U.S. patent application number 13/646400 was filed with the patent office on 2013-02-07 for system and method for the treatment of a patients eye working at high speed.
The applicant listed for this patent is Stefan Lang, Ronald Toennies. Invention is credited to Stefan Lang, Ronald Toennies.
Application Number | 20130035673 13/646400 |
Document ID | / |
Family ID | 37492479 |
Filed Date | 2013-02-07 |
United States Patent
Application |
20130035673 |
Kind Code |
A1 |
Lang; Stefan ; et
al. |
February 7, 2013 |
System and Method for the Treatment of a Patients Eye Working at
High Speed
Abstract
The invention relates to a system and a method for the treatment
of a patient's eye. The system comprises a laser apparatus, a
scanning apparatus and an eye tracking apparatus for determining
the actual position of the patient's eye and for generating
alignment data of the patient's eye relative to a reference
position of the patient's eye to the laser, said eye tracking
apparatus being provided with a desired treatment shot file. Said
scanning apparatus is connected via a first bidirectional bus to
the eye tracking apparatus, said laser apparatus is connected via a
second bidirectional bus to the eye tracking apparatus. The eye
tracking apparatus adjusts the position data for each shot based on
said alignment data of the patient's eye and provides aiming
control signals representative of the target position data to the
scanning apparatus for said shot via said first bidirectional bus.
The eye tracking apparatus comprises a comparator for comparing the
target position data with the actual position data provided by the
scanning apparatus for the shot to be fired. Moreover, said eye
tracking apparatus is sending a command signal to the laser
apparatus via said second bidirectional bus for firing the shot
when the target position data is equal to the actual position data
of the scanning apparatus for the shot to be fired.
Inventors: |
Lang; Stefan; (Markt
Schwaben, DE) ; Toennies; Ronald; (Olching,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lang; Stefan
Toennies; Ronald |
Markt Schwaben
Olching |
|
DE
DE |
|
|
Family ID: |
37492479 |
Appl. No.: |
13/646400 |
Filed: |
October 5, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12063900 |
Feb 15, 2008 |
8303578 |
|
|
PCT/EP2006/009394 |
Sep 27, 2006 |
|
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13646400 |
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Current U.S.
Class: |
606/4 |
Current CPC
Class: |
A61F 9/008 20130101;
A61B 2017/00022 20130101; A61F 2009/00846 20130101; A61F 9/00802
20130101; A61F 2009/00872 20130101 |
Class at
Publication: |
606/4 |
International
Class: |
A61F 9/008 20060101
A61F009/008 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2005 |
DE |
102005046130 |
Claims
1. A system for the treatment of a patient's eye comprising: a
laser apparatus, a scanning apparatus and an eye tracking
apparatus, said scanning apparatus being connected to the eye
tracking apparatus via a first bidirectional bus, said laser
apparatus being connected to the eye tracking apparatus, wherein
the eye tracking apparatus provides aiming control signals
representative of a target position data to the scanning apparatus
for said shot and wherein said eye tracking apparatus is capable of
sending a command signal to the laser apparatus for firing a shot
when the target position data is equal to the actual position data
of the scanning apparatus.
2. The system of claim 1, wherein the laser apparatus is sending a
feedback signal to the eye tracking apparatus when a shot has been
fired and wherein preferably the eye tracking apparatus processes
to the next shot when a feedback signal is received and wherein the
eye tracking apparatus is sending a shut-down signal to the laser
apparatus if no feedback signal is received within a predetermined
time.
3. The system of claim 1, wherein the scanning apparatus comprises
at least one movable mirror and detector means for providing
detection signals representative of the actual position of the
movable mirror for the shot to be fired to the patient's eye to the
eye tracking apparatus.
4. The system of claim 1, wherein the eye tracking apparatus
comprises protocoling means for storing protocol information.
5. The system of claim 1, further comprising a computer system
being connected to the eye tracking apparatus and the laser
apparatus via a bus, wherein said computer system provides the
desired treatment shot file to the eye tracking apparatus.
