Silent sinus syndrome causing cyclovertical diplopia masquerading as superior oblique paresis in the fellow eye.

Silent sinus syndrome is an insidious maxillary sinus inflammatory disease causing a lowering, thinning, or even absorption of the orbital floor. Patients usually present with progressive enophthalmos and hypoglobus. We report a 41-year-old man with silent sinus syndrome who presented with cyclovertical diplopia masquerading as superior oblique muscle paresis in the fellow eye. Inferior oblique myectomy in the fellow eye resulted in excellent alignment.