Acute inflammatory optic neuritis (retrobulbar optic neuritis) is an uncommon but described complication of acute sinusitis. It is due to a close anatomic relationship between the sinus and the optic nerve. Inflammatory mechanism is dominant with a possible bilateral neuritis, especially among children. In the reported case, as usual in childhood, visual acuity loss has been particularly severe, and recovery slow (it takes usually 6 weeks) but almost complete. Primary treatment is medical, with antibiotics and corticosteroids that must be prescribed for a prolonged time.