6. The system of claim 1 further comprising a computer system being
connected to the eye tracking apparatus and the laser apparatus via
a fast data transfer protocol, wherein said computer system
provides a desired treatment shot file to the eye tracking
apparatus, receives and stores protocol information from the eye
tracking apparatus, and transmits and receives control data to/from
the laser apparatus, and wherein and each of the eye tracking
apparatus, the scanning apparatus, the laser apparatus and the
computer system comprises a fast data transfer protocol.
7. The system of claim 1 wherein the scanning apparatus comprises
two moveable mirrors, which are positioned according to the target
position data, each one of the two mirrors being movable by a
respective actuator and the actual position of each moveable mirror
being detected by a respective position sensor and one fixed mirror
wherein preferably the two moveable mirrors are smaller in size
than the fixed mirror.
8. The system of claim 1 further comprising energy monitoring means
for monitoring the energy of the laser.
9. The system of claim 8 further comprising shutter means for
providing every n-th laser pulse from a series of laser pulses to
the reference surface, wherein n is a natural number greater than
two.
10. The system of claim 4 wherein the protocol information
comprises at least one of the following: actual position data of
the patient's eye, the actual position data of the scanning
apparatus, target position data, and malfunction data.
11. The system of claim 1 further comprising a computer system
being connected to the eye tracking apparatus and the laser
apparatus, wherein said computer system receives and stores
protocol information from the eye tracking apparatus.
12. The system of claim 1 further comprising a computer system
being connected to the eye tracking apparatus and the laser
apparatus, wherein said computer system transmits and receives
control data to/from the laser apparatus.
13. The system of claim 1, wherein the aiming control signals
provided by the eyetracker to the scanning apparatus for said shot
reflect adjusted position data based on alignment data of the
patient's eye.
14. The system of claim 13, wherein the eye tracking apparatus
comprises a comparator for comparing the target position data with
the actual position data provided by the scanning apparatus.
15. The system of claim 5, wherein the bus is a second
bidirectional bus.
16. The system of claim 5, wherein the laser apparatus sends a
feedback signal to the eye-tracking apparatus via a third
bidirectional bus, wherein the eye-tracking apparatus forwards this
signal to the computer system, and the computer system returns
control data destined for the laser to the eyetracker.
17. The system of claim 16, wherein the computer system sends
control data directly to the laser without transiting through the
eyetracker.
18. A method for the treatment of a patient's eye using: a laser
apparatus having a laser, a scanning apparatus and an eye tracking
apparatus, comprising the steps of: providing aiming control
signals representative of a target position data from the eye
tracking apparatus to the scanning apparatus via a first
bidirectional bus for said shot; and sending a command signal from
the eye tracking apparatus to the laser apparatus for firing the
shot when the target position data is equal to the actual position
of the scanning apparatus for the shot to be fired.
19. The method of claim 18, further comprising the eye tracker
comparing the target position data with the actual position data
provided by the scanning apparatus for the shot to be fired.
20. The method of claim 18, wherein the command signal is sent from
the eye tracking apparatus to the laser apparatus via a second
bidirectional bus.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. patent application
Ser. No. 12/063,900, filed on Feb. 15, 2008, and to
PCT/EP2006/009394, filed Sep. 27, 2006, and to GE 102005046130.1,
filed Sep. 27, 2005.
FIELD OF THE INVENTION
[0002] The present invention relates to a system and a method for
the treatment of the patient's eye with high speed, in particular
to a system and a method using a refractive laser system.
DESCRIPTION OF THE RELATED ART
[0003] WO 95/27453 A relates to an excimer laser eye surgery system
using an optical aiming system which is schematically shown in FIG.
