U.S. patent application number 09/790531 was filed with the patent office on 2001-09-27 for eye illumination system and method.
Invention is credited to Apple, Howard P., Han, Xiaofeng, Nevitt, Martin P..
Application Number | 20010024266 09/790531 |
Document ID | / |
Family ID | 22044204 |
Filed Date | 2001-09-27 |
United States Patent
Application |
20010024266 |
Kind Code |
A1 |
Apple, Howard P. ; et
al. |
September 27, 2001 |
Eye illumination system and method
Abstract
A system for illuminating an eye useful for tracking movement of
an eye during vision correction treatments includes a generally
arcuate main body having. The main body is constructed and arranged
to be mounted in spaced relation to an eye to be tracked. An
infrared light source is carried by the main body on at least a
significant portion of its inner circumferential surface to direct
infrared light toward the eye being treated at an angle from about
20 to 45 degrees with respect to an iris base plane of the eye
being tracked.
Inventors: |
Apple, Howard P.; (Winter
Park, FL) ; Nevitt, Martin P.; (Oviedo, FL) ;
Han, Xiaofeng; (Orlando, FL) |
Correspondence
Address: |
MANELLI DENISON & SELTER PLLC
7th Floor
2000 M Street, N.W.
Washington
DC
20036-3307
US
|
Family ID: |
22044204 |
Appl. No.: |
09/790531 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09790531 |
Feb 23, 2001 |
|
|
|
09472951 |
Dec 27, 1999 |
|
|
|
6193373 |
|
|
|
|
09472951 |
Dec 27, 1999 |
|
|
|
09176755 |
Oct 22, 1998 |
|
|
|
6007202 |
|
|
|
|
60062696 |
Oct 23, 1997 |
|
|
|
Current U.S.
Class: |
351/221 |
Current CPC
Class: |
A61F 9/008 20130101;
A61B 3/113 20130101; A61B 3/0008 20130101; A61F 2009/00846
20130101 |
Class at
Publication: |
351/221 |
International
Class: |
A61B 003/10 |
Claims
What is claimed is:
1. An eye illumination system comprising: a main body; and one or
more light sources distributed from said main body; wherein light
from said one or more light sources is directed to a pupil of an
eye to be illuminated at an angle between 20 degrees and 45 degrees
with respect to a plane tangential to an iris of said eye.
2. The eye illumination system according to claim 1, wherein: light
from said one or more light sources is directed to said pupil of
said eye at an angle greater than 25 degrees with respect to a
plane tangential to an iris of said eye.
3. An eye illumination system comprising: a main body; one or more
light sources distributed from said main body; wherein said one or
more light sources is directed to a pupil of an eye to be
illuminated at an angle between 20 degrees and about 45 degrees
with respect to a plane tangential to an iris of said eye.
4. An eye illumination system comprising: a main body; one or more
light sources distributed from said main body; wherein light from
said one or more light sources is directed to a pupil of an eye to
be illuminated at an angle between 20 degrees and about 40 degrees
with respect to a plane tangential to an iris of said eye.
5. The eye illumination system according to claim 1 wherein: said
one or more light sources are infrared light sources.
6. The eye illumination system according to claim 1 wherein: said
light sources include a plurality of light emitters.
7. The eye illumination system according to claim 1, in combination
with: an eye imaging device to receive light from said one or more
light sources reflected from said eye.
8. An eye illumination system comprising: a mount; and one or more
light sources distributed from said mount; wherein light from said
one or more light sources is directed to a pupil of said eye at an
angle between 20 degrees and 45 degrees with respect to a plane
tangential to an iris of said eye.
9. An eye illumination system comprising: a mount; one or more
light sources distributed from said mount; wherein light from said
one or more light sources is directed to a pupil of said eye at an
angle greater than 20 degrees and less than about 45 degrees with
respect to a plane tangential to an iris of said eye.
10. An eye illumination system comprising: a mount; one or more
light sources distributed from said mount; wherein light from said
one or more light sources is directed to a pupil of said eye at an
angle between about 25 degrees and 40 degrees with respect to a
plane tangential to an iris of said eye.
