Skew deviation and retinal photography.

A 50-year-old man was admitted for the acute onset of vertical diplopia worse on left gaze. The right eye appeared hypertropic. Either right fourth nerve palsy or skew deviation was possible.1,2 Nonmydriatic retinal photography revealed an excyclotorsion of the hypotropic eye associated with incyclotorsion of the hypertropic eye (figure 1, A and B) providing a key element for skew deviation. In case of an acquired fourth nerve palsy, an excyclotorsion of the hypertropic eye would have been expected. MRI showed a pontine ischemic stroke (figure 2). Nonmydriatic retinal photography is a noninvasive examination that can help to distinguish fourth nerve palsy from skew deviation. Damien Biotti, MD, Samuel Bidot, MD, Paris, France