We report the case of a 57-year-old patient with a presumed developmental anomaly of the medial orbital wall. The resultant protrusion of orbital contents into the ethmoidal complex was clearly demonstrated on coronal computed tomography (CT) scans of the paranasal sinuses. This anomaly presents a high risk of iatrogenic injury to the medial rectus and orbit during functional endoscopic sinus surgery and has not previously been described.