Dissociated vertical deviation (DVD) is a challenging condition
to manage, largely due to a poor understanding of its underlying etiology and
the dearth of clinical studies that deal with its treatment. Guyton analyzed
the vertical, horizontal, and torsional eye movements of six patients carrying
the diagnosis of DVD in an attempt to better understand its underlying etiology.
He proposed that the vertical vergence component of the DVD serves as a
cyclovertical analog of the horizontal convergence used by some patients to
help dampen the horizontal component of latent nystagmus, thereby preventing adecrease in vision that the latent nystagmus would otherwise cause. We are not
aware of any other postulates on the cause of DVD.
The association between DVD and horizontal strabismus, particularly
infantile esotropia has been well described, and DVD also occurs in the context
of acquired esotropia, congenital and acquired exotropia, and sometimes
intermittent exotropia. Oftentimes surgical correction of the horizontal
strabismus is performed at the time of DVD surgery. We were unable to find any
studies or discussion of the effect of DVD surgery on concurrent horizontal strabismus;
possible reasons are that the two are often repaired simultaneously, or the
horizontal strabismus alone is repaired if the DVD is not severe enough. The
purpose of the present study is to determine whether surgery for DVD alone in
patients with concomitant horizontal strabismus can improve control of the
latter, thereby avoiding additional horizontal muscle surgery.
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