Binocular coordination of saccades in Duane Retraction Syndrome

Disconjugate oculomotor adaptation is driven by the need to maintain binocular vision. Since binocular vision in Duane Retraction Syndrome (DRS) patients is normal in half of their horizontal field of gaze (i.e., sound-side of gaze), we wondered whether oculomotor adaptive capabilities are efficient despite such a severe impairment of eye motility towards the other half of the horizontal field of gaze (i.e., affected-side gaze). We compared properties of horizontal saccades of patients with congenital unilateral Duane Retraction Syndrome type I in binocular viewing and monocular viewing conditions by simultaneously recording both eyes with the search coil technique. Our results show a mismatch between the pulse and the step signal of the innervation for saccades. When tested in the affected eye viewing condition (sound eye covered), the eyes showed not only similarly-directed increases of the saccadic gain (pulse signal) in the two eyes but also disjunctive post-saccadic drifts (step signal). This behavior suggests that visuomotor errors presented only to the affected eye were transferred to the sound eye, producing conjugate changes of the saccadic command. The post-saccadic command remained unchanged, however, and controlled the final position of each eye separately. This suggests that monocular adaptation is possible only for the step of innervation (i.e., controlling the final eye position) but not for the pulse of innervation (i.e., controlling the saccadic gain), even though the peculiarity of unilateral DRS type I offers a clear advantage for separate pathways of control for the two eyes.     

Analysis of the SALL4 Gene in Patients with Duane Retraction Syndrome in a South Indian Population

Duane retraction syndrome (DRS) is a congenital eye movement disorder characterized most typically by partial or complete failure of abduction and narrowing of palpebral fissure with globe retraction on adduction. Recently mutations of the SALL4 gene on chromosome 20 have been linked to DRS associated with radial forearm malformations (Okihiro syndrome). In this prospective, non-interventional study we screened for SALL4 mutations in 72 patients clinically diagnosed as having isolated DRS or DRS associated syndromes. All four exonic and the neighboring intronic regions of SALL4 gene were amplified by sixteen sets of primers using polymerase chain reaction and were subjected to bi-directional sequencing and BLAST analysis. No genetic variations were detected in the coding region and in the neighboring intronic regions of the SALL4 gene suggesting an alternative mechanism in the pathogenesis of these disorders in the South Indian population.     

Anomalous Lateral Rectus Muscle Band in a Case of Duane Retraction Syndrome

Anomalous orbital structures are suspected in restrictive strabismus with features of severe globe retractions, overshoots, or synergistic movements. We report a case of suspected Duane syndrome that was found to have an anomalous band beneath the lateral rectus muscle. Such abnormal structures are rare, but it is important to identify and manage them to optimize outcomes.     

The Role of Botulinum Toxin in the Management of Ophthalmoplegia Secondary to Miller Fisher Syndrome

Miller Fisher syndrome is an acute demyelinating polyneuropathy classically presenting with ataxia, areflexia, and ophthalmoplegia. The authors report the case of a 27-year-old female, who presented with limb weakness and double vision following a prodromal pharyngitis. Ophthalmic examination revealed fluctuant ophthalmoplegia eventually consistent with bilateral sixth cranial nerve palsies, prompting investigation for anti-ganglioside antibodies, which returned positive. Due to disabling diplopia, the patient was treated with botulinum toxin, with a resulting favourable reduction in the size of strabismus. Four months following her presentation, the patient was orthophoric and resumed normal activities.     

Surgical Treatment of the Upshoot and Downshoot in Duanes' Retraction Syndrome

The upshoot and downshoot that occurs when the eye is rotated into the adducted position in Duanes' retraction syndrome is believed to be related to a taut or leash effect from the lateral rectus muscle. When the eye is adducted, the lateral rectus muscle is believed to “slip” over the globe, producing this abnormal movement. Five patients with Duanes' retraction syndrome demonstrated this finding and underwent a splitting of the lateral rectus into a Y configuration. All five patients demonstrated a marked decrease in the up- or downshoot after surgery.