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| United States Patent | 5997141 |
| Link to this page | http://www.wikipatents.com/5997141.html |
| Inventor(s) | Heacock; Gregory L. (New York, NY) |
| Abstract | The system of the present invention allows the interior of the eye to be
viewed and simultaneously treated with a laser without the use of an optic
in contact with the eye. The system scans illumination light into the eye
so that the interior of the eye can be observed and includes an integral
treatment laser that can be directed to a desired position in the interior
of the eye including the fundus. Light reflected from the patient's eye
and received by the system may be observed directly by the physician via
an eyepiece lens. In a preferred embodiment, however, the reflected light
is applied to an image detector that is coupled to a display for
displaying an image of the interior of the patient's eye. Because the
physician can view the interior of the eye via the display during
treatment, unwanted reflections of the treatment laser to the physician's
eye via the viewing system are prevented. |
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Title Information  |
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| Publication Date |
December 7, 1999 |
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| Filing Date |
March 6, 1998 |
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| Parent Case |
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. patent application Ser. No. 08/629,584
filed Apr. 9, 1996 and issued as U.S. Pat. No. 5,784,148; U.S. Pat. No.
5,673,097 and U.S. patent application Ser. No. 08/951,535 now U.S. Pat.
No. 5,861,939. |
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Title Information |
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Description |
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TECHNICAL FIELD
The present invention is directed to a system for treating the interior of
the eye including the fundus; and more particularly to a system that scans
illumination light into the eye so that the interior can be viewed and
having an integral treatment laser that can be directed to any desired
position within the illuminated area.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
BACKGROUND OF THE INVENTION
Various types of scanning laser ophthalmoscopes such as shown in U.S. Pat.
Nos. Webb 4,765,730; Webb 4,764,006; Webb 4,768,873 and Kobayashi
4,781,453 are known for scanning a laser that is directed onto the fundus
of a patient's eye to allow an interior portion of the eye to be viewed on
a display for diagnostic purposes alone.
In order to treat the eye after diagnosis, different devices are currently
used. For example, methods for treatment typically employ bright, white
light provided by a slit lamp or the like which is shone into the
patient's eye. While the eye is thus illuminated, the physician holds a
prismatic or focusing contact lens so that it touches the cornea of the
patient's eye and then directs a treatment laser through the contact lens.
There are several disadvantages associated with this method of treatment.
Bright, white light shone into a dilated eye is uncomfortable for the
patient. Moreover, when procedures are lengthy, such as a panretinal
photocoagulation which can take up to an hour, bright, white light
exposure to the retina can approach damaging levels. Further,
manipulations of the contact lens, as may be necessary during a procedure,
can cause corneal abrasions. Contact of the lens with the eye can also
result in the transmission of diseases. Since the contact lens is hand
held, unintentional movement can also result in misdirection of the
treatment laser.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, the disadvantages of prior
systems for treating the fundus of an eye have been overcome. The system
of the present invention allows the interior of the eye to be illuminated
with scanned light and viewed during treatment with a laser without the
need of a contact lens or bright, white light.
More particularly, the scanning system scans a two dimensional area of
illumination that is directed onto the fundus to illuminate the interior
of the eye. The illumination light can be coherent light such as generated
by a laser or non-coherent light such as generated by LEDs. Light
reflected from the eye is captured so that an image of the interior of the
eye can be viewed via a display or an eyepiece lens. While the interior of
the eye is being viewed, an aiming beam of a treatment laser is directed
to a desired position on the fundus, or other interior portion of the eye,
by a steering system. When the desired position of the treatment laser is
reached, a treatment beam that is coaxial with the aiming beam is actuated
to form a small therapeutic burn or otherwise treat the eye.
The steering system of the present invention includes one or more movable
optics to change the focal plane of the treatment light and to change the
position of the treatment light within that plane. A size control optic is
also provided for varying the size of the spot of the treatment light.
The system of the present invention is a non-contact system for treating
various conditions in the eye so that the risk of corneal abrasions and
disease transmission via a contact lens or the like is eliminated.
