Purpose: To determine whether the age of strabismus onset and the degree of stereopsis are related to the development of dissociated vertical deviation (DVD) in patients with intermittent exotropia and to describe the characteristics of DVD in patients with intermittent exotropia and DVD.
Methods: Retrospective record review of patients with (1) intermittent exotropia with DVD; (2) infantile esotropia with DVD; and (3) intermittent exotropia without DVD. Age of strabismus onset, stereopsis, strabismus measurements, and the response of DVD to the Bielschowsky head-tilt test were compared among the three groups.
Results: Fifty-two children with intermittent exotropia and DVD were identified. In patients with intermittent exotropia with DVD and intermittent exotropia without DVD group, the mean age of strabismus onset was 12.7 months and 28.9 months, respectively (p = 0.03), and mean stereopsis was 147 arcsec and 65 arcsec (p = 0.02). In patients with intermittent exotropia with DVD and infantile esotropia with DVD, the mean amount of DVD was 9.7(Delta) and 17.2(Delta), respectively (p < 0.01). Bielschowsky head-tilt test showed an increase of DVD on ipsilateral head tilt in 91% and 63.3%, respectively.
Conclusions: Intermittent exotropia with DVD is characterized by earlier onset of strabismus and worse stereopsis, suggesting that these factors may be related to the development of DVD in patients with intermittent exotropia. Unlike DVD in infantile esotropia, DVD in intermittent exotropia was smaller in amount and demonstrated a more uniform response to the Bielschowsky head-tilt test.