U.S. patent application number 16/796863 was filed with the patent office on 2020-06-18 for system and methods for depth detection in laser-assisted ophthalmic procedures.
The applicant listed for this patent is AMO Development, LLC. Invention is credited to Zsolt Bor, Michael Campos, Peter-Patrick De Guzman, Anthony Dennison.
Application Number | 20200188168 16/796863 |
Document ID | / |
Family ID | 50241571 |
Filed Date | 2020-06-18 |
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United States Patent
Application |
20200188168 |
Kind Code |
A1 |
Bor; Zsolt ; et al. |
June 18, 2020 |
SYSTEM AND METHODS FOR DEPTH DETECTION IN LASER-ASSISTED OPHTHALMIC
PROCEDURES
Abstract
Embodiments of this invention relate to systems and methods for
automatic depth (or Z) detection before, during, or after
laser-assisted ophthalmic surgery. When performing ophthalmic laser
surgery, the operator (or surgeon) needs to make accurate and
precise incisions using the laser beam. With the automatic depth
detection systems and methods, the same laser used for the surgical
procedure may be used for depth measurement of the surgical
incisions. The surgical laser system may include a laser delivery
system for delivering a pulsed laser beam to photoalter an eye, a
mirror to transmit at least a portion of reflected light of the
pulsed laser beam, a lens positioned to focus the transmitted
reflected lighted on to a detector, (such as a CCD), and a depth
encoder configured to automatically detect depth according to one
or more of color, intensity, or shape of the focused spot on the
CCD.
Inventors: |
Bor; Zsolt; (San Clemente,
CA) ; De Guzman; Peter-Patrick; (Santa Clarita,
CA) ; Dennison; Anthony; (Irvine, CA) ;
Campos; Michael; (Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AMO Development, LLC |
Santa Ana |
CA |
US |
|
|
Family ID: |
50241571 |
Appl. No.: |
16/796863 |
Filed: |
February 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13830072 |
Mar 14, 2013 |
10568764 |
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16796863 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 9/0084 20130101;
A61F 2009/00878 20130101; A61F 9/008 20130101 |
International
Class: |
A61F 9/008 20060101
A61F009/008 |
Claims
1. An ophthalmic surgical laser system comprising: a laser delivery
system for delivering a pulsed laser beam to a target in a
subject's eye; a mirror positioned to transmit at least a portion
of collected plasma light of the pulsed laser beam; a lens
positioned to focus the transmitted collected light onto a
detector; and a Z-position encoder operatively coupled to the
detector to determine a depth of the target in the subject's
eye.
2-5. (canceled)
6. The system of claim 1, wherein the lens is an L2 lens.
7. (canceled)
8. The system of claim 1, wherein the target is at least one of an
aqueous humor, a lens capsule, and a lens of the subject's eye.
9-10. (canceled)
11. The method of claim 1, wherein the target is at least one of an
aqueous humor, a lens capsule, and a lens of the subject's eye.
12. A system for measuring a treatment depth of a target laser beam
applied to an eye comprising: a laser delivery system for
delivering a pulsed laser beam to a subject's eye; a mirror
positioned to transmit at least a portion of collected plasma light
from the pulsed laser beam; a lens positioned to focus the
transmitted collected plasma light onto a detector; and a
Z-position encoder operatively coupled to the detector to determine
the treatment depth of the pulsed laser beam.
13. The system of claim 12, wherein the detector is a CCD.
14. The system of claim 12, wherein the detector is a
photodiode.
15. The system of claim 12, wherein the detector is a quadrant
detector.
16. The system of claim 12, wherein the mirror has a 10% or less
transmission rate.
17. The system of claim 12, wherein the lens is an L2 lens.
18. The system of claim 12, wherein the collected light focused on
the detector includes color, shape, and intensity.
