JP2013223759A - Eye axial length measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eye axial length measuring device capable of precisely measuring an eye axial length even if there is alignment deviation to an examinee's eye.SOLUTION: An eye axial length measuring device includes an interference optical system which has a light source for emitting low coherent light, irradiates the cornea and fundus of the examinee's eye with at least a part of the light emitted from the light source, and receives the reflected light from the cornea and the reflected light from the fundus as interference light by a light receiving element, and also includes an arithmetic means for obtaining eye axial length data of the examinee's eye based on the output signal from the interference optical system. The measurement light axis of the interference optical system can be moved to the up, down, right and left directions in relation to the examinee's eye, can be moved to the position deviated from the cornea vortex of the examinee's eye, and is provided with a correction means which corrects the eye axial length data based on the alignment deviation amounts of the measurement light axis of the interference optical system and the cornea vortex of the examinee's eye in the up, down, right and left directions, acquired beforehand.

Description

  The present invention relates to an axial length measuring device that optically measures the axial length of a subject's eye without contact.

  Conventionally, it has a measurement optical system that projects measurement light onto the subject's eye and receives the reflected light, and uses optical interference to optically measure the axial length of the subject's eye in a non-contact manner. Measuring devices are known. Such an apparatus has a drawback in that when measurement is performed on a subject's eye with opacity of the crystalline lens due to a cataract eye or the like, the measurement light beam is blocked by the turbid portion and the measurement accuracy is lowered. Further, Patent Document 1 discloses an axial length measuring device having a configuration in which the incident position of the measurement light beam is moved on the pupil of the subject's eye in order to avoid the turbid portion of the crystalline lens.

JP-A-7-222716

  However, when the measurement light beam is moved by moving the incident position of the measurement light beam on the pupil of the subject's eye in order to avoid the turbid portion of the crystalline lens as in the above-described apparatus, there is a deviation between the corneal apex of the subject's eye and the measurement optical axis. The larger the value, the larger the measurement error.

  In view of the above problems, it is an object of the present invention to provide an axial length measuring device that can accurately measure the axial length even if there is a misalignment with the subject's eye.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) having a light source that emits low-coherent light, irradiating at least part of the light emitted from the light source on the cornea and fundus of the eye to be examined, and using reflected light from the cornea and reflected light from the fundus as interference light It has an interference optical system that receives light by the light receiving element,
A ocular axial length measurement apparatus comprising a calculating means for obtaining the axial length data of the subject eye based on the output signal from the interference optical system,
The measurement optical axis of the interference optical system can be moved in the vertical and horizontal directions with respect to the subject's eye, and can be moved to a position shifted from the corneal apex of the subject's eye,
And a correction unit that corrects the axial length data based on an amount of misalignment in the vertical and horizontal directions between the measurement optical axis of the interference optical system acquired in advance and the corneal apex of the subject's eye.
(2) In the axial length measuring device according to (1),
A corneal shape measuring means for irradiating the subject's eye cornea with light for corneal shape measurement, receiving the reflected light and measuring the corneal shape of the subject's eye,
The correction means includes
Measure the corneal shape of the subject's eye based on the light reception signal from the corneal shape measurement optical system,
The ocular axial length data is corrected based on a measurement result of the misalignment amount and corneal shape measurement.

  According to the present invention, it is possible to accurately measure the axial length even when there is misalignment with the subject's eye.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external configuration diagram of an axial length measuring apparatus according to an embodiment. This device is a so-called stationary type device, and includes a base 1, a face support unit 2 attached to the base 1, a movable table 3 movably provided on the base 1, and a movable table 3. And a measurement unit 4 that irradiates measurement light toward the subject's eye and houses a measurement optical system for optically measuring the axial length of the subject's eye in a non-contact manner. The measuring unit 4 is moved in the left-right direction (X direction), the up-down direction (Y direction), and the front-rear direction (Z direction) with respect to the subject eye E by an XYZ driving unit 6 provided on the moving table 3. When the joystick 5 is operated by the examiner, the movable table 3 is moved in the X direction and the Z direction on the base 1 by a sliding mechanism (not shown). When the examiner rotates the rotary knob 5a, the measuring unit 4 is moved in the Y direction by the Y drive of the XYZ drive unit 6. A measurement start switch 5b is provided on the top of the joystick 5. A display monitor 9 is provided on the movable table 3.