Further, because the illumination light is scanned in accordance with the
system of the present invention, it can use lower light levels to
illuminate the interior of the eye than heretofore possible. Moreover, in
the preferred embodiment, where the eye can be observed during treatment
via a display, there is no risk of unwanted reflections of the treatment
beam reaching the physician's eye. With this embodiment of the invention,
the physician can view the interior of the eye when the treatment beam is
actuated. In the embodiment that utilizes an eyepiece lens, a shutter or
the like is actuated simultaneously with the treatment beam so that the
shutter blocks unwanted reflections of the treatment beam from reaching
the physician's eye.
These and other advantages and novel features of the present invention, as
well as details of an illustrated embodiment thereof, will be more fully
understood from the following description and drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a plan view of the system for treating the fundus of an eye in
accordance with the present invention;
FIG. 2 is a plan view of an alternative embodiment of the system of the
present invention with a noncoherent light source for illuminating the
eye;
FIG. 3 is a plan view of another embodiment of the system of the present
invention having an eyepiece lens;
FIG. 4 is a partial cross-sectional view of a movable optic for varying the
position of the treatment light within the focal plane thereof; and
FIG. 5 is a top view of a binocular eyepiece viewing arrangement.
DETAILED DESCRIPTION OF THE INVENTION
A system or device 10 for treating the fundus of a patient's eye 12 while
illuminating the fundus with scanned light for viewing is illustrated in
FIG. 1. The system 10 includes a scanning system 14 that receives light
from a source 16 and scans a two dimensional area of illumination that is
directed to the fundus of the eye 12 by a beam splitter 20 and a lens 22
so as to illuminate the interior of the eye 12. The illumination light
reflected from the patient's eye 12 is received by the lens 22 and passes
through the beam splitter 20 to a movable field lens 24. The position of
the field lens is varied to focus on images at varying depths within the
interior of the eye. The image of the interior of the eye focused on by
the lens 24 is captured for detected by a charged coupled device (CCD)
camera 26, the output of which is coupled to a display 28 so that a
physician can view the detected image. A treatment laser 30 is used to
treat various conditions in the interior of the eye without the need of an
optic in contact with the patient's eye. A steering system 32,
manipulatable by a physician, directs the treatment laser to the desired
position within the interior of the eye. The system components may be
contained in or mounted on a compact housing, not shown.
The illumination light source 16 generates a beam 34 of light that impinges
on a first scanning element 36. The first scanning element 36 is a
passive, stationary optical element such as a cylindrical lens that
generates a line 38 of light from the point of light impinging on the lens
36. The line 38 of light is then scanned in a direction perpendicular to
the length of the line by a second scanning element 40. The second
scanning element 40 may include for example a scanner mirror 42 that is
driven by a motor 44 coupled to the mirror 42 by a shaft 46. As the
scanner mirror 42 vibrates, it scans the line of light 38 across the face
of the beam splitter 20 so as to scan a two dimensional area of
illumination. As the illumination light is scanned it passes through a
specific reflector 48 and a lens 50. The specific reflector 48 is such
that it reflects the wavelength of the treatment light from the source 30
and passes all other wavelengths of light. The beam splitter 20 reflects
the two dimensional area of illumination as it is scanned towards the eye
12 so that it is centered on the real image plane 58 and the lens 22. The
illumination light as it travels towards the eye is slightly diverging.
The lens 22 is preferably an aspheric lens with a weaker surface 52 that
makes the slightly diverging illumination light parallel and directs the
light to the stronger surface 54 of the lens 22. The stronger surface 54
of the aspheric lens 22 focuses the illumination light to a point 88 that
is centered on the patient's pupil or generally proximate thereto. The
illumination light continues its path until it strikes the retina of the
eye 12, thus illuminating an area of the patient's eye.
The scanners 36 and 40 used to scan a two dimensional area of illumination
directed to the eye 12 can take forms other than depicted in FIG. 1. For
example, acousto optic modulators can be used or various types of scanners
with moving mirrors. The use of a passive optical element 36 to scan or
convert a point of light to a line of light however simplifies the optical
system and allows a color image of the interior of the patient's eye at
varying depths within the eye to be obtained very easily.
