Dissociated Vertical Deviation

Dissociated Vertical Deviation(DVD) is an ocular condition which occurs in association with a squint, typically Infantile Esotropia. Patients with DVD show an upward movement of one eye when the eye is covered (i.e. when the two eyes are prevented from working together or are 'dissociated')and a downward movement of the same eye when the cover is removed. More distressingly, the same upward movement can occur spontaneously when the patient is 'daydreaming' and the corresponding downward movement occurs when the patient directs their gaze at a target.

Characteristics

The condition usually affects both eyes, but can occur unilaterally or asymmetrically. It is often associated with latent or manifest-latent nystagmus and, as well as occurring with Infantile esotropia, can also be found associated with exotropias and vertical deviations.

Differential Diagnosis

DVD is often mistaken for over-action of the inferior oblique extra-ocular muscles. DVD can be revealed on ocular movement testing when one eye is occluded by the nose on lateral gaze. This eye will then elevate, simulating an inferior oblique over action.

Testing for DVD

A test called the Bielschowsky Darkening Wedge Test can be used to reveal and diagnose the presence of Dissociated Vertical Deviation.

The patient is asked to look at a light. One eye is covered and a filter is placed in front of the other eye. The density or opacity of this filter is gradually increased, and the behaviour of the eye under the cover is observed NOT of the eye beneath the filter. Initially, if DVD is present, the covered eye will have elevated, but as the filter opacity is increased the eye under the cover will gradually move downwards.DVD

Onset

DVD typically becomes apparent between 18 months and three years of age, however, the difficulties of achieving the prolonged occlusion required for accurate detection in the very young, make it possible that onset is generally earlier than these figures suggest.

Treatment

Management of this condition is surgical and typically involves reducing the strength of the Inferior Oblique muscle of the affected eye(s).

References

*Mein J, Trimble R. Diagnosis and management of ocular motility disorders., 2nd ed. Oxford: Blackwell, 1991
*F Rowe, Clinical Orthoptics Blackwell Publishing; 2nd Ed edition (April 2004)