Periorbital cellulitis and OC are diagnosed largely by physical examination.The use of computed tomography (CT) in differentiating between PC and OC is controversial because definitive diagnosis and staging are difficult. However, CT may be indicated when patients exhibit central nervous system involvement or deterioration in visua1 acuity (Reference 71). Positive radiographic evidence of sinusitis in the ethmoid and maxillary cavities, as well as subperiosteal or orbital abscesses and diffuse fat infiltration, is seen more often in cases of OC than PC