A Toddler With Periodic Strabismus

Clinical Course

On the basis of the history and clinical examinations, cyclic esotropia was diagnosed. This disorder is noted for its curative response to surgery, so the patient was scheduled for strabismus surgery.

Discussion

Cyclic strabismus is a rare disorder of ocular motility that most pediatric ophthalmologists will encounter only once or twice in their entire career. Occurrence has been reported to be 1 in 3000-5000 cases of strabismus.^[1] The diagnosis can be easily made with a thorough history and repeated examinations to elicit the cyclic nature of the deviation. Patients with cyclic strabismus often have a family history of strabismus.

Cyclic strabismus is typically an acquired condition that may occur at any age, but usually presents between the ages of 2 and 6 years.^[3] Most cases occur in the preschool years and may explain the frequency of the mild hyperopic refractive error that is seen. Variable presentations, with onset at birth and in adulthood, have been reported. Surgical and accidental traumas have also been associated with cyclic strabismus in a few reported cases. Windsor and Berg suggested that posttraumatic cyclic strabismus may be secondary to the unmasking of a previously latent cyclic deviation.^[4] Hutcheson and Lambert^[5] reported a case of cyclic esotropia with onset following a traumatic sixth nerve palsy. The cyclic phase followed a 48-hour alternating-day pattern and persisted for more than 2 years. After strabismus surgery, the deviation was corrected and the eyes remained aligned.

The most common form of cyclic strabismus is an esodeviation that is classically a large-angle esotropia alternating with orthophoria or a small-angle esodeviation.^[4] Patients cycle between straight eyes and esotropia typically every 24 to 48 hours; however, the interval may vary greatly. Cycles of 1, 3, 4, and 5 days have been reported, as well as cycles of 48 hours of esotropia and 24 hours of orthophoria. The duration of the cycle can be as short as 2 weeks, in which case the diagnosis is often missed, or it may persist for several years before becoming a constant deviation.^[4] Parents may be asked to record on a calendar when the eyes are straight versus when they are crossed, to help establish a pattern. Variations may also include a vertical deviation or incomitance that may manifest as a V pattern or an exotropia.^[3]

A patient with cyclic strabismus usually has absent or defective binocular vision and stereoacuity when the eyes are misaligned, with marked improvement when the eyes are straight.^[1] Windsor and Berg suggested that the periodicity of the deviation may be beneficial in the maintenance of fusion.^[4] Diplopia on strabismic days is rare and found only in older patients who are unable to develop suppression.

Various theories on cyclic strabismus have been proposed. Some have postulated that it may be the result of an aberration in the biological clock. Metz and Begelow described a patient with cyclic esotropia who experienced a change in the circadian pattern of her exotropia following rapid time travel through 6 time zones, thereby supporting the biological clock theory.^[4] Gadoth and colleagues, however, after investigating a patient with minimal brain dysfunction and cyclic esotropia, failed to establish that the hypothalamic-hypophyseal axis is the site of the abnormal clock.^[6]

Cyclic esotropia has an unpredictable response to various forms of therapy except surgery, which is curative in most cases. Occlusion therapy often converts a cyclic strabismus to a constant one. The condition is progressive, and in most cases the deviation eventually becomes constant over several months to years.^[2] Some cases of cyclic esotropia are associated with hypermetropia. In these cases, a full cycloplegic refraction should be prescribed. However, the effectiveness of giving the full hyperopic correction to reduce ocular misalignment is unpredictable. A patient described by Windsor and Berg^[4] converted from a 24-hour cycle to a 48-hour cycle after full correction of hyperopia. Three of 14 patients reported by Helveston obtained fusion with spectacles.^[2] Therefore, any significant refractive error must be corrected in a patient with cyclic esotropia before surgery is undertaken. For patients who have no significant refractive error, surgery for the full deviation should be performed with the goal of achieving eye alignment and preserving binocularity and fusion.

For cyclic esotropia, surgical correction for the total esodeviation with either a bilateral medial rectus recession or a unilateral medial rectus recession with lateral rectus resection has been the most successful therapy.^[4] Surgical correction of the maximum deviation generally corrects the esotropia without resulting in alternating periods of exotropia, as might be expected if the periodicity continued postoperatively. Surgery might not result in complete, immediate resolution of the deviation, and further surgery may be necessary in some cases.

Unlike cyclic esotropia in children, adult cases have often been associated with severe acquired impairment of monocular vision. The response to surgical treatment is typically the same as that in children. Garg and Archer,^[7] however, reported an exception in which an adult patient developed cyclic exotropia following surgical correction of acquired cyclic esotropia.

Conclusion

The diagnosis of cyclic esotropia and the patient's need for surgery were discussed with the parents. The patient underwent bilateral medial rectus recessions for 35 prism diopters of esotropia. Surgical outcome was excellent.

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Cite this: Monica Verma, Kimberly G. Yen. A Toddler With Periodic Strabismus - Medscape - Sep 08, 2010.