1. The excimer laser eye surgery system 10 is used for a
non-invasive resculpting of the surface of the eye 44 by providing
shots from an excimer laser 20 at desired locations on a determined
treatment area of an eye. With a typical excimer laser, a pulsed
beam 22 is provided with typical repetition rates of 60 to 100
pulses per second with a typical pulse length of 10 to 30 ns and
having a pulse energy of about 200 mJ/pulse. An aiming laser 32
provides an aiming beam spot which coincides with the central axis
of the laser shot of the pulsed beam. A registration laser 35
provides a registration beam which is coaxially aligned with the
pulsed beam. The pulsed beam coaligned with the aiming beam from
the aiming laser 32 and the registration beam from the registration
laser 35 passes from optics through an adjustable diaphragm 36
which allows the beam size of the pulsed beam to be adjusted before
it enters the final optics. Following the adjustable diaphragm 36,
a focusing lens 40 directs the pulsed beam onto a scanning mirror
42, which then reflects the beam onto a patient's eye 44. The
scanning mirror is capable of moving a beam at 5000 mm/s at the
surface of the eye. The focussing lens 40 focuses light such that
when the eye is at the optimal distance, the pulsed beam is
properly focussed onto the eye. Also provided in the system is a
focusing laser 46 whose beam travels through optics and impinges on
the eye 44 at an angle. The distance of the eye from the eye
surgery system is adjusted such that both the beam from the aiming
laser 32 and the beam from the focusing laser 46 impinge on the
surface of the eye at the same point. This known system comprises a
control unit 64 which controls all components of the eye surgery
system 10 including the diaphragm 36, the scanning mirror 42 and
shutters 28, 33 and 48 for blocking transmission of the pulsed
beam, the aiming beam and the focusing beam. A microscope 56 is
provided for the physician to observe progress during ablation of
the surface of the eye, wherein the microscope focuses through the
scanning mirror 42 and a splitting mirror 58. The splitting mirror
58 provides a view of the eye 44 to a video camera 60. The control
unit 64 further contains an eye tracking system 70. The video
camera 60 provides an image output to the control unit 64 and a
capturing video screen 62. An ablation profile software running in
the control unit 64 calculates the coordinates relative to the
origin of a desired target point, which denotes the centre of the
next desired excimer pulse on the eye 44 from the excimer laser 20.
Having received the absolute coordinates of where the origin is
located on the video image from the eye tracking system 70, the
ablation profile software then knows the absolute coordinates of
the target point. Then, the image from a video camera 60 allows the
eye tracking system 70 to locate and provide the absolute
coordinates of a registration spot where the registration beam from
the registration laser impinges on the eye. This registration spot
denotes the centre point of where the next pulse from the excimer
laser would impinge on the eye if the shot were immediately fired.
In case this point is not in alignment with the desired target
point because of any intervening movement of the eye, the aim of
the pulsed beam is therefore corrected such that the registration
spot coincides with the target point. This alignment is then again
checked and when within acceptable limits, the excimer laser 20 is
fired.
[0004] An advantage of this technique is the fact that the
registration beam from the registration laser 35 is aligned with
the pulsed beam from the pulsed excimer laser 20. If the movable
mirror 42 is uncalibrated, this does not matter, because one always
knows where the next shot from the excimer laser will actually
fall. Further, misalignment of the video camera 60 along the
optical axis is similarly of no consequence, as the control unit
using the video camera can always determine where the next shot
from the pulsed excimer laser will strike relative to the origin.
Further, slight misalignment of the registration laser 35 is
similarly of no consequence as that misalignment will result in a
fixed offset from the centre of the pulsed beam. Simple calibration
software can determine this offset, and then corrects for this
offset in determining where the centre of the next shot from the
excimer laser 20 will fall relative to the registration spot. Using
a specific software routine in conjunction with the registration
laser 35 and the eye tracking system 70, the ablation profile
software can accurately position the pulsed beam for the firing of
the next shot.
[0005] WO 01/028476 A1 relates to a system and method using iris
recognition for adjustment during diagnosis and during surgery.
Based on data provided by a diagnostic tool, a treatment is
developed. This treatment is normalized to the spot representation
of the iris image. The treatment itself is aligned to the iris of
the patient. Normalization can take very general forms, such as a
translation of the aim of the laser to an appropriate point, or
more sophisticated forms, such as by rotation or even scaling and
skewing of the treatment to match the iris image that is presented
to the laser system. The laser treatment is then performed. During
the laser treatment, the system can periodically or even
continuously match the iris data to the stored representation of
the iris data, in essence tracking the patient's eye. It is
possible for each shot to be appropriately rotated and translated.
