detected only to ensure the determination mechanism when determining changes in the line of sight direction SL or SR, it may not necessarily be detected.

[0117] Furthermore, in the ophthalmic apparatus 1 of the first embodiment, an example is shown in which the estimated results of fatigue of the left and right eyes EL and ER, or the anterior ocular images E′ of the left and right eyes EL and ER as the brightness difference of the visual targets is gradually increased, are displayed on the display unit 31 of the tester controller 30. However, the display unit 31 only needs to be visible to at least the tester, so for example, a monitor provided on the eye examination table 12 or a display provided on the measurement unit 20 may also be used as the display unit.

[0118] In addition, in the first embodiment, an example is shown where the brightness (contrast of the target relative to the background) of the target presented to the non-dominant eye is reduced, while the brightness (contrast of the target relative to the background) of the target presented to the dominant eye is fixed. However, when widening the brightness difference between the left and right targets, the control unit 40 can widen the brightness difference between the left and right targets by reducing the brightness of the target presented to the dominant eye and fixing the brightness of the target presented to the non-dominant eye.

[0119] Furthermore, in the ophthalmic device 1 of the first embodiment, an example is shown whereby, at the moment when the viewing directions SL and SR, after the brightness difference is amplified, deviate from the average angle of the reference viewing directions SL and SR by a predetermined amount (e.g., ±0.5°), it is determined that the viewing directions SL and SR have changed, and the brightness difference at that moment is taken as the "brightness difference at the moment the viewing change begins." In other words, in the first embodiment, the moment when the viewing directions SL and SR deviate from the reference viewing directions SL and SR by a predetermined amount is determined as the "moment when the viewing directions SL and SR have changed."

[0120] However, the method for determining the moment when the line of sight SL and SR changes (the start time of the line of sight change) and the method for determining the brightness difference at the start time of the line of sight change are not limited to this. For example, the control unit 40 continuously monitors the line of sight SL and SR at predetermined intervals (e.g., 30Hz). Furthermore, the control unit 40 may also take the moment when the first straight line representing the values ​​of the line of sight SL and SR that have undergone a slight change relative to the reference line of sight SL and SR (with a slope of 0) intersects with the second straight line representing the values ​​of the line of sight SL and SR that have undergone a straight line approximation relative to the reference line (before widening the brightness difference of the target) as the "start time of the line of sight change", and take the brightness difference of the left and right targets at that moment as the "brightness difference at the start time of the line of sight change". In this case, the control unit 40 can determine that the line of sight SL and SR has changed before the line of sight SL and SR deviates from the reference line by a predetermined amount.

[0121] Furthermore, in the ophthalmic device 1 of the first embodiment, an example is shown where the increase in the brightness difference of the target is stopped at the moment when the gaze direction SL, SR begins to change, and the "brightness difference at the moment the gaze change begins" is determined. However, the control unit 40 may also continue to detect changes in the gaze direction SL, SR until the brightness of one target becomes 0, that is, until the brightness of one target becomes the same color as the background. In this case, the method for determining the "moment of the gaze change" and the "brightness difference at the moment the gaze change begins" can be the method described above. Alternatively, other methods may also be used. That is, the control unit 40 first graphically displays the amount of gaze change (the amount of eye position change) from the reference (before the brightness change) gaze direction SL, SR to the gaze direction SL, SR when the brightness of the target is 0. Furthermore, the control unit 40 can, in this graph, take the moment when the line connecting the line of sight change ratio of 0.1 (10%) (that is, the moment when the sight change ratio is 10%) and the line of sight change ratio of 0.9 (90%) (the moment when the sight change ratio is 90%) intersects with the line representing the sight change amount of the reference (before the brightness change) (slope 0) as the "start time of sight change", and take the brightness difference between the left and right targets at this time as the "brightness difference at the start time of sight change".

[0122] Furthermore, in the ophthalmic device 1 of the first embodiment, the display of the detection results of the anterior eye image E′ and the gaze directions SL and SR of the left and right examined eyes EL and ER is continuously displayed even during the period of increased brightness difference of the visual targets. However, the detection results of the anterior eye image E′ or the gaze directions SL and SR may also be displayed at the moment when it is determined that the gaze directions SL and SR have changed or at the moment when the brightness of one visual target is 0, that is, at the moment when one visual target becomes the same color as the background, etc.

