Surgery – Instruments – Light application
Reexamination Certificate
2001-03-26
2004-11-16
Shay, David M. (Department: 3739)
Surgery
Instruments
Light application
C606S005000, C606S010000, C606S013000, C606S017000
Reexamination Certificate
active
06817998
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to laser surgery apparatus and methods adapted for use, for example, in the monitoring of laser systems used in ophthalmic laser surgery.
BACKGROUND OF THE INVENTION
Laser systems have been used in ophthalmic surgery for modifying the cornea of the patient. Systems such as shown in U.S. Pat. No. 4,729,372 to L'Esperance contemplate the controlled ablation of the cornea of the patient with a pulsed excimer laser. Operations performed with the system include corneal transplants and keratotomics.
The application of laser light to the cornea may be controlled by spot scanning of the cornea or by the use of masks. As shown in U.S. Pat. No. 5,108,388 to Trokel, the masks may, for example, employ slits or holes. Repeated scanning or pulsing through properly selected masks are employed to reshape or reprofile the curvature of the cornea to treat myopic or hyperopic conditions. The system can also be used, for example, to remove corneal sections for corneal replacements or transplants.
Three types of laser vision correction surgery techniques are known in the art: broad beam, slit scanning and spot scanning. Broad beam systems use a relatively large beam (e.g. 6.0 to 8.0 mm) pulsed at a relatively low pulse rate (e.g. 10 to 50 Hz). The spot delivered to the cornea may be, for example, from ½ mm to 8 mm in diameter depending on the iris opening of the system set to various positions in accordance with a treatment sequence for the patient. Spot scanning systems also called “flying spot” scanners typically employ reciprocating or rotating optical devices to make a series of overlapping laser shots, that for example, spiral out from the center of the cornea. Spot scanning systems use a relatively small spot (e.g. 1 to 2 mm in diameter). A typical treatment using a spot scanning system may require several thousand shots at 50 to 200 Hz. In a slit scanning laser, the laser beam is focused through a slit in a rotational device. The slit may be gradually enlarged to increase the ablated area on the cornea. Various scanning systems are described, for example, in U.S. Pat. No. 6,136,012 to Chayet et al., which is hereby incorporated by reference.
A system used by applicant for performing ophthalmic laser surgery is shown in FIG.
1
. The system includes an Excimer laser
10
such as a COMPex 201 Excimer laser. An optical rail
12
contains optical elements for controlling the laser pulses and delivers spatially modulated pulses to a shuttling device
14
, which acts as a selectively positionable turning mirror, for directing the laser pulses to a selected one of the two surgical stations,
16
and
18
. The system allows surgery to be performed on one patient while a second patient is readied, and improves the utilization efficiency of the operating room, laser and optical rail.
FIGS.
2
(
a
) and (
b
) are vertical and horizontal cross-sectional views and ray traces of an optical path which may be used in the system of
FIG. 1
to deliver pulses from the laser
10
′ to the cornea of the patient at
20
. A light beam from the laser is shaped and focused by a series of lenses
22
,
24
and
26
. A beam homogenizer
28
is located next in the optical path as shown. A spatial modulator
30
provides beam dimensions and orientations in accordance with predetermined treatment parameters appropriate for the surgery required by the patient. The spatial modulator may include a conventional iris and variable, slit mask(s) as well as controls for changing the axis of orientation of the mask(s). These systems are motor driven on command from a treatment computer containing a treatment algorithm into which the treatment parameters have been programmed.
The shuttling turning mirror
32
selectively directs the laser beam to one or the other surgical stations along one of the system arms
34
or
36
shown in FIG.
1
. An imaging lens
38
is located in each arm. Pulses from the imaging lens are reflected by end turning mirror
40
toward the target area
42
on the patient's cornea.
It is important that pulses delivered to the cornea have the appropriate energy to ensure that the reprofiling, cutting or ablation produced is consistent with the prescribed treatment for the patient. Systems of the type shown in
FIG. 2
have employed photo detectors selectively positionable in the main optical path of the system at the end turning mirror for the purpose of calibrating or adjusting the energy delivered by the system during a preliminary calibration phase. See U.S. Pat. No. 5,772,656 to Kloptek.
Other control systems have been proposed such as disclosed in U.S. Pat. No. 4,941,093 to Marshall et al., which includes a measurement device to measure the cornea surface profile and a feedback control system to control the laser operation in accordance with the measured and desired profiles. U.S. Pat. No. 5,423,801 to Marshall et al. discloses further control of the laser by a measurement signal from a beam-shaping means and/or cornea while it is exposed to irradiation by the laser. U.S. Pat. No. 4,973,330 to Azema et al. discloses a photo detector associated with a semi-transparent mirror, which is intended to furnish a treatment computer with information relative to the energy of the pulses exiting the laser before the laser beam reaches the controlling device. A laser calibration device is shown in U.S. Pat. No. 5,464,960 to Hall et al. which employs a phantom cornea with superimposed thin films of alternating colors. U.S. Pat. No. 5,984,916 to Lai discloses a surgical laser system with a feedback system for controlling the treatment laser beam.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a more efficient and reliable technique for monitoring laser surgery, including broad beam, slit scanning and spot scanning systems.
It is another object of the present invention to monitor the energy of actual laser pulses used in the ophthalmic laser surgery as they exit the optical rail.
It is another object of the present invention to monitor a sequence of laser pulses of varying beam dimensions and locations used in ophthalmic laser surgery.
It is another object of the present invention to provide a parallel, fail-safe system for detecting discrepancies between a programmed treatment and the laser pulses actually administered to the cornea of the patient.
These and other objects and features will be apparent from the following description of the present invention contained herein.
The present invention relates to methods for laser surgery and particularly for the modification of the cornea of a patient with a laser system in accordance with treatment parameters appropriate for the patient and for continuously verifying that a predetermined sequence of laser pulses of correct energy are being delivered to the cornea of the patient. In practicing the method, pulses of laser light are generated and controlled. The controlled pulses are simultaneously directed to the cornea of the patient and to a photo detector. Advantageously, the system uses a beam splitter for this purpose. The beam splitter is the last optical element in the optical path leading to the cornea of the patient. An output signal of the photo detector is converted into a value representative of the light energy delivered to the cornea of the patient. Alternatively, the photo detector may be a two-dimensional array of photo sensing cells capable of producing signals indicative of the spacial energy distribution of the treatment pulses. Such an array may, for example, be a CCD or CMOS device.
Light energy values may be compared to a reference values derived from system calibration information and from the treatment parameters for the patient. An indication of the performance of the laser system is provided in response to this comparison. When a two-dimensional detector array is used, a histogram may be produced, displayed and stored showing the amount of energy delivered to incremental areas of the cornea over selected time intervals.
In preferred embo
Burns Doane Swecker & Mathis L.L.P.
Shay David M.
LandOfFree
Method and apparatus for monitoring laser surgery does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for monitoring laser surgery, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for monitoring laser surgery will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3357162