Medial and Lateral Rectus Muscle Insertion Distance and Width in Esotropia and Exotropia Patients

PURPOSE: The hypothesis that the extraocular muscle insertion distance and muscle width may be associated with the type and size of deviation was tested. METHODS: This was a prospective study of 129 patients who had surgery for horizontal strabismus or retinal detachment. The insertion distances and widths of the medial rectus (MR) and lateral rectus (LR) muscles were measured intraoperatively in esotropia, exotropia, and buckling surgery (control group) patients. Statistical analysis was performed to compare measured factors between the groups. RESULTS: Median medial and lateral muscle insertions were 5.7 and 6.9 mm in esotropia (ET), 6.0 and 7.1 mm in exotropia (XT), and 5.5 and 6.7 mm in the control groups (p > 0.05). The widths of the medial and lateral muscles ranged from 7.0 to 13.0 mm in ET and XT groups and from 9.5 to 11.0 mm in the control group (p > 0.05). Muscle insertion distance and LR muscle width were not correlated with deviation size. Only the MR muscle width was positively correlated with the deviation size. CONCLUSIONS: Insertion distances of the medial and LR muscles are not statistically different in ET, XT, and control patients. Only MR muscle width was affected by the size of the deviation in ET patients.