[0123] Explanation of reference numerals in the attached figures

[0124] 1: Ophthalmic devices,

[0125] 20: Measurement unit,

[0126] 22: Measurement head,

[0127] 23L: Left eye drive mechanism (convergence adjustment mechanism)

[0128] 23R: Right eye drive mechanism (convergence adjustment mechanism)

[0129] 24L: Left measuring section,

[0130] 24R: Right measuring section,

[0131] 25L: Left measuring optical system,

[0132] 25R: Right measuring optical system,

[0133] 41: Observation System (Eye Information Acquisition Unit)

[0134] 42: Visual target projection system (visual target prompting mechanism)

[0135] 42a: Display (First Display, Second Display)

[0136] 43: Ocular refractive power measurement system (ocular information acquisition unit)

[0137] 30: The tester uses a controller,

[0138] 31: Display section

[0139] 40: Control Department

[0140] L1: Convergence distance

[0141] L2: Beacon distance indication

[0142] P1: Optical target intersection point.

Claims

1. An ophthalmic device, characterized in that, When the distances from the left and right examined eyes to the visual target are used as the visual target cues distance, the point where the lines of sight from the left and right examined eyes intersect are used as the line-of-sight intersection point, and the distances from the left and right examined eyes to the line-of-sight intersection point are used as the convergence distance, have: The optotype prompting mechanism prompts the optotype to both the left and right eyes being examined, and is capable of changing the brightness difference between the optotype prompted to the left eye and the optotype prompted to the right eye. The convergence adjustment mechanism optically adjusts the lines of sight of the left and right eyes being examined to adjust the convergence distance to a distance different from the distance indicated by the visual target. The eye information acquisition unit acquires eye information of the left and right examined eyes, and The control unit controls the visual target prompting mechanism, the convergence adjustment mechanism, and the eye information acquisition unit; The control unit controls the convergence adjustment mechanism to set the convergence distance to a distance different from the target prompt distance, and prompts the target at the target prompt distance through the target prompt mechanism, and gradually increases the brightness difference. Based on the eye information acquired by the eye information acquisition unit, the line of sight of the left eye and the line of sight of the right eye are detected.

2. The ophthalmic device according to claim 1, characterized in that, The control unit estimates the fatigue level of the left or right eye based on the change in the direction of the line of sight of the left eye or the right eye caused by the change in the line of sight direction of the left eye or the right eye at the line of sight intersection at the convergence distance due to the brightness difference.

3. The ophthalmic device according to claim 2, characterized in that, It has a display unit that allows at least the inspector to visually confirm its functionality. The control unit displays the estimated fatigue level on the display unit.

4. The ophthalmic device according to any one of claims 1 to 3, characterized in that, The control unit sets the convergence distance to a distance shorter than the target indication distance.

5. The ophthalmic device according to any one of claims 1 to 3, characterized in that, The visual target prompting mechanism has a first display and a second display. The first display prompts the visual target to the left eye being examined and can arbitrarily change the brightness of the visual target. The second display prompts the visual target to the right eye being examined and can arbitrarily change the brightness of the visual target.

6. The ophthalmic device according to claim 4, characterized in that, The visual target prompting mechanism has a first display and a second display. The first display prompts the visual target to the left eye being examined and can arbitrarily change the brightness of the visual target. The second display prompts the visual target to the right eye being examined and can arbitrarily change the brightness of the visual target.

7. The ophthalmic device according to any one of claims 1 to 3, characterized in that, When detecting the direction of gaze, the control unit detects the focal position of the left eye and the focal position of the right eye based on the eye information acquired by the eye information acquisition unit.

8. The ophthalmic device according to claim 6, characterized in that, When detecting the direction of gaze, the control unit detects the focal position of the left eye and the focal position of the right eye based on the eye information acquired by the eye information acquisition unit.

9. The ophthalmic device according to any one of claims 1 to 3, characterized in that, It has a display unit that allows at least the inspector to visually confirm its functionality. When the control unit gradually increases the brightness difference through the visual target prompting mechanism, it displays the eye information acquired by the eye information acquisition unit on the display unit.

10. The ophthalmic device according to any one of claims 1 to 3, characterized in that, The control unit detects the eye position of the left eye and the eye position of the right eye based on the eye information acquired by the eye information acquisition unit, and sets the target prompting distance and the convergence distance based on the eye position of the left eye and the eye position of the right eye.

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