The iris image can be tracked and the scaling functions applied
dynamically to each specific shot or sequence of shots in the
desired treatment pattern. In this manner, the movement of the eye
can be accommodated shot-by- shot.
[0006] U.S. Pat. No. 5,624,436 relates to an apparatus for ablating
an object by laser beam having means to correct the refractive
power of the laser beam. In order to control the ablating
operation, in particular the ablating depth per pulse, it is
suggested to use a reference plate which is disposed at a position
where usually the cornea of the eye is to be disposed. After
performing an ablation operation, the resulting ablation depth is
determined. As a reference plate, a transparent plate made from
polymethylmetacrylate resin (PMMA) may be used and the refractive
power of the simulated lens produced on the transparent plate can
be measured and compared with the refractive power of a lens to be
formed at the referenced ablation rate. Where the reference plate
is made of non-transparent material, a reflection focal length by
collimator can be measured.
[0007] U.S. Pat. No. 5,772,656 relates to a calibration apparatus
for measuring the properties of a laser beam. The calibration
apparatus includes a photo reactive element which is formed from a
erodable material having ablation characteristics similar to that
of biological tissue, for example polymeric coating of
polymetylmetacrylate (PMMA), polymethylstyrene, polycarbonate or
mixtures thereof, and as an example polycarbonate calibration
records fabricated from LEXAN.RTM. resins (commercially available
from General Electrical, Pitsfield, Mass. or from CR-39.RTM. resins
(PPG Industries, Pittsburgh, Pa.). After performing a reference
treatment of the photoreactive element, the resulting change
following exposure to the ablative laser radiation is detected by
inspection of the change of the optical properties. The records can
be analyzed to generate or feedback signals.
[0008] U.S. Pat. No. 6,195,164 B1 relates to systems and methods
for calibrating laser ablation. The optical power and shape of a
test surface that has been ablated by energy delivered from a laser
is measured. The known optical properties of the ablated test
surface may be used to adjust the laser ablation system by varying
treatment parameters such as laser pulse intensity and exposure
time.
SUMMARY OF THE INVENTION
[0009] The object underlying the present invention is to provide a
system and a method for the treatment of a patient's eye working at
high speed.
[0010] This object is solved with the features of the claims.
[0011] The present system and method is particularly suitable for
treatment with a laser working at a high pulse rate of for example
200 Hz, preferably 500 Hz and more preferably 1000 Hz or more.
[0012] In the system according to the present invention, the eye
tracking apparatus which determines the actual position of the
patient's eye and which generates alignment data of a patient's eye
relative to a reference position of the patient's eye is provided
with a desired treatment shot file. The eye tracking apparatus
adjusts the position data for each shot to be fired based on said
alignment data of the patient's eye and provides aiming control
signals representative of the target position data to the scanning
apparatus for said shot. The eye tracking apparatus comprises a
comparator for comparing the target position data with actual
position data provided by the scanning apparatus for the shot to be
fired and as soon as the target position data is equal to the
actual position of the scanning apparatus for the shot to be fired,
a command signal is sent to the laser for firing the shot. In the
system according to the present invention, the eye tracking
apparatus, and the scanning apparatus are connected via a first
bidirectional bus and the eye tracking apparatus and the laser are
connected via a second bidirectional bus. The first bidirectional
bus preferably comprises a wire connection. The second
bidirectional bus preferably comprises an optical fiber connection.
This has the advantage that the optical data transmission is not
disturbed by any electromagnetic field.
[0013] The system of the present invention has the advantage that
the eye tracking apparatus is provided with the desired treatment
shot file and performs control over the scanning apparatus and the
laser apparatus. Compared to known systems, the system according to
the present invention provides faster control of the scanning
apparatus and the laser apparatus.
[0014] According to a preferred embodiment of the present system,
the laser apparatus sends a feedback signal to the eye tracking
apparatus via said second bidirectional bus as soon as a shot has
been fired. If the eye tracking apparatus receives this feedback
signal within a predetermined time, the eye tracking apparatus
processes to the next shot otherwise the eye tracking apparatus
stops further processing of the treatment shot file. The
predetermined time t amounts to 1 ms to 100 ms. The minimum amount
is selected corresponding to the pulse rate of the laser.
