A method and apparatus for blocking an unfinished optical lens member on a blocker for manufacturing an optical lens from the unfinished optical lens member, the latter being provided with a finished surface having a first reference frame, the blocker having a second reference frame, includes: placing the unfinished optical lens member on the blocker; measuring the relative positioning of the first reference frame of the finished surface of the placed unfinished lens member with respect to the positioning of the second reference frame of the blocker; comparing the measured relative positioning with a predetermined relative positioning to determine a relative positioning shift; moving at least the blocker and/or the lens member to change the relative positioning of the first reference frame with respect to the second reference frame to compensate for the relative positioning shift; and blocking the unfinished lens member on the blocker at the changed relative positioning.