U.S. patent application number 14/095224 was filed with the patent office on 2014-03-27 for fundus observation apparatus.
This patent application is currently assigned to KABUSHIKI KAISHA TOPCON. The applicant listed for this patent is KABUSHIKI KAISHA TOPCON. Invention is credited to Takefumi Hayashi.
Application Number | 20140085605 14/095224 |
Document ID | / |
Family ID | 43031906 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140085605 |
Kind Code |
A1 |
Hayashi; Takefumi |
March 27, 2014 |
FUNDUS OBSERVATION APPARATUS
Abstract
The controller 210 changes the projection region of the Landolt
ring T on the fundus Ef by changing, based on the scanning region
R, the relative display position of the Landolt ring T and the
fixation target V on the LCD 39, thereby overlapping the scanning
region R and the projection region each other. Under this
condition, the fundus observation apparatus 1 executes the eyesight
measurement and OCT measurement, obtains the eyesight value at the
site of interest of the fundus Ef, and forms a tomographic image of
the fundus Ef in the scanning region R. The controller 210 stores
in the storage 212 the eyesight value at the site of interest and
the tomographic image corresponding to the scanning line closest to
the measurement position of eyesight while correlating them with
each other, and allows them to be displayed on the display device
3.
Inventors: |
Hayashi; Takefumi; (Tokyo,
JP) |
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Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOPCON |
Tokyo |
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JP |
|
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Assignee: |
KABUSHIKI KAISHA TOPCON
Tokyo
JP
|
Family ID: |
43031906 |
Appl. No.: |
14/095224 |
Filed: |
December 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13266148 |
Oct 25, 2011 |
8622547 |
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PCT/JP2010/002428 |
Apr 2, 2010 |
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14095224 |
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Current U.S.
Class: |
351/206 |
Current CPC
Class: |
A61B 3/102 20130101;
A61B 3/1225 20130101; A61B 3/12 20130101; A61B 3/14 20130101; A61B
3/032 20130101 |
Class at
Publication: |
351/206 |
International
Class: |
A61B 3/12 20060101
A61B003/12 |
Claims
1. A fundus observation apparatus comprising: a projection part
that projects visual target for measuring vision displayed on a
display part to the fundus of an eye; an optical system that splits
light outputted from a light source into signal light and reference
light, generates interference light by superposing said signal
light that has passed through said fundus and said reference light
that has passed through a reference optical path, and detects said
interference light; a scanning part that scans said fundus with
said signal light; a controlling part that controls the scanning
region of said signal light scanned by said scanning part each
other; an image forming part that forms an image of said fundus
based on the detection results of interference light generated by
superposing said signal light with which said scanning region is
scanned and said reference light; and an operation part for
inputting response contents for said visual target for measuring
vision projected to said fundus; and a vision measurement part that
examines vision of the eye based on the response contents.
2. The fundus observation apparatus according to claim 1, wherein:
said display part displays a fixation target for fixing said
eye.
3. The fundus observation apparatus according to claim 2, wherein:
said controlling part begins the measurement in the scanning region
at the same time as the start of the eyesight measurement.
4. The fundus observation apparatus according to claim 1, wherein:
said controlling part controls so as to overlap the projection
region of said visual target for measuring vision projected by said
projection part and the scanning region of said signal light
scanned by said scanning part each other.
5. The fundus observation apparatus according to claim 4, further
comprising a storage part that stores said formed image and a
vision value measured using said visual target for measuring vision
while correlating them with each other.
6. The fundus observation apparatus according to claim 1, wherein:
said controlling part controls said projection part based on the
scanning region of said signal light scanned by said scanning part
to overlap the projection region of said visual target for
measuring vision in said fundus on the scanning region of said
signal light.
7. The fundus observation apparatus according to claim 6, wherein:
said display part displays a fixation target for fixing said eye
along with said visual target for measuring vision; said projection
part projects said displayed fixation target on said fundus along
with said visual target for measuring vision; and said controlling
part changes said projection region by changing, based on said
scanning region, the relative display positions of said visual
target for measuring vision and said fixation target displayed by
said display part.
8. The fundus observation apparatus according to claim 1, wherein:
said controlling part controls said scanning part based on the
display position of said visual target for measuring vision
displayed by said display part to overlap the scanning region of
said signal light in said fundus on the projection region of said
visual target for measuring vision.
9. The fundus observation apparatus according to claim 1, wherein:
said controlling part allows said visual target for measuring
vision corresponding to different vision values to be projected on
said fundus, by allowing said visual target for measuring vision of
different sizes to be displayed on said display part to change the
size of said projection region.
10. The fundus observation apparatus according to claim 9, wherein:
said projection part projects said displayed visual target for
measuring vision to the fundus of an eye via a predetermined
optical path, said optical system conducts said signal light via a
predetermined optical path, said predetermined optical path is
provided with a focusing lens that moves along an optical axis
thereof to change the focus position of light towards said fundus;
and said controlling part adjusts the size of said visual target
for measuring vision displayed on said display part based on the
position of said focusing lens.
11. The fundus observation apparatus according to claims 9 or 10,
wherein: said controlling part changes the size of said visual
target for measuring vision displayed on said display part based on
said input response contents, and determines the vision value of
said eye based on said response contents according to this
change.
12. The fundus observation apparatus according to claim 1, wherein:
said controlling part controls said projection part to project said
visual target for measuring vision corresponding to a predetermined
vision value to said fundus, determines whether said input response
contents for this visual target for measuring vision are true or
false, and if it is determined that they are correct, then controls
said scanning part to scan said scanning region overlapping the
projection region with said signal light.
13. The fundus observation apparatus according to claim 1, wherein:
said light source outputs invisible light as said low-coherence
light.
14. The fundus observation apparatus according to claim 13,
wherein: said light source outputs near-infrared light of center
wavelength within the range substantially from 1050 to 1060 nm.
Description
RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/266,148 filed on Oct. 25, 2011, which is incorporated
herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a fundus observation
apparatus configured to form images of a fundus of an eye by using
optical coherence tomography.
BACKGROUND ART
[0003] In recent years, optical coherence tomography that forms
images of the surface morphology and internal morphology of an
object by using a light beam from a laser light source or the like
has attracted attention. Unlike an X-ray CT apparatus, optical
coherence tomography is noninvasive to human bodies, and is
therefore expected to be utilized in the medical field and
biological field.
[0004] Patent Document 1 discloses a device to which optical
coherence tomography is applied. This device has such a
configuration that: a measuring arm scans an object by a rotary
deflection mirror (a Galvano mirror); a reference arm is provided
with a reference mirror; and an interferometer is mounted at the
outlet to analyze, by a spectrometer, the intensity of an
interference light of light fluxes from the measurement arm and the
reference arm. Moreover, the reference arm is configured to
gradually change the light flux phase of the reference light by
discontinuous values.
[0005] The device of Patent Document 1 uses a technique of
so-called "Fourier Domain OCT (Optical Coherence Tomography)." That
is to say, the device irradiates a low coherence light beam to an
object, superposes the reflected light and the reference light to
generate an interference light, and acquires the spectral intensity
distribution of the interference light to execute Fourier
transform, thereby imaging the morphology in the depth direction
(the z-direction) of the object. The technique of this type is also
called Spectral Domain.
[0006] Furthermore, the device described in Patent Document 1 is
provided with a Galvano mirror that scans with a light beam (a
signal light), and is thereby configured to form an image of a
desired measurement target region of the object. Because this
device is configured to scan with the light beam only in one
direction (the x-direction) orthogonal to the z-direction, an image
formed by this device is a two-dimensional tomographic image in the
depth direction (the z-direction) along the scanning direction (the
x-direction) of the light beam.
[0007] Patent Document 2 discloses a technique of scanning with a
signal light in the horizontal direction (x-direction) and the
vertical direction (y-direction) to form a plurality of
two-dimensional tomographic images in the horizontal direction, and
acquiring and imaging three-dimensional tomographic information of
a measured range based on the tomographic images. As the
three-dimensional imaging, for example, a method of arranging and
displaying a plurality of tomographic images in the vertical
direction (referred to as stack data or the like), and a method of
executing a rendering process on a plurality of tomographic images
to form a three-dimensional image are considered.
[0008] Patent Documents 3 and 4 disclose other types of OCT
devices. Patent Document 3 describes an OCT device that images the
morphology of an object by sweeping the wavelength of light that is
irradiated to an object, acquiring the spectral intensity
distribution based on an interference light obtained by superposing
the reflected lights of the light of the respective wavelengths on
the reference light, and executing Fourier transform. Such an OCT
device is called a Swept Source type or the like. The Swept Source
type is a kind of the Fourier Domain type.
[0009] Further, Patent Document 4 describes an OCT device that
irradiates a light having a predetermined beam diameter to an
object and analyzes the components of an interference light
obtained by superposing the reflected light and the reference
light, thereby forming an image of the object in a cross-section
orthogonal to the travelling direction of the light. Such an OCT
device is called a full-field type, en-face type or the like.
[0010] Patent Document 5 discloses a configuration in which the OCT
is applied to the ophthalmologic field. Before the OCT device was
applied to the ophthalmologic field, a fundus observation apparatus
such as a retinal camera had been used (for example, refer to
Patent Document 6).
[0011] Compared to a retinal camera that can only photograph a
fundus from the front, a fundus observation apparatus using OCT has
a merit that tomographic images and 3-dimensional images of a
fundus are obtained. Therefore, contribution to increase of the
diagnosis accuracy and early detection of a lesion are
expected.
[0012] The fundus observation apparatus using optical coherence
tomography thus occupies an important place in diagnosis and
treatment of diseases. However, in reality, eyesight values are
currently used in order to determine the necessity of treatment and
the presence or absence of its effect.
[0013] This is due to the fact that the main purpose of treatment
is the improvement of eyesight, and the change in the morphology of
the fundus (for example, hole shrinkage due to treatment of the
macular hole) can be confirmed by the fundus observation apparatus,
but it cannot be determined whether or not the change in the
morphology results in improvement of eyesight without relying on
eyesight measurement.