[0015] According to a further embodiment of the invention, the
scanning apparatus comprises at least one movable mirror and
detector means for providing detection signals representative of
the actual position of the movable mirror for the shot to be fired
to the patient's eye. Alternatively or additionally, the aiming
means comprises an aiming laser for providing an aiming beam to the
actual position of a shot to be fired on the patient's eye and
wherein the eye tracking apparatus determines the actual position
of the aiming beam on the patient's eye.
[0016] According to an improvement of the invention, the eye
tracking apparatus comprises protocoling means for storing protocol
information with respect to the operation of the eye tracking
apparatus, the scanning apparatus and/or the laser apparatus for
every shot. The protocol information preferably comprises at least
one of the actual position data of the patient's eye, the actual
position data of the scanning apparatus, target position data and
any malfunction data.
[0017] According to another aspect of the present invention, the
system comprises a computer system being connected to the eye
tracking apparatus via a third bidirectional bus wherein the
computer system provides the desired treatment shot file to the eye
tracking system and/or receives and stores protocol information
from the eye tracking apparatus, and/or transmits and receives
control data to and from the laser apparatus for every shot. Said
protocol information may be stored in the computer system alone or
additionally in the eye tracking apparatus. The protocol
information may be used for any later quality control or for
completing an interrupted treatment.
[0018] The first, second and third bidirectional busses are
independent from each other. This has the advantage that high speed
data communication can be performed on each respective bus.
[0019] In the system, the third bidirectional bus is used for fast
transfer of data between the individual components. This third
bidirectional bus is preferably a CAN-bus. Each of the eye tracking
apparatus, the laser and the computer comprises a CAN-bus
controller. Any other bidirectional bus system according to
industrial standard for fast transfer of data may be used.
[0020] According to a further aspect of the present invention, the
scanning apparatus comprises two moveable mirrors and one fixed
mirror wherein the two moveable mirrors are smaller in size than
the fixed mirror. The two moveable mirrors are positioned according
to the aiming control signals, each one of the two mirrors being
moveable by a respective actuator and the actual position of each
mirror being detected by a respective position sensor. This has the
advantage that compared to known systems using one larger movable
mirror the aiming of the laser can be performed at higher speed
with two movable mirrors which are smaller and lighter. At the same
time, the fixed mirror may be larger than the two movable mirrors
and can be used as a half-mirror at a position above the patient's
eye so that other optical means like a microscope can be used.
[0021] According to a further improvement of the invention, the
system comprises further monitoring means for monitoring the energy
of the laser. The monitoring means preferably comprise an
acoustical sensor for detecting the noise which is generated when a
laser pulse of the laser hits on a reference surface. The reference
surface is preferably a plate made of plastics, preferably
PMMA.
[0022] The acoustical sensor may comprise a microphone, which
provides a voltage signal, when a laser pulse hits on the reference
surface. The acoustical sensor further comprises processing means
which receives said voltage signal and generates a reference data
which is a measure of the laser energy of the laser pulse and
correspondingly a measure of the ablation rate. For a more detailed
description of this monitoring means reference is made to the
co-pending patent application of the present applicant with the
title "Apparatus and Method for monitoring the energy of a
laser".
[0023] The laser apparatus may further comprise energy control
means, which receives the reference data and adjusts the energy of
the laser in response to the reference data such that the ablation
rate is adjusted.
[0024] According to a preferred embodiment of the invention, every
n-th laser pulse from a series of laser pulses is directed to a
defined position on the reference surface, where n is a natural
number greater than 2, preferably 25. The corresponding voltage
signal of every n-th laser pulse is evaluated. This has the
advantage that the processing means for evaluating the voltage
signal can be simplified while the laser is tested under normal
operating condition, i.e. at a high pulse rate.
