Acute Primary Angle Closure (APAC) or Acute Glaucoma is a condition where intraocular pressure rapidly increases due to the occlusion of the trabecular meshwork by the iris. This case report aims to present the clinical manifestations of APAC and evaluate the initial treatment strategies to immediately reduce intraocular pressure (IOP) and prevent visual loss. A 63-year-old woman presented with a sudden onset of pain in her left eye, accompanied by redness, headache, blurred vision, and nausea. Her visual acuity in the left eye was 1/300, with an IOP of 69.3 mmHg. Slit-lamp examination revealed hyperemic conjunctiva, mixed conjunctival and pericorneal injection, corneal edema, a shallow anterior chamber with Van Herrick grade I, radially dilated iris, a mid-dilated pupil (4 mm in diameter), and a cloudy lens. Gonioscopy confirmed a closed angle and peripheral anterior synechiae (PAS). The right eye had a shallow anterior chamber with normal IOP. Initial treatment included oral glycerin, intravenous analgesic, oral acetazolamide 250 mg, potassium chloride 600 mg, and topical beta-blocker 0.5%, but showed no improvement. Subsequently, a trabeculectomy was performed. The patient also underwent Laser Peripheral Iridotomy (LPI) on the right eye. This case underscores that acute primary angle closure is an ophthalmic emergency, and timely management is crucial to prevent further complications and visual loss. Postoperative follow-up indicated a significant reduction in IOP and stabilization of visual acuity, highlighting the importance of rapid intervention in APAC cases.