Management of Mechanical Strabismus After Complicated Functional Endoscopic Sinus Surgery (FESS).

Although considered a safe procedure, functional endoscopic sinus surgery (FESS) can cause various significant ophthalmic complications, i.e., serious extraocular muscle (EOM) damage. The aim of this study is to review the surgical management outcomes of patients with mechanical strabismus and diplopia as a complication of FESS, who referred to ophthalmological department in Norbert Barlicki University Teaching Hospital No. 1 over the 5-year period from 2018 to 2023. The records of seven consecutive patients with diplopia following endoscopic sinus surgery were retrospectively reviewed. Demographics, ophthalmological and orthoptic examination, the results of orbital imaging, type of FESS, type of strabismic surgery, and the timing of the first intervention were analysed. The time from FESS to referral for strabismic intervention varied from one day to two months. Two patients, who were operated upon immediately after the FESS procedure, underwent direct reunion of the proximal and distal parts of the ruptured medial rectus muscle. One patient required maxillofacial intervention in order to improve prominent enophthalmos. The remaining five demonstrated severe adhesion formation around at least one of the EOMs and orbital walls. Only patients who were operated upon within a short period after complicated FESS achieved orthotropia and lack of diplopia in the primary position with a single surgery. Early recognition of the orbital complications subsequent to FESS and prompt referral are essential for achieving a satisfactory surgical result. Appropriate treatment should be based on the mechanism, location, type, and severity of muscle damage.