In particular, the light beam 34 may be formed of a single wavelength of
coherent light such as a laser. Alternatively, the source of illumination
light 16 may include a number of lasers 61-63, each of which produces a
laser beam of a different wavelength preferably associated with blue,
green and red laser light. The laser light of different wavelengths
generated by the lasers 61-63 are combined to form a single beam 34 by a
number of dichroic mirrors 64-65. Each of the dichroic mirrors has a
coating so that the mirror reflects only the wavelength of light
associated with its respective laser source. In particular, the dichroic
mirror 64 reflects light having a wavelength of the source 61. This
reflected light passes through the dichroic mirror 65 where it is combined
with coaxial light reflected by the mirror 65 from the laser source 62
thus combining light of the two wavelengths associated with the lasers 61
and 62. This combined beam passes through the dichroic mirror 66 where it
is combined with light having the selected wavelength of the laser 63 that
is reflected coaxially therewith so as to form the single beam 34
comprised of the three lasers of different wavelengths from the sources
61-63.
As the beam 34 is scanned onto the patient's eye 12, different parts of the
eye at different depths therein respond to different wavelengths of laser
light by reflecting laser light of a particular wavelength. The light
reflected from the patient's eye 12 is received and focused by the
aspheric lens 22 to a point on the image plane 58. The reflective light
then passes through the beam splitter 20 to the movable field lens 24.
From the field lens 24, the reflected light passes through a polarizer
film 70 to focusing optics comprised of a pair of lenses 72 and 74 of the
CCD camera 26. The lenses 72 and 74 focus the rays reflected from the
patient's eye onto the image plane of the CCD camera 26.
By changing the position of the field lens 24 so that it is moved farther
from the patient's eye, the real image plane 58 shifts to a position that
is closer to the beam splitter 20. With this shift in the image plane, the
image focused on the CCD camera 118 is an image plane in the interior of
the eye 12, closer to the front of the eye. Thus, by merely moving the
field lens 24 to a different position, various images of the interior of
the patient's eye 12 at varying depths therein can be obtained. Further,
by coupling the CCD camera to a color display 28, as the field lens 34 is
moved to bring into focus an image at varying depths within the interior
of the patient's eye, the image displayed on the color display 28
automatically changes to display the changed image in the color of the
associated wavelength of laser light that is reflected by the portion of
the eye at that particular depth.
In order to pass only desired light to the detection circuitry of the CCD
camera 26, the laser light from the source 16 is polarized in a first
direction and the polarizer film 70 is polarized in a second direction
that is different from the first direction. In particular, the polarizer
film 70 is preferably polarized in a direction perpendicular to the
polarization of the light from the source 16. This polarization of the
polarizer film 70 blocks unwanted reflections from the patient's cornea,
the aspheric lens 22 and other elements of the system from reaching the
image plane of the CCD camera 26 so that only the randomized reflected
image from the interior of the patient's eye passes through the optical
system to the camera 26.
Further, by orienting the scanning of lines onto the patient's eye in a
particular manner with respect to the orientation of a raster line of the
CCD camera, beating and blanking problems in the video image depicted on
the display 28 from the CCD camera are eliminated. More particularly, the
raster lines extend horizontally across the CCD camera 118. The
illumination light line 38 when reflected by the beam splitter 20 onto the
eye extends in a generally vertical direction and is scanned horizontally.
When the line of light is thus scanned on the patient's eye 12 it extends
vertically, i.e. perpendicularly, to the direction of the horizontal
raster line of the CCD camera. Because the line of light scanned onto the
patient's eye 12 extends perpendicular to the direction of the raster line
of the CCD camera, beating and blanking problems in the displayed video
image are eliminated.
