Advances in research of divergence insufficiency

Abstract

Divergence insufficiency is acquired esotropia at distance fixation with symptomatic uncrossed diplopia but fusion at near. It can be divided into two forms: primary isolated form and secondary form associated with neurologic abnormalities, also called divergence palsy. The clinical features of divergence insufficiency include small esotropia only at distance but orthotropia or small esophoria at near, comitant deviation at lateral gaze, reduced divergence fusion, full abduction and normal saccadic velocities in abduction. Primary divergence insufficiency is a benign condition predominantly occurring in adults older than 50 years. Recently, studies on the etiology of age-related distance esotropia, also called sagging eye syndrome, have demonstrated that the degenerative changes of orbital tissue could induce the inferior displacement of the inferior rectus pulley, different from the neurological etiology in abducens nerve palsy and secondary divergence insufficiency. The treatment goal is to relieve diplopia. Both prism and regular surgeries including medial rectus recession and lateral rectus resection are effective. Some unusual surgeries have been applied in divergence insufficiency, but further investigations with large samples are needed. The recent research advances in the etiology, diagnosis, differential diagnosis and treatment of divergence insufficiency are reviewed in this article. (Chin J Ophthalmol, 2017, 53: 552-556).