Crouzon syndrome: Relationship of eye movements to pattern strabismus

Abstract

PURPOSE. To characterize conjugate eye movements in Crouzon syndrome (CS) patients with and without strabismus. METHODS. Smooth pursuit, saccades, horizontal optokinetic nystagmus (OKN), and horizontal vestibulo-ocular reflex (VOR) were recorded using binocular video-oculography (VOG) in 10 children with CS (5 orthotropic, 5 strabismic) and 12 age-matched controls. Hess-Lancaster plots were generated from Orbit 1.8 using rectus muscle pulley locations from computed tomography imaging. Two-dimensional eye scan paths from VOG recordings were compared with the Hess-Lancaster plots. RESULTS. Targeted saccades were normometric on average but variable, and followed the main sequence in both CS groups. Smooth pursuit gains were normal for both CS groups; however, SP gains of the fixating eye in subjects with strabismus were significantly lower. Optokinetic nystagmus gains were reduced in both CS groups (P < 0.02) but were lower in subjects with strabismus. Shifting misalignments of binocular eye position in primary and eccentric gazes were associated with reduction in OKN gain in both CS groups. Vestibulo-ocular reflex gains for both CS groups were largely normal despite the presence of an off-axis vertical component. CONCLUSIONS. Normal gains for saccades and smooth pursuit in CS patients with strabismus are consistent with accurate execution of both movements despite extorsion of the globe. Vestibulo-ocular reflex in CS patients with strabismus had an off-axis vertical component consistent with extorted muscle pulleys. Optokinetic nystagmus is reduced in CS without strabismus owing to binocular position disparities and in CS with strabismus is likely due to cortical suppression associated with cross-axis orientation and exotropia.