  2 and 3 are diagrams for explaining the optical system of the axial length measuring apparatus according to the present embodiment. The measurement optical system housed in the measurement unit 4 includes an interference optical system 10, and the interference optical system 10 includes a fundus irradiation optical system 100a and a cornea irradiation optical system 200a, a fundus light reception optical system 100b and a cornea light reception optical system 200b, and a reference light. An optical system 500.

  The fundus illumination optical system 100a and the cornea illumination optical system 200a have a light source 11 that emits a light beam having a low coherent length, and a part of the light beam emitted from the light source 11 is subjected to first measurement light (corneal measurement light) and second measurement light. Light (fundus measurement light) is condensed on the cornea and fundus of the subject's eye.

  As shown in FIG. 2A, a part of the light beam emitted from the light source 11 is a collimator lens 12, a half mirror 13, a condenser lens 14, a triangular prism 15, a half mirror 13, a relay lens 18, and a relay lens. 19, the fundus of the subject eye E is irradiated through the half mirror 20, the dichroic mirror 21, and the objective lens 22. That is, these optical members disposed between the optical path between the collimator lens 12 and the objective lens 22 are disposed as a fundus illuminating optical system 100a. Then, the reflected light from the fundus of the subject eye E is in the opposite direction of the optical path from the objective lens 22 to the condenser lens 14 of the fundus illumination optical system 100 with respect to the traveling direction of the fundus measurement light until the fundus is irradiated. The light travels and enters the end portion 25 a of the optical fiber 25 through the half mirror 13 and the condenser lens 24. In other words, the optical member disposed between the optical path between the objective lens 22 and the end 25a of the optical fiber 25 is disposed as the fundus light receiving optical system 100b.

  Further, as shown in FIG. 2B, a part of the light beam emitted from the light source 11 is collimator lens 12, half mirror 13, movable triangular prism 23, half mirror 13, relay lens 18, relay lens 19, The light is irradiated near the cornea of the eye E through the half mirror 20, the dichroic mirror 21, and the objective lens 22. That is, these optical members disposed between the optical path between the collimator lens 12 and the objective lens 22 are disposed as a cornea irradiation optical system 200a. Then, the reflected light from the cornea of the subject's eye E reverses the optical path from the objective lens 12 to the movable triangular prism 23 of the cornea irradiation optical system 200 with respect to the traveling direction of the cornea measurement light until the cornea is irradiated. The light travels and is reflected by the half mirror 13. Thereafter, the light is condensed by the condenser lens 24 and then incident on the end 25 a of the optical fiber 25. That is, these optical members disposed between the optical path between the objective lens 22 and the end 25a of the optical fiber 25 are disposed as a corneal light receiving optical system 200b.

  The reference light optical system 500 that generates the reference light combined with the fundus measurement light and the cornea measurement light described above, in order from the light source side, the light source 11, the collimator lens 12, the movable triangular prism 23, the half mirror 13, the relay lens 18, The relay lens 19, the reflection mirror 51, the reflection mirror 52, the relay lens 53, and the reference mirror 54 are included. The movable triangular prism 23 that moves in the direction of arrow A is driven by the drive unit 82 and used to change the optical path length of the reference light. Note that, according to the optical arrangement of the present embodiment, as the triangular prism 23 moves, the optical path length of the cornea measurement light and the optical path length of the reference light change simultaneously. The low-coherent light emitted from the light source 11 travels through the same optical path as that of the cornea irradiation optical system 200 until it is transmitted through the half mirror 20. Then, the light transmitted by the half mirror 20 reaches the reference mirror 54 through the mirror 51, the mirror 52, and the relay lens 53. The light that reaches the reference mirror 54 is turned back by the reference mirror 54, passes through the relay lens 53, the mirror 52, and the mirror 51, and passes through the half mirror 20. The reflected light transmitted through the half mirror 20 is combined with the corneal reflection light to be interference light, and then enters the end 25a of the optical fiber 25 through the same optical path as that of the corneal light receiving optical system 200b. In this case, even if the position of the movable triangular prism 23 changes, the total optical path length of the cornea measurement light (light source 11 to cornea, cornea to end 25a of the optical fiber 25) and the total optical path length of the reference light (light source 11 to reference) The mirror 54 and the reference mirror 54 to the end 25a of the optical fiber 25 are maintained in an approximately equal relationship within a range where interference can occur.

