A V-pattern is defined as the eyes converging more than 15 diopters in moving from upgaze to downgaze. The eyes are seen to be more exotropic or less esotropic in upgaze. In downgaze, the eyes are less exotropic or more esotropic.
V-patterns may or may not be associated with oblique muscle overaction. If overaction is present, it will be see both on duction testing in the direction of the primary action of the oblique muscle in question and also as a hypertropia in horizontal gaze.
In this patient, the V-pattern is felt to be secondary to inferior oblique muscle overaction, which is acting primarily as an abductor in upgaze, causing the eyes to diverge more than in downgaze.
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