[0014] It should be noted that eyesight measurement is an eye
examination in which a visual target for measuring eyesight such as
a Landolt ring is presented to the subject, commonly carried out
using a subjective optometer (see, for example, Patent Document
7).
PRIOR ART DOCUMENTS
Patent Documents
[Patent Document 1]
[0015] Japanese Unexamined Patent Application Publication No. Hei
11-325849
[Patent Document 2]
[0015] [0016] Japanese Unexamined Patent Application Publication
No. 2002-139421
[Patent Document 3]
[0016] [0017] Japanese Unexamined Patent Application Publication
No. 2007-24677
[Patent Document 4]
[0017] [0018] Japanese Unexamined Patent Application Publication
No. 2006-153838
[Patent Document 5]
[0018] [0019] Japanese Unexamined Patent Application Publication
No. 2008-73099
[Patent Document 6]
[0019] [0020] Japanese Unexamined Patent Application Publication
No. Hei 9-276232
[Patent Document 7]
[0020] [0021] Japanese Unexamined Patent Application Publication
No. 2008-148930
DISCLOSURE OF THE INVENTION
Problem that the Invention is to Solve
[0022] However, with eyesight measurement, it cannot be determined
which site of the fundus is used to see the target (i.e., it cannot
be determined which site of the fundus is projected with the
target), and it cannot be determined if the eyesight value of the
treatment sight has actually improved. For example, in a healthy
eye, the target is projected on the macula flava due to the target
being recognized in the macula flava having the highest visual
ability; however, when there is a disorder in the macula flava, the
target tends to be captured by a site other than the macula flava,
so the eyesight value of the affected site actually cannot always
be measured. In such a case, it is preferable that the visual
ability be able to be confirmed by conducting eyesight measurement
at the site of interest (treatment site, diagnosed site, etc.) of
the fundus, while being able to confirm the morphology of the
fundus by obtaining an image of the site of interest. However,
conventional devices have not been able to obtain an image of the
eyesight measurement position. Consequently, for example, it has
not been possible to determine whether or not the treatment is
actually reflected in improvement of eyesight.
[0023] Moreover, the viewing angle (size) of the visual target for
measuring eyesight projected on the fundus is sometimes changed due
to the refractive power (eye refractive power) of the eye, and
there has been a problem in that the eyesight value cannot be
precisely measured in such a case.
[0024] Furthermore, it is also conceivable that a conventional
fundus observation apparatus is added with a target presenting
function, but in such a case the subject has to simultaneously
visually confirm the signal light, the fixation target and the
visual target for measuring eyesight, increasing the complexity of
the examination and possibly causing adverse effects.
[0025] This invention resolves the above-mentioned problem, with
the purpose of providing a fundus observation apparatus capable of
obtaining an image at the eyesight measurement site of the
fundus.
Means for Solving the Problem
[0026] In order to achieve the aforementioned objects, an invention
according to claim 1 is a fundus observation apparatus comprising:
a projection part that includes a display part to display a visual
target for measuring eyesight, and projects, via a predetermined
optical path, said displayed visual target for measuring eyesight
to the fundus of an eye; a light source that outputs low-coherence
light; an optical system that splits said output low-coherence
light into signal light and reference light, generates interference
light by superposing said signal light that has passed through said
fundus via said predetermined optical path and said reference light
that has passed through a reference optical path, and detects said
interference light; a scanning part that scans said fundus with
said signal light; a controlling part that overlaps the projection
region of said visual target for measuring eyesight projected by
said projection part and the scanning region of said signal light
scanned by said scanning part each other; an image forming part
that forms an image of said fundus based on the detection results
of interference light generated by superposing said signal light
with which said scanning region is scanned and said reference
light; and a storage part that stores said formed image and an
eyesight value measured using said visual target for measuring
eyesight while correlating them with each other.
[0027] Further, an invention according to claim 2 is the fundus
observation apparatus according to claim 1, wherein said
controlling part controls said projection part based on the
scanning region of said signal light scanned by said scanning part
to overlap the projection region of said visual target for
measuring eyesight in said fundus on the scanning region of said
signal light.
[0028] Further, an invention according to claim 3 is the fundus
observation apparatus according to claim 2, wherein: said display
part displays a fixation target for fixing said eye along with said
visual target for measuring eyesight; said projection part projects
said displayed fixation target on said fundus along with said
visual target for measuring eyesight; and said controlling part
changes said projection region by changing, based on said scanning
region, the relative display positions of said visual target for
measuring eyesight and said fixation target displayed by said
display part.
[0029] Further, an invention according to claim 4 is the fundus
observation apparatus according to claim 1, wherein said
controlling part controls said scanning part based on the display
position of said visual target for measuring eyesight displayed by
said display part to overlap the scanning region of said signal
light in said fundus on the projection region of said visual target
for measuring eyesight.
[0030] Further, an invention according to claim 5 is the fundus
observation apparatus according to claim 1, wherein said
controlling part allows said visual target for measuring eyesight
corresponding to different eyesight values to be projected on said
fundus, by allowing said visual target for measuring eyesight of
different sizes to be displayed on said display part to change the
size of said projection region.
[0031] Further, an invention according to claim 6 is the fundus
observation apparatus according to claim 5, wherein: said
predetermined optical path is provided with a focusing lens that
moves along an optical axis thereof to change the focus position of
light towards said fundus; and said controlling part adjusts the
size of said visual target for measuring eyesight displayed on said
display part based on the position of said focusing lens.
[0032] Further, an invention according to claim 7 is the fundus
observation apparatus according to claim 5, further comprising an
operation part for inputting response contents for said visual
target for measuring eyesight projected on said fundus, wherein
said controlling part changes the size of said visual target for
measuring eyesight displayed on said display part based on said
input response contents, and determines the eyesight value of said
eye based on said response contents according to this change.
[0033] Further, an invention according to claim 8 is the fundus
observation apparatus according to claim 1, further comprising an
operation part for inputting response contents for said visual
target for measuring eyesight projected on said fundus, wherein
said controlling part controls said projection part to project said
visual target for measuring eyesight corresponding to a
predetermined eyesight value to said fundus, determines whether
said input response contents for this visual target for measuring
eyesight are true or false, and if it is determined that they are
correct, then controls said scanning part to scan said scanning
region overlapping the projection region with said signal
light.
[0034] Further, an invention according to claim 9 is the fundus
observation apparatus according to claim 1, wherein said light
source outputs invisible light as said low-coherence light.
[0035] Further, an invention according to claim 10 is the fundus
observation apparatus according to claim 9, wherein said light
source outputs near-infrared light of center wavelength within the
range substantially from 1050 to 1060 nm.
Effect of the Invention
[0036] According to the fundus observation apparatus related to the
present invention, an image of the scanning region of the signal
light on the fundus can be formed with said scanning region being
superposed on the projection region of the visual target for
measuring eyesight, and it is possible to measure the eyesight in
the projection region and then store the formed image and the
measured eyesight value while associating them with each other,
allowing an image of the eyesight measurement site of the fundus to
be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIG. 1 is a schematic view showing an example of a
configuration of an embodiment of a fundus observation apparatus
according to the present invention.
[0038] FIG. 2 is a schematic view showing an example of a
configuration of an embodiment of a fundus observation apparatus
according to the present invention.
[0039] FIG. 3 is a schematic block diagram showing an example of a
configuration of an embodiment of a fundus observation apparatus
according to the present invention.
[0040] FIG. 4 is a flowchart showing an example of an action of an
embodiment of a fundus observation apparatus according to the
present invention.
[0041] FIG. 5 is a schematic view for explaining an example of an
action of an embodiment of a fundus observation apparatus according
to the present invention.
[0042] FIG. 6 is a schematic view for explaining an example of an
action of an embodiment of a fundus observation apparatus according
to the present invention.
[0043] FIG. 7 is a flowchart showing an example of an action of an
embodiment of a fundus observation apparatus according to the
present invention.
[0044] FIG. 8 is a schematic view for explaining an example of an
action of an embodiment of a fundus observation apparatus according
to the present invention.
[0045] FIG. 9 is a schematic view for explaining an example of an
action of an embodiment of a fundus observation apparatus according
to the present invention.
[0046] FIG. 10 is a schematic block diagram showing an example of a
configuration of a modification example of an embodiment of a
fundus observation apparatus according to the present
invention.
MODE FOR CARRYING OUT THE INVENTION
[0047] An example of an embodiment of a fundus observation
apparatus according to the present invention will be described in
detail with reference to the drawings.
[0048] The fundus observation apparatus according to the present
invention forms tomographic images of a fundus using optical
coherence tomography. Optical coherence tomography of an arbitrary
type involving scanning with a signal light such as a Fourier
Domain type, a swept source type, etc. are applicable to the fundus
observation apparatus. It should be noted that an image obtained by
optical coherence tomography is sometimes referred to as an OCT
image. Furthermore, a measuring action for forming an OCT image is
sometimes referred to as an OCT measurement.
[0049] In the following embodiments, a configuration to which a
Fourier-Domain-type is applied will be described in detail. To be
specific, in these embodiments, similar to a device disclosed in
Patent Document 5, a fundus observation apparatus that is capable
of obtaining both tomographic images and photographed image of a
fundus will be picked up.
[Configuration]
[0050] A fundus observation apparatus 1, as shown in FIG. 1 and
FIG. 2, includes a retinal camera unit 2, an OCT unit 100, and an
arithmetic and control unit 200. The retinal camera unit 2 has
almost the same optical system as a conventional retinal camera.
The OCT unit 100 is provided with an optical system for obtaining
an OCT image of a fundus. The arithmetic and control unit 200 is
provided with a computer that executes various arithmetic
processes, control processes, and so on.
[Retinal Camera Unit]
[0051] The retinal camera unit shown in FIG. 1 is provided with an
optical system for forming a 2-dimensional image (fundus image)
representing the surface morphology of the fundus Ef of an eye E.