  Further, when the optical path length of the reference light is changed by the movement of the position of the prism 23, the total optical path length of the fundus measurement light that varies depending on the total optical path length of the reference light by the reference light optical system 500 and the axial length of the subject's eye. In some cases, the light sources 11 to the fundus and the fundus to the end 25a of the optical fiber 25 have substantially the same relationship within a range where interference can occur. In this case, the light that has reached the reference mirror 54 is folded by the movable triangular prism 23 and reflected by the half mirror 13, and then is combined with the fundus reflection light folded by the triangular prism 15 to be interference light. The light is incident on the end 25a of the optical fiber 25.

  FIG. 3 is a schematic configuration diagram of a spectroscopic optical system included in the measurement unit 4 according to the present embodiment. The spectroscopic optical system 600 (spectrometer unit) includes a collimator lens 60, a grating mirror (diffraction grating) 61, a condenser lens 62, a cylindrical lens 63, and a light receiving element 64. The light receiving element 64 is a one-dimensional element (line sensor) having sensitivity in the infrared region.

  Interfering light by the cornea measurement light and reference light and incident light by the fundus measurement light and reference light incident on the end portion 25 a of the optical fiber 25 are emitted from the other end portion 25 b through the optical fiber 25. Then, the two interference lights emitted from the end portion 25 b are spread by the collimator lens 60 and then split into frequency components by the grating mirror 61. The interference light split into frequency components is condensed on the light receiving surface of the light receiving element 64 through the condenser lens 62 and the cylindrical lens 63.

  The measurement optical system for optically measuring the axial length of the subject's eye in a non-contact manner is not limited to this, and irradiates a part of the light from the light source to the subject's eye fundus as measurement light, If the measurement optical system includes an interference optical system that irradiates a part of the light from the light source as a reference light to the reference surface and receives the interference light obtained by combining the reference light and the reflected light of the measurement light Good. For example, using an interference optical system that uses the cornea of the subject's eye as a reference surface, irradiates the fundus and cornea of the subject's eye with light from a light source, and receives the interference light obtained by combining the reflected light of the fundus and cornea of the subject's eye Thus, the axial length may be obtained (see, for example, JP-A-2005-348755).

  Returning to the description of FIG. Reference numeral 700 denotes an observation optical system for photographing the anterior segment of the subject's eye, and includes an objective lens 22, a dichroic mirror 21, a relay lens 71, an imaging lens 72, and an imaging element 73 having sensitivity in the infrared region from the front of the subject's eye. . Note that the pupil position of the subject eye E and the image sensor 73 have a substantially conjugate relationship.

  Further, in front of the anterior segment of the eye E, a ring index projection optical system that emits near-infrared light for projecting a ring index onto the cornea Ec of the eye E and having infrared light having a wavelength different from that of the light source 11. 46 is arranged with the measurement optical axis L1 as the center, and a working distance that emits near-infrared light for detecting misalignment in the working distance direction with respect to the subject's eye by projecting an infinity index onto the cornea Ec of the eye E The index projection optical system 45 is arranged symmetrically with respect to the measurement optical axis L1. The ring projection optical system 46 is used as illumination light for anterior ocular segment observation for illuminating and observing the anterior segment of the eye E, and is also used as an index projection optical system for corneal shape measurement. That is, the corneal shape of the eye E is measured based on the shape of the ring index image captured together with the anterior segment image by the image sensor 73.

  FIG. 4 is a schematic configuration diagram for explaining the configuration of the control system of the ophthalmologic apparatus according to the present embodiment. The control unit 80 that controls the entire apparatus, calculates measurement values, and the like is a display monitor that displays the anterior segment image, measurement results, and the like taken by the observation optical system 700 in addition to the members provided in the measurement unit 4. 9, an XYZ drive unit 6, a memory 85 for storing measurement results, a rotary knob 5a, a measurement start switch 5b, a control unit 86 on which switches for performing various settings are arranged. Here, the memory 85 calculates the axial length data of the subject's eye based on the output signal from the measurement optical system provided in the measurement unit 4, and the cornea of the subject's eye based on the imaging (light reception) signal from the imaging element 73. An arithmetic processing program for measuring the shape, measuring the amount of misalignment in the vertical and horizontal directions between the optical axis of the measurement light beam based on the imaging signal from the imaging element 73 and the subject's eye, and the like are stored. Further, the arithmetic processing program includes a program for correcting the axial length data based on the alignment deviation amount at the time of measuring the axial length and the measurement result of the corneal shape measurement. Note that the control unit 80 performs data arithmetic processing based on the above-described arithmetic processing program.