11. The eye illumination system according to claim 8, wherein: each
of said one or more light sources are infrared light sources.
12. A method of illuminating an eye, comprising: providing one or
more light sources; and mounting said one or more light sources in
spaced relation from an eye being illuminated such that light from
said one or more light sources is directed toward a pupil of said
eye at an angle between 25 degrees and 45 degrees with respect to a
plane tangential to an iris of said eye.
13. A method of illuminating an eye, comprising: providing one or
more light sources; and mounting said one or more light sources in
spaced relation from an eye being illuminated such that light from
said one or more light sources is directed toward a pupil of said
eye at an angle between about 25 degrees and 40 degrees with
respect to a plane tangential to an iris of said eye.
14. A method of illuminating an eye, comprising: providing one or
more light sources; mounting said one or more light sources in
spaced relation from an eye being illuminated such that light from
said one or more light sources is directed toward a pupil of said
eye at an angle greater than about 25 degrees with respect to a
plane tangential to an iris of said eye; and spacing said one or
more light sources greater than about 100 mm from said eye.
15. The method of illuminating said eye according to claim 14,
further comprising: spacing said one or more light sources greater
than about 165 mm from said eye.
16. A method of illuminating and tracking a position of an eye,
said method comprising: illuminating a pupil of an eye with one or
more light sources from a distance of at least about 100 mm and at
an angle of between 20 degrees and 45 degrees; and tracking a
position of said pupil of said eye with an eye tracking system.
17. The method of illuminating and tracking the position of an eye
according to claim 16, wherein: said step of illuminating said
pupil of said eye spaces said one or more light sources at least
about 165 mm from said pupil of said eye.
18. The method of illuminating and tracking the position of an eye
according to claim 16, wherein: said step of illuminating said
pupil of said eye directs said illumination of said pupil of said
eye at an angle greater than about 25 degrees.
19. A method of illuminating and tracking a position of an eye,
said method comprising: illuminating a pupil of an eye with one or
more light sources from a distance of at least about 100 mm and at
an angle of greater than 20 degrees; and tracking a position of
said pupil of said eye with an eye tracking system; wherein said
step of illuminating said pupil of said eye directs said
illumination of said pupil of said eye at an angle less than about
45 degrees.
20. A method of illuminating and tracking a position of an eye,
said method comprising: illuminating a pupil of an eye with one or
more light sources from a distance of at least about 100 mm and at
an angle of greater than 20 degrees; and tracking a position of
said pupil of said eye with an eye tracking system; wherein said
step of illuminating said pupil of said eye directs said
illumination of said pupil of said eye at an angle less than about
40 degrees.
Description
[0001] This is a continuation of Application Ser. No. 09/472,951,
filed on Dec. 27, 1999, by Howard P. Apple, Martin P. Nevitt and
Xiaofeng Han, which in turn was a continuation of Application Ser.
No. 09/176,755, filed on Oct. 22, 1998, by the same inventors,
which claimed priority from Provisional Application Ser. No.
60/062,696, filed on Oct. 23, 1997, by the same inventors entitled
"Eye Tracker Lighting System for Laser Vision Correction."
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a lighting system for illuminating
the eye and more particularly to a lighting system for video based
tracking and correcting for eye movement during vision correction
treatments.
[0004] 2. Description of Related Art
[0005] Pupil position data obtained by eye tracking systems is used
to detect eye motion during vision correction treatments.
Conventional video based eye tracking systems automatically
recognize and track the position of eye positions based on
landmarks present within an image of a human eye. Such equipment
requires illumination of the eye by infrared (IR) light. IR light
typically 850 to 930 nanometers (nm) is used because it provides a
good picture contrast between the pupil and iris. Additionally, the
use of IR light decouples this lighting source from other visual
sources which do not contain the infrared wavelengths.