In order to treat various conditions of the interior of the eye 12 as
viewed on the display 28, the treatment laser 30 is used. Light from the
treatment laser 30 diverges at the exit angle of a fiber optic 76 that
directs the light towards a focusing lens 78. The focusing lens 78 directs
the light from the treatment laser source 30 to a negative lens 80. The
lens 80 is movable to change the size of the spot of the treatment light
to a desired size for treating the particular condition in the interior of
the eye 12. From the negative lens 80, the light passes through a focusing
lens 82 that focuses the light from the treatment laser source 30 at a
real image plane outside of the eye and a focal plane in the interior of
the eye. The lens 82 is movable so as to change the focal plane of the
treatment laser within the interior of the eye 12. The treatment light
passing through the movable focusing lens 82 impinges on the specific
reflector 48. The specific reflector 48 as discussed above reflects the
wavelength of light from the treatment laser source 30 and passes the
illumination light from the source 16 therethrough. The reflector 48 is
movable so as to direct the treatment light to any point within a given
area of the focal plane of the treatment light as discussed below with
reference to FIG. 4. The lens 50 is a collimating lens that renders the
illumination light from the source 16 parallel and concentrates the
illumination light at the image plane 58 so that it is brighter for a
given low power level as described below. The collimating lens 50 also
operates in conjunction with the lens 82 to focus the treatment light to a
point.
In accordance with the present invention, the interior of the patient's eye
12 can be viewed via the display so that the physician can observe the
interior of the eye not only for diagnostic purposes but in order to treat
various conditions observed in the interior of the eye. In practice, the
source of treatment light 30 preferably includes both an aiming beam and a
treatment beam. An Argonne laser of this type is available from Coherent
Medical, Inc. and a Diode laser of this type is available from Iris
Medical, Inc. The physician directs the aiming beam from the source 30 by
moving the various optics of the steering system 32 so as to position the
aiming beam at a desired location in the interior of the eye 12 for
treating the eye. Once the aiming beam is positioned to the desired
location as viewed by the physician on the display 28, the physician
actuates the treatment beam from the treatment laser source 30 that is
coaxial with the aiming beam so as to treat the eye at the position
determined by the aiming beam. Because the physician views the interior of
the eye 12 during treatment and in particular during the actuation of the
treatment beam from the source 30 via the display 28, no unwanted
reflections of the treatment laser can reach the physician's eye via the
viewing system.
In accordance with another embodiment of the present invention as shown in
FIG. 2, light from a noncoherent light source 100 is scanned by a scanning
system to illuminate the interior of the patient's eye 12 so that it can
be viewed during treatment with the treatment laser 30. The noncoherent
light source 100 may include, for example, a linear array 102 of light
emitting diodes (LEDs) 104 that can be individually actuated in a
sequence. The scanning system in this embodiment includes the cylindrical
lens 36 for scanning or converting a point of light from one of the LEDs
104 to a line of light that is reflected by the beam splitter 20 to the
lens 22. The light from each of the LEDs 104 passes through a slit
aperture 103 to the cylindrical lens 36 wherein the width of the slit 103
is parallel to a diameter of the lens 36. The line of light generated by
the cylindrical lens 36 from a single point of light from the array 102 is
such that when it is projected onto the beam splitter 20, the line of
light extends in a direction that is perpendicular to the line of light
which would be projected on the beam splitter 20 if the lens 36 were
removed and all of the LEDs in the array 102 were turned on
simultaneously. Lines of light are scanned across the beam splitter 20 by
the sequential actuation of the LEDs 104 in the array 102 by the
controller 106 so as to scan a two dimensional area of illumination
directed to the interior of the eye 12. In this embodiment, the
collimating lens 50 concentrates light from the LEDs at the image plane so
that the power of the illumination light source 100 may be lowered. The
illumination light reflected by the patient's eye 12 is received by the
aspheric lens 22 and passes through the optics 20, 24, 70, 72 and 74 to
the CCD camera 26 so that an image of the interior of the eye 12 can be
viewed on the display 28 as discussed above.
It is noted that any type of controller 106 may be used to sequentially
actuate the point sources of light in the array 102. The controller 106
may be as simple as a timer coupled to a counter that actuates a switching
array coupled to the LEDs 104. Alternatively, a more sophisticated
controller such as a microprocessor or the like may be used. The rate of
the scan of illumination light generated by the controller 72, the array
102 and cylindrical lens 36 with the slit aperture 103 is preferably
between 70 hertz and 90 hertz.
