Extraocular Muscle Palsy in Patients with Chronic Orbital Myositis

Background: Orbital myositis (OM) is a subgroup of idiopathic orbital inflammation. It can involve single or multiple extraocular muscles and result in restriction or paresis of extraocular muscles. Method: We reported two unusual cases of extraocular muscle paresis in the fibrotic stage of chronic OM and reviewed the literature related to this finding. Results: The first case was of a 38-year-old woman with chronic OM with large-angle right eye exotropia and right medial rectus paresis. She received a botulinum A toxin injection into the right lateral rectus muscle as a first treatment, but it was unsuccessful in correcting her deviation. Subsequently, she underwent two strabismus surgeries, which successfully resolved her diplopia in primary gaze. The second case was of a 35-year-old woman with chronic OM and left lateral rectus palsy, which was managed with a botulinum A toxin injection. Conclusion: OM can cause extraocular muscle palsy in the chronic fibrotic stage of the disease.