(1) This unexpected finding, which can also occur at the time of intended surgery on the superior oblique tendon (Harada-Ito procedure or tuck) can be suspected by observing marked to moderate facial asymmetry, associated horizontal strabismus, amblyopia, and underaction of the superior oblique muscle; however, it cannot be predicted reliably on the basis of preoperative findings and not infrequently occurs as a real surprise! Nevertheless the surgeon must be prepared to encounter it and to consider alternative procedures if surgery on the superior oblique tendon is planned but the tendon cannot be located.24, p.487
(2) The primary procedure for superior oblique underaction is inferior oblique weakening, but this alone is usually insufficient treatment.
(3) Restricted passive infraduction is associated with apparent overaction of the contralateral superior oblique and is caused by contracture of the ipsilateral superior rectus muscle.71 If present, this sign calls for recession of the tight superior rectus.
(4) Inferior oblique overaction is one of the hallmarks of superior oblique paralysis or absence. If this muscle has been weakened by previous surgery, the only alternative is to recess the contralateral inferior rectus muscle.
(5) Pure excyclotropia without vertical misalignment is infrequently encountered in connection with congenital absence of a superior oblique but has been observed by one of us (GKvN). If the patient is symptomatic, horizontal transposition of the vertical rectus muscles should be considered68
