A device (100) enabling automatic detection of the index marks of an ophthalmic lens (10), includes a support (110) which is adapted in such a way as to receive the lens, and, on each side of the support, first elements (120) for the illumination of the ophthalmic lens installed on the support, and first elements (130) for analysis and acquisition of the light transmitted by the lens. The device also includes an activatable and deactivatable pattern filter (140) arranged between the first illuminating elements and the support.