ABSTRACT
Compaison of excyclotorsion induced by horizontal transposition of vertical rectus muscles versus vertical transposition of horizontal rectus muscles in rabbit eyes. In this exprimental study, group 1 underwent full tendon nasal transposition of the superior rectus and full tendon temporal transposition of the inferior rectus [10 adult rabbits]; group 2 underwent superior transposition of the lateral rectus and inferior tranposition of the medical rectus [10 adult rabbits]. External limbal marking was used to estimate the magnitude of excyclotorsion resulting from muscle surgery. The mean angle of excyclotorsion in group 1 was 31 +/- 1.8 degree, ranging from 28-35 degree. The mean angle of excyclotorsion in group 2 was 12.85 +/- 1.6 degree, ranging from 10-16 degree. Excyclotorsion induced by horizontal transposition of vertical rectus muscles was significantly larger than that induced by vertical transposition of horizontal rectus muscles [P<0.001]. The amount of excyclotorsion after LR displacement [1.1 +/- 0.8 degree] was significantly smaller than the amount of excyclotorsion after MR displacement [12.6 +/- 1.7 degree] [P<0.001]. Althaugh the mean angle of excyclotorsion induced by horizontal transposition of vertical rectus muscles was larger than that of vertical transposition of horizontal rectus muscles, superior displacement of the LR muscle induced no significant change in globe torsion. The torsional effect of horizontal transposition of vertical rectus muscles can be changed varying amounts of globe torsion