Fundus images include observation images, photographed images, etc.
The observation image is, for example, a monochrome image formed at
a prescribed frame rate using near-infrared light. The photographed
image is, for example, a color image captured by flashing visible
light. It should be noted that the retinal camera unit 2 may also
be configured so as to be capable of capturing other types of
images such as a fluorescein angiography image or an indocyanine
green fluorescent image.
[0052] The retinal camera unit 2 is provided with a chin rest and a
forehead placement for retaining the face of the subject, similar
to a conventional retinal camera. Moreover, like a conventional
retinal camera, the retinal camera unit 2 is provided with an
illumination optical system 10 and an imaging optical system 30.
The illumination optical system 10 irradiates an illumination light
to the fundus Ef. The imaging optical system 30 guides a fundus
reflected light of the illumination light to imaging devices (CCD
image sensors 35, 38). Moreover, the imaging optical system 30
guides a signal light LS coming from the OCT unit 100 to the fundus
Ef, and guides the signal light propagated through the fundus Ef to
the OCT unit 100.
[0053] An observation light source 11 of the illumination optical
system 10 comprises, for example, a halogen lamp. Light
(observation illumination light) output from the observation light
source 11 is reflected by a reflection mirror 12 with a curved
reflection surface, and becomes near infrared after passing through
a visible cut filter 14 via a condenser lens 13. Furthermore, the
observation illumination light is once converged near an imaging
light source 15, reflected by a mirror 16, and passes through relay
lenses 17, 18, diaphragm 19, and relay lens 20. Then, the
observation illumination light is reflected on the peripheral part
(the surrounding region of an aperture part) of an aperture mirror
21 and illuminates the fundus Ef via an object lens 22.
[0054] The fundus reflection light of the observation illumination
light is refracted by the object lens 22, passes through the
aperture part formed in the center region of the aperture mirror
21, passes through a dichroic mirror 55 and, travels through a
focusing lens 31, and is reflected by a dichroic mirror 32.
Furthermore, the fundus reflection light passes through a
half-mirror 40 and forms an image on the light receiving surface of
the CCD image sensor 35 by a condenser lens 34 after being
reflected by a dichroic mirror 33. The CCD image sensor 35 detects,
for example, the fundus reflection light at a prescribed frame
rate. An image (observation image) K based on the fundus reflection
light detected by the CCD image sensor 35 is displayed on a display
device 3.
[0055] The imaging light source 15 consists of, for example, a
xenon lamp. The light (imaging illumination light) output from the
imaging light source 15 is irradiated to the fundus Ef via a route
that is similar to the observation illumination light. The fundus
reflection light of the imaging illumination light is guided to the
dichroic mirror 33 via the same route as that of the observation
illumination light, passes through the dichroic mirror 33, and
forms an image on the light receiving surface of the CCD image
sensor 38 by a condenser lens 37 after being reflected by a mirror
36. An image (photographed image) H based on the fundus reflection
light detected by the CCD image sensor 38 is displayed on the
display device 3. It should be noted that the display device 3 for
displaying an observation image K and the display device 3 for
displaying a photographed image H may be the same or different.
[0056] An LCD (Liquid Crystal Display) 39 displays a fixation
target or a visual target for measuring eyesight. The fixation
target is a visual target for fixing the eye E, and is used when
photographing a fundus or forming a tomographic image. The visual
target for measuring eyesight is a visual target used for measuring
an eyesight value of the eye E, for example, such as Landolt rings.
It should be noted that the visual target for measuring eyesight is
sometimes simply referred to as a target.
[0057] Part of the light output from the LCD 39 is reflected by a
half-mirror 40, reflected by the dichroic mirror 32, passes through
the aperture part of the aperture mirror 21 via the focusing lens
31 as well as a dichroic mirror 55, is refracted by the object lens
22 and projected to the fundus Ef. LCD 39 is an example of a
"display part" of the invention. Moreover, LCD 39 and the
above-mentioned group of optical elements that project light output
from LCD 39 on the fundus Ef are a "projection part" of the
invention.
[0058] By changing a display position of the fixation target on the
screen of the LCD 140, it is possible to change a fixation position
of the eye E. As the fixation position of the eye E, there are a
position for acquiring an image centered on the macula of the
fundus Ef, a position for acquiring an image centered on the optic
papilla, a position for acquiring an image centered on the fundus
center between the macula and the optic papilla, and so on, for
example, as in conventional retinal cameras.
[0059] Furthermore, as with conventional fundus cameras, the
retinal camera unit 2 is provided with an alignment optical system
50 and a focus optical system 60. The alignment optical system 50
generates a target (alignment target) for matching the position
(alignment) of the device optical system with respect to the eye E.
The focus optical system 60 generates a target (split target) for
matching the focus with respect to the eye Ef.
[0060] Light (alignment light) output from the LED (Light Emitting
Diode) 51 of the alignment optical system 50 is reflected by the
dichroic mirror 55 via diaphragms 52, 53 and a relay lens 54,
passes through the aperture part of the aperture mirror 21, and is
projected onto the cornea of the eye E by the object lens 22.
[0061] Part of cornea reflection light of the alignment light is
transmitted through the dichroic mirror 55 via the object lens 22
and the aperture part, passes through the focusing lens 31, is
reflected by the dichroic mirror 32, transmitted through the
half-mirror 40, reflected by the dichroic mirror 33, and projected
onto the light receiving surface of the CCD image sensor 35 by the
condenser lens 34. An image (alignment target) captured by the CCD
image sensor 35 is displayed on the display device 3 along with the
observation image K. A user conducts alignment by an operation that
is the same as conventional fundus cameras. It should be noted that
alignment may be performed, by an arithmetic and control unit 200,
as a result of analyzing the position of the alignment target and
moving the optical system.
[0062] In order to conduct focus adjustment, the reflection surface
of a reflection rod 67 is provided in a slanted position on the
light path of the illumination optical system 10. Light (focus
light) output from an LED 61 of the focus optical system 60 passes
through a relay lens 62, is split into two light fluxes by a split
target plate 63, passes through a two-hole diaphragm 64, is
reflected by a mirror 65, and is reflected after an image is formed
once on the reflection surface of the reflection rod 67 by a
condenser lens 66. Furthermore, the focus light is reflected at the
aperture mirror 21 via the relay lens 20 and an image is formed on
the fundus Ef by the object lens 22.
[0063] The fundus reflection light of the focus light passes
through the same route as the cornea reflection light of the
alignment light and is detected by the CCD image sensor 35. A light
(split target) captured by the CCD image sensor 35 is displayed on
the display device 3 along with an observation image K. The
arithmetic and control unit 200, as in the past, analyzes the
position of the split target, and moves the focusing lens 31 and
the focus optical system 60 for focusing. It should be noted that
focusing may be performed manually while visually recognizing the
split target.
[0064] An optical path including a mirror 41, collimator lens 42,
and Galvano mirrors 43, 44 is provided behind the dichroic mirror
32. The optical path is connected to the OCT unit 100.
[0065] The Galvano mirror 44 performs scanning with a signal light
LS from the OCT unit 100 in the x-direction. The Galvano mirror 43
performs scanning with a signal light LS in the y-direction.
Scanning may be performed with the signal light LS in an arbitrary
direction in the xy-plane due to the two Galvano mirrors 43 and
44.
[OCT Unit]
[0066] The OCT unit 100 shown in FIG. 2 is provided with an optical
system for obtaining a tomo graphic image of the fundus Ef. The
optical system has a similar configuration to a conventional
Fourier-Domain-type OCT device. That is to say, the optical system
is configured to split a low coherence light into a reference light
and a signal light, make the signal light propagated through a
fundus and the reference light propagated through a reference
optical path interfere with each other to generate an interference
light, and detects the spectral components of this interference
light. This detection result (detection signal) is transmitted to
the arithmetic and control unit 200.
[0067] A light source unit 101 outputs a low coherence light L0.
The low coherence light L0 is, for example, light (invisible light)
consisting of wavelengths that is impossible to be detected by
human eyes. Furthermore, the low coherence light L0 is, for
example, near-infrared light having the center wavelength of about
1050-1060 nm. The light source unit 101 is configured to include
light output device, such as an SLD (super luminescent diode), SOA
(Semiconductor Optical Amplifier) and the like. A light source unit
101 is an example of a "light source" of the invention.
[0068] The low coherence light L0 output from the light source unit
101 is guided to a fiber coupler 103 by an optical fiber 102 and
split into signal light LS and reference light LR. It should be
noted that the fiber coupler 103 acts both as a means to split
light (splitter) as well as a means to synthesize light (coupler),
but herein the same is conventionally referred to as a "fiber
coupler."
[0069] The signal light LS is guided by the optical fiber 104 and
becomes a parallel light flux by a collimator lens unit 105.
Furthermore, the signal light LS is reflected by Galvano mirrors 44
and 43, converged by the collimator lens 42, reflected by the
mirror 41, transmitted through a dichroic mirror 32, and irradiated
to the fundus Ef after passing through a route that is the same as
the light from the LCD 39. The signal light LS is scattered and
reflected at the fundus Ef. The scattered light and the reflection
light are sometimes all together referred to as the fundus
reflection light of the signal light LS. The fundus reflection
light of the signal light LS progresses along the same route in the
reverse direction and is guided to the fiber coupler 103.
[0070] The reference light LR is guided by an optical fiber 106 and
becomes a parallel light flux by a collimator lens unit 107.
Furthermore, the reference light LR is reflected by mirrors 108,
109, 110, dimmed by an ND (Neutral Density) filter 111, and
reflected by a mirror 112, with the image formed on a reflection
surface of a reference mirror 114 by a collimator lens 113. The
reference light LR reflected by the reference mirror 114 progresses
along the same route in the reverse direction and is guided to the
fiber coupler 103. It should be noted that an optical element for
dispersion compensation (pair prism, etc.) and/or an optical
element for polarization correction (wave plate, etc.) may also be
provided for the optical path (reference optical path) of the
reference light LR.
