Severely impacted third molars have a high risk of developing a dentigerous cyst. Dental cysts in the maxilla can cause acute infection of the maxillary sinus that can involve the orbital cavity. Possible complications of infections of the orbital cavity are eyesight reduction, including blindness, and disseminated infections, including brain abscesses. This article reports on a 53-year-old male patient with diplopia caused by acute rectus inferior muscle palsy as symptoms of an empyema of the maxillary right sinus. An infected follicular cyst due to the impacted and displaced maxillary right third molar caused the empyema. An emergency trepanation with drainage of the right maxillary sinus was performed. Additionally, intravenous antibiotic therapy with penicillin G and metronidazole resulted in improvement. In a secondary surgical process 2 weeks later, the cyst and the third molar were removed. Complete recovery was noted. It is important to be familiar with clinical diagnostics in cases of undefined pain of the teeth and jaws. Radiographic imaging is indicated in such cases. Disseminated odontogenic infections must be considered as the primary origin of pain and diplopia.