Purpose: Vertical transpositions of the horizontal rectus muscles is the preferred operation in cases of A and V pattern strabismus in which oblique muscle dysfunction is inadequate to allow oblique surgery. The purpose of this study was to assess the results of performed transpositions and to point out factors that influence outcome so as to establish an equation correlating magnitude of transposition to be performed for a given pattern size. Methods: 43 patients with nonparetic horizontal strabismus associated with A or V pattern, without oblique muscle dysfunction, who underwent bilateral and symmetrical vertical transpositions of the horizontal rectus muscles, were retrospectively studied. Results: 81.4% of patients had esotropia of A pattern. The mean pattern size was 19 PD and most transpositions were 4 mm shifts, with a success rate of 66.7 to 79.5%, that is, residual A pattern up to 5 PD or V pattern up to 10 PD. The pattern correction is closely related to the preoperative pattern size and with the magnitude of transpostion carried out, mostly with the former, therefore suggesting that the procedure is self-adjustable. The linear equation with 3 variables was clinically incoherent and was, therefore, abandoned. Conclusions: Symmetrical vertical transpositions of the horizontal rectus muscles is a effective long term procedure for collapsing A and V pattern, whenever oblique muscle dysfunction is absent.
Transposition; A and V pattern