[0071] The fiber coupler 103 superposes the fundus reflection light
of the signal light LS and the reference light LR reflected by the
reference mirror 114. Interference light LC thus generated is
guided by an optical fiber 115 and output from an exit end 116.
Furthermore, the interference light LC is converted to a parallel
light flux by a collimator lens 117, spectrally divided (spectrally
decomposed) by a diffraction grating 118, converged by the
convergence lens 119, and projected onto the light receiving
surface of a CCD image sensor 120.
[0072] The CCD image sensor 120 is for example a line sensor, and
detects the respective spectral components of the spectrally
decomposed interference light LC and converts the components into
electric charges. The CCD image sensor 120 accumulates these
electric charges and generates a detection signal. Furthermore, the
CCD image sensor 120 transmits the detection signal to the
arithmetic and control unit 200.
[0073] Although a Michelson-type interferometer is employed in this
embodiment, it is possible to employ any type of interferometer
such as a Mach-Zehnder-type as necessary. Instead of a CCD image
sensor, other types of image sensors, such as a CMOS (Complementary
Metal Oxide Semiconductor) image sensor, can be used.
[Arithmetic and Control Unit]
[0074] A configuration of the arithmetic and control unit 200 will
be described. The arithmetic and control unit 200 analyzes the
detection signals inputted from the CCD image sensor 120, and forms
an OCT image of the fundus Ef. An arithmetic process for this is
the same as that of a conventional Fourier-Domain-type OCT
device.
[0075] Further, the arithmetic and control unit 200 controls each
part of the retinal camera unit 2, the display device 3 and the OCT
unit 100.
[0076] As control of the retinal camera unit 2, the arithmetic and
control unit 200 executes: control of action of the observation
light source 101, the imaging light source 103 and LED's 51 and 61;
control of action of the LCD 39; control of movement of the
focusing lens 31; control of movement of the reflection rod 67;
control of movement of the focus optical system 60; control of
action of the respective Galvano mirrors 43 and 44; and so on.
[0077] Further, as control of the OCT unit 100, the arithmetic and
control unit 200 executes: control of action of the light source
unit 101; control of movement of the reference mirror 114 and the
collimator lens 113; control of action of the CCD image sensor 120;
and so on.
[0078] The arithmetic and control unit 200 includes a
microprocessor, a RAM, a ROM, a hard disk drive, a communication
interface, and so on, as in conventional computers. The storage
device such as the hard disk drive stores a computer program for
controlling the fundus observation apparatus 1. The arithmetic and
control unit 200 may be provided with a circuit board dedicated for
forming OCT images based on detection signals from the CCD image
sensor 120. Moreover, the arithmetic and control unit 200 may be
provided with operation devices (input devices) such as a keyboard
and a mouse, and/or display devices such as LCD.
[0079] The retinal camera unit 2, display device 3, OCT unit 100,
and arithmetic and control unit 200 may be integrally configured
(that is, within a single case), or configured as separate
bodies.
[Input Device]
[0080] The input device 300 is used in order for the subject to
respond during the eyesight measurement. In the eyesight
measurement, a predetermined visual target for measuring eyesight
is projected onto the eye E. The subject inputs the result of
visual confirmation of this target using the input device 300. For
example, when a Landolt ring is used as a target, the subject
inputs the direction of the rift in the Landolt ring using the
input device 300.
[0081] The input device 300 is configured, for example, to include
a joy stick such as the one shown in FIG. 3. The subject tilts the
joystick in the direction corresponding to the result of visual
confirmation to the target. The input device 300 transmits an
electrical signal corresponding to this operation content (tilting
direction) to the arithmetic control unit 200. The input device 300
is one example of the "operation part" of the invention.
[Control System]
[0082] A configuration of a control system of the fundus
observation apparatus 1 will be described with reference to FIG.
3.
(Controller)
[0083] The control system of the fundus observation apparatus 1 has
a configuration centered on a controller 210 of the arithmetic and
control unit 200. The controller 210 includes, for example, the
aforementioned microprocessor, RAM, ROM, hard disk drive, and
communication interface. The controller 210 is an example of a
"controlling part" of the invention.
[0084] A controller 210 is provided with a main controller 211,
storage 212 and a target setting part 214. The main controller 211
performs the aforementioned various kinds of control. Specifically,
the main controller 211 controls a scan driver 70 as well as a
focus driver 80 of the retinal camera unit 2, and further controls
a reference driver 130 of the OCT unit 100.
[0085] The scan driver 70 is configured, for example, including a
servo motor and independently changes the facing direction of the
Galvano mirrors 43 and 44. The scan driver 70 consists of one
example of the "scanning part" in the invention along with the
Galvano mirrors 43 and 44.
[0086] The focus driver 80 is configured, for example, including a
pulse motor and moves the focusing lens 31 in the optical axis
direction. Thereby, the focus position of light towards the fundus
Ef is changed.
[0087] The reference driver 130 is configured, for example,
including a pulse motor and integrally moves the collimator lens
113 as well as the reference mirror 114 along the travelling
direction of the reference light LR.
[0088] The main controller 211 executes a process of writing data
into the storage 212, and a process of reading out the data from
the storage 212.
[0089] The storage 212 stores various kinds of data. The data
stored in the storage 212 is, for example, image data of OCT
images, image data of fundus images, and eye information. The eye
information includes information on the eye, for example,
information on a subject such as a patient ID and a name,
information on identification of left eye or right eye, and so
on.
[0090] Moreover, the eyesight value of the eye E measured by the
fundus observation apparatus 1 is stored in the storage 212.
Although the details will be described later, this eyesight value
is stored in correlation with the OCT image. The storage 212 is one
example of the "storage part" of the invention.
[0091] It should be noted that the storage part is not limited to
storage devices such as hard disk drives and RAM, and may be any
recording media writable by a drive device. As this recording
media, for example, optical disks, magnetic optical disks (such as
CD-R/DVD-RAM/MO), magnetic recording media (such as floppy
Disks.RTM./ZIP), SSDs (Solid State Drives), etc. may also be
used.
[0092] Moreover, OCT images and eyesight values may be transmitted
to the predetermined storage part to be stored via a network such
as the Internet and LAN. Furthermore, it is not necessary to store
OCT images and eyesight values in the same storage device, and they
may be stored in separate storage devices. It should be noted that
also in this case, the OCT images and the eyesight values must be
correlated with each other.
[0093] Furthermore, target size adjustment information 213 is
preliminarily stored in the storage 212. The target size adjustment
information 213 includes the information that associates the
position of the focusing lens 31 with the target size. Hereinafter,
the target size adjustment information 213 is described in
detail.
[0094] In this embodiment, eyesight measurement is conducted on the
eye E by projecting the visual target for measuring eyesight
displayed on the LCD 39 to the fundus Ef. The eyesight examination
is for determining the eyesight values based on the target size
that can be visually confirmed. (As a specific example, the
eyesight values are determined by presenting various sizes of
Landolt rings to the eye E, obtaining a response regarding the
direction of the rift in the presented Landolt ring, and then
determining whether the response is true or false.)
[0095] However, in the configuration in which the target displayed
on the LCD 39 is projected on the fundus Ef, even if the size of
the target displayed on the LCD 39 is the same, the size of the
image projected on the fundus Ef may be different due to the eye
refractive power of the eye E. Consequently, the accuracy of the
eyesight examination is lowered.
[0096] The target adjustment information 213 is referenced in order
to avoid a decrease in measurement accuracy due to such a
difference in eye refractive power. In this embodiment, as
described above, focusing of the optical system on the fundus Ef is
accomplished by projecting a split target on the fundus Ef using
the focus optical system 60 and moving the focusing lens 31 and the
focus optical system 60 based on the position of the split target.
The position of the split target is affected by the eye refractive
power of the eye E, i.e., the refractive power of the cornea and
the lens.
[0097] The target size adjustment information 213 includes, as
information for making the projection size of the visual target for
measuring eyesight onto the fundus independent of the eye
refractive power, information that correlates the position of the
focusing lens 31 and the size of the visual target for measuring
eyesight. For example, information correlating, for the target at
each eyesight value, the position of the focusing lens 31 and the
display size of the target on the LCD 39 is recorded in the target
size adjustment information 213. This information is in the form of
a table, graph, mathematical expression, etc.
[0098] This information may be created by, for example, a numerical
simulation such as a ray trace. Moreover, this information may also
be created by actually performing a measurement using an eye model,
an eye on a living body or an isolated eye.
[0099] It should be noted that the information recorded in the
target size adjustment information 213 is not limited to the above.
For example, each position of the focusing lens 31 may be
correlated with the display size of the target for each eyesight
value.
[0100] Moreover, the information recorded in the target size
adjustment information 213 may be information that correlates the
position of the focus optical system 60 and the target size. Here,
the focus optical system 60 and the focusing lens 31 are moved in
conjunction with each other, with the position of the focus optical
system 60 having a one-on-one correspondence with the position of
the focusing lens 31. Therefore, this modification example can be
considered equivalent to the case in which the position of the
focusing lens 31 and the target size are correlated.
[0101] Moreover, the information recorded in the target size
adjustment information 213 may be the information that correlates
the eye refractive power value and the target size. In this case,
the eye refractive power value of the eye E that is previously
acquired is input, and the target size is adjusted based on the
input value. Here, since the eye refractive power value corresponds
one-on-one with the position of the focusing lens 31 (at least
theoretically), this modification example can also be considered
equivalent to the case in which the position of the focusing lens
31 and the target size are correlated.
[0102] The target setting part 214 executes various setting
processes regarding the target projected on the eye E, such as a
visual target for measuring eyesight and a fixation target. The
target setting part 214 is provided with a target size setting part
215, a fixation target setting part 216 and an eyesight value
determination part 217.
[0103] The target size setting part 215 acquires the position
information of the focusing lens 31 and obtains the size of the
visual target for measuring eyesight based on the position
information and the target size adjustment information 213.
