Correction of Exotropia with A-or V-Patterns

Abstract

Pattern strabismus is usually accompanied by cyclotorsion. The patient also may attain an abnormal head posture to maintain binocular fusion. Head position will be toward the direction of maximum deviation (role of thumb). For example, V-pattern esotropia and A-pattern exotropia are associated by chin depression. However, chin elevation may occur in V-pattern exotropia and A-pattern esotropia to bring the eyes downward where the deviation is least. Vertically incomitant pattern strabismus is used to describe the type of strabismus wherein the amount of horizontal deviation changes during the excursion of the eye from upgaze to downgaze. It is a common association with many types of strabismus, especially infantile esotropia and intermittent exotropia. Several patterns have been described for the type of vertical incomitance observed (eg, “A” or “V” patterns), depending upon the relative increase or decrease in the horizontal deviation during the vertical eye movement. The pathophysiology of this phenomenon is multifactorial and has been attributed to factors including oblique muscle dysfunction, horizontal or vertical recti anomaly, displacement of muscle pulleys, and orbital anomalies. The identification of the pattern and its underlying mechanism is essential to plan a proper surgical management in strabismus.