[0025] The acoustical sensor preferably measures the propagation
time of the noise produced at the reference surface which is then
used for monitoring the distance between the reference surface and
the acoustical sensor. The acoustical sensor is connected to the
laser via said second bidirectional bus. This has the advantage
that the measurement of the propagation time can be triggered by
the command signal which is sent from the eyetracking apparatus to
the laser for firing the shot.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention will be further described by way of examples
with reference to the drawings, in which:
[0027] FIG. 1 is a diagram illustrating a known excimer laser eye
surgery system;
[0028] FIG. 2 is a block diagram illustrating the preferred
embodiment of an excimer laser eye surgery system according to the
present invention;
[0029] FIG. 3 is a diagram of the eye tracking apparatus shown in
FIG. 2;
[0030] FIG. 4 is a diagram illustrating optical path in the
preferred embodiment of an excimer laser eye surgery system
according to the present invention;
[0031] FIG. 5 is a diagram illustrating the timing of signals used
in an excimer laser eye surgery system according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] FIG. 2 shows a block diagram of the preferred embodiment of
an eye surgery system 100 according to the present invention. This
system comprises in the form of separate modules an excimer laser
apparatus 110, a scanning apparatus 120, a personal computer 150
and an eye tracking apparatus 200. The scanning apparatus 120
comprises a scanning control module 122 which is connected to a
first interface 124 for receiving data from the eye tracking
apparatus and a second interface 126 for transmitting data to the
eye tracking apparatus. In the preferred embodiment the interface
is realized by a SPDIFF (Siemens Philips data interface). The eye
tracking apparatus 200 comprises a first and a second interface,
224 and 226 which are preferably also realized as SPDIFF. The first
interface 224 of the eye tracking apparatus is connected to the
first interface 124 of the scanning apparatus via a first data
communication line 225. The second interface 126 of the scanning
apparatus is connected to the second interface 226 of the eye
tracking apparatus via a second data communication line 227. The
first and second data communication line in combination represent a
first bidirectional bus for a fast transfer of digital data between
the scanning apparatus and the eye tracking apparatus. In the
preferred embodiment the first and second data communication lines
are realized as electrical cables. The second data communication
line 227 is used for sending position data with regard to the x and
y position of the laser beam from the eye tracking apparatus to the
scanning apparatus. These position data are used for positioning at
least one movable scanning mirror provided in the scanning
apparatus. The first data communication line 225 is used for
transferring positioning feedback data from the scanning apparatus
to the eye tracking apparatus which represent the actual position
of the movable mirror in the scanning apparatus. Said positioning
feedback data can be for example provided by a detector which is
related to a controlling means for positioning the movable
mirror.
[0033] The excimer laser apparatus 110 comprises a first and a
second optical interface 114 and 116, respectively. The eye
tracking apparatus further comprises a first and second optical
interface 214 and 216, respectively. Said first optical interfaces
114 and 214 are connected via an energy monitoring means 320 by
means of first optical cables 215. The energy monitoring means 320
comprises a first and a second optical interface 314a, 314b. The
second optical interfaces 116 and 216 are connected by means of a
second optical cable 217. Both optical cables 215 and 217 in
combination represent a second bidirectional bus. Via the first
optical cable 215 a command signal is fed from the eye tracking
apparatus through the energy monitoring means to the excimer laser
apparatus. Via the second optical cable 217 a feedback signal is
fed from the excimer laser apparatus to the eye tracking apparatus.
Using optical data communication for the connection between the eye
tracking apparatus and the excimer laser apparatus has the
advantage that data communication is safe without distortion by
noise.
[0034] The excimer laser system 100 comprises a third bidirectional
bus 152 for connecting the personal computer 150 with the excimer
laser apparatus 110 and with the eye tracking apparatus 200.
Preferably, the third bidirectional bus is realized as a CAN-bus,
wherein each of the personal computer 150, the excimer laser
apparatus 110 and the eye tracking apparatus 200 comprises
respective CAN-controllers (not shown). The data connection between
the personal computer 150 and excimer laser apparatus 110 is used
for example for transferring data regarding a status of the excimer
laser apparatus, i.e. for determining whether the high voltage is
switched on or whether the excimer laser apparatus is in the
stand-by mode. FIG. 2 schematically shows an infrared camera 310
which is providing video data to the eye tracking apparatus 200
with respect to an image taken from an eye to be treated with the
excimer laser eye surgery system 100. FIG. 2 additionally shows an
infrared-light source 312 which is connected to the eye tracking
apparatus 200 and preferably illuminates the eye to be treated with
a pulsed infrared light.
