Esotropia Induced by Slipped Lateral Rectus Muscle After Orbital Fat Herniation Surgery: A Case Report

BACKGROUND Strabismus and diplopia are well-documented complications following various ophthalmic surgeries; however, no prior reports have linked these complications to orbital fat herniation surgery. Here, we report a case of secondary esotropia resulting from lateral rectus muscle injury following orbital fat herniation surgery. CASE REPORT A man in his 60s presented to our hospital with diplopia during distance fixation, which he noticed a few days after undergoing orbital fat herniation surgery on his right eye. His visual acuity was 24/20 in both eyes. Alternate prism cover testing revealed esotropia of 30 prism diopters for both distance- and near-vision. Mild limitation of abduction in the right eye and conjunctival scarring near the lateral rectus muscle were noted. Injury to the lateral rectus muscle during the previous surgery was suspected. However, due to the mild degree of abduction limitation, transient diplopia was also considered, and the patient was initially observed. However, no improvement in abduction limitation or esotropia was noted over the following months. Consequently, strabismus surgery was performed 8 months after the initial procedure. Intraoperatively, a slipped lateral rectus muscle was identified, and the muscle was advanced to a position 7 mm posterior to the limbus on the sclera. The patient's abduction improved, and satisfactory ocular alignment was achieved postoperatively. CONCLUSIONS When strabismus with ocular motility limitation is observed after orbital fat herniation surgery, the possibility of lateral rectus muscle injury should be considered. If observation does not show improvement, strabismus surgery may be necessary.