19. The system of claim 18, wherein the focused collected light
indicates whether the depth has reached at least one of an aqueous
humor, a lens capsule, and a lens of the subject's eye.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and is a continuation of
U.S. patent application Ser. No. 13/830,072, filed Mar. 14, 2013,
the entirety of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] Embodiments of the present invention generally relate to
laser-assisted ophthalmic procedures, and more particularly, to
systems and methods for depth detection during laser-assisted
ophthalmic surgery.
BACKGROUND OF THE INVENTION
[0003] With significant developments in laser technology and its
application to ophthalmology, laser surgery has become the
technique of choice for ophthalmic procedures, such as refractive
surgery for correcting myopia, hyperopia, astigmatism, and so on,
and cataract surgery for treating and/or removing a cataractic
lens. Laser eye surgery generally uses different types of laser
beams, such as ultraviolet lasers, infrared lasers, and near
infrared, ultra-short pulsed lasers, for various procedures and
indications.
[0004] A surgical laser beam is preferred over manual tools like
microkeratomes because it can be focused precisely on extremely
small amounts of ocular tissue, thereby enhancing accuracy and
reliability. For example, in the commonly-known LASIK (Laser
Assisted In Situ Keratomileusis) procedure, an ultra-short pulsed
laser is used to cut a corneal flap to expose the corneal stroma
for photoablation with an excimer laser. Ultra-short pulsed lasers
emit radiation with pulse durations as short as 10 femtoseconds and
as long as 3 nanoseconds, and a wavelength between 300 nm and 3000
nm. Besides cutting corneal flaps, ultra-short pulsed lasers are
used to perform cataract-related surgical procedures, including
capsulorhexis, capsulotomy, as well as softening and/or breaking of
the cataractous lens. Examples of laser systems that provide
ultra-short pulsed laser beams include the Abbott Medical Optics
iFS.TM. Advanced Femtosecond Laser and the IntraLase.TM. FS
Laser,
[0005] Conventional ophthalmic surgical laser systems generally
include an operator interface used by the system operator to
set-up, control, monitor, and direct the laser treatment. For
obvious reasons, the laser beam's ability to accurately and
precisely incise tissue, as well as its ability to properly
determine the incision depth,--(e.g., depth measured from the
surface of the cornea, the laser system interface, and/or the laser
source)--, are important.
[0006] As such, eye biometry information is often taken before
surgery to measure the location, depth, and length of all planes of
a patient's eye. A system for obtaining ophthalmic biometry data is
described in U.S. Pat. No. 7,887,184, issued to Baer et al., which
is incorporated here by reference in its entirety. Pre-surgical
measurements, however, may not account for how the internal
geometry of the eye is affected by an ophthalmic patient interface,
which is typically used to restrain eye movement during surgery.
Examples of ophthalmic patient interface devices used to stabilize
the eye are described in commonly-owned U.S. Pat. No. 6,863,667,
issued to Webb et al., U.S. Pat. No. D462,442 issued to Webb, U.S.
Pat. No. 6,623,476, issued to Juhasz et al., and co-pending U.S.
patent application Ser. No. 13/230,590, which are incorporated here
by reference. Furthermore, most pre-surgical measurements generally
require a separate or additional device from the surgical system,
adding cost. For example, some surgical systems add additional
pre-surgery imaging devices, such as an optical coherence
tomographer (OCT). Besides adding system costs, additional imaging
devices like OCT require regular calibration and maintenance to
maintain strong a spatial correlation between the surgical laser
and the OCT.
[0007] Accordingly, there is a need for improved systems and
methods for depth detection during laser ophthalmic surgery.
SUMMARY OF THE INVENTION
[0008] Embodiments of this invention generally relate to ophthalmic
laser procedures and, more particularly, to systems and methods for
automatic depth (or Z) detection before, during, or after
laser-assisted ophthalmic surgery. During an ophthalmic laser
procedure, the operator (or surgeon) needs to make accurate and
precise incisions using the laser beam. With the automatic depth
detection systems and methods, the same laser that makes the
surgical incisions also measures the tissue depth for where the
incisions should occur. In one embodiment, an ophthalmic surgical
laser system may include a laser delivery system to deliver a
pulsed laser beam to photoalter an eye, a mirror to transmit a
portion of the reflected light of the pulsed laser beam, a lens
positioned to focus the portion of reflected light onto a detector,
such as for example, a charge-coupled device (CCD), and a depth
encoder configured to detect treatment depth of the pulsed laser
beam according to one or more of color, intensity, or shape of the
focused spot on the detector.