[0104] An example of a process for acquiring the position
information of the focusing lens 31 is described. The focusing lens
31 is, as described above, moved by the focus drive 80 based on the
control by the main controller 211. Consequently, based on the
control content (control history) by the main controller 211, the
position information of the focusing lens 31 can be acquired. More
specifically, when the focus drive 80 includes a pulse motor, the
position information of the focusing lens 31 can be acquired with
reference to the pulse number transmitted from the main controller
211 to the focus drive 80. Moreover, it is also possible to use a
detector (for example, a potentiometer) that detects the position
of the focusing lens 31.
[0105] Upon acquisition of the position information of the focusing
lens 31, the target size setting part 215 obtains the target size
corresponding to that position information with reference to the
target size adjustment information 213.
[0106] The fixation target setting part 216 performs setting
regarding the fixation target displayed on the LCD 39.
Specifically, the fixation target setting part 216 sets the display
position of the fixation target on the LCD 39. For example, the
fixation target setting part 216 sets the display position of the
fixation target on the LCD 39 based on the region for scanning with
signal light LS (scanning region; described later) using Galvano
mirrors 43, 44. The operational example of the fixation target
setting part 216 will be described later.
[0107] The eyesight value determination part 217 executes various
processes for obtaining the eyesight value of the eye E. As these
processes, for example, conventional approaches are applicable in
which the visual targets for measuring eyesight corresponding to
various eyesight values are automatically switched to be presented
to the eye. (For example, see republished No. 03/041571.)
Hereinafter, an operational example of the eyesight value
determination part 217 is described.
[0108] First, the eyesight value determination part 217 determines
the visual target for measuring eyesight to be first presented to
the eye E. As a target to be first presented, a target
corresponding to the predetermined eyesight value is selected. This
first target is a target corresponding to, for example, the
eyesight value 0.1.
[0109] Moreover, when previously measured eyesight values can be
acquired for this eye E, the first target can be determined based
on this information. For example, when the previously obtained
eyesight value for the above eye E is 0.7, a target corresponding
to an eyesight value lower than that value (for example, 0.5) by a
predetermined value is selected as the first target.
[0110] Previous eyesight values may be input using, for example,
the operation part 250, or may be obtained from, for example, an
electronic medical record system through, for example, LAN.
Moreover, previous eyesight values can be correlated to the
above-mentioned information on the eye and stored in the storage
212. In addition, the previous eyesight value referenced in this
examination is preferably the newest among the previously measured
eyesight values. When the previous eyesight value is obtained from
the electric medical record system, it is possible to selectively
obtain the newest eyesight value with reference to the medical
examination date recorded in the electric medical records.
[0111] Furthermore, the eyesight value determination part 217
determines the target to be presented next, based on the response
to the target presented to the eye E from the subject. For this
process, for example, the same process as the conventional process
can be used. For example, if a correct answer is obtained twice for
targets with a certain eyesight value, then a target with the next
higher eyesight value is selected. In contrast, if a wrong answer
is obtained twice for targets with a certain eyesight value, then a
target with the next lower eyesight value is selected.
[0112] Furthermore, the eyesight value determination part 217
determines the eyesight value of the eye E based on the response
content from the subject according to the change in the target
size. This process is, for example, executed similarly to the
conventional process. For example, if a correct answer is obtained
twice for targets with a certain eyesight value, and a wrong answer
is obtained twice for targets with a next higher eyesight value,
then the former certain eyesight value is determined as the
eyesight value for the eye E. Moreover, if a correct answer is
obtained twice for targets at the highest presentable eyesight
value (for example, 2.0), that highest eyesight value is determined
as the eyesight value for the eye E. Furthermore, if a wrong answer
is obtained twice for targets with the lowest presentable eyesight
value (for example, 0.1), the result is that the eyesight value is
unmeasurable or less than a predetermined value.
[0113] The target setting part 214 may be configured such that it
can set the display position of the visual target for measuring
eyesight on the LCD 39.
(Image Forming Part)
[0114] An image forming part 220 forms image data of a tomographic
image of the fundus Ef based on the detection signals from the CCD
image sensor 120. Like the conventional Fourier-Domain OCT, this
process includes processes such as noise elimination (noise
reduction), filtering, and FFT (Fast Fourier Transform).
[0115] The image forming part 220 includes, for example, the
aforementioned circuit board and communication interface. It should
be noted that "image data" and the "image" presented based on the
image data may be identified with each other in this
specification.
(Image Processor)
[0116] An image processor 230 executes various image processing and
analysis on images formed by the image forming part 220. For
example, the image processor 230 executes various correction
processes such as luminance correction and dispersion correction of
images.
[0117] Further, the image processor 230 executes, for example, an
interpolation process of interpolating pixels between tomographic
images formed by the image forming part 220, thereby forming image
data of a three-dimensional image of the fundus Ef.
[0118] Image data of a three-dimensional image refers to image data
that the positions of pixels are defined by the three-dimensional
coordinates. The image data of a three-dimensional image is, for
example, image data composed of three-dimensionally arranged
voxels. This image data is referred to as volume data, voxel data,
or the like. For displaying an image based on the volume data, the
image processor 230 executes a rendering process (such as volume
rendering and MIP (Maximum Intensity Projection)) on this volume
data, and forms image data of a pseudo three-dimensional image
taken from a specific view direction. On a display device such as
the display 240, this pseudo three-dimensional image is
displayed.
[0119] Further, it is also possible to form stack data of a
plurality of tomographic images as the image data of a
three-dimensional image. Stack data is image data obtained by
three-dimensionally arranging a plurality of tomographic images
obtained along a plurality of scanning lines, based on the
positional relation of the scanning lines. That is to say, stack
data is image data obtained by expressing a plurality of
tomographic images defined by originally individual two-dimensional
coordinate systems by a three-dimensional coordinate system
(namely, embedding into a three-dimensional space).
[0120] The image processor 230 includes, for example, the
aforementioned microprocessor, RAM, ROM, hard disk drive, circuit
board, and so on.
[0121] The image forming part 220 (and the image processor 230) is
an example of the "image forming part" of the invention.
(Display and Operation Part)
[0122] The display 240 is configured including a display device of
the aforementioned arithmetic and control unit 200. The operation
part 250 is configured including an operation device of the
aforementioned arithmetic and control unit 200. Furthermore, the
operation part 250 may also include various kinds of buttons or
keys provided with the case of the fundus observation apparatus 1
or its outside. For example, if the retinal camera unit 2 has a
case that is the same as conventional fundus cameras, a joy stick,
operation panel, etc. provided with the case may also be included
in the operation part 250. Furthermore, the display 240 may also
include various display devices such as a touch panel monitor, etc.
provided with the case of the retinal camera unit 2.
[0123] The display 240 and the operation part 250 do not need to be
composed as separate devices. For example, like a touch panel LCD,
a device in which the display function and the operation function
are integrated can be used.
[Scan with Signal Light and OCT Image]
[0124] A scan with the signal light LS and an OCT image will be
described.
[0125] The scan aspect of the signal light LS by the fundus
observation apparatus 1 is, for example, a horizontal scan,
vertical scan, cruciform scan, radial scan, circular scan,
concentric scan, and helical scan. These scan aspects are
selectively used as necessary in consideration of an observation
site of the fundus, an analysis target (the retinal thickness or
the like), a time required to scan, the accuracy of a scan, and so
on.
[0126] A horizontal scan is a scan with the signal light LS in the
horizontal direction (x-direction). The horizontal scan includes an
aspect of scanning with the signal light LS along a plurality of
scanning lines extending in the horizontal direction arranged in
the vertical direction (y-direction). In this aspect, it is
possible to set any interval between scanning lines. By setting the
interval between adjacent scanning lines to be sufficiently narrow,
it is possible to form the aforementioned three-dimensional image
(three-dimensional scan). A vertical scan is also performed in a
similar manner.
[0127] A cruciform scan is a scan with the signal light LS along a
cross-shape trajectory formed by two linear trajectories (line
trajectories) orthogonal to each other. A radial scan is a scan
with the signal light LS along a radial trajectory formed by a
plurality of line trajectories arranged at predetermined angles.
The cruciform scan is an example of the radial scan.
[0128] A circular scan is a scan with the signal light LS along a
circular trajectory. A concentric scan is a scan with the signal
light LS along a plurality of circular trajectories arranged
concentrically around a predetermined center position. The circular
scan is regarded as a special example of the concentric scan. A
helical scan is a scan with the signal light LS along a helical
trajectory while making the turning radius gradually smaller (or
greater).
[0129] With the configuration as described before, the Galvano
mirrors 43 and 44 are capable of scanning with the signal light LS
in the x-direction and the y-direction independently, and is
therefore capable of scanning with the signal light LS along an
arbitrary trajectory on the xy-plane. Thus, it is possible to
realize various types of scan aspects as described above.
[0130] By scanning the signal light LS in the mode described above,
it is possible to form tomographic images of the depthwise
direction (z-direction) along scanning lines (scan trajectory).
Moreover, in a case that the interval between scanning lines is
narrow, it is possible to form the aforementioned three-dimensional
image.
[0131] A region on the fundus Ef subjected to scanning by the
signal light LS as above is referred to as a scanning region. For
example, a scanning region in three-dimensional scanning is a
rectangular-shaped region in which a plurality of horizontal scans
are arranged. Furthermore, a scanning region in a concentric
circular scan is a disc-shaped region surrounded by the
trajectories of a circular scan of a maximum diameter. Moreover,
the scanning region in a radial scan is a disc-shaped (or
polygonal-shaped) region linking end positions of scanning
lines.
[Operation]
[0132] The operation of the fundus observation apparatus 1 is
described. The flow chart shown in FIG. 4 represents an example of
the operation of the fundus observation apparatus 1.
[0133] First, as in the conventional manner, the main controller
211 controls, for example, the alignment optical system 50 to
perform alignment to the eye E, and also controls, for example, the
focus optical system 60, the focus drive 80, etc., to perform
focusing on the fundus Ef (S1).
