[Pseudodysfunction of oblique muscles]

The authors offer a hypothesis on the possibility of development of vertical components of deviation in concomitant eso- or exotropia as a result of specific functioning of horizontal muscles in subjects with oblique palpebral fissure. Such a vertical deviation clinically corresponds to dysfunction (imbalance) of oblique muscles in its symmetrical variant and is therefore termed by the authors "pseudodysfunction of oblique muscles". Differential diagnostic basis for differentiation between true and false dysfunction of oblique muscles in concomitant strabismus is formulated.