  The operation of the ophthalmologic apparatus having the above configuration will be described. The examiner fixes the face of the subject to the face support unit 2 and instructs to fixate a fixation target (not shown), and then aligns the measurement unit 4 with respect to the subject eye E in the X, Y, and Z directions. The examiner operates the joystick 5 and the rotary knob 5 a while observing the monitor 9, and performs rough alignment so that the anterior segment image captured by the two-dimensional image sensor 73 is displayed on the monitor 9. As a result, the anterior segment of the subject's eye is photographed by the image sensor 73, and on the display monitor 40, the anterior segment image, the reticle mark 101, the ring index image R projected by the ring projection optical system 46, and the working distance projection. The infinity index image M projected by the optical system 45 is displayed (see FIG. 5A).

  The examiner operates the joystick 5 while viewing the ring image R displayed on the display monitor 40, and adjusts the position of the measurement unit 4 in the vertical and horizontal directions so that the ring image R and the reticle mark 101 are concentric circles ( (Refer FIG.5 (b)). Thereafter, the position of the measuring unit 4 in the working distance direction is adjusted so that the ring image R becomes the thinnest. Then, when the alignment is completed and the measurement start switch 5b is pushed by the examiner, the measurement is performed.

  Here, the control unit 80 can detect the misalignment of the measurement unit 4 with respect to the subject's eye based on the imaging signal from the imaging element 73, and drives the XYZ driving unit 6 based on the detection result to measure the measurement unit 4. May be moved (automatic alignment function), or misalignment information in the XY direction and misalignment information in the Z direction (see the indicator in FIG. 5) may be displayed on the monitor 9. In addition, the detection result of the alignment shift in the vertical and horizontal directions with respect to the subject's eye is used for correction processing described later. In this case, the control unit 80 obtains the vertical / horizontal misalignment of the measurement unit 4 with respect to the subject's eye based on the center coordinates of the ring index R (the center coordinates of the ring visual target image received by the image sensor 73). Further, when the measuring unit 4 is displaced in the working distance direction, the control unit 80 says that the image interval in the predetermined meridian direction of the ring index changes while the interval of the infinity index M hardly changes. Using the characteristic, the misalignment in the working distance direction with respect to the subject's eye is obtained (for details, refer to Japanese Patent Laid-Open No. 6-46999).

  When the control unit 80 emits low-coherent light from the light source 11 based on the trigger signal for starting measurement, spectrum information of interference fringes is recorded on the light receiving element 64. Then, the spectral information is input to the control unit 80 and analyzed using Fourier transform, whereby the eye characteristic information in the depth direction of the subject's eye can be measured.

  Here, when obtaining the axial length of the subject eye E, the control unit 80 moves the movable prism 23 by driving the drive unit 82 and is obtained based on the spectrum information received by the light receiving element 64. The axial length of the subject eye E is obtained from the interference signal and the optical path length of the reference light that is changed by the movement of the prism 23 (the driving result of the optical path length varying means).

  The control unit 80 drives the driving unit 82 to move the movable triangular prism 23 from the reference position indicated by a solid line (here, the position where the optical path of the corneal irradiation optical system is the shortest) in the direction of arrow A, and The optical path length of the optical system through which the reference light passes is changed.

  Here, when the movable triangular prism 23 is moved in the direction of the arrow, the optical path length of the reference light becomes longer, and when the optical path difference between the optical path length of the fundus measurement light and the optical path length of the reference light decreases, the fundus measurement Interference light between the light and the reference light is generated. FIG. 6 is an example showing the intensity of the interference signal in the depth direction of the subject's eye when the interference signal by the cornea measurement light and the reference light and the interference signal by the fundus measurement light and the reference light are detected. AC is an interference signal due to reflected light from the front surface of the cornea, PC is an interference signal due to reflected light from the back surface of the cornea, AR is an interference signal due to reflected light from the front surface of the retina of the subject's eye, and PR is the back surface of the subject's eye. It is an interference signal by the reflected light from.

