[Advances in research of synergistic divergence]

Synergistic divergence is a rare condition characterized by complete absence of adduction that is associated with simultaneous abduction of the affected eye on attempted adduction. This causes the affected eye to move further into abduction on gaze to the normal side and results in extreme divergence of both eyes. It is sometimes referred to as exotropic Duane syndrome with synergistic divergence (type 4 Duane syndrome) or congenital fibrosis syndrome with synergistic divergence. Diseases combined with synergistic divergence fall within the category of congenital cranial dysinnervation disorders (CCDDs). The ocular associations reported with synergistic divergence are uncommon and include Horner syndrome, ocular albinism, foveal hypoplasia, Goldenhar syndrome and pupillary abnormalities. MRI and electro-oculographic study suggested that this is the result of CCDDs. Various surgical techniques have been tried in individual cases including large recession of the lateral rectus muscle, lateral rectus muscle extirpation, large resection of the medial rectus (MR) muscle, weakening procedures of the oblique muscles, combination of lateral rectus orbital wall fixation with MR resection, but further investigations with large-scale samples are needed. Recent research advances in the definition, etiology, and treatment of synergistic divergence are reviewed in this article. (Chin J Ophthalmol, 2019, 55:63-67).