Abstract
Improved laser eye surgery and/or eye tracking systems, methods, and devices make use of two image capture devices, generally with both image capture devices disposed off the optical axis of the eye and/or any laser delivery system. This provides an enhanced imaging contrast for an imaging capture device such as a camera with 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 or Z axis.
Patent number: 6322216
Filing date: Apr 7, 2000
Issue date: Nov 27, 2001
Inventors: Kingman Yee, Charles R. Munnerlyn
Assignee: VISX, Inc
downloadWhat is claimed is:
1. An apparatus for sculpting a corneal tissue of an eye so as to effect a desired change in a patient's vision, the apparatus comprising:
- an energy delivery system selectively directing an energy stream along a treatment axis toward the corneal tissue;
- first and second image capture devices oriented toward the eye, each image capture device having an imaging axis angularly offset from the treatment axis by between about 10 and 70 degrees; and
- a processor coupling the image capture devices to the energy delivery system so that 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, and so that the energy delivery system laterally deflects the energy stream along a second axis in response to movement of the eye sensed by the second image capture device.
2. The apparatus of claim 1, further comprising a laser generating the energy stream, the energy stream comprising a laser beam adapted for ablating the corneal tissue.
3. The apparatus of claim 2, wherein the energy delivery system comprises at least one offset imaging lens along an optical path of the laser beam, the imaging lens moving laterally relative to the laser beam in response to the signals from the first and second image capture devices.
4. The apparatus of claim 1, further comprising an infrared light source oriented toward the eye, wherein each image capture devices comprises a CCD sensitive to infrared light reflected by an iris and sclera of the eye, and wherein the processor comprises first and second tracker modules associated with the first and second image capture devices, respectively, the first and second tracker modules determining a position of a centroid of a pupil of the eye from the reflected infrared light.
5. An apparatus for sculpting a corneal tissue of an eye so as to effect a desired change in a patient's vision, the apparatus comprising:
- an energy delivery system selectively directing an energy stream along a treatment axis toward the corneal tissue, wherein the energy stream defines a treatment axis;
- first and second image capture devices oriented toward the eye, wherein the eye is disposed within first and second fields of view of the first and second image capture devices, respectively, the fields of view being angularly offset from the treatment axis; and
- a processor coupling the image capture devices to the energy delivery system so that 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, and so that the energy delivery system laterally deflects the energy stream along a second axis in response to movement of the eye sensed by the second image capture device.
6. The apparatus of claim 5, wherein the second field of view is offset circumferentially from the first field of view about the treatment axis.
7. The apparatus of claim 6, wherein the second field of view is offset circumferentially by about 90 degrees from the first field of view about the treatment axis.
8. The apparatus of claim 6, the eye defining an X-Y-Z coordinate system with a Z axis along an optical axis of the eye, and X-Z plane along the first axis, and a Y-Z plane along the second axis, wherein the first image capture device is disposed along the Y-Z plane and off the X-Z plane, and wherein the second image capture device is disposed along the X-Y plane and off the Y-Z plane.
9. The apparatus of claim 8, wherein the processor generates a signal indicating a distance between the energy delivery system and a feature of the eye in response to lateral positions of the feature within the first and second fields of view as sensed by the first and second image capture devices.
10. An apparatus for sensing motion of an eye, the eye having an optical axis and first and second lateral optical axes, the apparatus comprising:
- a first tracker with a first image capture device and a first processor module, the first image capture device having a first imaging optical train oriented toward the eye along a first imaging axis and generating a first image, the first imaging axis angularly offset from the optical axis, the first processor module generating a first signal indicating lateral movement of the eye relative to the first imaging axis in response to the first image; and
- a second tracker with a second image capture device and a second processor module, the second image capture device having a second imaging optical train oriented toward the eye along a second imaging axis and generating a second image, the second imaging axis angularly offset from the optical axis and displaced circumferentially from the first imaging axis relative to the optical axis, the second processor module generating a second signal indicating lateral movement of the eye relative to the second imaging axis in response to the second image.
11. The apparatus of claim 10, further comprising a third processor module coupled to the first and second trackers, the third processor module calculating lateral displacement of the eye relative to the first and second lateral optical axes from the first and second signals.
12. The apparatus of claim 10, further comprising a laser directing a laser beam along the optical axis toward the eye so as to ablate corneal tissue of the eye to effect a predetermined change in an optical characteristic of the eye.
13. A method for sensing movement of an eye having an optical axis and first and second lateral axes, the method comprising:
- sensing movement of the eye along the first lateral axis with a first imaging capture device, the first image capture device disposed along a first imaging path offset from the optical axis by an angle in the range from about 10 degrees to about 70 degrees; and
- sensing movement of the eye along the second lateral axis with a second imaging capture device disposed along a second imaging path offset from the optical axis by an angle in the range from about 10 degrees to about 70 degrees, the second imaging path displaced circumferentially about the optical axis relative to the first imaging path.
14. The method of claim 13, further comprising directing a pattern of laser energy toward the eye so as to effect a desired change in an optical characteristic of the eye, and laterally displacing the laser energy in response to the sensed movement of the eye from the first and second image capture devices to enhance alignment between the pattern and the eye when the eye moves.
15. The method of claim 14, wherein the laser energy is laterally displaced in response to sensed voluntary movements of the eye or head, and wherein rapid saccadic movements of the eye are not tracked.
16. The method of claim 13, further comprising determining positional information of the eye along the optical axis using signals from at least one of the image capture devices.