inferior oblique overaction

Inferior oblique overaction is a marked elevation of an eye as it moves into adduction under binocular viewing. Usually no vertical deviation is present in primary position; in the bilateral form, a right hypertropia appears in left gaze and a left hypertropia in right gaze.¹

Primary overaction carries a negative head-tilt test and normal depression in adduction, and it typically accompanies an esotropia or exotropia with a V pattern.¹ Secondary overaction follows paresis of the ipsilateral superior oblique, or paresis of the contralateral superior rectus when the patient fixates with the paretic eye.² Overaction secondary to superior oblique paresis shows a positive head-tilt test.¹ After surgery for early-onset esotropia, inferior oblique overaction may develop despite an initially good result, most commonly at age 2 years, and an initially unilateral overaction frequently becomes bilateral within 6 months.³

Dissociated vertical deviation is sometimes confused with inferior oblique overaction. In dissociated vertical deviation the covered eye elevates in abduction, primary position and adduction, while an overacting inferior oblique elevates the eye primarily in adduction and never in abduction, unless the ipsilateral superior rectus is contracted.²