[0009] This summary and the following detailed description are
merely exemplary, illustrative, and explanatory, and are not
intended to limit, but to provide further explanation of the
invention as claimed. Additional features and advantages of the
invention will be set forth in the descriptions that follow, and in
part will be apparent from the description, or may be learned by
practice of the invention. The objectives and other advantages of
the invention will be realized and attained by the structure
particularly pointed out in the written description, claims and the
appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Understanding this invention will be facilitated by the
following detailed description of the preferred embodiments
considered in conjunction with the accompanying drawings, in which
like numerals refer to like parts throughout the different views.
Like parts, however, do not always have like reference numerals.
Further, the drawings are not drawn to scale, and emphasis has
instead been placed on illustrating the principles of the
invention. All illustrations are intended to convey concepts, where
relative sizes, shapes, and other detailed attributes may be
illustrated schematically rather than depicted literally or
precisely.
[0011] FIG. 1 is a perspective view of a surgical ophthalmic laser
system according to an embodiment of the present invention.
[0012] FIG. 2 is a simplified diagram of a computer system
according to an embodiment of the present invention.
[0013] FIG. 3 is an illustration of a light path in a surgical
ophthalmic laser system according to an embodiment of the present
invention.
[0014] FIG. 4 is a flowchart illustrating a process according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Embodiments of this invention are generally directed to
systems and methods for ophthalmic laser surgery, and more
particularly to systems and methods for depth (or Z) detection
before, during, or after laser-assisted ophthalmic surgery. In one
embodiment, the same laser used for the surgical operation is also
utilized for the depth measurement for the surgical incision
before, during, or after the surgery.
[0016] According to an embodiment, the depth (or Z) position of a
patient's ocular lens capsule is detected during a laser cataract
surgery ("femtophaco") procedure performed with a surgical laser
system, such as for example, the Abbott Medical Optics iFS.TM.
Advanced Femtosecond Laser or IntraLase.TM. FS Laser, as well as
other systems in the market providing ultra-short pulsed laser
beams for laser-assisted cataract surgery. The plasma light of the
ultra-short pulsed laser delivered at a focal point within the
patient's eye is collected and collimated by the surgical laser
system's objective lens and telescope. About ten percent of this
collected plasma light passes through a 45 degree mirror and is
focused by an L2 lens onto an imaging camera or detector, for
example, a charge-coupled device (CCD). The color, shape, and
intensity of the image or spot on the CCD will be different for
plasma light generated and collected from within the aqueous humor,
the capsule, or the lens. Further, using a Z (or depth) encoder
known in the art (see, e.g., U.S. application Ser. No. 12/275,518,
filed Nov. 21, 2008, entitled, "Apparatus, System, and Method for
Precision Depth Measurement," which is incorporated here by
reference in its entirety), the data captured by the CCD can be
used to determine the depth in microns, which can be used for the
incision. Generally, when the CCD is in the focal plane of the L2
lens, the spot on the CCD does not move during x/y scanning
primarily because of the placement of the L2 lens and the detector
before a laser beam steering apparatus, such as Galvo-driven
mirrors.
[0017] According to an embodiment, to detect the lens capsule in a
capsulorhexis operation, as is performed during cataract surgery,
the surgical laser system is first programmed for a predetermined
vertical side cut with a diameter of, for example, about 5-6 mm.
