Comparison Between Temporal Versus Nasal Anterior Transposition of the Inferior Oblique Muscle for Management of Dissociated Vertical Deviation with Inferior Oblique over Action: Two Years Follow Up

Background: anterior nasal transposition (ANT) is a relatively new procedure which can be used to eliminate inferior oblique over action. An advantage of this procedure over temporal anterior transposition is that it avoids ante-elevation syndrome. Objective: to compare anterior temporal transposition (ATIO) of the inferior oblique muscles versus anterior nasal transposition (ANT) in management dissociated vertical deviation (DVD) with inferior oblique muscle over action (IOOA). Patients and Methods: The study included 50 eyes of 28 patients with DVD of at least 10 prism dioptres ∆ in the eye involved. The patients were divided into two groups. Group A (25 eyes of 15 patients) managed by temporal anterior transposition (ATIO) of the inferior oblique muscles and Group B (25 eyes of 13 patients) managed by nasal anterior transposition (ANT) of the inferior oblique muscles. All patients were followed for at least 24 months postoperatively. The size of preoperative and postoperative angle of DVD, grade of IOOA preoperative and postoperative, need for repeated surgeries and complications were recorded and evaluated. Results: In group A the mean DVD angle was decreased in primary positions from 21.11±4.32 ∆ to 9.5 ±4.7 ∆ (P<0.001) and from 19.5±4.6 ∆ to 5.51 ±2.65∆ (P<0.001) in group B mean IOOA grade was 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. In group B, two patients developed hypotropia of 5 and 6 PD. Persistent IOOA (+1) was observed postoperatively in two eyes in each group. Limited elevations in abduction developed in 3 patients in group A, the incidence of recurrence rate after 24 months was 2 eyes 10% in group A and one eye 5% in group B. Conclusion: Anterior transpositions either temporal or nasal of the inferior oblique muscles are safe and effective in management of DVD with inferior oblique muscle over action. Anterior nasal transposition (ANT) is more effective in correction of DVD with less incidence of antielevation syndrome and recurrence of DVD, however may induce persistent hypotropia.