This invention relates to a method for estimating the optical power of corrective lenses in a pair a eyeglasses worn by a spectator, characterized in that it comprises the following steps: acquire two consecutive images of this spectator's face located in front of a means for acquiring these two images, one of these images being acquired with eyeglasses and the other without, calibrate one of the two acquired images with respect to the other, identify the position of the iris of each eye in each image, evaluate the size magnification or size reduction of each imaged iris, and estimate the optical power of the corrective lenses based on the evaluated magnification or reduction.