  Here, the position of the prism 23 when both the interference signal AC and the interference signal PR are detected differs depending on the axial length of the subject's eye. Therefore, the control unit 80 specifies the spectrum information S in which the interference signal AC and the interference signal PR are detected from the spectrum information stored in the memory 85 for each movement position of the prism 23. Then, the position information of the prism 23 (for example, the movement amount of the prism 23 from the reference position (or the driving amount of the driving unit 82)) when the specified spectrum information S is obtained is obtained. Further, the control unit 80 obtains position information of the interference signal AC and the interference signal PR in the depth direction based on the spectrum information S when the interference signal AC and the interference signal PR are detected.

  More specifically, the control unit 80 obtains a dimension La in the depth direction from the interference signal AC to the interference signal PR based on the spectrum information S from which the interference signal AC and the interference signal PR are detected. Then, the dimension Lb is obtained based on the amount of movement of the prism 23 from the reference position when the spectrum information S is acquired. And the control part 80 calculates | requires the axial length of a test subject's eye by adding the dimension La and the dimension Lb (eye axial length = La + Lb).

  In addition, the control unit 80 measures the amount of misalignment in the vertical and horizontal directions between the optical axis L1 of the measurement light beam and the subject's eye based on the imaging signal from the imaging device 73 at the time of measuring the axial length, thereby determining the axial length. Get the amount of misalignment at the time of measurement. More specifically, the control unit 80 receives the trigger signal for measuring the axial length and emits the measurement light source, or based on the anterior segment image captured by the imaging element 73 before and after the measurement light source. Detecting a distance (alignment deviation amount) and a deviation direction between a predetermined alignment reference position (position of the measurement optical axis L1 on the imaging surface of the imaging element 73) and the center coordinate of the ring index R on the imaging surface of the imaging element 73; The detection result is stored in the memory 85.

  Further, the control unit 80 measures the corneal curvature of the subject's eye based on the shape of the ring index image R imaged by the imaging element 73 of the observation optical system 700 before and after the measurement of the axial length. More specifically, the control unit 80 calculates center coordinates from the edge coordinates of the ring image R, and calculates a distance from the center coordinates to the ring for each meridian at a predetermined angle (for example, every 1 degree). Then, when the distance for each meridian at a predetermined angle from the center coordinate to the ring is obtained, the data is obtained from a known curvature sphere and stored, and corneal curvature data for each meridian is obtained. . Thereby, the corneal curvature for each meridian direction can be obtained. Note that, even if the axial length measurement is performed in a state where the deviation between the corneal apex of the subject's eye and the measurement optical axis is large, the corneal curvature is measured with the corneal apex of the subject's eye and the measurement optical axis L1 being matched. It is preferred to do so. In this case, a switch dedicated to corneal curvature measurement is provided mechanically or electrically, and after adjusting the alignment independently of the measurement of the axial length, a trigger signal from the dedicated switch (trigger signal for starting the axial length measurement) The corneal curvature may be measured based on the above.

  When the corneal curvature of the subject's eye for each meridian is measured as described above, the control unit 80 corrects the corneal curvature data in the meridian direction corresponding to the direction of misalignment detected as described above as correction corneal curvature data. Get as r. FIG. 7 is a distribution diagram showing the radius of curvature for each meridian when the subject's cornea is a toric surface. Here, when the misalignment direction detected as described above is 45 degrees with respect to the horizontal direction (see arrow D in the figure), the control unit 80 performs a meridian direction of 45 degrees with respect to the horizontal direction. Is obtained as correction data r.

  When the axial length measurement data, the amount of misalignment with respect to the subject's eye at the time of measuring the axial length, and the correction corneal curvature data are obtained as described above, the control unit 80 corrects the measurement error due to the misalignment. Therefore, correction processing is performed.

