Strabismus in unicoronal synostosis: ipsilateral or contralateral?

Unicoronal synostosis is a premature fusion of one of the coronal sutures and is thought to carry an increased prevalence for strabismus. Studies suggest the nature of the strabismus to be a hypertropia occurring ipsilateral to the fused coronal suture. The aim of this study is to investigate the laterality of strabismus in unicoronal synostosis and report on ocular motility and refractive findings in a large, unbiased sample group. A retrospective case study analysis was carried out on 59 patients with a confirmed diagnosis of unicoronal synostosis referred to the Oxford Craniofacial Unit over a 14 year period. Manifest strabismus in the primary position was found in 34 (57.6%) cases. In 19 (55.9%) cases, this occurred contralateral to the fused suture, and in 9 (26.5%) cases, strabismus was on the ipsilateral side. Six had alternating strabismus. These results are contrary with apparent findings in the literature but are not statistically significant (P = 0.0872) for strabismus occurring more frequently on the nonsynostotic side. Esotropia with a vertical component was most common, found in 61% of all cases with strabismus. Apparent inferior oblique overaction was found in 30 of the 59 (50.8%) cases, with this occurring bilaterally in 14 cases. Significant refractive error was found in 46% of all cases, most of which showed anisometropia and astigmatism that occurred more frequently on the contralateral, nonsynostotic side (P = 0.0106). All cases of unicoronal synostosis with a mutation of the FGFR2 or FGFR3 gene had manifest strabismus. Manifest strabismus was found in 57.6% of cases reviewed, but this was found to be no more likely to occur on the side contralateral or ipsilateral to the fused suture (P = 0.0872). Anisometropia and astigmatism were found more frequently in the eye contralateral to the fused suture.