The surgical laser system directs the vertical side cut to move
down to the direction of the lens capsule. The starting depth is
typically about 3 mm. As such, the programmed depth typically
extends from about 3 mm to about 4 mm. This is the depth range
where the anterior lens capsule surface is most likely to be
located. When the plasma light generated by the laser is from
within the aqueous humor, the intensity of the spot on the CCD will
be low. When the laser beam first reaches the lens capsule, there
will be a sudden increase in spot intensity. If the patient's
ocular lens is tilted with respect to the optical axis of the
objective lens, or is otherwise de-centered, the spot intensity
will pulsate as the plasma is generated either in the aqueous
humor, in the lens capsule, or in the lens. When the laser proceeds
deeper into the ocular tissue and is entirely within the lens, the
captured plasma light intensity detected via the CCD is nearly
constant over each side cut revolution. A constant intensity of the
spot indicates that capsulorhexis has been completed.
[0018] According to another embodiment, the ability to monitor what
tissue is undergoing laser treatment, and consequently where the
laser surgery is taking place, enables one to reduce the treatment
process time through use of variable depth incrementations. For
example, the vertical depth may be incremented in steps (or layered
separations) of 10 .mu.m. When the first plasma signal appears on
the CCD and has a predetermined intensity, the layer separation is
changed to 2 .mu.m. The incision continues with 2 .mu.m layer
separation until the capsulorhexis is completed.
[0019] According to an embodiment, the surgical laser system is
programmed to perform a side cut pattern that is repeated over
depth so as to detect the cornea while performing a penetrating
corneal incision. The side cut pattern can start from above the
anterior surface of the cornea or below the posterior cornea, in
the anterior chamber. In this case, the plasma light generated by
the laser in glass (as found in a cone-lens of a patient interface
device), cornea, or aqueous humor will produce a spot with
differing color, shape, or intensity on a detector, such as a CCD.
Hence, by monitoring the spot characteristics on the CCD, the depth
encoder, as well as the beam steering for direction, one can
determine where the laser is currently firing, and can decide
whether to proceed with the treatment, or to stop.
[0020] According to an embodiment, when the laser beam is focused
onto an optical interface, the back-reflected beam is also focused
onto the CCD. The spot size on the CCD will be about 30 .mu.m (when
using a 100 mm focal length L2 lens). When the laser beam is
focused above or below the interface by about 10 .mu.m, the spot
size on the CCD will be about 60 .mu.m. Using the spot size
variance, the system can measure the depth with an accuracy of
about 3-5 .mu.m. This automatic depth (or auto-z) measurement can
thus be used to compensate for any optical interface position
variation, which may shift the zero depth reference of a laser
surgical system. It is noted that this auto-z technique does not
require laser beam intensities which may cause optical damage to
the optical interface cone glass.
[0021] When the laser beam is focused on any of the interfaces (for
example, patient interface lens-cone-glass/air, patient interface
lens-cone-glass/cornea, cornea/aqueous humor, aqueous
humor/capsule, and the like), a spot with sharp intensity will
appear on the CCD. Taking into account the reflectivity of the
different interfaces (for example, 3.4% for patient interface
lens-cone-glass/air, 0.61% for patient interface lens-cone
glass/cornea, 0.034% for cornea/aqueous humor, and 0.19% for
aqueous humor/capsule), the depth and spatial relation of the
various interfaces can be measured without causing optical damage.
The depth data can be displayed graphically, or in
three-dimensional renderings to assist treatment planning.
[0022] According to an embodiment, the spot on the CCD may further
be used as an onboard automated laser spot size/quality monitor,
thus replacing the external spot size camera used in the surgical
laser system.
[0023] According to an embodiment, one can integrate the onboard
laser spot size/quality monitor as feedback into an adaptive optics
configuration. Deformable mirrors, or any wavefront altering
device, in the laser delivery path provides the main mechanism for
compensating optical aberration, thereby tightly focusing the laser
spot. A mapping of optical aberration over the surgical volume
(plane and depth) may be used to guide aberration management. The
effectiveness of aberration management is confirmed via the spot
quality imaged by the CCD. Note that this aberration management can
be performed either prior to, or during laser treatment.
