Dissociated Vertical Deviation
- Disorder of vertical ocular alignment of uncertain origin with onset at birth or in early childhood
- Isolated ocular abnormality or accompanied by infantile esotropia, latent nystagmus, and amblyopia
- No diplopia
- Eyes usually aligned if both eyes have an unobscured view
- Affected eye drifts slowly upward and outward if its view is obscured and returns to a normal position when its view is no longer obscured
- May affect one eye
- May affect both eyes
- During the cover test, neither eye refixates with an upward movement, differentiating this condition from other forms of ocular misalignment
- In some cases, one eye drifts upward under normal viewing conditions
- Overaction of the inferior oblique muscles
- Acquired vertical misalignment of many causes
- Look for the characteristic slow ocular downward movement during the cover tests
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Tip: the clue to diagnosis is the absence of an upward refixational movement, which would occur in all other forms of vertical ocular misalignment
- Patients do not have diplopia, so the main issue is the blemish of an upward drift of one affected eye
- Surgical weakening of the superior rectus muscle in the drifting eye may be effective
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Trap: patients are often misdiagnosed as having a condition causing acquired ocular misalignment and subjected to unnecessary investigations