[0134] Next, the main controller 211 adjusts the position of the
reference mirror 114 (as well as the position of the collimator
lens 113) to adjust the interference state of the signal light LS
and the reference light LR (S2). At this time, adjustment is made
so that the image of the desired depthwise position of the fundus
Ef becomes clear. Moreover, it is desirable to adjust the position
of the reference mirror 114 so that the image of the predetermined
depthwise position (for example, the retina surface) is located
within a predetermined range in the frame. It should be noted that
the position adjustment of the reference mirror 114 may be manually
performed using the operation part 250 or may be automatically
performed.
[0135] Upon completion of the adjustment of the interference state,
the fixation target setting part 216 sets the display position of
the fixation target on the LCD 39 corresponding to the
predetermined scanning region (for example, a rectangular region
for three-dimensional scanning) (S3). It should be noted that the
scanning region is set, for example, before or after step 1.
[0136] Furthermore, the fixation target setting part 215 adjusts
the size of the visual target for measuring eyesight based on the
position of the focusing lens 31, which is moved during focusing in
step 1, and the target size adjustment information 213 (S4).
[0137] The main controller 211 controls the LCD 39 to display the
fixation target in the display position set in step 3 and fixate
the eye E (S5). Furthermore, the main controller 211 allows the
first visual target for measuring eyesight, of which the size has
been adjusted in step 4, to be displayed on the LCD 39, and begins
the eyesight measurement (S6). This eyesight measurement is for
measuring the eyesight at the position on the fundus Ef (i.e.,
projection position of the fixation target) corresponding to this
fixation position.
[0138] In this operational example, as shown in FIG. 5, the
fixation target V is displayed in the central position of the
display screen of the LCD 39, and the Landolt ring T is displayed
such that the central position of the Landolt ring T matches the
position of the fixation target V.
[0139] At the same time as the start of the eyesight examination,
the main controller 211 controls the light source unit 101 and the
Galvano mirrors 43 and 44 to begin the measurement in the
predetermined scanning region (for example, three-dimensional
scanning) (S7).
[0140] The positional relationship between the scanning region of
the signal light LS and the target projection region on the fundus
Ef is shown in FIG. 6. In this operational example, as in the FIG.
5, the fixation target V is projected on the central position of
the projection region of the Landolt ring T, and furthermore, the
projection region of the fixation target V is matched to the
central position of the scanning region R (rectangular region). It
should be noted that the fixation target displayed on the LCD 39
and the projected image of this fixation target on the fundus Ef
are denoted by the same symbol V, and the Landolt ring displayed on
the LCD 39 and the projected image of this Landolt ring on the
fundus Ef are denoted by the same symbol T.
[0141] Such a projection mode is achieved, for example, as follows.
First, the central position of the display screen of the LCD 39 is
placed on an optical axis of the imaging optical system 30.
Moreover, the scanning region R is set such that its central
position is located on the optical axis of the imaging optical
system 30. Therefore, by displaying the fixation target V in the
central position of the display screen of the LCD 39 and setting
this scanning region R as such, the central position of the
scanning region R is matched to the projection region of the
fixation target V (i.e., both are placed on the extended line of
the optical axis). Furthermore, since the Landolt ring T is
displayed on the LCD 39 such that its central position is placed in
the central position of the display screen, the central position of
the Landolt ring T, the projection region of the fixation target V
and the central position of the scanning region R are matched on
the fundus Ef.
[0142] The controller 210 executes the eyesight measurement at the
position of the fundus Ef projected with the fixation target V
while scanning the scanning region R with the signal light LS. At
this time, the signal light LS is used to sequentially scan a
plurality of lines of horizontal scanning (scanning lines) included
in the three-dimensional scanning. Then, the image forming part 220
forms a tomographic image corresponding to each scanning line based
on the detection results of interference light LC of the signal
light LS and the reference light LR (S8). Tomographic images that
are formed sequentially are stored in the storage 212 while being
correlated with position information of corresponding scanning line
(scanning position information). The scanning position information
is, for example, information based on the control to the scan drive
70 (i.e., the direction of the Galvano mirrors 43, 44). When the
scanning along all scanning lines is completed, the scanning may be
ended or similar scanning may be executed again. Here, the eyesight
measurement is executed by the eyesight value determination part
217 in the manner described above.
[0143] When the eyesight value is obtained by the eyesight value
determination part 217 (S9), the main controller 211 selects a
tomographic image corresponding to the scanning line closest to the
eyesight measurement position (the position projected with the
fixation target V) (S10), and stores this tomographic image and the
eyesight value in the storage 212 while correlating them with each
other (S11). Here, the selection process of the tomographic image
is executed with reference to the above-mentioned scanning position
information.
[0144] The main controller 211 allows the tomographic image and the
eyesight value to be displayed on the display device 3 (or the
display 240) (S 12). Consequently, the examiner can observe the
tomographic image of the fundus Ef at the eyesight measurement
position.
[0145] In this operational example, examination at the fixation
position is conducted as described above. Therefore, for the eye E
that has no disorder in the macula flava (including a healthy eye),
the eyesight value and the tomographic image in the macula flava
are generally obtained. On the other hand, for the eye E that has,
for example, a disorder in the macula flava, the fixation target V
tends to be viewed by the site having the highest visual ability in
the fundus Ef (other than the macula flava), so the eyesight value
and the tomographic image in such a site are generally
obtained.
[0146] Instead of conducting an examination on the fixation
position in this way, it is also possible to conduct an examination
on the site of interest (treatment site, diagnosed site, etc.)
other than the fixation position. To this end, as described in
detail in the following operational example, it is effective to
conduct an examination under the condition that the display
position of the fixation target V is shifted from the display
position of the visual target for measuring eyesight on the LCD
39.
Another Operational Example
[0147] In this operational example, eyesight measurement is
conducted on various positions in the fundus Ef by changing the
relative position of the projection region of the visual target for
measuring eyesight and the projection region of the fixation
target, and furthermore, a tomographic image covering the eyesight
measurement position is obtained. Hereinafter, the operational
example shown in the flowchart shown in FIG. 7 is described.
[0148] As a preliminary stage of the examination, as in the
operational example described above, the alignment, focusing,
determination of the scanning region, and adjustment of the
interference state are performed (S21).
[0149] The fixation target setting part 216 sets the display
position of the fixation target on the LCD 39 corresponding to the
scanning region (for example, a rectangular region for
three-dimensional scanning) (S22). Moreover, the target setting
part 214 sets the display position of the visual target for
measuring eyesight on the LCD 39 (S23). Furthermore, the target
size setting part 215 adjusts the size of the visual target for
measuring eyesight based on the position of the focusing lens 31
after focusing and the target size adjustment information 213
(S24).
[0150] It should be noted that, in this operational example, as
opposed to the case shown in FIG. 5, it is not necessary to display
the fixation target on the central position of the display screen,
and furthermore, it is not necessary to match the central position
of the visual target for measuring eyesight to the position of the
fixation target. For example, as shown in FIG. 8, the fixation
target V is displayed in a position deviating from the central
position of the display screen of the LCD 39, and the Landolt ring
T is displayed with its central position deviating from the
position of the fixation target V. It should be noted that, in the
example shown in FIG. 8, the display positions of the fixation
target V and the Landolt ring T both deviate from the central
position of the display screen, but one of these positions may be
displayed in this central position while the other is displayed in
other positions.
[0151] The important point here is that the fixation target V and
the Landolt ring T are displayed in different positions.
Specifically, when the fixation target V and the Landolt ring T are
displayed in different positions, on the assumption that the eye E
is fixed by the fixation target V, the eyesight in the position on
the fundus Ef that is different from the fixation position can be
measured. (In the above operational example, the eyesight in the
fixation position is measured.) Moreover, by changing the relative
position of the fixation target V and the Landolt ring T, eyesight
in various positions on the fundus Ef can be measured.
[0152] The main controller 211 controls the LCD 39 to display the
fixation target in the display position set in step 22 and fix the
eye E (S25). Furthermore, the main controller 211 controls the LCD
39 to display the first visual target for measuring eyesight in the
display position set in step 23, and begins the eyesight
measurement (S26).
[0153] At the same time as the start of the eyesight measurement,
the main controller 211 begins the measurement in the scanning
region (for example, three-dimensional scanning) (S27).
[0154] The positional relationship between the scanning region of
the signal light LS and the target projection region on the fundus
Ef is shown in FIG. 9. In this operational example, as in FIG. 8,
the fixation target V and the Landolt ring T are projected at
different positions. Moreover, as in the operational example
described above (FIG. 6), the scanning region R is set such that
its central position is located on the optical axis of the imaging
optical system 30. Consequently, the fixation target V and the
Landolt ring T are projected at a position different from the
central position of the scanning region R. It should be noted that,
as described above, when the fixation target V or the Landolt ring
T is displayed at the central position of the display screen of the
LCD 39, the target displayed at this central position is projected
at the central position of the scanning region R.
[0155] The controller 210 executes the eyesight measurement on the
position of the fundus Ef projected with the Landolt ring T while
scanning the scanning region R with the signal light LS. At this
time, the signal light LS is used to sequentially scan a plurality
of scanning lines included in the three-dimensional scanning. The
image forming part 220 forms a tomographic image corresponding to
each scanning line (S28). Tomographic images that are formed
sequentially are stored in the storage 212 while being correlated
with the scanning position information. The scanning position
information is, for example, information based on the control to
the scan drive 70 (i.e., the direction of the Galvano mirrors 43,
44). When the scanning along all scanning lines is completed, the
scanning may be ended or similar scanning may be executed again.
Here, the eyesight measurement is executed by the eyesight value
determination part 217 in the manner described above.
[0156] When the eyesight value of this measurement position is
obtained (S29), the main controller 211 selects a tomographic image
corresponding to the scanning line closest to the eyesight
measurement position (S30), and stores the measurement position,
the tomographic image and the eyesight value in the storage 212
while correlating them with each other (S31). Here, the correlation
of the tomographic image and the eyesight value can be achieved
similarly to the above operational example. Moreover, the
measurement position can be determined based on, for example, the
relative position of the fixation target V and the Landolt ring T
(the relative position of both display positions).