[0024] According to an embodiment, a program code, algorithm, or
software periodically or continuously monitors information received
from the eye E on the CCD. This monitoring may or may not be based
on real-time data acquisition and processing. The depth position
may be dynamically detected based on this information.
[0025] FIG. 1 illustrates a surgical laser system 10 according to
an embodiment. The surgical laser system 10 includes a laser 12
that produces a laser beam 14 which generates laser beam pulses.
Laser 12 is optically coupled to laser delivery optics 16, which,
under the direction of a computer system 22, directs laser beam 14
to an eye E of patient P. A delivery optics support structure (not
shown here for clarity) extends from a frame 18 supporting laser
12. A microscope 20 is mounted on the delivery optics support
structure. A visual fixation system 15 is generally coupled to
laser 12, laser delivery optics 16 and the delivery optics support
structure. The visual fixation system 15 may also operate under the
direction of computer system 22. Laser 12 may be designed to
provide a feedback stabilized fluence at the patient's eye,
delivered via delivery optics 16.
[0026] U.S. Pat. No. 7,351,241 describes methods of
photoalteration, and is incorporated here by reference. Other
devices or systems may also be used to generate pulsed laser beam
14. For example, non-ultraviolet (UV), ultra-short pulsed laser
technology can produce pulsed laser beam 14 having pulse durations
measured in the femtoseconds and picoseconds range. Some of the
non-UV, ultra-short pulsed laser technology may be used in
ophthalmic applications. For example, U.S. Pat. No. 5,993,438,
incorporated here by reference, discloses a device for performing
ophthalmic surgical procedures to effect high-accuracy corrections
of optical aberrations, as well as an intrastromal photodisruption
technique for reshaping the cornea using a non-UV, ultra-short
(e.g., femtosecond pulse duration), pulsed laser beam that
propagates through corneal tissue and is focused at a point below
the surface of the cornea to photodisrupt stromal tissue at the
focal point.
[0027] Although the laser system 10 may be used to photoalter a
variety of materials (e.g., organic, inorganic, or a combination
thereof), the laser system 10 is suitable for ophthalmic
applications in one embodiment. In this case, the focusing optics
direct the pulsed laser beam 14 toward an eye E (for example, onto
or into a cornea) for plasma mediated (for example, non-UV)
photoablation of superficial tissue, or into the stroma of the
cornea for intrastromal photodisruption of tissue. In this
embodiment, the surgical laser system 10 may also include a lens to
change the shape (for example, flatten or curve) of the cornea
prior to scanning the pulsed laser beam 14 toward the eye E. The
laser system 10 is capable of generating the pulsed laser beam 14
with physical characteristics similar to those of the laser beams
generated by a laser system disclosed in U.S. Pat. Nos. 4,764,930
and 5,993,438, which are incorporated here by reference.
[0028] For example, the ophthalmic laser system 10 can produce an
ultra-short pulsed laser beam 14 for use as an incising laser beam
14. This pulsed laser beam 14 preferably has laser pulses with
durations as long as a few nanoseconds or as short as a few
femtoseconds. For intrastromal photodisruption of the tissue, the
pulsed laser beam 14 has a wavelength that permits the pulsed laser
beam 14 to pass through the cornea without absorption by the
corneal tissue. The wavelength of the pulsed laser beam 14 is
generally in the range of about 3 .mu.m to about 1.9 nm, preferably
between about 400 nm to about 3000 nm, and the irradiance of the
pulsed laser beam 14 for accomplishing photodisruption of stromal
tissues at the focal point is typically greater than the threshold
for optical breakdown of the tissue. Although a non-UV, ultra-short
pulsed laser beam is described in this embodiment, the pulsed laser
beam may have other pulse durations and different wavelengths in
other embodiments.
