Method of preparing an ophthalmic lens with special machining of its engagement ridge

A method of preparing an ophthalmic lens (20) for mounting in a surround (11) of an eyeglass frame (10), the method comprising:

• an acquisition step of acquiring a first longitudinal profile (12) of said surround (11) and an orientation parameter of said first longitudinal profile (12) relative to a horizon line (A2) or to a verticality line (A3) of said surround (11) about an orientation axis (A1) that is substantially perpendicular to a mean plane of said surround (11);
• and
• an edging step of edging the ophthalmic lens (20) with an engagement ridge (24) being formed on its edge face (23), the ridge being generally profiled with a desired section and extending along a second longitudinal profile (27) that is derived from the first longitudinal profile (12) and whose orientation relative to the ophthalmic lens (20) about said orientation axis (A1) is derived from said orientation parameter;
• wherein the method includes a determination step of determining at least one singular portion (Z1-Z56) of the second longitudinal profile (27) as a function of said orientation parameter;
• and
• in that during the edging step, the engagement ridge (24) is formed so that the second longitudinal profile (27) is derivable from the first longitudinal profile (12) by a mathematical relationship that is different over said singular portion (Z1-Z56) than for the remainder of the second longitudinal profile (27) in such a manner that the mean radius of curvature of said singular portion (Z1-Z56) of the second longitudinal profile (27) is increased relative to the mean radius of curvature that said singular portion (Z1-Z56) would have presented if said mathematical relationship had been the same over said singular portion (Z1-Z56) as over the remainder of the second longitudinal profile (27).