Yokoyama procedure for cyclic strabismus with axial high myopia:a case report

A cyclic strabismus is characterized by periodic alternating strabismus and orthotropia. The most common manifestation is a 48-h cycle consisting of a 24-h period of strabismus followed by a 24-h period of orthotropia. Cycles with 72-h, 96-h and monstrual periods may also occur [9, 10]. Cyclic strabismus is not known to have a mechanism, although biological clocks and diurnal and circadian rhythms may play a role [1, 2, 11]. For cyclic pattern, following theories have been proposed in the literature – aberration of the central nervous system disease [2], peripheral disease such as traumatic aphakia[3], optic atrophy [4], strabismus surgery [5, 6], high AC/A ratio [7] and dysthyroid ophthalmopathy [8]. Children with cyclic strabismus usually begin experiencing it around 3 to 4 years of age without any triggering events. In the strabismus phase, patients have poor stereopsis and suppression. Cyclic strabismus can occur after visual maturity due to conditions disrupting fusion or causing diplopia [4]. In our present case, due to the enlarged left globe herniation through the supertemporal muscle cone associated with axial high myopia, binocular fusion was disrupted, which may have triggered the onset of the cyclic esohypotropia.

There have been reports of high myopic patients developing horizontal and vertical strabismus during adulthood, generally after the third decade. Symptoms range from small-angle esotropia with mild abduction deficit to severe restriction [12, 13]. A variety of surgical procedures are used in traditional surgery, such as tenotomy or recession of the medial rectus muscle, tenotomy of the nasal conjunctiva, regular resections and recessions, and traction sutures [13, 14]. In our present patients, her left eye was esohypotropic with mild abduction deficit, ordinary recession and resection procedure that performed 2 years ago was effective, but it relapsed 12 months later. The axial length (AL) of left globe is 28.43 mm. CT scan showing supertemporal dislocation of the posterior portion of the elongated globe out from the muscle cone. Probable reason for relapse of highly myopic strabismus in our case was the result of redislocation of the globe after temporary placement back within the muscle cone by medial rectus muscle recession and lateral rectus muscle resection.

The most common treatment about cyclic strabismus is extraocular muscle surgery based on the maximal deviation measured on “squint” days. Also reported are botulinum injections [15] and prismatic corrections [16]. In our case, due to supertemporal dislocation of the posteriormost portion of the globe out of the muscle cone, we performed Yokoyama procedure by uniting the superior and lateral rectus muscles without scleral suture plus medial rectus recession. This procedure was effective and successfully terminates the cycle without overcorrection on no squint days. At 6 months of postoperative follow-up, no recurrence of esohypotropia was observed.

In summary, cyclic strabismus is a rare condition of unknown origin. We first report Yokoyama procedure for cyclic strabismus with axial high myopia, the Yokoyama procedure was effective and successfully terminates the cycle without overcorrection on no squint days.The purpose of this procedure is to put the dislocated globe back into its muscle cone by uniting the muscle bellies of the superior rectus and lateral rectus.