Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Reexamination Certificate
2000-04-07
2001-11-27
Manuel, George (Department: 2873)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
C606S005000
Reexamination Certificate
active
06322216
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is generally related to measurements of the eye, and in a particular embodiment, provides methods, systems, and devices for measuring a position of an eye during laser eye surgery.
Laser-based systems are now used in opthalmological surgery on corneal tissues to correct vision defects. These systems use lasers to achieve a desired change in corneal shape, with the laser removing thin layers of corneal tissue using a technique generally described as ablative photodecomposition. Laser eye surgery techniques are useful in procedures such as photorefractive keratectomy, photothcrapeutic keratectomy, laser in situ keratomileusis (LASIK), and the like.
The ability to track or follow movements of a patient's eye is recognized as a desirable feature in laser eye surgery systems. Movements of the eye include both voluntary movements and involuntary movements. In other words, even when the patient is holding “steady” fixation on a visual target, eye movement still occurs. Tracking of the eye during laser eye surgery has been proposed to avoid uncomfortable structures which attempt to achieve total immobilization of the eye. Tracking may enhance known laser eye surgery procedures, and may also facilitate new procedures, such as treatment of irregular astigmatism.
A variety of structures and techniques have been proposed for both tracking of eye movements and scanning of a laser beam across the corneal tissue. An exemplary linear array eye-tracking system and method are described in co-pending U.S. patent Ser. No. 09/365,428 filed on Aug. 2, 1999, the full disclosure of which is incorporated herein by reference. Other systems for tracking movement of an eye, particularly for use in laser eye surgery, arc described in U.S. Pat. Nos. 5,865,832; 5,632,742; and 4,848,340, the full disclosures of which are also incorporated herein by reference.
An exemplary “offset imaging” scanning system for selective ablation and sculpting of corneal tissue is described in European Patent Application Publication No. 628298, the full disclosure of which is hereby incorporated by reference. This offset imaging system allows a relatively laser beam to be accurately directed on to a surface of a corneal tissue so as to mitigate myopia, hyperopia, astigmatism, and combinations of these ocular defects, particularly when the scanning or offset imaging system is combined with one or more variable apertures for profiling the laser beam. As described in co-pending U.S. patent Ser. No. 09/274,499, filed on Mar. 23, 1999, entitled Multiple Beam Sculpting System and Method (the disclosure of which is incorporated herein by reference), the laser beam may ideally be separated into a plurality of beamlets to minimize discontinuities adjacent the ablation edges. Alternative scanning systems are described in the following U.S. Patents, which are also incorporated herein by reference: U.S. Pat. Nos. 5,556,395; 5,683,379; 5,391,165; and 5,637,109.
Although known scanning systems have proven both effective and safe for sculpting the cornea to improve vision, work in connection with the present invention has shown that integrating eye-tracking capabilities into known laser eye surgery systems can present significant challenges. For example, known laser eye surgery systems often include an optical imaging path which is co-axial with, and shares optical elements of the laser delivery system. While it has previously been proposed to utilize imaging-based tracking systems, this shared optical path can limit the available imaging contrast, and therefore the effectiveness of the tracking arrangement.
In light of the above, it would be desirable to provide improved laser eye surgery systems, devices, and methods. It would also be desirable to provide improved eye-tracking techniques, particularly for use with laser eye surgery, with the tracker ideally providing both lateral tracking and information regarding the position of the eye along the optical axis. It would be especially beneficial if these improvements provided enhanced tracking effectiveness and allowed the incorporation of eye-tracking capabilities into known laser eye surgery systems, ideally without having to modify the laser delivery system.
SUMMARY OF THE INVENTION
The present invention generally provides improved laser eye surgery and/or eye tracking systems, methods, and devices. The invention makes use of two image capture devices, generally with both image capture devices disposed off the optical axis of the eye and/or the optical axis of any laser delivery system. This provides an enhanced imaging contrast for image capture devices such as cameras having a charge-couple device (CCD), particularly when using infrared imaging to track a pupil of the eye. The two off-axis cameras may be used independently to track movements of the pupil along two orthogonal lateral axes of the eye (often called X-Y tracking), and may also indicate a position of the eye along the optical/treatment or Z axis.
In a first aspect, the invention provides an apparatus for sculpting a corneal tissue of an eye so as to effect a desired change in a patient's vision. The apparatus comprises an energy delivery system selectively directing an energy stream toward the corneal tissue. First and second image capture devices are oriented toward the eye. A processor couples the image capture devices to the energy delivery system. The energy delivery system laterally deflects the energy stream along a first axis in response to movement of the eye sensed by the first image capture device. The energy delivery system also laterally deflects the energy stream along a second axis in response to movement of the eye sensed by the second image capture device.
The energy stream often defines a treatment axis, the eye generally being disposed within first and second fields of view of the first and second image capture devices, respectively. These fields of view are preferably angularly offset from the treatment axis, and will typically be circumferentially offset from each other about the treatment axis, often by an angle of about 90°.
Where the first image capture device is used to measure movement of the eye along an X axis of the eye, the first image capture device will preferably be disposed along an X-Z plane and angularly offset from the Y-Z plane. Similarly, where the second image capture device is used to sense movement of the eye along the Y axis of the eye, the second image capture device will often be disposed along the Y-Z plane and angularly offset from the X-Z plane. The offset angles of the first and second image capture device will typically be in a range from about 10° to 70°, the offset angle often being from about 15° to about 65°, preferably being from about 20° to about 50°, and more preferably being from about 25° to about 45°. The exemplary embodiment has offset angles of about 27°.
In another aspect, the invention provides an apparatus for sensing motion of an eye. The eye has an optical axis and first and second lateral optical axes. The apparatus comprises a first tracker with a first image capture device and a first processor module. The first image capture device is oriented towards the eye along a first imaging axis. The first imaging axis is angularly offset from the optical axis. The first processor module generates a first signal indicating lateral movement of the eye relative to the first imaging axis. A second tracker with a second image capture device and a second processor module is also provided. The second image capture device is oriented toward the eye along a second imaging axis. The second imaging axis is angularly offset from the optical axis and displaced circumferentially from the first imaging axis relative to the optical axis. The second processor module generates a second signal indicating lateral movement of the eye relative to the second imaging axis.
A third processor module can be coupled to the first and second trackers. The third processor module calculates lateral displacement of the eye along the fir
Munnerlyn Charles R.
Yee Kingman
Manuel George
Thompson Lynn M.
Townsend & Townsend & Crew LLP
VISX, Inc
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