In a further embodiment of the present invention illustrated in FIG. 3,
light reflected from the patient's eye from an illumination light source
122 and scanning system 124 is captured by an optical system 120 so that a
magnified image of an interior portion of the patient's eye can be viewed
directly by the physician through an eyepiece lens 126. As in previous
embodiments, the light reflected from the patient's eye 14 passes through
the beam splitter 20 to the field lens 24. The field lens 24 is movable so
as to change the position of the image plane 58 closer to or farther from
the lens 22. The light reflected from the patient's eye passes through the
field lens 24 and from there through a polarizer film 128 to an image lens
130. The image lens 130 and field lens 24 form a magnified image at an
image plane 132 of the interior of the patient's eye which is observed by
the physician as he looks through the eyepiece lens 126.
In order to pass only desired light to the eyepiece lens 22, the light from
the source 122 is polarized in a first direction and the polarizer film
128 of the optical system 120 is polarized in a second direction that is
different from the first direction. In particular, the polarizer film 128
is preferably polarized in a direction perpendicular to the polarization
of the light from the source 122. This polarization of the polarizer film
112 blocks unwanted reflections from the patient's eye, the aspheric lens
22 and other elements of the system from reaching the image lens 130 and
eyepiece lens 126 so that only the randomized reflected image from the
interior of the patient's eye passes through the optical system into the
eyepiece lens 22.
In order to insure that no treatment laser light passes through the system
to the eyepiece lens 126 and to the physician's eye, a shutter 136 is
employed. The shutter may be any well-known type of shutter for blocking
unwanted treatment laser reflections. It may be for example a glass with a
laser safety coating that is moved into position by a solenoid that is
actuated by an actuator 140 simultaneously with the actuation of the
treatment beam from the treatment laser source 30. Thus, after the
physician has steered the aiming beam of the treatment laser to a desired
position, the physician actuates a switch forming a portion of the
actuator 140. Actuation of the switch 140 simultaneously actuates the
shutter 136 and treatment beam so that the shutter is moved into position
when the treatment beam is actuated to treat the eye. Unlike the
embodiment of FIG. 3 wherein the shutter 136 temporarily blocks the view
of the physician during the exact moment when the treatment laser is being
applied to the eye 12 so as to protect the physician's eye, the
physician's view of the eye 12 is not blocked during the application of
the treatment laser to the eye 12 by the embodiments of the invention
depicted in FIGS. 1 and 2 wherein the physician views the eye via the
display 28.
The embodiment of FIG. 3 also illustrates an alternative position for the
treatment laser and steering system 32 wherein the specific reflector 48
is positioned between the beam splitter 20 and the aspheric optic 22. In
this embodiment, the light reflected from the patient's eye 12 to the
optical system 120 capturing the image to be viewed, passes through the
specific reflector 48.
It is noted that the beam splitter 20 separates the scanning system in the
various embodiments from the optical path between the patient's eye and
the image capturing system which may include the CCD camera 26 and display
28 or the eyepiece lens 126. The beam splitter 20 is a partially
reflecting illumination mirror that reflects at least 25% of the
illumination light from the scanning system 24 to the patient's eye 14 and
that reflects the treatment laser from the source 30 to the patient's eye
while passing therethrough light reflected from the patient's eye 14 so
that the interior of the eye can be viewed for treatment. The present
invention eliminates problems with shading off which can occur when
optical elements such as a scanner are placed in the optical path from the
patient's eye to the eye image capturing system. These optical elements
can block the chief ray from any given image position on its route from
the patient's eye to the image capturing optics thereby causing shading
off. This problem is eliminated in the present invention by the separation
of the image capturing system from the scanning system and by employing
optical elements within the optical path from the patient's eye to the eye
image capturing system that do not block the chief rays from any given
image position on their route to the eye image capturing system.
It should be appreciated, that various combinations of lenses can be used
in place of the aspheric lens 22. However, the use of an aspheric lens is
desirable because it accomplishes a number of functions with one optical
element. The aspheric lens may be such that the surfaces 52 and 54 of the
lens are described by the polynomial function:
##EQU1##
where A.sub.2, A.sub.4 and A.sub.6 are constants; C represents the
curvature of the surface; and cc represents the conic constant. For the
stronger surface 54 of the lens 22, these values should be within the
following ranges:
0.0<A.sub.2 <0.003
-0.02<A.sub.4 <0.02
-0.01<A.sub.6 <0.01
-0.1<C<0.0
-2.0<cc<1.0
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