[0006] The eye, illuminated by invisible IR light, is scanned by an
infrared sensitive video camera. Under normal conditions, the pupil
of the eye appears as a dark hole to the illumination. The dark
pupil image is input to a real-time eye tracking system consisting
of a digital image processor that outputs pupil size and position
coordinates relative to the scan of the camera. The eye tracking
system includes a circuit and processor designed to acquire and
track the dark pupil position even in the presence of shadows or
other clutter normally found in images of the eye.
[0007] FIG. 1 shows a conventional eye tracking system including
illumination of the eye during laser vision correction surgery. The
conventional illumination system includes one or two infrared light
bundles 10, mounted on a central hub 12, to illuminate the eye for
tracking by the eye tracking system. The path of a visible light
beam used during vision correction treatments is shown at 14. A
camera 18, sensitive to IR illuminations and fixed with respect to
the subject's head, scans the eye to provide a video image for
tracking the position of the eye.
[0008] Conventional illumination systems such as that shown in of
FIG. 1 require that light bundles 10 be relatively close to the eye
in order to achieve an evenly distributed illumination. Generally,
the light bundles 10 are about 80 millimeters (mm) from the eye
being treated, as shown by the dimension A in FIG. 1. This narrow
spacing is a significant disadvantage because the light bundles 10
may interfere with the physician's hands either prior to or during
the actual vision correction treatment. Additionally, the
physician's hands can inadvertently block light emitted from one or
both of the light bundles 10 causing a system efficacy and/or
safety problem. Under certain circumstances, the patient's brow or
nose can block light emitted from the light bundles 10 causing
uneven illumination of the eye.
[0009] Additionally, conventional illumination systems such as that
shown in FIG. 1 require the light bundles 10 to be within 0 to
+/-20 degrees to the visual axis in order to achieve generally
presumption of an even illumination. If not, the light bundles 10
must be painstakingly adjusted for each patient at the time of
treatment to achieve the best possible illumination based on the
shape of that particular patient's face, eyes, etc. This is a
time-consuming process and may result in errors.
[0010] However, even if the light bundles 10 are positioned within
the conventionally preferred 0 to +/-20 degrees to the visual axis,
there is an additional problem caused by specular reflections. FIG.
2 and FIG. 3 show specular reflections 21 at an eye 17 caused by
any illumination system composed of point sources, e.g. light
bundles 10. Because of the relatively narrow angle (0 to +/-20
degrees) at which the light beams 19 (FIG. 3) are delivered, the
specular reflections 21 can occur either within the pupil 18 or
even worse at the pupil/iris border 20. This makes the machine
vision computer task of defining the pupil/iris border 20 much more
complex and error prone.
[0011] The system shown in FIG. 1 was originally designed for
research studies of normal eyes in which the epithelium is intact
with a tear layer providing distinct specular reflections. These
conditions no longer hold true for current laser vision correction
techniques. In particular, either the epithelium is removed under a
technique called surface Photorefractive Keratectomy (PRK), or a
flap is cut with a microkeratome, the flap is folded back, and the
treatment is performed on the underlying stromal layer (called
LASIK). Both LASIK and PRK markedly affect Illumination for eye
tracking systems. The eye, rather than being shiny and smooth,
becomes dryer and more diffusely reflective. This often leads to
additional time-consuming physician adjustment of the light bundles
10 during a critical time period of the surgery.
[0012] Another problem exists with conventional eye tracking
lighting systems when used with laser vision correction treatments.
An ablating laser beam dries and roughens the eye surface further
obscuring the camera's view of the pupil/iris border 20 and the
peripheral limbal border. Empirically, this disadvantageous effect
is accentuated by relatively coaxial lighting provided by singular
light sources placed close to the eye at angles of less that +/-20
degrees.
SUMMARY OF THE INVENTION
[0013] It is an object of the invention to provide a lighting
system for illuminating the eye during vision correction treatments
that does not physically interfere with preoperative and
postoperative procedures, requires little or no physical
adjustment, is insensitive to inadvertent light blockage, and
minimizes or eliminates disadvantageous specular reflections at the
pupil/iris border. These objects are attained in accordance with
the principles of the present invention by providing a method and
system which includes a generally arcuate main body. The main body
is constructed and arranged to be mounted in spaced relation to an
eye to be tracked. An infrared light source is carried by the main
body on at least a portion of its inner circumferential surface to
direct infrared light toward the eye being treated at an angle from
about 20 to 45 degrees with respect to an iris base plane of the
eye being tracked.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Features and advantages of the present invention will become
apparent to those skilled in the art from the following description
with reference to the drawings, in which.
