JP2763584B2 - Front and rear diameter distance measuring device for living eye - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a first method of the living eye by observing interference fringes.
The present invention relates to an improvement of an anterior-posterior diameter measurement apparatus for a living eye, which can measure an axial length, an anterior chamber depth, a lens thickness, etc. as a front-rear diameter distance from a measurement target surface to a second measurement target surface without contact.

(Prior Art) Conventionally, an anterior-posterior diameter of a living eye for measuring an axial length, an anterior chamber depth, a lens thickness, and the like as a front-back radial distance from a first measurement target surface to a second measurement target surface of a living eye. As a distance measurement device, the reflected waves of the ultrasonic wave projected from the front of the eye using ultrasonic waves on the front of the cornea, the front of the lens, the rear of the lens, and the fundus surface are drawn on a CRT, and the echogram drawn on the CRT is drawn. There is a known thing that measures by shooting.

(Problems to be Solved by the Invention) However, this conventional living eye front-rear diameter measuring apparatus has a measurement accuracy of about ± 0.2 mm, and uses, for example, an IOL ( Intraocular Len
In determining the power of s), there is a problem that the measurement accuracy of the axial length is insufficient.

In addition, this conventional ultrasonic measuring apparatus for measuring the front and rear diameter of a living eye has to be troublesome in that a probe must be brought into contact with the living eye during measurement, so that precautionary measures such as infection must be taken.

Therefore, in recent years, by observing interference fringes,
An anterior-posterior diameter distance measuring apparatus for a living eye capable of measuring anterior chamber depth, lens thickness, and the like in a non-contact manner has been proposed.

FIG. 5 shows an example of a device for measuring the axial length of a living eye, which is used to measure the axial length of the living eye.
Fercher et al. (OPTICS LETTER VOL.13 NO.3 PP.186−
188 (March 1988) Optical Socity of America).

The apparatus for measuring the front-to-rear diameter distance of the living eye shown in FIG. 5 is roughly composed of a semiconductor laser 1, a collimator lens 2, two parallel flat plates 3, 4, a beam splitter 5, a condenser lens 6, and an imaging camera 7. ing. Laser light emitted from the semiconductor laser 1 is converted into a parallel light beam by the collimator lens 2 and guided to two parallel flat plates 3 and 4. A parallel light beam (referred to as a light beam) that has passed through the two parallel flat plates 3 and 4 is guided as convergent light to the fundus 9 of the living eye 8 via the beam splitter 5 and is reflected by the fundus 9 to be substantially parallel light beam (plane wave). As a result, the light is emitted from the living eye 8, is reflected by the reflection surface 10 of the beam splitter 5 in the direction in which the condenser lens 6 exists, is condensed by the condenser lens 6, and is guided to the imaging camera 7. A part of the parallel light flux passing through the parallel flat plate 3 is reflected by the parallel flat plate 4, and the reflected light beam (referred to as a light flux) returns to the parallel flat plate 3, and is reflected again by the parallel flat plate 3 to be parallel flat plate. 4, and passes through the beam splitter 5 to the cornea 11 of the living eye 8. The light reflected by the cornea 11 is guided to the beam splitter 5 as divergent light (spherical wave), reflected by the reflection surface 10 in the direction in which the condenser lens 6 exists, and condensed by the condenser lens 6. To the camera 7. In FIG. 5, reference numeral 12 denotes a light receiving sensor for monitoring the amount of light of the semiconductor laser 1.

In this conventional device, the distance 1 between the parallel flat plate 3 and the parallel flat plate 4 is variable, the refractive index of a substance existing between the parallel flat plate 3 and the parallel flat plate 4 is n, and the refractive index of the intraocular substance is n. Assuming that the refractive index is N and the axial length of the eye (the distance from the vertex of the cornea 11 to the fundus oculi 9) obtained by the measurement is X, the parallel flat plates 3 and 4 satisfy the equation of nl = NX.
Is adjusted, the luminous flux becomes equal in optical path length, and the camera 7 observes interference fringes.

