Diagnosis and surgical treatment of dissociated horizontal deviation strabismus

Obtaining satisfactory binocular alignment in patients with Dissociated Horizontal Deviation (DHD) requires a proper diagnosis and a specific surgical strategy. Clinical characteristics, surgical treatment and the results obtained in 20 patients with DHD are reported with a mean of 35 months postsurgical follow up.

Retrospective record review of patients with DHD who underwent surgery between 2000 and 2007. Patient data were recorded, including age, sex, history of prior surgery, visual acuity, pre-operative angle with each eye fixing, Reversed Fixation Test (RFT) when available, type of operation performed, and final binocular alignment.

Twenty patients were identified, mean age 11.7 years old, all of them with age less than 12 months at the time of strabismus onset. Ten of them had had prior surgery for congenital esotropia. Nine showed exotropia (XT), 9 esotropia (ET) and 2 had ET when fixing with OS and XT when fixing with OD. All of them also had an associated Dissociated Vertical Deviation (DVD). Seven patients had amblyopia in the non-dominant eye. Six patients underwent a single operation, 13 underwent 2 operations and 1 needed 3 surgeries to obtain satisfactory binocular alignment.

Patients with DHD also exhibit bilateral and, very often, asymmetric DVD. Therefore, a surgical plan for both the horizontal and vertical dissociation drift of the eyes is needed. Bilateral surgery is almost always necessary, even in cases with a strong fixation preference, in order to obtain satisfactory binocular alignment.