Page last modified: June 14, 2009
Disorders where one eye is higher than the other often cause vertical double vision (diplopia).
Common causes include:
The situation where one eye is higher than the other. When this only occurs when one or both are covered, it is called a "hyperphoria". When it occurs even when both eyes are viewing, it is called a "hyper deviation". Hyperphoria and hyperdeviation generally refer to the situation where the cause is known. For example, ocular palsies such as 4th nerve palsy can cause a hyper deviation or phoria.
Skew deviation refers to a vertical misalignment of the eyes without an ocular cause. It is typically caused by brainstem damage, and in this instance, attributed to asymmetry in utricular projections. Rostral (upper) pontomesencephalic lesions cause ipsilesional hypertropia, and caudal (lower) pontomedullary lesions cause contralesional hypertropia. Skew deviation can also occur in cerebellar lesions (Wong and Sharpe, 2005). Skew deviation is rarely associated with vestibular lesions and suggested by some to be specific for vestibular "pseudoneuritis" -- a brainstem lesion emulating vestibualr neuritis(Cnyrim, Newman-Toker, et al. 2008). . However, it is not a specific sign as there is good evidence that it occurs in purely peripheral lesions (Vibert. et al., 1996)
Acutely, utricular damage can also cause hyperdevation. It would seem to us that saccular damage might also cause hyperdeviation, but this has not been reported in the literature to our knowledge.
Alternating skew deviation, in which the hypertropic eye occurs on the side of horizontal gaze direction, is associated with lesions of the cervicomedullary junction or cerebellar pathways.
In normal humans, static lateral head tilt causes sustained low-amplitude counter-roll of the eyes and a small vertical misalignment, so that the lower eye is a little higher than the upper eye. This has the effect of modestly realigning the axis between the eyes with horizontal.
Pathologically, the ocular tilt reaction consists of a triad of skew deviation, ocular torsion and head tilt.