The invention relates to a goniometer that enables precise marking of the desired ocular axis in the phase immediately after surgery for the treatment of astigmatism. It essentially consists of two circular, transparent discs, one of which is at least axially stationary, in which the angles from 0° to 180° are marked, which are aligned with the angles from 0° to 180° of the patient's eye; and the other one of which is movable both angularly and axially, with a reference mark (9) and moving rigidly connected to a marking part (12), impregnated with die, which is responsible for marking the eye. Not only does the device make it possible to carry out said marking in a precise and comfortable manner, it also makes it possible to measure the angle of toric lenses already implanted.