[0015] FIG. 1 is a perspective view of a conventional lighting
system for illuminating the eye during vision correction treatment,
shown disposed above an eye being treated;
[0016] FIG. 2 is an enlarged plan view of specular reflections
which occur on a pupil of an eye being illuminated with the
conventional system of FIG. 1;
[0017] FIG. 3 is an elevation view of specular reflections which
occur on an eye being illuminated with the conventional system of
FIG. 1;
[0018] FIG. 4 is a perspective view of a lighting system for
illuminating the eye during laser vision correction treatment
provided in accordance with the principles of a first embodiment
the invention and shown disposed above an eye being treated;
[0019] FIG. 5 is a plan view of the lighting system of FIG. 4,
showing light sources in the form of a light pipe or in the form of
a plurality of light emitters
[0020] FIG. 6 is a perspective view of a lighting system for
illuminating the eye during laser vision correction treatment
provided in accordance with the principles of a second embodiment
of the invention and shown disposed above an eye being treated;
[0021] FIG. 7 is an elevation view of the lighting system of FIG. 6
shown disposed above an eye to be treated; and
[0022] FIG. 8 is a plan view of an eye showing the location of
specular reflections outside the pupil/iris border, which result
from the lighting system of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] With reference to FIG. 4, a first embodiment of an eye
illumination system is shown, generally indicated at 100, which
embodies the principles of the present invention.
[0024] The eye illumination system 100 includes an illuminating
device in the form of a generally arcuate main body 110 constructed
and arranged to be mounted in spaced relation to an eye being
treated. As shown in FIG. 5, the main body 110 is in the form of a
continuous ring having an inner diameter generally sufficient to
ensure that adequate space is provided above the patient's face for
the surgeon to maneuver. It has been determined that an inner
diameter greater that about 140 mm is sufficient to ensure adequate
space for maneuverability.
[0025] In the illustrated embodiment, the inner diameter of the
ring-shaped main body 110 is approximately 280 mm. This 280 mm
diameter permits the main body 110 to be disposed away from the eye
120 a distance of approximately 165 mm, as shown by the dimension B
in FIG. 4. The main body 110 includes an infrared light source 125
for directing infrared light towards the eye being treated. The
light source 125 may comprise a plurality of infrared light
emitters 130 (FIG. 5) that are evenly or randomly spaced along an
inner circumferential surface 135 of the main body 110. The light
emitters 130 may be fiber bundles, light emitting diodes, lasers,
electro luminescent panels, etc. It has been determined that for
the disclosed embodiment 180 light emitters 130 spaced evenly about
the inner circumferential surface 135 provides sufficient
illumination, although more or less light emitters 130 may be
employed. Further, the number of light emitters 130 may be reduced
by eliminating light emitters 130, e.g., at the 3, 6, 9, and/or 12
o'clock locations, without noticeable illumination degradation.
Eliminating light emitters in these regions also simplifies eye
tracker measurements.
[0026] Alternatively, the light source 125 may be an infrared light
pipe 140 disposed on the inner circumferential surface 135, a
portion of which is shown in FIG. 5. The light pipe 140 is
preferably provided along the entire inner circumferential surface
135, but may be disposed only along significant portions
thereof.
[0027] In the illustrated embodiment, a hub or mount 150 is coupled
to the main body 110 by a plurality of spokes 155 so that the hub
150 is generally concentric with the ring-shaped main body 110. The
hub may be used for mounting the main body 110 to a fixed location
and/or for mounting a visible light source (not shown) thereto. The
hub 150 includes a passage 160, through which a visible light beam
165 may be delivered to the eye 120 being treated.
