Note: Descriptions are shown in the official language in which they were submitted.
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VIRTUAL MICROSCOPE SYSTEM FOR MONITORING THE PROGRESS OF
CORNEAL ABLATIVE SURGERY AND ASSOCIATED METHODS
FIELD OF INVENTION
This Application Claims the Priority of U.S. Provisional Application No.
60/015,853
Filed December 21, 2007.
The. present invention generally relates to surgical methods and, in
particular, to
systems and methods for monitoring the progress of corneal ablative surgery.
BACKGROUND
The performance of LASIK (laser in situ keratomileusis) surgery is typically
accompanied by the cutting of a thin flap in the cornea, which is then lifted
and folded back
along a hinge to expose the corneal stroma beneath. An ablating laser is used
to perform
refractive surgery, and the flap is replaced.
Several methods have been used to avoid or detect any "wrinkles," or striae,
in the
corneal flap after replacement atop the stroma. For example, the cornea can be
marked prior
to cutting so that the markings can be used to realign the flap. Another
method employs the
operating (direct-view) microscope and a diffuse, broadband, white light
source to detect
striae. Alternatively, the refractive surgeon may use a dedicated apparatus,
such as a
handheld slit lamp, to project a thin line of visible broadband, white light
onto the cornea to
scan for surface aberrations or edges.
However, the flooding of the eye with such illumination to detect flap
position, debris,
and hydration can be uncomfortable for the patient, and the use of a slit lamp
to detect flap
replacement and general eye condition can compromise work flow. Further, white
light may
not provide optimal enhancement of parts of the eye for visualization. To view
at alternate
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wavelengths, external camera systems with standard video monitors can be used,
but, in order
to eliminate the high illuminations required for direct-view microscopes,
larger apertures
must be used, mandating a tradeoff between patient safety and doctor view.
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SUMMARY OF THE INVENTION
The present invention is directed to a system and method for visualizing an
eye of a
patient during corneal surgery. The system comprises a processor and a first
and a second
camera in signal communication with the processor. The first and the second
cameras are
positionable for focusing on a cornea of the eye that is positioned for
undergoing surgery.
A first and a second display and optics therefor are in signal communication
with the
processor and are positionable for viewing through a first and a second
eyepiece of a stereo
microscope, respectively. The microscope is associated with a surgical field
of the cornea.
Software is resident on the processor that comprises code segments for
receiving a
first and a second image of the cornea from the first and the second cameras,
and for
processing the received first and second images for display. A code segment is
also provided
for transmitting the processed first and second image to the first and the
second displays,
respectively, via the display optics. The first and the second displays can
then be viewed by a
surgeon through the microscope at least during the surgery, and, preferably,
before and after
the surgery as well.
The invention is also directed to a method for monitoring a process of corneal
surgery.
The method comprises the steps of illuminating an eye comprising a cornea
positioned for
undergoing surgery and stereoscopically imaging the cornea onto a first and a
second display.
The first and the second display can be viewed through a first and a second
eyepiece of a
stereo microscope, respectively.
The features that characterize the invention, both as to organization and
method of
operation, together with further objects and advantages thereof, will be
better understood
from the following description used in conjunction with the accompanying
drawing. It is to
be expressly understood that the drawing is for the purpose of illustration
and description and
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is not intended as a definition of the limits of the invention. These and
other objects attained,
and advantages offered, by the present invention will become more fully
apparent as the
description that now follows is read in conjunction with the accompanying
drawing.
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BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic of the eye imaging and display system of the present
invention.
FIG. 2 is a schematic of the cameras imaging an eye.
FIG. 3 is a side perspective view of a display assembly.
FIG. 4 is a side perspective view of the viewing and display assembly.
FIG. 5 is a top plan view of the display elements.
FIG. 6 is a schematic of the eye imaging and display system of the present
invention
incorporated into a LASIK apparatus.
FIG. 7 is a flowchart of an embodiment of the eye imaging and display method
of the
present invention.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A description of the preferred embodiments of the present invention will now
be
presented with reference to FIGS. 1-7.
The system schematic of FIG. 1 illustrates the elements of an exemplary
embodiment
of a system 10 of the present invention for monitoring a process of corneal
surgery by a
surgeon. The system 10 comprises a first 11 and second 12 high-resolution
color camera
(FIG. 2) that in a particular embodiment are adjustable in angular separation
13 and can focus
on a portion of an eye 14, for example, the cornea 15. An exemplary surgical
procedure for
which the system 10 is applicable is LASIK surgery, although this is not
intended as a
limitation, and is also applicable to pupilometry, where pupil dynamics can be
monitored and
recorded, and other eye measurements, such as corneal birefringence, and to
other ophthalmic
surgeries, where a surgical microscope might be useful. For this type of
surgery, the system
10 can be useful for imaging the cornea 15, a flap cut in the cornea, the
underlying stroma, the
limbus, and any other portion of the eye desired to be imaged, and can provide
depth
perception.
The cameras 11, 12 can be optimized for low light levels, wide band, or speed.
Preferably, the speed is sufficient so as not to show a noticeable lag in
imaging. The
waveband should preferably encompass the wavelengths expected to be used for
image
enhancement, and the sensitivity should allow comfortable light levels on the
patient.