Therefore, the plane parallel plate l when this interference fringe is observed
Is obtained as a measurement value, the eye axis length X can be obtained.

However, in a living eye's front-to-rear radial distance measuring device that measures the axial length by observing the interference fringes, the reflected light flux from the corneal surface is almost a spherical wave, whereas the reflected light flux from the fundus oculi is almost the same. Since it is a plane wave, the number of interference fringes becomes very large as it goes away from the vertex of the cornea to the periphery. Therefore, observation of interference fringes cannot be performed well. Also,
The optical axis of the condenser lens 6 and the camera 7 is
Alignment must be performed accurately, but there is a problem that this alignment is extremely troublesome.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a living eye capable of easily observing interference fringes and improving measurement accuracy without accurately performing alignment with the living eye. An object of the present invention is to provide a front-rear diameter measuring device.

(Means for Solving the Problems) In order to achieve the above-mentioned object, a longitudinal diameter distance measuring apparatus for a living eye according to the present invention includes: a longitudinal distance distance from a first measuring surface to a second measuring surface of a living eye; A model eyesight used to measure the distance; an observation optical system for observing interference between a reflected light beam from the model eyesight and a reflected light beam from the living eye; A light beam splitting member that guides a coherent split light beam to a device, wherein the model eyesight has a first light beam corresponding to the first measurement target surface.
At least a model surface and a second model surface corresponding to the second measurement target surface are provided, and interference fringes between the first model surface and the first measurement target surface are observed, and the second model surface and the second model surface are observed. The method is characterized by observing interference fringes with a measurement target surface and measuring a front-rear radial distance from the first measurement target surface to the second target surface.

(Action) According to the living eye longitudinal distance measuring apparatus according to the present invention, the wavefront shapes of the reflected wavefront from the first model surface and the reflected wavefront from the first measurement target surface are substantially the same, and The reflected wavefront from the two model surfaces and the reflected wavefront from the second measurement target surface are also substantially the same, and interference fringes are obtained by causing the same wavefront shapes to interfere with each other, so that the obtained interference fringes are good.

(Embodiment 1) FIG. 1 shows an optical system of a first embodiment of a living eye longitudinal distance measuring apparatus according to the present invention, which is used for measuring an axial length as a longitudinal distance of a living eye. In FIG. 1, reference numeral 20 denotes a semiconductor laser, 21 denotes a collimator lens, 22 denotes a beam splitter, 23 denotes a model eyesight, 24 denotes a living eye, 25 denotes a condensing lens, 26 denotes a CCD camera, and 27 denotes a television monitor. . The semiconductor laser 2 laser has a coherent length of 0.
1 mm or less is used. If a coherent length of 0.1 mm or more is used, interference fringes can be obtained at any position even if the model formula 23 is slightly moved in the optical axis direction described later, and a measurement accuracy of about 0.1 mm cannot be obtained. Because. It is also undesirable to use a semiconductor laser 20 having an extremely short coherent length. This is because the measurement accuracy is improved, but interference fringes are not easily obtained, and the measurement takes time. In particular, the interference fringes based on the interference between the fundus and the second model surface, which will be described later, have a complicated shape due to the complicated shape of the fundus, and have the interference fringes been obtained by using the semiconductor laser 20 having an extremely short coherent length? It is not easy to determine whether or not.

The laser light emitted from the semiconductor laser 20 is converted into a parallel light beam by the collimating lens 21. As the parallel light flux into a parallel light beam P ₁ is guided to the living eye 24 by the reflecting surface 28 of the beam splitter 22 as a light beam splitting member is divided into a parallel light flux and P ₂ is guided to the model view 23.

