A 48-year-old middle-aged female was admitted to our hospital with decreased vision in the left eye associated with nasal obstruction for 20 days, and nasoendoscopy revealed an outward bulging at the posterior end of the nasal septum with cystic changes. Visual acuity testing showed only light perception in the left eye and essentially normal vision in the right eye. Pituitary gonadal hormones were grossly normal. CT and MRI showed that there is a large mucous cyst in the middle area of the nose, which were also confirmed by intraoperative pathology. The patient's visual acuity returned to normal in the left eye on the day after fenestration of the cyst and nasal congestion resolved.