Dissociated Vertical Deviation (DVD)

Definition

DVD is a congenital ocular motility phenomenon in which the affected eye spontaneously drifts upward with excyclorotation (extorsion) when it is covered, deprived of fixation, or during periods of visual inattention. When the cover is removed, the eye drifts back down - crucially, without a corresponding downward movement of the fellow eye. This non-adherence to Hering's law (that both eyes receive equal innervation simultaneously) is the defining feature that sets DVD apart from all other vertical strabismus.

Key Clinical Features

Feature	Detail
Eye movement	Upward drift + extorsion under cover; returns to alignment on uncovering
Laterality	Almost always bilateral, but frequently asymmetric
Prevalence in infantile esotropia	Develops in ~80% of cases by age 3 years
Symptoms	Usually asymptomatic - no diplopia, discovered incidentally
Detection	Cover test or pupil light reflex testing

Fig. 18.54 (A) from Kanski: Eyes straight in the primary position - no overt deviation is visible at rest.

Fig. 18.54 (C): Up-drift of the right eye when it is covered.

Associations

DVD is almost never an isolated finding. It is strongly linked to:

Infantile (congenital) esotropia - the most common association
Inferior oblique overaction (IOOA) - must be carefully distinguished from DVD (see below)
Latent nystagmus - fast phase toward the fixating eye when one eye is covered
Amblyopia - develops in ~50% of cases, as a unilateral fixation preference commonly emerges postoperatively
"A" and "V" pattern deviations

Pathophysiology

The exact mechanism remains incompletely understood. DVD violates Hering's law of equal innervation - when the covered eye rises, the fellow eye does not fall. Evoked potential studies have suggested a possible role for excessive crossing of axons at the optic chiasm, but this remains controversial. It is considered a congenital anomaly with no other clinical neurological significance.

Distinguishing DVD from Inferior Oblique Overaction

This is a clinically important distinction:

Feature	DVD	Inferior Oblique Overaction
Elevation	On cover (when deprived of fixation)	In adduction (fellow eye moves into adduction gaze position)
Hering's law	Violated - no corresponding depression of fellow eye	Obeyed
Bilaterality	Usually bilateral	Usually bilateral, but symmetrical
Torsion	Extorsion of the deviating eye	Extorsion present
Timing	Develops later (~age 3)	May be present initially or develop at ~age 2

Clinical Tip (Kanski): "Inferior oblique overaction needs to be distinguished from dissociated vertical deviation." Both can coexist in the same patient.

Management

Treatment is indicated for psychosocial/cosmetic reasons (the deviation itself is asymptomatic). Surgical options include:

Superior rectus recession - with or without posterior fixation (Faden) sutures
Inferior rectus resection or tuck
Inferior oblique anterior transposition (IOAT) - particularly useful when DVD coexists with inferior oblique overaction; the anteriorly transposed IO acts as a depressor

No single procedure is universally superior; choice depends on whether IOOA coexists and the severity of the deviation.

Summary of Congenital Esotropia Sequence

DVD is part of the "infantile esotropia complex":

Esotropia present by 6 months (large angle, >40 prism diopters)
Inferior oblique overaction emerges ~age 2
DVD develops in 80% by age 3
Latent nystagmus present
Amblyopia in ~50% postoperatively

Sources: Kanski's Clinical Ophthalmology: A Systematic Approach, 10th ed., pp. 753-754 | Bradley and Daroff's Neurology in Clinical Practice, p. 299 | The Wills Eye Manual, 8th ed., pp. 498-499

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