  FIG. 8 is a diagram for explaining the correction processing according to the present embodiment. In FIG. 8, ER corresponds to the uncorrected ocular axial length measurement data obtained at the time of measurement, and the intersection of the optical axis ES of the subject eye E and the retina (fundus) Ef from the intersection a of the measurement optical axis L1 and the cornea Ec. Represents the distance to f. EL corresponds to the axial length measurement data obtained by correction processing described later, and represents the distance from the corneal vertex Ev of the subject eye E formed on the optical axis ES of the subject eye E to the intersection point f on the retina. Further, r corresponds to the corneal curvature radius of the subject eye E, Cc corresponds to the center of corneal curvature, h corresponds to the amount of misalignment obtained as described above, and the measurement optical axis L1 and the optical axis ES of the subject eye E in the vertical and horizontal directions. Represents the amount of optical axis deviation. Further, θ represents the inclination angle of the line segment aCc with respect to the optical axis Es, and is obtained by the following equation.

φ represents the inclination angle of the line segment af with respect to the optical axis Es, and is obtained by the following equation.

  The distance t between the intersection point b of the perpendicular drawn from the intersection point a to the optical axis ES and the corneal curvature center Cc can be obtained by the equation t = r cos θ. Thereby, the distance EL1 from the corneal apex Ev to the intersection point b is obtained by the expression EL1 = rt. Further, the distance EL2 between the intersection point b and the intersection point f can be obtained by the expression EL2 = ERcosφ.

  Here, when EL1 and EL2 obtained as described above are added together, the distance EL can be obtained (EL = EL1 + EL2). That is, in the present embodiment, a perpendicular line is drawn on the subject eye optical axis ES from the intersection point a between the subject eye cornea Ec and the measurement optical axis L1 of the interference optical system 10 based on the misalignment amount h and the cornea shape data r. The distance EL1 from the intersection point b to the corneal apex Ev is obtained as a first distance, and the measurement optical axis between the subject's cornea Ec and the interference optical system 10 is determined based on the misalignment amount h and the uncorrected axial length data ER. The distance from the intersection point b when the perpendicular line is drawn to the subject eye optical axis ES from the intersection point a with the L1 to the intersection point f between the optical axis ES of the subject eye and the fundus eye fundus is obtained as the second distance EL2. By adding EL1 and the second distance EL2, the distance EL from the corneal apex of the subject's eye to the intersection of the optical axis of the subject's eye and the fundus of the subject's eye is calculated as corrected axial length data.

  In other words, correct ocular length measurement data EL can be obtained by correcting the axial length measurement data ER obtained at the time of measurement based on the amount of misalignment at the time of measuring the axial length and the measurement result of the corneal shape measurement. Therefore, even if there is a positional deviation between the optical axis ES of the subject's eye and the measurement optical axis L1, the measurement error can be eliminated. Thereby, in order to avoid opacity of the crystalline lens due to cataract, even if measurement is performed in a state where the measurement optical axis L1 is placed at a position shifted from the corneal apex of the subject's eye, a measurement result with little measurement error can be obtained. . In addition, since it is not always necessary to strictly align with the subject's eye, the allowable range of alignment is widened, and the labor for alignment with the subject's eye is reduced.

  As described above, the calculated axial length data is displayed by the monitor 9 and a printer (not shown), and communicated as data to other devices. In this case, when a plurality of corrected axial length data are obtained by measuring at a plurality of positions on the cornea, an average of the axial length values can be obtained from the plurality of data. High-quality data can be obtained.

  In the above description, one ring index is projected onto the subject's ocular cornea, and the distance from the intersection point a to the corneal center Cc and the distance from the corneal vertex Ev to the corneal center Cc are set to one. Although the correction processing is performed by approximating the corneal curvature radius r obtained by the ring-shaped index, it is not limited to this. In other words, projecting multiple ring-shaped indicators onto the subject's eye cornea and measuring the corneal curvature at multiple positions in the meridian direction to measure the overall corneal curvature distribution from the vicinity of the corneal apex to the periphery of the cornea The structure which acquires data may be sufficient. If such measurement data is obtained, the distance G from the intersection point a to the corneal center Cc based on the corneal curvature in the vicinity of the intersection point a, and the distance G from the corneal vertex Ev to the corneal center Cc based on the corneal curvature in the vicinity of the corneal vertex Ev. A distance H is determined. In this case, the distance EL1 from the corneal apex Ev to the intersection point b is obtained by EL1 = H−Gcos θ. As a result, the distance EL1 from the corneal apex Ev to the intersection point b can be obtained more accurately, so that correction with higher accuracy is possible. In the above description, the corneal curvature of the subject's eye has been obtained. However, any corneal shape that can measure the corneal shape of the subject's eye may be used. It may be calculated based on the image position of the ring-shaped index, and the distance EL1 may be obtained from the height difference in the optical axis ES direction from the corneal apex of the subject eye to the intersection point a.

