System and method for plasma-mediated modification of tissue

1. A method for cataract surgery on an eye of a patient, comprising:

scanning a first focus position of a first pulsed laser beam at a first pulse energy in a first scanning pattern to photodisrupt a tissue structure of a lens of the eye with a plurality of pulses of the first laser beam to form a cut within the lens, the cut defining a two-dimensional cut surface formed by the scanned first focus positions of the first pulsed laser beam, the two-dimensional cut surface extending in a depth direction of the lens and being short of reaching an edge of the lens and further being short of reaching a posterior surface of the lens, and being configured to divide the lens into two or more segments which are attached to each other in regions adjacent the edge of the lens; and

thereafter, completely separating the two or more segments of the lens from each other by scanning a second focus position of a second pulsed laser beam having a second pulse energy higher than the first pulse energy in a second scanning pattern, wherein the scanned second focus positions of the second pulsed laser beam are disposed on the two-dimensional cut surface which have been formed by the scanned first focus positions of the first laser beam, wherein at least some of the scanned second focus positions are located deeper than some of the scanned first focus positions and shallower than some other scanned first focus positions, wherein a plurality of pulses of the second laser beam further photodisrupt the tissue structure of the lens along the two-dimensional cut surface formed by the scanned first focus positions of the first laser beam to drive the segments apart from each other,

wherein the completely separating step comprises:

scanning the second focus position of the second pulsed laser beam in a portion of the second scanning pattern;

using an imaging system or an optical coherence tomography (OCT) system, monitoring bubble creation and tissue displacement resulting from the scanning of the second focus position of the second pulsed laser beam in the portion of the second scanning pattern;

based on the monitored bubble creation and tissue displacement, determining whether a predefined level of tissue separation of the lens has occurred; and

if the predefined level of tissue separation of the lens has not occurred, scanning the second focus position of the second pulsed laser beam in another portion of the second scanning pattern.

2. The method of claim 1 , wherein the first pulse energy is between one-half microjoule and 50 microjoules.

3. The method of claim 1 , wherein the second pulse energy is between 50 microjoules and 5,000 microjoules.

4. The method of claim 1 , wherein the pulses of the first laser beam scanned in the first scanning pattern have a pulse duration between 100 femtoseconds and 10 picoseconds.

5. The method of claim 1 , wherein the pulses of the second laser beam scanned in the second scanning pattern have a pulse duration between 10 picoseconds and 10 nanoseconds.

6. The method of claim 1 , wherein a pulse duration of the pulses of the second laser beam scanned in the second scanning pattern is longer than a pulse duration of the pulses of the first laser beam scanned in the first scanning pattern.

7. The method of claim 1 , wherein a spacing between the second focus positions of adjacent pulses of the second laser beam in the second scanning pattern is larger than a spacing between the first focus positions of adjacent pulses of the first laser beam in the first scanning pattern.