[0157] If the examination is not completed at all the measurement
positions (S32: No), the target setting part 214 sets the display
positions of the fixation target V and the Landolt ring T on the
LCD 39 corresponding to the next measurement position. The main
controller 211 allows the fixation target V and the Landolt ring T
to be displayed at the set display positions. Consequently, each
projection region of the fixation target V and the Landolt ring T
on the fundus Ef is changed. Under the condition that the eye E is
fixed by this fixation target V, the Landolt ring T is projected at
the next measurement position described above (S33). Then, the
eyesight measurement at this new measurement position is started
(S26). At this time, scanning with the signal light LS may be
executed again (S27).
[0158] It should be noted that, when the new measurement position
deviates from the prior scanning region R, the controller 210 newly
sets the scanning region to include the new measurement position
(i.e., so that a new projection region of the Landolt ring T is
overlapped), and performs scanning with the signal light LS to form
a tomographic image.
[0159] The change in the measurement position as described above
is, for example, sequentially executed for a predetermined number
of positions. As a specific example, the eyesight measurement is
first conducted on the central position of the scanning region R as
shown in FIG. 6, and then the eyesight measurement is further
conducted on each apex position of a rectangle enclosing this
central position.
[0160] Moreover, it is also possible to set the measurement
position based on the condition of the eye E. For example, it is
also possible to set the site of interest and its peripheral
position of the eye E as the measurement position. Such a
measurement position can be set based on, for example, the
positional relationship of the site of interest relative to the
macular area. Moreover, this positional relationship can be
obtained based on, for example, the fundus image. In addition, it
is also possible to set the measurement position so as to avoid the
region on the fundus Ef that is thought to have low eyesight (for
example, a region affected due to cataracts, a region that has an
untreatable retinal disease, etc.)
[0161] When the examination of all measurement positions is
completed (S32: Yes), the main controller 211 selects the highest
value among the acquired eyesight values (S34). The main controller
211 allows the selected eyesight value and the measurement position
and tomographic image correlated to this eyesight value to be
displayed on the display device 3 (or the display 240) (S35).
Consequently, the examiner can recognize the site having good
eyesight on the fundus Ef, and furthermore, can observe the
tomographic image of the fundus Ef at this site.
[0162] When such an examination is applied at follow-ups, the
measurement position in which the highest eyesight value is
obtained may be changed. For example, in the follow-ups after the
treatment of the disease in the macula flava, the highest eyesight
value is obtained first at a site other than the macula flava, and
then, in the course of treatment, the highest eyesight value may be
obtained in the macula flava. In this way, therapeutic effect may
appear not only as the improvement of the eyesight value, but also
the change in the measurement position in which the highest
eyesight value is obtained. Moreover, it is also possible to
specify the measurement position at which the highest eyesight
value is obtained as an actual fixation position.
Actions and Effects
[0163] The actions and effects of the fundus observation apparatus
1 as described above will be described.
[0164] According to the fundus observation apparatus 1, it is
possible to execute the OCT measurement and the eyesight
measurement while superposing the scanning region R of the signal
light LS on the projection region of the visual target for
measuring eyesight (Landolt ring T) to form the tomographic image
of the fundus Ef at the scanning region R, and it is also possible
to store the eyesight value measured using the Landolt ring T and
the tomographic image while correlating them to each other.
[0165] Here, the fundus observation apparatus 1 controls the LCD 39
based on the scanning region R of the signal light LS to superpose
the projection region of the Landolt ring T on the fundus Ef on the
scanning region R. Furthermore, the fundus observation apparatus 1
can display the fixation target V on the LCD 39 along with the
Landolt ring T to project them on the fundus Ef, and changes the
projection region of the Landolt ring T on the fundus Ef by
changing the relative display position of the Landolt ring T and
the fixation target V based on the scanning region R.
[0166] According to such the fundus observation apparatus 1, it is
possible to acquire an image (tomographic image) of the eyesight
measurement site in the fundus Ef. In particular, when the
projection region and the scanning region are set to include a site
of interest in the fundus Ef, the tomographic image and the
eyesight value of that site of interest can be acquired.
Consequently, the condition of the eyesight and the morphology of
the retina, etc., can be recognized, and furthermore, their
relationship can also be recognized.
[0167] For example, even if the morphology of the retina is
improved, the patient cannot realize the therapeutic effect unless
the eyesight is improved. By using the fundus observation apparatus
1, it is possible to closely investigate whether or not such a
situation has occurred.
[0168] Moreover, the fundus observation apparatus 1 allows
different sizes of visual targets for measuring eyesight to be
displayed on the LCD 39 to change the size of the projection region
on the fundus Ef, thereby making it possible to project the visual
target for measuring eyesight corresponding to different eyesight
values on the fundus Ef. It should be noted that the size of the
projection region on the fundus Ef can also be changed with a
target of the same size being displayed by providing an optical
element such as a lens between the LCD 39 and the eye E.
[0169] Furthermore, the fundus observation apparatus 1 can adjust
the size of the visual target for measuring eyesight displayed on
the LCD 39 based on the position of the focusing lens 31. It should
be noted that, in place of adjusting the display size, the size of
the projection region may be changed by the optical element
described above.
[0170] With such a configuration, it is possible to precisely
measure the eyesight value without being affected by the eye
refractive power of the eye E.
[0171] Moreover, the fundus observation apparatus 1 is configured
to change the size of the visual target for measuring eyesight
displayed on the LCD 39 based on the response contents from the
subject against the visual target for measuring eyesight presented
to the eye E, and furthermore, to determine the eyesight value of
the eye E based on the response contents according to the change of
the visual target for measuring eyesight.
[0172] With such a configuration, it is possible to automatically
measure the eyesight at a predetermined site in the eye E (macula
flava, site of interest, etc.).
[0173] Moreover, the low-coherence light L0 used in the OCT
measurement by the fundus observation apparatus 1 is preferably
invisible light. By using such invisible light, even when the
eyesight measurement and the OCT measurement are conducted
simultaneously, the signal light LS is not visually recognized by
the subject. Consequently, the complexity in the examination can be
reduced and the examination can be smoothly conducted, thereby
further improving the accuracy and precision of the examination
results. It should be noted that it is necessary for the subject to
visually confirm the fixation target and the visual target for
measuring eyesight.
[0174] Furthermore, the invisible light used in the OCT measurement
is preferably near-infrared light of center wavelength within the
range from about 1050 to 1060 nm. Here, if the center wavelength is
shorter than 1050 nm, there is a risk that the signal light LS may
not certainly reach the fundus Ef. On the other hand, if the center
wavelength is longer than 1060 nm, there is a risk that the signal
light LS will be absorbed by the water content within the eyeball
so that it may not certainly reach the fundus Ef.
[0175] The configuration described above is merely one example for
favorably implementing the present invention. Therefore, it is
possible to properly make arbitrary modification within the scope
of the present invention.
[0176] In the above embodiment, the configuration in which the
projection region of the visual target for measuring eyesight on
the fundus is superposed on the scanning region by controlling the
display part based on the scanning region of the signal light, but
it is also possible to apply a configuration for performing the
opposite process. Specifically, it is possible to apply a
configuration in which the scanning region of the signal light on
the fundus is superposed on the projection region of the visual
target for measuring eyesight by controlling the scanning part
based on the display position of the visual target for measuring
eyesight on the display part.
[0177] Such a configuration is shown in FIG. 10. It should be noted
that the retinal camera unit 2 and the OCT unit 100 have the same
configuration as that in the above embodiment (refer to FIG. 1,
FIG. 2).
[0178] Moreover, it is possible to apply various configurations
described in the above embodiments to this modification example.
For example, it is possible to apply the configuration in which the
visual targets for measuring eyesight corresponding to various
eyesight values is presented, the configuration in which the size
of the visual target for measuring eyesight is adjusted, the
configuration in which the eyesight value is automatically
obtained, the configuration for the light source, etc.
[0179] The block diagram shown in FIG. 10 is almost the same as
that shown in FIG. 3. However, it is different from the
configuration in FIG. 3 in that the controller 210 of this
modification example is provided with a scan setting part 218 and
in that the fixation target setting part 216 is not provided. It
should be noted that the fixation target setting part 216 may also
be provided in this modification example.
[0180] The scan setting part 218 performs setting in regard to
scanning with the signal light LS. Specifically, the scan setting
part 218 sets the scanning region of the signal light LS by the
Galvano mirrors 43, 44. For example, the scan setting part 218 sets
the scanning region based on the display position of the visual
target for measuring eyesight on the LCD 39 so that the projection
region of the visual target for measuring eyesight and the scanning
region are overlapped with each other.
[0181] An operation example of the scan setting part 218 is
described. The display position of the visual target for measuring
eyesight on the LCD 39 can be recognized by the main controller 211
because it is controlled by the main controller 211. For example,
when the central position of the display screen of the LCD 39 is
located on an optical axis of the imaging optical system 30, the
display position of the target can be recognized as a displacement
of the central position of the target relative to the central
position of the display screen. Moreover, the display region of the
target on the display screen can be recognized based on the display
size of the target.
[0182] Furthermore, the direction of each of the Galvano mirrors
43, 44 can be recognized by the main controller 211. Specifically,
the main controller 211 can recognize the position (reference
position) of each Galvano mirror 43, 44 for directing the signal
light LS such that it is guided in a direction parallel with the
optical axis.
[0183] Moreover, the scanning mode of the signal light LS
(three-dimensional scanning, radial scanning, etc.) is selected
beforehand, and the scan setting part 218 sets the position of the
scanning region in the selected scanning mode based on the display
position of the target.