[0029] Computer system 22 may comprise (or interface with) a
conventional or special computer, for example, PC, laptop,
workstation, embedded real-time operating system/processor, field
programmable gate array (FPGA), and so on, including the standard
user interface devices such as a keyboard, a mouse, a touch pad,
foot pedals, a joystick, a touch screen, an audio input, a display
monitor, and the like. Computer system 22 typically includes an
input device such as a magnetic or optical disk drive, or an input
interface such as a USB connection, a wired and/or wireless network
connection, or the like. Such input devices or interfaces are often
used to download a computer executable code to a storage media 29,
and may embody any of the methods of the present invention. Storage
media 29 may take the form of an optical disk, a data tape, a
volatile or non-volatile memory, RAM, or the like, and the computer
system 22 includes the memory and other standard components of
modern computer systems for storing and executing this code.
Storage media 29 includes one or more fixation maps, and may
optionally include a treatment map, and/or an ablation table.
Storage media 29 may alternatively be remotely operatively coupled
with computer system 22 via network connections such as LAN, the
Internet, or via wireless methods such as WLAN, Bluetooth, or the
like.
[0030] Additional components and subsystems may be included with
laser system 10, as should be understood by those of skill in the
art. For example, spatial and/or temporal integrators may be
included to control the distribution of energy within the laser
beam, as described in U.S. Pat. No. 5,646,791, which is incorporate
here by reference. Ablation effluent evacuators/filters,
aspirators, and other ancillary components of the surgical laser
system are known in the art. Further details of suitable systems
for performing a laser ablation procedure can be found in commonly
assigned U.S. Pat. Nos. 4,665,913, 4,669,466, 4,732,148, 4,770,172,
4,773,414, 5,207,668, 5,108,388, 5,219,343, 5,646,791 and
5,163,934, which are incorporated here by reference.
[0031] FIG. 2 illustrates a simplified block diagram of an
exemplary computer system 22 that may be used by the laser surgical
system 10 according to an embodiment of this invention. Computer
system 22 typically includes at least one processor 52 which may
communicate with a number of peripheral devices via a bus subsystem
54. These peripheral devices may include a storage subsystem 56,
comprising a memory subsystem 58 and a file storage subsystem 60
(which may include storage media 29), user interface input devices
62, user interface output devices 64, and a network interface
subsystem 66. Network interface subsystem 66 provides an interface
to outside networks 68 and/or other devices.
[0032] User interface input devices 62 may include a keyboard,
pointing devices such as a mouse, trackball, touch pad, or graphics
tablet, a scanner, foot pedals, a joystick, a touch screen
incorporated into the display, audio input devices such as voice
recognition systems, microphones, and other types of input devices.
User interface input devices 62 are often used to download a
computer executable code from a storage media 29 embodying any of
the methods of the present invention. User interface input devices
62 are also used to control an eye fixation system. In general, the
term "input device" is intended to include a variety of
conventional and proprietary devices and ways to input information
into computer system 22.
[0033] User interface output devices 64 may include a display
subsystem, a printer, a fax machine, or non-visual displays such as
audio output devices. The display subsystem may be a cathode ray
tube (CRT), a flat-panel device such as a liquid crystal display
(LCD), a projection device, or the like. The display subsystem may
also provide a non-visual display such as via audio output devices.
In general, the term "output device" is intended to include a
variety of conventional and proprietary devices and ways to output
information from computer system 22 to a user.
[0034] Storage subsystem 56 can store the basic programming and
data constructs that provide the functionality of the various
embodiments of the present invention. For example, a database and
modules implementing the functionality of the methods of the
present invention, as described herein, may be stored in storage
subsystem 56. These software modules are generally executed by
processor 52. In a distributed environment, the software modules
may be stored on a plurality of computer systems and executed by
processors of the plurality of computer systems. Storage subsystem
56 typically comprises memory subsystem 58 and file storage
subsystem 60.
[0035] Memory subsystem 58 typically includes a number of memories
including a main random access memory (RAM) 70 for storage of
instructions and data during program execution and a read only
memory (ROM) 72 in which fixed instructions are stored. File
storage subsystem 60 provides persistent (non-volatile) storage for
program and data files, and may include storage media 29 (FIG. 1).
