Methods and systems for tracking a torsional orientation and position of an eye
Methods and systems for tracking a position and torsional orientation of a patient's eye. In one embodiment, the present invention provides methods and software for registering a first image of an eye with a second image of an eye. In another embodiment, the present invention provides methods and software for tracking a torsional movement of the eye. In a particular usage, the present invention tracks the torsional cyclorotation and translational movement of a patient's eye so as to improve the delivery of a laser energy to the patient's cornea.
1. A method for tracking an eye, the method comprising:
obtaining a first image of the eye;
processing the first image of the eye so as to identify an iris image;
processing the first iris image so as to identify a plurality of natural tissue markers separated across the iris image;
processing a second image of the eye so as to identify at least one of the plurality of markers within the second image;
determining a rotational offset between the first image of the eye and the second image of the eye using the identified markers; and
processing a third image of the eye after determining the rotational offset between the first image of the eye and the second image of the eye, and wherein the third image is processed so as to identify: (1) at least one of the previously identified plurality of markers, (2) a previously unidentified natural tissue marker, or (3) an artificial landmark within the third image
tracking the eye using the tissue marker or landmark identified by processing the third image.
2. The method of claim 1 , wherein the markers are circumferentially separated across the first iris image, and wherein a marker of the first image is not accurately identified in the second image.
3. The method of claim 2 , wherein the processing of the second image generates a false match between a region of the second image the inaccurately identified marker.
4. The method of claim 2 , wherein the rotational offset is calculated using an iterative weighted estimation using angular coordinates of the markers.
5. The method of claim 1 , wherein the markers are identified in the second image of the eye by evaluating a sum of absolute errors for corresponding block portions of the images.
6. The method of claim 1 , wherein the markers are identified in the second images by calculating a dot product of mean-subtracted block portions of the images.
7. The method of claim 1 , wherein the markers are identified in the first iris image by calculating block values within the first iris image, each block value associated with an iris image texture within a portion of the iris image.
8. The method of claim 1 , where each marker is separated from an inner iris boundary and an outer iris boundary.
9. The method of claim 1 further comprising directing a femtosecond laser toward the eye per the rotational offset.
10. The method of claim 9 wherein the femtosecond laser is configured to produce an incision in the cornea.
11. The method of claim 10 wherein the incision in the cornea is radial.
12. The method of claim 9 further comprising introducing an intraocular lens to the eye.
13. The method of claim 1 further comprising tracking the torsional movement of the eye over a period of time by monitoring the rotation offset over the period of time.
14. The method of claim 13 wherein the period of time at least comprises a time frame for delivering a femtosecond laser toward the eye and the method further comprising adjusting the femtosecond laser delivery per the tracked torsional movement.
15. The method of claim 14 wherein the femtosecond laser delivery is configured to produce a radial incision in the cornea.
16. The method of claim 14 further comprising introducing an intraocular lens to the eye.
17. The method of claim 1 further comprising directing an ultraviolet laser toward the eye per the rotational offset.
18. The method of claim 17 wherein the ultraviolet laser utilizes frequency multiplying.
19. The method of claim 17 further comprising introducing an intraocular lens to the eye.
20. The method of claim 1 , wherein the rotational offset is determined by using a plurality of identified markers in the first and second images of the eye; and wherein the third image is processed using fewer markers than the plurality of identified markers in the first and second images of the eye.
21. The method of claim 20 , wherein the third image is processed by a high speed eye tracker.