The model eyesight 23 has a first model surface 30 corresponding to the cornea 29 as a first measurement target surface, and a second model surface 32 corresponding to the fundus 31 as a second measurement target surface. The radius of curvature of the first model surface 30 is set to an average value of the radius of curvature of the cornea 29. Here, the radius of curvature of the first model surface 30 is 7 to 8 mm. The radius of curvature of the second model surface 32 is set to an average value of the radius of curvature of the fundus 31. Also, the refractive index n of the model eyesight 23
Is approximately the same as the refractive index N of the intraocular substance, and the first model surface 30
Distance l ₁ from to the second model surface 32 is set to the average value of the axial length of the living eye 24. Here, the distance l ₁ is from 22 mm
24 mm. Further, the distance l ₁ and the first model surface 30 are set so that the parallel light beam entering the model eyesight 23 is converged on the second model surface 32.
, The radius of curvature of the second model surface 32, and the refractive index n are selected. Its Model vision 23 is movable in the direction of the optical axis O _1.

The light beam reflected by the cornea 29 and the first model surface 30 becomes a substantially divergent light beam (substantially spherical wave). On the other hand, the reflected light beam reflected by the fundus 31 and the reflected light beam reflected by the second model surface become substantially parallel light beams (substantially plane waves) when emitted from the cornea 29 and the first model surface 30, respectively.

According to the apparatus for measuring the longitudinal distance of the living eye according to this embodiment, the model eyesight 23 is connected to the first model surface 30 by the beam splitter.
When the reflecting surface 28 of the lens 22 is moved in the direction of the optical axis O ₁ so as to be conjugate with the cornea 29 of the living eye 24, the light flux P ₂ ′ reflected by the first model surface 30 and the light flux reflected by the cornea 29 P ₁ ′
Are condensed by a condenser lens 25 constituting a part of the observation optical system and guided to a CCD camera 26, and interference fringes based on the light fluxes P ₁ ′ and P ₂ ′ are projected on a television monitor 27. Also, moving a model view 23 in the direction of the optical axis O ₁ so the fundus 31 and the conjugate of a living eye 24 with respect to the reflecting surface 28 of the second model surface 32 the beam splitter 22, the second model surface 32 The interference fringes based on the light beam P ₂ ″ reflected by the light beam and the light beam P ₁ ″ reflected by the fundus 31 are similarly projected on the television monitor 27.

Assuming that the axial length of the living eye 24 is X, the cornea 29 and the first model surface 30
The optical axis O ₁ when the interference fringes based the position of the optical axis O ₁ direction of the model view 24 when the interference fringe based on the bets were obtained and X _1, the fundus 31 and the second model surface 32 obtained X ₂ position of model eyesight 24 in direction
When a _{N · X = (X 1 -X} 2) + n · l 1.

Therefore, by modifying the above equation, As a result, the axial length is obtained.

According to the biological eye longitudinal distance measuring device that measures the interference fringe by observing interference fringes using this model eyesight 23, since the wavefront shapes of the light beams that cause interference are substantially the same, An appropriate number of interference fringes can be obtained, and the obtained interference fringes can be favorably observed.

(Embodiment 2) FIG. 2 shows a second embodiment of the optical system of the longitudinal distance measuring apparatus for a living eye according to the present invention, in which two model visual instruments which are separate optical objects are used. In FIG. 2, reference numeral 33 denotes a model eyesight provided with a first model surface 30 corresponding to the cornea 29 of the living eye 24, and 34 denotes a fundus 31 of the living eye 24. Is a model eyesight provided with a second model surface 32 corresponding to. Between the beam splitter 22 and the living eye 24, the beam as a light beam splitting member for splitting into a light beam guided to the light beam and a living eye 24 guided the split light beams P ₁ to be guided to the living eye 24 on the model view 33 A splitter 35 is provided, and 36 is a reflection surface of the beam splitter 35. An optical path having substantially the same shape, substantially the same thickness, and substantially the same refractive index as the beam splitter 35 at a position conjugate with the projection of the beam splitter 3 with respect to the reflection surface 28 of the beam splitter 22 between the model visual instrument 34 and the beam splitter 22. A length correcting optical member 37 is provided, and the optical distance from the model visual device 34 to the reflection surface 28 of the beam splitter 22 and the optical distance from the model visual device 33 to the reflection surface 28 of the beam splitter 22 via the beam splitter 35 are provided. The optical distance is set to be substantially equal. It should be noted that the split light beam incident on the model
An anti-reflection treatment film is formed so that P ₂ ′ is not reflected as much as possible on its surface 32 ′.

