Excyclotropia of the nonparetic eye in unilateral superior oblique muscle paralysis.

The Maddox double rod test showed subjective excyclotropia of the nonparetic eye in 15 of 60 patients with unilateral superior oblique muscle palsy. This response was reported consistently by patients who habitually fixated with the paretic eye. This phenomenon is the results of a monocular sensorial adaptation to the cyclodeviation by means of a reordering of the spatial response of retinal elements along new horizontal and vertical meridians. This study showed that the fixation preference must be determined to interpret correctly the results of the Maddox double rod test in patients with unilateral superior oblique muscle paralysis.