The invention concerns a method for determining a minimum value of L.A.S.E.R. energy necessary to form, by using a LASER source, a gas bubble in an ocular tissue, the method comprising: acquisition (200) of a reference image, emission (210) at a sampling point, of a L.A.S.E.R. beam, acquisition (220) of one (or more) current image(s) of the ocular tissue, detection (230) of one (or more) gas bubble(s) by comparing the current image(s) and the reference image, determination (240, 250) of the minimum value based on the detected gas bubble(s).