[A case of blindness caused by mucocele of frontal sinus]

A case of blindness caused by frontal sinus mucocele was reported. The patient presented with pain and swelling in his left eye and decreased visual acuity with only light sensation for 3 days. Orbital imaging examination suggested a mass of communication in the left frontal sinus and the upper quadrant of left orbit, which was considered as a mucinous cyst involving the left superior orbital wall, surrounding the left lacrimal gland, pushing down the left superior rectus muscle, squeezing the left eyeball and protruding forward and downward. The patient was diagnosed with a left frontal sinus cyst with infection and a left orbital subperiosteal abscess. After admission, frontal sinus drainage was performed urgently, but the vision loss in the left eye was not recovered.