[0028] An eye imaging camera 170 (FIG. 4) may be provided in the
conventional manner to scan the eye 120. The camera 170 may be
connected to a conventional pupil tracking system, such as, for
example, the RK-416PC Pupil Tracking System manufactured by ISCAN
INC. of Cambridge, Mass. This conventional ISCAN Tracking System
comprises a real time digital image processor that automatically
tracks the center of the patient's pupil and measures pupil size
and pupil position from a video image of the patient's eye. Another
example of an eye imaging camera and digital imaging system that
may be employed with an eye illumination system in accordance with
the principles of the present invention is disclosed in U.S. Pat.
No. 5,684,562, the content of which is hereby incorporated into the
present specification by reference.
[0029] In operation, the eye is illuminated with a low-level
(preferably 850 to 930 nm) infrared eye illumination source
according to the principles of the invention. The pupil acts a sink
to the IR light and while surrounding areas of the pupil reflect
the IR light back to the camera 170, yielding dark pupil" eye
images. A bright corneal reflection corresponds to the reflection
of the IR light off of the cornea. The eye imaging camera 170 is
fitted with an optics package having an infrared pass filter to
obtain a clear, in-focus image of the eye.
[0030] With reference to FIG. 6, a second embodiment of an eye
illumination system of the present invention is shown generally at
200. The main body 210 is of the second embodiment is generally
C-shaped. All other components of the eye illumination system 200
are as described with respect to the eye illumination system 100
shown in FIG. 4.
[0031] The inner diameter of the main body 210 is preferably
greater than about 140 mm, as in the first embodiment of the
invention. The embodiment shown in FIG. 6 has an inner diameter of
about 280 mm. The C-shaped main body 210 has an open portion 220 to
allow an unobstructed view for the physician. The C-shaped main
body 210 is typically configured with respect to the patient such
that the open region is toward the top of the patient's head, where
illumination is typically blocked by the patient's brow. Thus, even
though the embodiment of FIG. 6; does not encompass a full 360
degrees, there is generally no compromise in eye illumination.
[0032] With the eye illumination system in accordance the
principles of the present invention, as shown in FIG. 7, light rays
230 are emitted towards the eye at an angle .theta. which is
approximately between 20 to 45 degrees, and preferably between 25
to 40 degrees to an iris base plane 121. The iris base plane 121 is
considered to be the plane which is tangential to the outer edge of
the iris.
[0033] As shown in FIG. 8, an illumination system in accordance
with the principles of the present invention eliminates specular
reflections at the pupil/iris border 20. Thus, eye tracking
performance can be improved significantly.
[0034] The main body of a ring-shaped or C-shaped eye illumination
system works equally well in treating left and right eyes with no
adjustment. The lights become automatically centered under
conventional laser vision correction centering methods. Thus,
advantageously, no further adjustment of the eye illumination
system is required during surgery.
[0035] With an eye illumination system in accordance wit the
principles of the present invention, the main body may be mounted
sufficiently distance from the patient's face so as to not
interfere with the physician's hands. If a physician's hand should
inadvertently block some of the light from the eye illumination
system, there is sufficient light from other portions of the main
body to achieve adequate and even illumination of the eye.
[0036] Moreover, the infrared light beams are directed at a
sufficiently oblique angle such that specular reflections caused by
the light source do not interfere with the pupil/iris border,
particularly during eye movement encountered during patient
fixation. This leads to greater increased accuracy and reliability
of eye tracking.
[0037] It can be appreciated that the eye illumination system of
the present invention provides an effective way of illuminating an
eye, particularly for the purposes of tracking and correcting eye
movements during vision correction treatments. Since the eye
illumination system is constructed and arranged to be significantly
spaced from the patient's face, there is less likelihood of the
physician's hand interfering with the overall light source.
Further, the angle at which the light is directed to the eye
ensures that specular reflection interference at the iris/pupil
border is minimized or eliminated.
[0038] While the invention has been described in accordance with
what is presently considered to be the preferred embodiments, it is
to be understood that the invention is not limited to the disclosed
embodiments, but on the contrary, is intended to cover various
modifications and equivalent arrangements included within the
spirit and scope of the appended claims.
* * * * *