The cameras 11, 12 are in signal communication with a processor 16 that has
image
processing software 17 resident thereon. The cameras 11, 12 are positioned and
focused for
receiving reflected radiation 18 from the eye 14, radiation 19 incident on the
eye 14 from a
source of illumination 20. The illumination source 20 can, in a preferred
embodiment,
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comprise a source of a plurality of wavelength ranges, although this is not
intended as a
limitation, the use of which will be described in the following.
In use, the software 17 receives images from the cameras 11, 12 and processes
the
images for display through a stereo microscope 21 that is typically an element
of the surgical
system, and with the use of which the surgeon is familiar in such procedures.
The software
17 can also comprise code segments for superimposing additional data upon the
output
display, including, but not intended to be limited to, microscope information
(zoom, scale
factor, measurement bars, etc.) and surgical system information (percent
complete of
procedure, laser power statistics, etc.). Incorporating such data into the
display obviates the
need for the surgeon to remove his/her attention from the patient and onto an
external display,
and these data, as well as any processed image data, can be stored and
retrieved for future
reference if desired.
The processed images are transmitted to a first 22 and a second 23 display via
display
optics 24 for viewing through, respectively, a first 25 and a second 26
eyepiece of the
microscope 21 (FIGS. 3-5). The displays 22, 23 can comprise microdisplays for
allowing a
form factor similar to that of the microscope 21. The displays 22, 23 should
preferably have a
resolution sufficient so that the surgeon does not see individual pixels
thereon. Preferably the
displays 22, 23 should have adjustable intensity and contrast. The display
optics 24 provide a
microscope-like view of the eye 14, having adjustable parallax and focus for
each eyepiece
25, 26.
The system 10 can additionally comprise zoom optics 27, which can comprise,
for
example, true zoom, step-zoom, or true zoom with detents, although these are
not intended as
limitations. Since the performance of the optics is keyed to the pixel size of
the cameras 11,
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12 and not retinal resolution, the system design is more flexible, and larger
apertures can be
used if desired. Preferably the optics should perform over the desired
waveband.
The system 10 can further comprise spectral filters 28 that can be
interchangeable or
switchable, and can be manually switched, placed on a filter wheel, or
electrically inserted
into the optical pathway. Thus the illumination and the images received by the
cameras 11,
12 can be chosen to selectively enhance a desired portion of the eye 14, a
feature that is not
available when using direct-view microscopes such as known in the art. For
example, near-
infrared radiation can be used to enhance the pupil, or ultraviolet light can
be used to image
the corneal surface, which is transparent to visible light but is opaque to
ultraviolet light.
Non-visible light would appear in black and white on the displays. During a
corneal ablation
procedure, near-infrared radiation would permit improved visualization of the
cornea, and
improve patient comfort, since this wavelength range is not visible to the
patient. Further, the
processor 16 can process the image to enhance the flap and the flap's edge to
visualize the
stroma. Prior to the flap's being cut, the spectral filters 28 can assist in
aligning the patient.
Additionally, lower light levels can be used that those that are typically
required in direct
viewing, since the cameras and processor can be used to adjust gain without
flooding the
patient's eye with an uncomfortable level of illumination.
In an exemplary embodiment, not intended as a limitation, the surgical
monitoring
system 10 can be incorporated into a LASIK apparatus for performing corneal
ablation (FIG.
6). Two of the aspects of the LASIK apparatus include an optical pathway for
the image 30
and for the tracker 31, each of which receives data via beamsplitters 32, 33.
Here two
illumination sources are illustrated as being directed toward the eye 14, an
infrared
illuminator 20a and a visible light illuminator 20b. The zoom lenses 27 can
comprise
continuous or step-zoom lenses, and optical filters 28 may be included. The
cameras 11, 12
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comprise high-resolution 2K x 2K cameras. A dual frame grabber and video
processor 16
display an image onto the two high-resolution (2K x 2K) displays 22, 23.
A method 100 (FIG. 7) for monitoring a process of corneal or other eye surgery
comprises the steps of positioning the patient for surgery (block 101) and
illuminating the
patient's eye with a desired wavelength range (block 102). If desired, light
reflected from the
eye 14 can be spectrally filtered 28 (block 103). The cornea 15 or other eye
portion is then
imaged stereoscopically onto the first and second displays 22, 23 (block 104),
which can be
zoomed if desired to a desired magnification (block 105). Parallax and/or
focus of the
displays 22, 23 can also be adjusted as desired (block 106). The surgeon can
view the
displays 22, 23 (block 107) through the eyepieces 25, 26 of the surgical
microscope 21, prior
to, during, and/or following the surgical procedure (block 108).
In the foregoing description, certain terms have been used for brevity,
clarity, and
understanding, but no unnecessary limitations are to be implied therefrom
beyond the
requirements of the prior art, because such words are used for description
purposes herein and
are intended to be broadly construed. Moreover, the embodiments of the system
and method
illustrated and described herein are by way of example, and the scope of the
invention is not
limited to the exact details disclosed.
Having now described the invention, the construction, the operation and use of
preferred embodiments thereof, and the advantageous new and useful results
obtained
thereby, the new and useful constructions, and reasonable mechanical
equivalents thereof
obvious to those skilled in the art, are set forth in the appended claims.
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