[0184] When achieving the condition shown in FIG. 6, since the
Landolt ring T and the fixation target V are displayed on the
optical axis, the scan setting part 218 sets a rectangular scanning
region R centered on the reference position of the Galvano mirrors
43, 44. The main controller 211 allows the Landolt ring T and the
fixation target V to be displayed at the central position of the
LCD 39, and also controls the scan drive 70 to sequentially scan
with the signal light LS along a plurality of scanning lines
included in the set scanning region R. Consequently, as shown in
FIG. 6, it is possible to conduct the examination with the scanning
region R and the Landolt ring T overlapped with each other.
[0185] Moreover, when achieving the condition shown in FIG. 9,
since the Landolt ring T and the fixation target V are displayed at
any position on the display screen, the scan setting part 218 sets
the scanning region R (i.e., the driving range of the Galvano
mirrors 43, 44) so that it is superposed on the projection region
of the Landolt ring T based on the display position of the Landolt
ring T. The main controller 211 allows the Landolt ring T and the
fixation target V to be displayed on the LCD 39, and also controls
the scan drive 70 to sequentially scan with the signal light LS
along a plurality of scanning lines included in the set scanning
region R. Consequently, as shown in FIG. 9, it is possible to
conduct the examination with the scanning region R and the Landolt
ring T overlapped with each other.
[0186] According to such a modification example, it is possible to
acquire an image of the eyesight measurement site in the fundus Ef.
It should be noted that in the above embodiment the examination is
conducted by setting the projection region of the target superposed
on the preliminarily set scanning region, but in this modification
example, conversely, the examination can be conducted by setting
the scanning region superposed on the preliminarily set projection
region of the target.
[0187] In the above embodiment, the Landolt ring is used as the
visual target for measuring eyesight, but it is possible to apply
various targets other than this. For example, the target pattern
can be changed such as by displaying various characters. Moreover,
the target is not limited to a still image, and may be a moving
image. Moreover, it may be configured so that not only the size of
the target but also various presentation modes can be changed. For
example, it is possible to change the color or brightness
(contrast) of the target.
[0188] In the above embodiment, the tomographic image and the
eyesight value are stored while being correlated to each other, but
the OCT image correlated to the eyesight value is not limited to a
tomographic image. For example, a three-dimensional image obtained
by three-dimensional scanning and an eyesight value can also be
stored while being correlated to each other. In this case, it is
possible to recognize the three-dimensional positional relationship
between the site of interest in the fundus Ef and the fixation
position. Moreover, it is also possible to recognize the size (area
or volume) of the affected site. By making it possible to acquire
such information, the therapeutic effect can be assessed in more
detail than in the case in which two-dimensional tomographic images
are captured.
[0189] Moreover, it is also possible to form a tomographic image on
any cross-section passing near the eyesight measurement position
based on the volume data obtained by the three-dimensional scanning
and store this tomographic image and the eyesight value while
correlating them with each other. This tomographic image is formed
by the image processor 230.
[0190] In the above embodiment, the OCT measurement is started at
the same time as the start of the eyesight measurement, but the
start timing of these two operations may be of any timing. For
example, since the eyesight measurement takes more time than the
OCT measurement, the OCT measurement may start in the course of the
eyesight measurement. Moreover, it is sufficient if the OCT
measurement is executed at least once for one scanning region.
[0191] When the configuration of above embodiment is utilized, the
following OCT measurement can be performed. In this OCT
measurement, the actual fixation position of the eye E is
identified by performing scanning with the signal light LS in two
steps.
[0192] In the first step, a scanning mode that can be executed for
a relatively short time is applied, while in the second step, a
scanning mode that can form a three-dimensional image is applied.
It should be noted that it is possible to reverse the first step
and the second step.
[0193] As a specific example, the case in which cruciform scanning
is applied in the first step and three-dimensional scanning is
applied in the second step is described. In the first step, a
fixation target is first presented to an eye E for fixation. Then,
OCT measurement by cruciform scanning is performed on the fundus Ef
of the fixed eye E to form a tomographic image corresponding to
horizontal scanning (horizontal tomographic image) and a
tomographic image corresponding to vertical scanning (vertical
tomographic image). Here, since cruciform scanning is executed
instantly, it is believed that there is no deviation of the
fixation position of the eye E during the measurement.
[0194] Next, as the second step, OCT measurement by
three-dimensional scanning is performed on the eye E fixed by the
same fixation target as that in the first step to form a plurality
of tomographic images corresponding to a plurality of horizontal
scanning (scanning lines). Moreover, the image processor 230
generates volume data or stack data based on these tomographic
images. Since three-dimensional scanning takes some time (on the
order of a few seconds), the fixation position of the eye E may
deviate during the measurement.
[0195] Subsequently, the image processor 230 calculates the image
correlation between the horizontal tomographic image acquired in
the first step and each tomographic image acquired in the second
step, and identifies the cross-sectional position of the
tomographic image in the second step with the highest correlation
value. At this time, the correlation value between various
cross-sectional images in the horizontal direction of the volume
data generated in the second step and the horizontal tomographic
image may be calculated and the cross-sectional position in the
horizontal direction of the volume data with the highest
correlation value may be identified.
[0196] Similarly, the image processor 230 calculates the image
correlation between the vertical tomographic image acquired in the
first step and various cross-sectional images in the vertical
direction of the volume data acquired in the second step, and
identifies the cross-sectional position in the vertical direction
of the volume data with the highest correlation value.
[0197] The crossing position of the horizontal cross-sectional
position and the vertical cross-sectional position in the
three-dimensional image as identified above is the fixation
position of the eye E. Consequently, the fixation position of the
eye E on the three-dimensional image acquired in the second step
can be easily identified. Furthermore, three-dimensional morphology
of the fundus Ef near this fixation position can be recognized,
allowing the recognized information to possibly aid in diagnosis
and treatment.
[0198] A modification example in which the OCT measurement is
performed based on the eyesight measurement results is described.
In this modification example, a visual target for measuring
eyesight corresponding to a predetermined eyesight value is
projected on the fundus Ef. This process is performed by the
controller 210. This predetermined eyesight value is a
preliminarily set eyesight value such as an eyesight value
considered as having good eyesight (for example, 1.0). The subject
inputs the response content against this visual target for
measuring eyesight using the input device 300.
[0199] The controller 210 determines whether the input response
content is true or false. This process is executed by, for example,
judging whether or not the direction indicated by the input device
300 matches the direction of the rift in the Landolt ring displayed
on the LCD 39 as a visual target for measuring eyesight, and
determining it as a correct answer if they match or determining it
as a wrong answer if they do not match.
[0200] If the response content is determined as a correct answer,
the controller 210 controls the scan drive 70 to change the
direction of the Galvano mirrors 43, 44 and scans the scanning
region superposed on the projection region of said visual target
for measuring eyesight on the fundus Ef with the signal light
LS.
[0201] The CCD image sensor 120 detects interference light LC of
the signal light LS and the reference light LR. The image forming
part 220 forms a tomographic image of the above-mentioned scanning
region based on the detection results. When this scanning region is
a two-dimensional region, the image forming part 220 forms a
tomographic image on each of a plurality of cross sections
(scanning lines) within this scanning region, and the image
processor 230 forms a three-dimensional image of this scanning
region based on these tomographic images. The main controller 211
stores the formed OCT image (tomographic image or three-dimensional
image) and above-mentioned predetermined eyesight value in the
storage 212 while correlating them to each other. At this time,
information indicating the projection region of the visual target
for measuring eyesight on the fundus Ef (for example, display
position of the visual target for measuring eyesight on the LCD 39,
position of the projection region on the fundus image, etc.) may be
stored while being correlated with the OCT image and the
predetermined eyesight value.
[0202] According to such a modification example, an OCT image of a
site in the fundus Ef having at least the predetermined eyesight
value can be automatically acquired.
[0203] As a further modification example, it is also possible to
configure such that the OCT image of the measurement site can be
acquired even when the eyesight value of the measurement site in
the fundus Ef is below the predetermined value. As a specific
example, if the response to the visual target for measuring
eyesight of a predetermined eyesight value (for example, 1.0) is
determined to be wrong, the controller 210 allows the visual target
for measuring eyesight corresponding to the next lower eyesight
value (for example, 0.8) to be displayed on the LCD 39. Then, if a
correct answer is obtained for this visual target for measuring
eyesight projected on the fundus Ef, the controller 210 controls
the scan drive 70 to change the direction of the Galvano mirrors
43, 44 and scan the scanning region superposed on the projection
region of this visual target for measuring eyesight on the fundus
Ef with the signal light LS. The image forming part 220 etc. forms
an OCT image based on the detection results of interference light
LC of the signal light LS and the reference light LR. The main
controller 211 stores the formed OCT image and above-mentioned
eyesight value in storage 212 while correlating them to each other.
At this time, information indicating the projection region of the
visual target for measuring eyesight on the fundus Ef may be stored
while being correlated to the OCT image and the eyesight value.
[0204] It should be noted that, if a wrong answer is obtained
again, the visual target for measuring eyesight corresponding to
still lower eyesight values may be used to conduct the examination.
Moreover, it is also possible to preset the lowest eyesight value
for conducting the eyesight measurement.
[0205] In the above embodiment, the position of the reference
mirror 114 is changed so as to change an optical path length
difference between the optical path of the signal light LS and the
optical path of the reference light LR. However, a method for
changing the optical path length difference is not limited thereto.
For example, it is possible to change the optical path length
difference by moving the retinal camera unit 2 and the OCT unit 100
with respect to the eye E to change the optical path length of the
signal light LS. Moreover, in a case that an object is not a living
site or the like, it is also effective to change the optical path
length difference by moving the object in the depth direction
(z-direction).
[0206] The computer program used in the above embodiments can be
stored in any kind of recording medium that can be read by a drive
device of a computer. As this recording medium, for example, an
optical disk, a magneto-optic disk (CD-ROM, DVD-RAM, DVD-ROM, MO,
and so on), and a magnetic storage (a hard disk, a floppy Disk.TM.,
ZIP, and so on) can be used. Moreover, it is possible to store into
a storing device such as a hard disk drive and a memory. Besides,
it is possible to transmit/receive this program through a network
such as internet or LAN etc.
* * * * *