Fig. 2

A-D: Congenital absence of the right inferior rectus muscle in a 51-year-old female. A Clinical 9-gaze photo showing a > 45° hypertropia of the right eye. It was not possible to view the right cornea in the primary position and her right eye was nearly fixed in an extremely high position. B Orbital CT scans revealed an absence of a right inferior rectus muscle. However, based upon images from the coronal plane of the CT scan it initially “appeared” that an inferior rectus muscle was present. After careful review of the CT scans, what appeared to be the inferior rectus muscles in the coronal plane was actually the optic nerve which had altered its position due to the extremely high position of the right eye (the white arrow). C It was not possible to locate the inferior rectus muscle during the strabismus surgery, however, the anterior ciliary vessels coming from the inferior rectus did exist in this patient. D A superior rectus myotomy and anterior transposition of the inferior oblique muscle to the original position of the IR after 8 mm resection of the inferior oblique muscle of right eye was performed. Picture was taken 2 months after the strabismus surgery when she was orthophoria in the primary position, with −2 under-action in downward gaze and − 1 under-action in up gaze motility