Method and device for determining a minimum value of laser energy necessary for the formation of a gas bubble

A device for causing a femtosecond L.A.S.E.R. source to emit a minimum value of L.A.S.E.R. energy necessary to form a gas bubble in at least one elementary area extending in a cutting plane of an ocular tissue, the device including:

• an imaging system for the acquisition of images;
• and
• a data processing unit configured to execute a method comprising:
• a) Receiving a reference image of the ocular tissue, wherein the reference image is an Optical Coherence Tomography (OCT) image, said reference image having been acquired by the imaging system prior to the emission of a plurality of L.A.S.E.R. beams able to focus at least at one sampling point of each elementary area, each L.A.S.E.R. beam having a respective energy different from the other L.A.S.E.R. beams of the plurality,
• b) Receiving at least one current image of the ocular tissue, wherein the at least one current image is an OCT image, each current image having been acquired by the imaging system subsequently to the emission of at least one L.A.S.E.R. beam of the plurality of L.A.S.E.R. beams,
• then for each elementary area:
• c) Detecting at least one gas bubble formed in the elementary area by comparing the reference image with each current image, each gas bubble being associated with a respective L.A.S.E.R. beam, wherein the step of detecting comprises, for each current image:
• calculating, for each sampling point, an intensity variation of backscattered light received by the imaging system between the pixels of the respective current image and the pixels of the reference image, and
• comparing this calculated intensity variation with a threshold value to identify the formation of a gas bubble if the calculated intensity variation is greater than the threshold value,
• d) Determining, based on the at least one gas bubble, a minimum value of energy necessary for the formation of a gas bubble in the elementary area, and
• e) Causing the femtosecond L.A.S.E.R source to emit radiation with the determined minimum value of energy.

A method for causing a femtosecond L.A.S.E.R. source to emit a minimum value of L.A.S.E.R. energy necessary to form a gas bubble in an elementary area extending in a cutting plane of an ocular tissue, wherein the method comprises:

• acquiring a reference image of the ocular tissue, wherein the reference image is an Optical Coherence Tomography (OCT) image;
• emitting, after acquiring the reference image, a plurality of L.A.S.E.R. beams, wherein each L.A.S.E.R. beam of the plurality of L.A.S.E.R. beams is focused on a different sampling point of the elementary area, and wherein each L.A.S.E.R. beam of the plurality of L.A.S.E.R. beams has a different energy value from the other L.A.S.E.R. beams of the plurality of L.A.S.E.R. beams;
• acquiring, after emitting the plurality of L.A.S.E.R. beams, a current image of the ocular tissue, wherein the current image is an OCT image;
• detecting at least one gas bubble formed in the elementary area by comparing the reference image with the current image, each detected gas bubble being associated with a L.A.S.E.R. beam of the plurality of L.A.S.E.R. beams, wherein the detecting comprises:
• calculating, for each sampling point of the elementary area, an intensity variation of backscattered light between the pixels of the current image and the pixels of the reference image,
• comparing this calculated intensity variation with a threshold value, and
• identifying the formation of a gas bubble at a sampling point if the calculated intensity variation for that sampling point is greater than the threshold value;
• determining based on the at least one detected gas bubble, a minimum value of energy necessary for the formation of a gas bubble in the elementary area;
• and
• causing the femtosecond L.A.S.E.R. source to emit radiation with the determined minimum value of energy.