Anterior transposition vs anterior and nasal transposition of inferior oblique muscle in treatment of dissociated vertical deviation associated with inferior oblique overaction.

PURPOSE: To compare results of two surgical techniques; anteriorization (ATIO) vs anterior nasalization (ANT) of IO muscle in management of DVD associated with IOOA.

METHODS: Twenty-one patients with DVD associated with IOOA were included in this study. Group A consists of 11 patients who underwent ATIO and group B with 10 patients who underwent anterior transposition of IO to the nasal border of inferior rectus ANT. All patients were followed for at least 6 months postoperatively. The primary outcome variables were changes in DVD in primary position and side gazes, IO action and V pattern.

RESULTS: The average of correction of DVD in primary position, in adduction and in abduction was 10.63 PD, 24.6 PD (P<0.001) and 0.45 PD5 (P>0.05) in ATIO group and 14.6 PD, 25.2 PD and 1.7 PD (P<0.001) in ANT group respectively. Mean IOOA decreased from +2.0±0.7 to +0.18±0.4 in group A (P<0.001) and from +2.5±0.7 to +0.1±0.5 (P<0.001) in group B. Mean V pattern was corrected from 19.18±7.1 PD to 11.18±4.9 PD (P<0.01) in group A and from 17.8±7.9 PD to 6.0±2.49 PD (P<0.001) in group B. In group B, two patients developed hypotropia of 2 and 4 PD and one patient developed consecutive exotropia.

CONCLUSIONS: In DVD associated with IOOA, both surgical techniques are almost similar in alleviating true hypertropia in side gaze, IOOA, and V pattern. ANT gives more statistically significant DVD correction in primary position and in abduction while in adduction; there is no significant difference between both groups. However, ANT may induce hypotropia and consecutive horizontal strabismus.