A case report on a 49-year-old female with diagnoses of ocular hypertension in her left eye (LE) treated with 250 mg/day acetazolamide for 2 years. During the slit-lamp examination, complete occlusion of both iridocorneal angles was detected. Intraocular pressure (IOP) was 10 and 35 mmHg in the right eye and LE, respectively. Phacotrabeculectomy was performed in the LE. After 1 month of the procedure, the patient developed a slowly progressive miopization from −1 to −3 diopters (D) the following months. Approximately 3 months after surgery, the patient developed an episode of acute pain, athalamia, and IOP 45 mmHg in her LE. Late-onset malignant glaucoma was suspected and the patient was treated with topical hypotensive and cycloplegic agent until a prompt vitrectomy was performed. Deepening of the anterior chamber and restoration of IOP to normal range was obtained after surgery.