Costenbader lecture. Anatomy and surgery of the inferior oblique muscle: recent findings.

BACKGROUND Surgery of the inferior oblique muscle (IO) has undergone significant changes in the past 160 years. Many investigators have contributed to our understanding of the action of this muscle and to the surgical options that have developed. This article reviews the history of IO surgery with particular emphasis on the anterior transposition procedure. METHODS Anatomic and physiologic studies on the neurofibrovascular bundle of the IO are presented. RESULTS The ligamentous structure of the neurofibrovascular bundle of the IO provides the ancillary origin for the posterior temporal fibers of the IO when its insertion is transposed anteriorly. DISCUSSION Recent anatomic findings have helped explain the effects of the anterior transposition procedure and allow further development of our surgical armamentarium for vertical strabismus problems. Further nasal transposition of that insertion should reduce or eliminate the incidence of the antielevation syndrome. If transposed far nasally, the IO could convert to an intorter, as well as to an antielevator and tonic depressor.