Methods and systems for tracking a torsional orientation and position of an eye

1. A laser surgery system for treatment of an eye having an iris with an iris pattern between a pupil and an outer iris boundary, the system comprising:

a computer processor configured to receive a first image of the eye from an imaging assembly of a measurement system, and an associated ablation pattern for the eye, the processor including:

an eye tracker that tracks a position of the eye under an optical axis of a laser beam; and

a torsional tracker that tracks a torsional orientation of the eye; and

an imaging device for obtaining a second image of the eye while the eye is positioned for treatment with the laser beam, the second imaging device coupled to the torsional tracker;

wherein the computer processor is configured to:

register the ablation pattern with the eye by determining a translation between the first image of the eye and the second image of the eye with reference to the outer iris boundary of the eye, and by determining a torsional rotation between the first image of the eye and the second image of the eye with reference to the iris pattern of the eye; and

adjust a delivery of the ablation pattern based on a change of position and/or torsional orientation of the eye during treatment of the eye with the laser beam.

2. The system of claim 1 wherein the computer processor is configured to register the first image with a real-time image of the eye under the optical axis of the laser beam, the imaging device transmitting the real-time image.

3. The system of claim 1 further comprising a laser coupled to the computer processor and configured to deliver the ablation pattern to the eye.

4. The system of claim 1 further comprising a wavefront measuring device that obtains the wavefront measurement, the measurement system comprising the wavefront measurement device.

5. The system of claim 1 , wherein the computer processor is configured to, when registering the ablation pattern with the eye, accommodate changes in size of the pupil induced by a difference in illumination of the eye between the first image and the second image.

6. The system of claim 5 , wherein the computer processor is configured to accommodate the changes in size of the pupil during determination of the torsional rotation by scaling the iris pattern in response to a width of the iris between the pupil and the outer iris boundary.

7. The system of claim 5 , wherein the outer iris boundary of the first image of the eye corresponds in size with the outer iris boundary of the second image of the eye despite the difference in illumination of the eye.

8. The system of claim 1 , wherein the computer processor is configured to identify a circumferentially distributed plurality of discrete markers in the pattern of the iris, and wherein the computer processor is configured to determine the torsional rotation between the first image of the eye and the second image of the eye with reference to the discrete markers.

9. The system of claim 8 , wherein the computer processor is configured to identify the discrete markers by identifying a discrete marker corresponding to each of a circumferential series of regions of the iris.

10. The system of claim 8 , wherein the torsional tracker determines the torsional orientation of the eye with reference to a subset of the markers.

11. A system for use on an eye having an iris with an iris pattern between a pupil and an outer iris boundary, the system comprising:

a first imaging assembly configured to acquire a first image of the eye under a first illumination, the eye in the first image having a first pupil size;

a second imaging assembly configured to acquire a second image of the eye under a second illumination, the eye in the second image having a second pupil size;

a computer processor in communication with the first imaging assembly and the second imaging assembly so as to receive the first image of the eye and the second image of the eye, the computer processor configured to register the first and second images of the by determining a translation between the first image of the eye and the second image of the eye with reference to the outer iris boundary of the eye, and by determining a torsional rotation between the first image of the eye and the second image of the eye with reference to the iris pattern of the eye.

12. The system of claim 11 wherein the computer processor is further configured to register the first image with a real-time image of the eye so as to allow adjustment while a treatment is directed toward the eye, the second imaging assembly transmitting the real-time image.

13. The system of claim 11 further comprising a laser coupled to the computer processor and configured to deliver an ablation pattern of laser energy to the eye.

14. The system of claim 11 further comprising a wavefront measuring device that obtains a wavefront measurement, the wavefront measurement device being coupled to the first imaging device so that the pattern of laser energy is associated with the first image of the eye.

15. The system of claim 11 , wherein the computer processor is configured to, when registering the ablation pattern with the eye, accommodate changes in size of the pupil induced by a difference between the first illumination and the second illumination.

16. The system of claim 15 , wherein the computer processor is configured to accommodate the changes in size of the pupil during determination of the torsional rotation by scaling the iris pattern in response to a width of the iris between the pupil and the outer iris boundary.

17. The system of claim 15 , wherein the outer iris boundary of the first image of the eye corresponds in size with the outer iris boundary of the second image of the eye despite the difference in illumination of the eye.

18. The system of claim 11 , wherein the computer processor is configured to identify a circumferentially distributed plurality of discrete markers in the pattern of the iris, and wherein the computer processor is configured to determine the torsional rotation between the first image of the eye and the second image of the eye with reference to the discrete markers.

19. The system of claim 18 , wherein the computer processor is configured to identify the discrete markers by identifying a discrete marker corresponding to each of a circumferential series of regions of the iris.

20. The system of claim 18 , further comprising a torsional tracker configured to determine a torsional orientation of the eye in real-time with reference to a subset of the markers.