Pigeon-Cantonnet stereoscope

Description Of Item: This is a stereoscope for clinical ophthalmic investigation and treatment of strabismus and other disorders of binocular vision, originally devised c 1904. It consists of three black card boards, 230 x 320 mm, attached together as in a book, with a plane mirror fixed on one face of the middle leaf and targets can be placed and moved around on the inside of the other two leaves. The inside surface of each of the outer boards has a numeric linear scale. The central leaf acts as a septum and one eye sees one target directly while the other eye sees the other by reflection in the mirror. The angle of convergence may be controlled by the angle between the leaves, which can be adjusted to one of two positions by a cord attached to the edges of the outer leaves with a metal loop in the middle of the cord to attach it to one of two positions on the middle leaf. A plane mirror is fixed on one side of the middle board and has a truncated triangular shape with a hinged metal flap and a clip to cover the mirror when the instrument is not in use. The outside of one outer flap is marked THE PIGEON-CANTONNET / STEREOSCOPE / MADE IN ENGLAND / E. O. Co. There is one of a pair of stereocards with the instrument.