Anterior Transposition of the Inferior Oblique Muscles: Incidence and Prevention

nterior transposition of the inferior oblique muscle (ATIO) was first suggested by Scott,4 on the basis of computer simulations. ATIO was first reported by Elliott and Nankin,5 who found that the anterior trans-position was an effective way to reduce inferior oblique (IO) muscle overaction. Elliott and Parks6 performed asymmetric IO muscle surgical procedures in a series of patients to compare the effectiveness of ATIO with dener-vation extirpation. In 67 % of their patients there appeared to be a recurrent overaction of the inferior oblique muscle (OAIO) on the side of the IO muscle that had previously received the denervation extirpation. Stein and Ellis1 pointed out that this difference in the postoperative recur-rence of OAIO could be explained by the difference in the surgery that had been performed in the other eye in each series. They proposed that the difference was related to the limitation of elevation in abduction of the contralater-al eye caused by the anterior transposition procedure. After ATIO, the normal, increased innervation of the IO muscle on supraduction produces a powerful force vec-tor directed inferiorly, an effect Kushner termed “antiele-vating. ” This antielevating force can produce overaction of the contralateral elevators in adduction that mimics recur-rent or new overaction of the IO muscle of the other eye. This phenomenon may be termed the antielevation syn-drome (AES). The purpose of this study is to correlate the frequency of this syndrome in a large series of patients with the mm of lateral displacement (spreading) of the IO muscle reattachment site and to suggest how to prevent the development of AES. SUBJECTS AND METHODS A retrospective chart review was conducted on all of the author’s patients on whom an ATIO was performed from l982 to l994. The location of the posterior fibers was tabu-lated according to the inspection of the typed operative notes from the hospital records. Although the lateral end of the inferior rectus (IR) muscle insertion curves posteriorly, when the muscle is placed on a straight muscle hook,