Z-myotomy of the inferior oblique for small incomitant hypertropias.

Background Small hypertropic deviations due to inferior oblique muscle overaction may cause symptomatic diplopia and frustration because incomitant deviations render prism correction unsatisfactory. The several most common surgical options for inferior oblique weakening risk overcorrection of these smaller deviations. In this study we report the results of a “Z-myotomy” of the inferior oblique muscle to correct small incomitant hypertropias due to mildly overacting inferior oblique muscle. Methods The medical records of patients who underwent inferior oblique Z-myotomy at a single center from 2000 to 2005 were retrospectively reviewed. All patients had a mildly overacting inferior oblique (≤+2) and demonstrated fusion. All patients were diplopic, which was the indication for surgery. Pre- and postoperative deviation was measured and ocular motility was assessed. Results A total of 38 patients were included. Of these, 24 underwent unilateral inferior oblique Z-myotomy; 5, bilateral Z-myotomy; 5, simultaneous contralateral inferior rectus recession; and 4, simultaneous contralateral inferior oblique recession. In most cases the postoperative measurements demonstrated an almost complete “collapse” of the strabismus pattern. On average, a Z-myotomy procedure required 5-7 minutes to perform. There were no intraoperative complications or deviation overcorrections. Conclusions The inferior oblique Z-myotomy is a straightforward, quick, sutureless procedure. It can serve as an effective alternative weakening procedure for normalization of ductions in cases of minimally overacting inferior oblique muscle with small incomitant hypertropias. The risk for symptomatic overcorrection is very small.