[0035] The excimer laser eye surgery system according to the
present invention has the advantage that the individual apparatuses
are connected to each other via input/output interfaces which
allows for fast and standardized data communication. As will become
clear from the further description, the eye tracking apparatus 200
receives the necessary data for providing control over the scanning
apparatus on the one hand and the excimer laser apparatus on the
other hand. This allows a fast processing of data so that in the
system for processing a determined treatment a pulsed beam may be
provided with a repetition rate of 1000 pulses per second and
more.
[0036] The system shown in FIG. 2 further comprises an energy
monitoring means 320 for monitoring the pulse energy of the pulses
which are applied to a patient's eye. When a command signal is sent
from the eye tracking apparatus 200 to the excimer laser apparatus
110 through the energy monitoring means 320 both start operation.
The energy monitoring means 320 is further connected to the
personal computer 150. Depending on the output of the energy
monitoring means the personal computer will provide data to the
excimer laser apparatus for adjusting the laser energy by for
example changing the high voltage or provide warning signals or a
shut down signal to the excimer laser apparatus when the energy of
laser is out of the determined range for operating the system.
[0037] The eye tracking apparatus 200 as schematically shown in
FIG. 3 comprises a microprocessor 202, a memory 204 in particular
for storing a shot file representing a desired treatment of a
patient's eye, protocoling means 206, detector means 208 for
processing video data from the infrared camera 310 to provide
position data of the eye or the pupil. The eye tracking apparatus
further comprises a comparator means 210 for comparing target
position data received from the microprocessor 202 with actual
position data received from the scanning apparatus 120. The
comparator means provide position data to the scanning apparatus
120 for adjusting the movable mirror to the desired position.
[0038] The eye tracking apparatus further comprises a timer 212
being connected to the micro-processor 202 for controlling the
processing of the system.
[0039] The eye tracking module comprises said first and second
interface 224 and 226 for data communication with the scanning
apparatus 120. It further comprises said first and second optical
interfaces 214 and 216 for data communication with the excimer
laser apparatus. In addition it comprises a CAN-controller 232 for
data communication to and from the personal computer 150. In
addition, the eye tracking apparatus provides a control signal for
operating the infrared-light source 312.
[0040] When starting the excimer laser eye surgery system in
principle the following steps are performed. At the beginning the
eye tracking apparatus is provided with the desired treatment shot
file from the personal computer via the CAN-controller 232. This
treatment shot file is stored in the memory 204. Before starting
the treatment a physician will decide when the eye tracking
apparatus is switched on. Thereafter any movement of the patient's
eye is detected by processing video data from the infrared camera
and determining the actual position of the eye or the pupil. The
actual position data of the eye is provided from the detector 208
to the microprocessor 202. The microprocessor combines the position
data provided from the treatment shot file for a specific shot to
be fired and the actual position data of the eye or the pupil and
generates target position data. The target position data are
provided from the microprocessor via the first interface 224 to the
scanning apparatus. The target position data are also provided to
the comparator means 210 which further receive said actual position
feedback data from the scanning apparatus via the second interface
226. As soon as the comparator means 210 decide that the target
position data is equal to the actual position data of the scanning
apparatus the comparator means 210 provides a signal to the
microprocessor 202 where upon the microprocessor 202 sends a
command signal via the first optical interface 214 through the
energy monitoring means to the excimer laser apparatus. Using the
timing signals provided by the timer 212 the microprocessor 202
monitors whether a feedback signal is received from the excimer
laser apparatus via the second optical interface 216. Protocoling
means 206 are connected to the microprocessor 202 for storing
status information for the individual steps which are performed
trough the control of the eye tracking apparatus.
[0041] The eye tracking apparatus of the present invention provides
the advantage that data can be processed in a fast manner allowing
a fast and reliable control of the scanning apparatus and the
excimer laser apparatus.
