Congenital superior oblique palsy of the left eye

(A) A typical abnormal head position is shown. The head is tilted to the right, away from the side of the palsied muscle. The chin is tilted downward slightly. In this head posture, the child fuses and avoids diplopia.
(B) There is a small left hypertropia (upward deviation) in primary gaze when the head is nearly straightened; this is the first step in the "three-step test".
(C) The left hypertropia is worse in gaze to the right; this is the second step in the "three-step test".
(D) A large left hypertropia is seen on forced (by the mother's hand) left head tilt; this is the third step in the "three-step test".