Background  

Cyclic strabismus is a rare disorder in which strabismus and orthotropia regularly alternate over a period of mostly 48 h. It may occur spontaneously, upon squint surgery, or in association with lesions of the central nervous system. In most cases the deviations are convergent.

Methods  

Clinical case report.

Results  

A 34-year-old woman with bilateral recurrent ocular myositis for 2 years had developed cyclic vertical deviation 6 months after clinical remission. A hypotropia of the left eye alternated with an orthotropia, following a 48-h rhythm. Three months after recession of the inferior rectus muscle the alternating squint had disappeared.

Discussion  

The aetiology of cyclic eye deviations, most of them occurring in a constant rhythm, is not known. The association with lesions of the central nervous system indicates a primary central dysregulation of a “biological clock”. Their well-known occurrence, however, after squint surgery and, as in the present case, after orbital myositis, suggests that alteration of peripheral structures may contribute to a central dysregulation. Squint surgery seems to be the treatment of choice, even in rare cases with vertical deviations.