[0042] Furthermore, the protocoling means allows for storing
protocol information with respect to the operation of the eye
tracking apparatus, the scanning apparatus for every shot to be
fired wherein the protocol information comprises one or several of
the following data, the actual position data of the patient's eye,
the actual position data of the scanning apparatus the target
position data and any malfunction data.
[0043] FIG. 4 shows a diagram of an excimer laser eye surgery
system in particular the optical path of the pulsed beam from an
excimer laser apparatus 110 via a scanning apparatus 120 to a
patient's eye 44. More specifically, the pulsed beam from the
excimer laser apparatus is guided via a first and a second mirror
134 and 136 to the scanner block 120. The second mirror 136 is a
half mirror and allows that the laser beam of an aiming laser 132
is coaligned with a pulsed beam. The pulsed beam is guided through
a lens 138 then reflected by a first movable mirror 140, a second
movable mirror 142 and a third fixed mirror 144. The first movable
mirror is movable in one direction whereas the second movable
mirror 142 is moveable in another direction which is preferably
orthogonal to the first direction. This allows to direct the pulsed
beam to any desired position on the patient's eye 44. On the other
hand, the third fixed mirror 144 can be realized as a half-mirror
through which a physician may observe the progress during ablation
of the surface of the eye through a microscope (not shown). The use
of two small movable mirrors has the advantage that smaller mirrors
have a lower weight therefore can be brought into position in a
very short time.
[0044] The two movable mirrors are preferably provided with
integrated galvanometers for positioning the mirrors and for
providing the actual position. This allows a closed loop scanning
as described above with reference to FIGS. 2 and 3.
[0045] FIG. 4 further shows a microphone 146 which is arranged at a
distance from the treatment surface where the patient's eye is
positioned. FIG. 4 further shows a reference surface 148 next to
the patient's eye 44 to which the pulsed laser may be directed. The
microphone 146 and the reference surface 148 is used for monitoring
the pulse energy of the pulsed beam. Before starting a treatment a
series of laser pulses will be directed to the reference surfaces
148 which is preferably a PMMA plate. The microphone 146 provides a
voltage signal to the energy monitoring means 320. The energy
monitoring means compares the received voltage signal with a
reference voltage previously measured during a calibration mode.
The energy monitoring means compares the actual voltage signal with
the reference voltage signal and provides a measure for the laser
energy of the laser pulse. The system shown in FIG. 4 further
comprises shutter means 149 for providing every n-th laser pulse
from a series of laser pulses to the reference surface 148. This
has the advantage that the energy monitoring means will process
only every n-th laser pulse so that simple processing means can be
used.
[0046] The signal of the microphone can be additionally used for
determining the distance between the treatment surface and the
microphone 146. This is achieved by proving the command signal from
the eye tracking apparatus not only to the excimer laser apparatus
but also to the energy monitoring 320. A command signal triggers a
timer inside the energy monitoring means which measures the time
until when the microphone 146 receives the noise resulting from
hitting the laser pulse onto the reference surface 148. The
corresponding time delay can be used for determining the
distance.
[0047] FIG. 5 shows the timing diagram for a series of shots fired
by the excimer laser apparatus. More specifically, at a time
t.sub.1 a command signal is sent to the laser apparatus and at a
time t.sub.2 the feedback signal is received from the laser
apparatus. The time t.sub.3 indicates the time window within which
the feedback signal from the laser apparatus needs to be received.
In case the feedback signal is received within the predetermined
time t.sub.3 after the command signal is sent to the laser
apparatus at time t.sub.1 then the system is working properly.
However, if a feedback signal would not be received within the
predetermined time t.sub.3 after a command signal is sent to the
laser apparatus a malfunction has occurred and therefore the system
stops further processing of the treatment shot file.
[0048] The foregoing disclosure and description of the invention
are illustrative and explanatory thereof, and whereas changes in
the size, shape, materials, components, circuit elements, wiring
connections and contacts, as well as in the details of the
illustrated circuitry and construction and method of operation may
be made without departing from the scope of the invention.
* * * * *