[Alternate day squint (author's transl)].

3 cases of cyclical convergent strabismus (48 hour rhythm) were investigated. In contrast to intermittant strabismus, cyclical strabismus is not fatigue dependant. An alteration in the rhythm of the cyclical esotropia was produced by wearing prisms, red glasses or occlusion for several days. This observation indicates that centrally inaugurated rhythm processes can be altered by peripheral sensory influcences. In the case of our third patient, who was not operated upon, there was a cyclical strabismus which persisted from the age of 4 to 19 years, before changing to a constant convergent strabismus. The other two patients, following strabismus surgery, had a small angle esophoria with good fusion and stereopsis.