Acute angle-closure glaucoma is one of the common ophthalmic emergencies caused by acute closure of the atrial angle of the eye, resulting in impaired drainage of intraocular atrial fluid. Patients experience severe eye pain, eye swelling, and vision loss, as well as headache, migraine, nausea, and even vomiting. These symptoms are due to a sharp increase in intraocular pressure. Why does eye pressure rise sharply? It starts with the physiology of the eye. Inside the eye, there is a part similar to a well called the ciliary process, which secretes atrial fluid to nourish the eye and support the eye along with other structures in the eye, so that there is a certain pressure in the eye to support the eye and form a regular sphere, which is good for light convergence. Since there is a constant secretion of atrial fluid in the eye, there must be a “sewer” that allows a constant flow of atrial fluid out of the eye, otherwise the intraocular pressure would be high, leading to glaucoma. The sewer of the eye is located in a crypt called the atrial horn, and the function of this crypt is very much related to the atrial horn. If the atrial angle is wide, the crypt will be large, and the atrial fluid will flow smoothly and the IOP will not be high. If the atrial angle is narrow, the atrial fluid will flow out from the crypt with difficulty, which may lead to an increase in IOP. Acute angle-closure glaucoma is caused by acute closure of the atrial angle, which leads to a rapid increase in intraocular pressure, causing severe eye pain, eye distention, vision loss and nausea and vomiting. If not treated promptly it may lead to lifelong blindness and there is no way to recover. Since atrial angle closure is what causes acute angle-closure glaucoma to occur, treatment should reopen the closed atrial angle to restore atrial fluid flow. Currently, the argon or krypton laser can reopen the closed angle and restore atrial aqueous drainage in a simple, short procedure (about 3-5 minutes) that is much less painful for the patient than previous infusions, peripheral iridotomies, or trabeculectomies. The so-called trabeculectomy involves reopening an opening on the side of the atrial angle, and the intraocular atrial fluid flows out of the eye through the opened opening to achieve a reduction in intraocular pressure. After surgery, the atrial horn that has been closed may still be closed, and because there is an opening in the wall of the eye after trabeculectomy, the operated eye should avoid trauma, and its ability to withstand trauma has been reduced. When should I suspect that I have acute closed angle glaucoma? Acute angle-closure glaucoma is mainly seen in middle-aged and older women who had good vision, and some even have mild hyperopia. In people with these characteristics, the atrial angle is mostly narrow, the atrial fluid can usually barely drain, the intraocular pressure is not high, and there is no sensation. Once the pupil becomes dilated, the patient’s atrial angle will quickly close and acute angle-closure glaucoma will break out. What conditions tend to trigger dilated pupils and glaucoma attacks? Common causes include spending a lot of time in a dark environment (especially when it is dark, and long hours of darkness in winter), emotional outbursts of great sadness and joy, loss of voice and crying, long hours of reading, drops of pupil dilating medication, etc., which may lead to the onset of the disease. When it occurs, it starts with eye swelling, rainbow-like circles when looking at light bulbs, random vision loss, blurring, and gradually headaches, nausea, and even vomiting. Patients should seek prompt medical attention. Within three days of the onset, a laser peripheral iridoplasty can be a good way to lower the IOP. After the IOP has dropped, another laser iridoplasty can be done to prevent the next recurrence.