Oculomotor paresis with cyclic spasms (OPCS) is a rare and usually congenital disorder. It typically presents at birth or within
the first 2 years of life. Acquired OPCS resulting from aneurysm compression on the nerve and after irradiation therapy has been
reported. OPCS is characterized by unilateral third nerve paresis with periodic spasms causing eyelid elevation, miosis, and
contraction of 1 or more of the extraocular muscles innervated by the third nerve. Here we report four patients with this rare ocular
condition and propose possible mechanisms and differential diagnoses for their presentation. In case of patient #4 the symptoms
secondary to gamma knife radiosurgery is confusingly similar to that of Ocular neuromyotonia (ONM). The association of COPS
and gamma knife radiosurgery is hitherto unreported in the literature. It seems likely that COPS may share some similarity on
peripheral mechanisms of ONM.