Objective: This article reports identical twin sisters who were found to have acute angle-closure glaucoma at the same time.

Methods: Two case reports.

Results: Two 73-year-old identical twin sisters presented to the emergency room with a complaint of decreased vision and eye pain after having been in a fist fight with each other the previous night. One sister exhibited signs of angle-closure glaucoma with an intraocular pressure > 50 mmHg in the left eye, while her twin sister presented with bilateral angle-closure glaucoma and similar intraocular pressures. Both patients were treated with anti-glaucoma medications and bilateral laser iridotomies.

Conclusions: Polygenetic factors influence the configuration of the anterior chamber, but other environmental factors contribute to the risk of developing primary angle-closure glaucoma. Potentially occludable angles are more common in individuals with a first-degree relative with acute angle closure. Screening of these patients (especially twins) for occludable angles is recommended.