Between the model sight 33 and the beam splitter 35, the model sight 34
Between the optical path length correcting optical member 37 and the optical path length correcting optical member 37, light amount adjusting optical members 38 and 39 are provided. This optical member for adjusting the amount of light
For 38, an optical density variable filter whose density is variable in the direction indicated by the arrow in FIG. 3 is used. The lens of the living eye 24, the transmittance of the vitreous body has individual differences depending on the living eye, and if the reflected light flux from the living eye 24 and the reflected light flux from the model eyes 33 and 34 are significantly different, the contrast of the interference fringe is remarkable. Model eyesight so that the contrast of interference fringes is good.
The light amount adjusting optical members 38 and 39 are rotated about their axes 38 'and 39' to adjust the light amounts of the reflected light beams from the 33 and 34 so as to approach the light amount of the reflected light beam from the living eye 24.

The model eyes 33 and 34 are simultaneously movable in the directions of the optical axes O ₁ and O _{2. When} the first model surface 30 and the cornea 29 of the model eyes 33 are almost conjugate, The interference fringes based on the eyesight 33 are projected on the television monitor 27, and the interference fringes based on the model vision 34 when the second model surface 32 of the model vision 34 and the fundus 31 are almost conjugated are also projected on the television monitor 27. It is.

Therefore, when the known eye axis length X ₀ is measured, the position of the model visual instrument 33 in the optical axis O ₂ direction is X ₁₀ , and the position of the model visual instrument 34 in the optical axis O ₁ direction is X _20. Assuming that the positions of the model visual instruments 33 and 34 in the directions of the optical axes O ₁ and O ₂ when measuring the axial length X of the eye 24 are X ₃ and X ₄ , respectively, (X ₃ −X ₁₀ ) + n · (X ₄₋ X ₂₀ ) = N · (X−X ₀ ) where n is the refractive index of the model eyesight 34.

 Thus, the unknown axial length X is obtained.

According to the second embodiment, since the model eyesights 33 and 34 are simultaneously moved, the interference fringe obtained by the cornea 29 and the interference fringe obtained by the fundus 31 can be simultaneously projected on the television monitor 27 and observed. The measurement time can be reduced as compared with the embodiment.

(Embodiment 3) FIG. 4 shows a third embodiment of a living eye longitudinal distance measuring apparatus, which is used for measuring the anterior chamber depth as the longitudinal distance of a living eye. The first corresponding to the cornea 29 of
The second corresponding to the model surface 30 and the front surface 41 of the crystalline lens 40 of the living eye 24
A model visual field 43 having a model surface 42 is used to observe interference fringes between the first model surface 30 and the cornea 29, and to use the second model surface 42 and the front surface 41 of the crystalline lens 40. The interference fringes are observed to measure the anterior chamber depth.

As described above, the embodiment has been described.
By observing the interference fringes using a model eyesight having a first model surface corresponding to the first lens surface and a second model surface corresponding to the rear surface 44 of the lens 40, the lens lens as the front-rear radial distance of the living eye can be obtained. The thickness of the crystalline lens 40 from the front surface to the rear surface can be measured.

(Effect) As described above, the front-rear radial distance measuring apparatus for a living eye according to the present invention has substantially the same wavefront shape as the reflected wavefront from the first model surface and the reflected wavefront from the first measurement target surface. Since the reflected wavefront from the second model surface and the reflected wavefront from the second measurement target surface are almost the same, the same wavefront shapes interfere with each other, and the observed interference fringes can be obtained well. Become.

