A four-step test for diagnosis of pseudo superior oblique palsy.

An 8-year-old boy presented with an ocular torticollis that had appeared many months after a ptosis repair. The three-step test was positive for a superior oblique palsy. However, at the time of surgery the forced duction test showed a marked restriction in depression of the eye. These findings were duplicated before the second procedure normalized the ocular movements. The surgical microscope was of great help for the extensive dissection necessary to correct the condition. The fourth step, the forced duction test, was essential for accurate differential diagnosis between true superior oblique palsy and a mechanical hypertropia.