  In the above description, the corneal shape (for example, corneal curvature) of the subject's eye is obtained by projecting an index on the cornea of the subject's eye. However, the present invention is not limited to this. However, it may be configured to irradiate the corneal shape measurement light and receive the reflected light to measure the corneal shape of the subject's eye. For example, the anterior segment of the subject's eye is optically cut by slit light, and a cross section of the anterior segment is obtained by a photographing optical system arranged based on the principle of Scheinproof, and the cornea of the subject's eye is obtained based on the obtained sectional image of the anterior segment of the eye The shape may be measured. Moreover, you may make it measure the cornea shape of a test subject's cornea based on the acquired anterior segment OCT image using the anterior segment OCT apparatus which image | photographs the cross-sectional image of a test subject's anterior segment.

  Further, in the above description, the corneal shape data of the subject's eye is used for correcting the axial length data, but the present invention is not limited to this. Pre-set corneal shape data (for example, in the above correction formula, r = 8 mm) may be used. Thereby, it is possible to correct the axial length data based on the amount of misalignment when measuring the axial length. In this case, a table of correction values corresponding to the combination of the axial length measurement data before correction and the amount of misalignment is created in advance using corneal shape data set in advance, and stored in the memory 85. Also good.

  Further, the corneal shape measurement data of the subject's eye acquired by another ophthalmologic apparatus having the corneal shape measurement optical system as described above is stored in the memory 85 and stored in the memory 85 when correcting the axial length data. The measured corneal shape measurement data may be used. In addition, a program for correcting the axial length data as described above is stored in the memory of the external PC, and the axial length data obtained from the apparatus main body having the axial length measuring optical system and the anterior ocular segment imaging optical system; Correction of the axial length data may be performed based on the amount of misalignment.

It is an external appearance block diagram of the axial length measuring apparatus which concerns on embodiment. It is a figure explaining the optical system of the optic axis length measuring device concerning this embodiment. It is a schematic block diagram of the spectroscopic optical system which the measurement optical system which concerns on this embodiment has. It is a schematic block diagram for demonstrating the structure of the control system of the ophthalmologic apparatus which concerns on this embodiment. It is a figure which shows the anterior eye part image displayed on the screen of a display monitor. It is an example which shows the intensity | strength of the interference signal in the depth direction of a test subject eye when the interference signal by a cornea measurement light and a reference light and the interference signal by a fundus measurement light and a reference light are detected. It is a distribution map showing the curvature radius for every meridian when a subject's cornea is a toric surface. It is a figure explaining the correction process concerning this embodiment.

4 Measurement unit 10 Interferometric optical system 80 Control unit 700 Anterior ocular segment observation optical system ER Axis length measurement data before correction EL Axis length measurement data obtained by correction processing h Optical axis shift amount r Corneal shape data

Claims (2)

A light source that emits low-coherent light, irradiates at least part of the light emitted from the light source to the cornea and fundus of the eye to be examined, and receives light reflected from the cornea and reflected from the fundus as interference light by a light receiving element With interference optical system to receive light,
A ocular axial length measurement apparatus comprising a calculating means for obtaining the axial length data of the subject eye based on the output signal from the interference optical system,
The measurement optical axis of the interference optical system can be moved in the vertical and horizontal directions with respect to the subject's eye, and can be moved to a position shifted from the corneal apex of the subject's eye,
Axial length measurement characterized by comprising correction means for correcting the axial length data based on the amount of misalignment in the vertical and horizontal directions between the measurement optical axis of the interference optical system acquired in advance and the corneal apex of the subject's eye apparatus. In the axial length measuring device according to claim 1,
A corneal shape measuring means for irradiating the subject's eye cornea with light for corneal shape measurement, receiving the reflected light and measuring the corneal shape of the subject's eye,
The correction means includes
Measure the corneal shape of the subject's eye based on the light reception signal from the corneal shape measurement optical system,
An ocular length measurement apparatus that corrects the ocular length data based on the alignment deviation amount and a measurement result of corneal shape measurement.

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