Varying a numerical aperture of a laser during lens fragmentation in cataract surgery
Some embodiments disclosed here provide for a method fragmenting a cataractous lens of a patient's eye using an ultra-short pulsed laser. The method can include determining, within a lens of a patient's eye, a high NA zone where a cone angle of a laser beam with a high numerical aperture is not shadowed by the iris, and a low NA zone radially closer to the iris where the cone angle of the laser beam with a low numerical aperture is not shadowed by the iris. Laser lens fragmentation is accomplished by delivering the laser beam with the high numerical aperture to the high NA zone, and the laser beam with the low numerical aperture to the low NA zone. This can result in a more effective fragmentation of a nucleus of the lens without exposing the retina to radiation above safety standards.
1. A laser eye surgery control system comprising:
a controller comprising one or more physical processors;
a fragmentation module configured to use the one or more physical processors to determine a laser fragmentation treatment plan by determining:
a high numerical aperture zone in a patient's eye, the high numerical aperture zone comprising a region where a cone angle of a laser beam with a high numerical aperture is not shadowed by an iris of the patient's eye; and
a low numerical aperture zone in the patient's eye, the low numerical aperture zone comprising a region where the cone angle of the laser beam with a low numerical aperture is not shadowed by the iris, the low numerical aperture being lower than the high numerical aperture, wherein at any given depth within a depth range along a central axis of the patient's eye, the low numerical aperture zone is radially closer, on average, to the iris of the patient's eye than the high numerical aperture zone; and
a laser control module in communication with a laser source and configured to:
control the laser source to deliver the laser beam having the high numerical aperture to the high numerical aperture zone without delivering the laser beam with the high numerical aperture to the low numerical aperture zone; and
control the laser source to deliver the laser beam having the low numerical aperture to the low numerical aperture zone, wherein at any given depth within the depth range along the central axis of the patient's eye, the laser beam having the high numerical aperture is delivered to the high numerical aperture zone and the laser beam having the low numerical aperture is delivered to the low numerical aperture zone.
2. The control system of claim 1 , further comprising an image processing module in communication with an imaging system, the image processing module configured to receive an image of the patient's eye and to determine, using the at least one physical processor and based on the received image, a total laser treatment region in a lens of the patient's eye.
3. The control system of claim 2 , wherein the image processing module is configured to determine, using the at least one physical processor and based on the received image, a size of a pupil of the patient's eye and a relative location and size of the lens of the patient's eye.
4. The control system of claim 3 , wherein the fragmentation module is configured to receive the size of the pupil and the size of the lens of the patient's eye from the image processing module, and to use the size of the pupil and the size of the lens to determine the high numerical aperture zone and the low numerical aperture zone.
5. The control system of claim 4 , wherein the high numerical aperture zone is configured to maximize a volume in the lens where the laser beam having the high numerical aperture is used to perform laser lens fragmentation, wherein a maximum radius of the high numerical aperture zone from the center of the lens of the patient's eye is determined by a shadowing effect caused by the iris of the patient's eye.
6. The control system of claim 2 , wherein the imaging system is an optical coherence tomography system.
7. The control system of claim 2 , wherein the fragmentation module is further configured to determine a safety zone comprising a region of the patient's eye that will not receive focused laser radiation, the safety zone being, on average, closer to the iris of the patient's eye than the low numerical aperture zone,
wherein the high numerical aperture zone, the low numerical aperture zone, and the safety zone occupy, in aggregate, approximately the entirety of the total laser treatment region.
8. The control system of claim 7 , wherein the safety zone is a region of the lens of the patient's eye comprising a volume that is at least about 0.5 mm inwards from an edge of an iris of the patient's eye and at least about 0.5 mm from an anterior lens capsule and at least about 0.5 mm from a posterior lens capsule.
9. The control system of claim 1 , wherein the fragmentation module is further configured to determine a third zone of a lens of the patient's eye, the third zone being located between the high numerical aperture zone and the low numerical aperture, and
wherein the laser control module is further configured to control the laser source to deliver the laser beam having a third numerical aperture to the third zone, the third numerical aperture being less than the high numerical aperture and greater than the low numerical aperture.
10. The control system of claim 1 , wherein the high numerical aperture is greater than or equal to 0.25.
11. The control system of claim 1 , wherein the low numerical aperture is less than or equal to 0.15.
12. The control system of claim 1 , wherein the laser control module is further configured to control the laser source to track a position of the laser beam with a laser scanning system of the laser source.
13. The control system of claim 1 , wherein the laser control module is further configured to control the laser source to adjust a set of lens elements of the laser source to adjust a numerical aperture of the laser beam when delivery of the laser beam passes between the high numerical aperture zone and the low numerical aperture zone.