Walsh & Hoyt: Cyclic Esotropia and Its Relationship to Abducens Nerve Palsy

Cyclic, or alternate-day, esotropia is a rare condition characterized by a regularly recurring esotropia that may at first be mistaken for an unusual form of abducens paralysis. It usually appears in children 3 to 4 years old, but it occurs also in adults. Usually 24 hours of unilateral esotropia and diplopia alternates with 24 hours of orthophoria and fusion. It is unrelated to visual activity, accommodation, or interruption of fusion. On esotropic days, a constant deviation of 3040 prism diopters is typical. Cyclic esotropia occurs without any abnormalities of eyelid or pupillary activity, suggesting that it is not caused by oculomotor nerve hyperactivity. Most cases occur with regular 48-hour cycles, although some recur every 3rd or 4th day. Although cyclic esotropia usually begins spontaneously, it may develop after strabismus surgery, after cataract extraction, after tumor removal, in association with retinal detachment, in patients with optic atrophy, after traumatic aphakia, and after acquired sixth nerve palsy. All of these conditions have the potential for interrupting binocularity. Eventually the esotropia may become constant.