Further, since the wavefront shapes to be interfered are substantially the same, a good interference fringe can be easily obtained without strictly performing alignment with the living eye.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical system of a first embodiment of a living eye longitudinal distance measuring apparatus according to the present invention, and FIG. 2 is a second embodiment of a living eye longitudinal distance measuring apparatus according to the present invention. FIG. 3 shows an optical system, FIG. 3 is a plan view of a light amount adjusting optical member shown in FIG. 2, and FIG. 4 shows an optical system of a living eye longitudinal distance measuring apparatus according to a third embodiment of the present invention. FIG. 5 is a diagram showing an optical system of a conventional apparatus for measuring the longitudinal distance of a living eye. 20 ... Semiconductor laser 22 ... Beam splitter (beam splitting member) 23 ... Model eye, 24 ... Live eye, 27 ... TV monitor 28 ... Reflective surface, 29 ... Cornea, 30 ... First model surface 31 ... Fundus, 32 ... 2 model surfaces 33, 34, 43 ... model visual, 35 ... beam splitter 40 ... crystalline lens, 41 ... front, 44 ... rear

Claims (9)

(57) [Claims] 1. A model eyesight used for measuring a front-rear radial distance from a first measurement object surface to a second measurement object surface of a living eye, a reflected light beam from the model eyesight and a reflection from the living eye An observation optical system for observing interference with the light beam; and a light beam splitting member that splits the light beam and guides the coherent split light beam to the living eye and the model visual device. At least a first model surface corresponding to one measurement target surface and a second model surface corresponding to the second measurement target surface are provided, and interference fringes between the first model surface and the first measurement target surface are observed. Observing interference fringes between the second model surface and the second measurement target surface, and measuring a front-rear diameter distance from the first measurement target surface to the second target surface, the front-rear diameter of the living eye, Distance measuring device. 2. The living-body eye front-rear diameter measuring apparatus according to claim 1, wherein the front-rear diameter distance is any one of an axial length, an anterior chamber depth, and a lens thickness. . 3. A model eyesight used for measuring an axial length as a front-back distance from a first measurement target surface to a second measurement target surface of a living eye, a reflected light beam from the model eyesight and the living body An observation optical system for observing interference with a light beam reflected from the eye, and a light beam splitting member that splits the light beam and guides the coherent split light beam to the living eye and the model visual device; The first corresponding to the corneal surface of the living eye
A model surface and a second model surface corresponding to the fundus of the living eye are provided, and interference fringes between the first model surface and the corneal surface are observed and interference between the second model surface and the fundus oculi is observed. An apparatus for measuring an axial length of a living eye as observing a stripe and measuring an axial length as an anteroposterior radial distance from the corneal surface to a fundus oculi. 4. A method according to claim 1, wherein said first model surface is formed substantially corresponding to a curvature of said corneal surface, and said second model surface is formed substantially corresponding to a curvature of said fundus fundus. 4. The apparatus for measuring a front-to-rear diameter distance of a living eye according to claim 1 or 3. 5. The model eyesight wherein the first model surface and the second model surface are integrally formed by using an optical object, and the refractive index of the optical object is a refractive index of an intraocular substance of the eye to be examined. 4. The apparatus according to claim 3, wherein the ratio is substantially equal to the ratio. 6. An optical object having said first model surface and said optical object having said second object formed separately from said optical object.
4. The apparatus according to claim 3, comprising an optical object having a model surface. 7. A front and rear view of a living eye according to claim 3, wherein a light beam emitted from a semiconductor laser is divided and guided by said light beam splitting member to said model eyesight and said living eye. Diameter measuring device. 8. The semiconductor laser has a coherent length.
8. The apparatus for measuring a front-to-rear diameter distance of a living eye according to claim 7, wherein the apparatus has a diameter of 0.1 mm or less. 9. An optical object having the first model surface, wherein the model visual device is formed separately from the optical object, and
A light beam emitted from a semiconductor laser is divided and guided by the light beam splitting member to each of the model eyesight and the living eye, and the semiconductor laser has a coherent length. 4. An optical object having a thickness of 0.1 mm or less is used, and an anti-reflection coating is applied to a surface of the optical object having the second model surface.
4. The apparatus for measuring a front-to-rear diameter distance of a living eye according to claim 1.