To investigate the feasibility of rectus muscle insertion measurement with anterior segment optical coherence tomography (AS-OCT) after corrective surgery of concomitant exotropia.

A cross-sectional study was performed.Twenty-five eyes of 25 patients with concomitant exotropia were included in Shenyang Aier Eye Hospital from March 2018 to February 2019, and all patients received concomitant exotropic corrective surgery.The distance of limbus to rectus muscle insertion was measured before operation, at the beginning and at the end of operation with a caliper and at postoperative 2 weeks, 1 month, 3 months and 6 months with AS-OCT, respectively.Degree of strabismus was examined by the alternate prism cover test at 33 cm.The research followed the Declaration of Helsinki and the protocol was approved by a Medical Ethics Committee of Shenyang Aier Eye Hospital (No.2017KJB005). Written informed consent was obtained from the patients/custodians prior to any medical examination and treatment.

A total of 44 rectus muscles of 25 eyes with concomitant exotropia were measured, including 25 lateral rectus muscles and 19 medial rectus muscles.The detection rate of the muscle insertion by AS-OCT was low at 2 weeks and 1 month after surgery.The mean distance of limbus to lateral rectus muscle insertions was (12.30±1.40), (11.72±1.45) and (11.84±1.27)mm at the end of operation and postoperative 3 and 6 months, respectively, showing a significant difference among them (F=4.085, P=0.023), and the distance measured at the end of operation was significantly larger than that at postoperative 3 months (P=0.018). The mean distance of limbus tomedial rectus muscle insertion was (5.12±0.42), (5.56±0.61) and (5.28±0.57)mm at the end of operation, postoperative 3 and 6 months, respectively, and there was no significant difference among the three time points (F=3.912, P=0.055). The degree of strabismus of the patients at various time points after surgery were significantly reduced in comparison with that before surgery (all at P<0.05).

AS-OCT can track the position of extraocular muscle insertions after concomitant exotropic corrective surgery.

Concomitant exotropia; Biometry; Optical coherence tomography, anterior segment; Extraocular muscle; Muscle insertion