File storage subsystem 60 may include a hard disk drive along with
associated removable media, a Compact Disk (CD) drive, an optical
drive, DVD, solid-state removable memory, and/or other removable
media cartridges or disks. One or more of the drives may be located
at remote locations on other connected computers at other sites
coupled to computer system 22. The modules implementing the
functionality of the present invention may be stored by file
storage subsystem 60.
[0036] Bus subsystem 54 provides a mechanism for letting the
various components and subsystems of computer system 22 communicate
with each other as intended. The various subsystems and components
of computer system 22 need not be at the same physical location but
may be distributed at various locations within a distributed
network. Although bus subsystem 54 is shown schematically as a
single bus, alternate embodiments of the bus subsystem may utilize
multiple busses.
[0037] Computer system 22 itself can be of varying types including
a personal computer, a portable computer, a workstation, a computer
terminal, a network computer, a control system in a wavefront
measurement system or laser surgical system, a mainframe, or any
other data processing system. Due to the ever-changing nature of
computers and networks, the description of computer system 22
depicted in FIG. 2 is intended only as an example for purposes of
illustrating one embodiment of the present invention. Many other
configurations of computer system 22, having more or fewer
components than those depicted in FIG. 2, are possible.
[0038] FIG. 3 shows an exemplary implementation 400 in laser
surgical system 10 to enable automatic depth detection. In general,
the optics delivery system includes, among other components,
semitransparent mirror 420 with 10% transmission (e.g., R=90,
T=10%), Galvo mirrors 460, a 6.times. telescope 465, and an
objective L2 lens 430. The laser beam 410 is directed to an eye E.
The laser produces plasma light 440 in the focal point of the laser
beam in the eye E. The plasma light is collected and collimated by
the objective lens 430. Ten percent of the backward propagating
plasma light 450 is transmitted by mirror 420 and is focused by L2
lens 431 onto the CCD 470. The Z-encoder 480, coupled to the CCD
470, uses data from the CCD 470 to generate the depths for the
aqueous humor, the capsule, and the lens of the eye E. The data on
the CCD includes, for example, the color, shape, and intensity of
the spot on the CCD 470.
[0039] In alternative embodiments, mirror 420 may have a less than
10%, for example, as low as 1%, transmission rate. Further, a
sensitive photodiode, photodiode array, quadrant detector (not
shown), or a CMOS imaging sensor may be used in place of the CCD
470. Photodiodes are typically faster, more sensitive, and less
expensive. Similarly, CMOS sensors are generally faster and may
cost less than other detectors. More than one mirror may also be
positioned between the L2 lens 431 and the first Galvo mirror 460.
A beam-splitter may be used to separate out light for the CCD 470.
It may also be used to enable both an imaging sensor and a
photodiode configuration.
[0040] FIG. 4 illustrates a process 500 of the laser system 10
according to an embodiment. The laser surgical system 10 starts the
surgical procedure with a predetermined depth (Action Block 510).
When the laser beam is focused on a target in the patient's eye, at
least a portion of the plasma light is detected on CCD 470 (Action
Block 520). Based on at least one of the color, shape, and
intensity of the focused spot on the CCD 470, the laser system 10
determines whether the target (the focal point of the laser beam in
the eye E) is the aqueous humor, the capsule, or the lens (Action
Block 530). The data from the CCD is also used by the Z-encoder to
determine the depth for the target (Action Block 540).
[0041] Although this invention has been described and pictured in
an exemplary form with a certain degree of particularity, and
describes the best mode contemplated of carrying out the invention,
and of the manner and process of making and using it, those skilled
in the art will understand that various modifications, alternative
constructions, changes, and variations can be made in the device
and method without departing from the spirit or scope of the
invention. Thus, it is intended that this invention cover all
modifications, alternative constructions, variations, and
combination and arrangement of parts and steps that come within the
spirit and scope of the invention as generally expressed by the
following claims and their equivalents.
* * * * *