Headache is a common symptom, and most patients only focus on headache and systemic symptoms, while ignoring eye symptoms generally only go to internal medicine for treatment. In fact, eye disease is also a common cause of headache. Closed-angle glaucoma is a relatively common eye disease, mostly occurring in older people over 50 years of age, with sequential or simultaneous onset in both eyes. At first onset, there is only occasional mild headache, eye swelling or loss of vision, and when looking at a light bulb, there is a red and green circle around it, which is medically known as the “iris phenomenon”. The symptoms are often triggered by emotional stress, trauma, overexertion and other factors. With proper rest, the discomfort can disappear completely. Because the symptoms can resolve on their own, they are often overlooked. When the disease develops into an acute attack, patients can have severe headache and eye pain in a very short period of time, the eye is hard when in pain, vision decreases sharply, and in severe cases, only the index of the hand in front of the eyes can be distinguished or there is only light perception, which can be accompanied by nausea, vomiting, chills, fever, etc. A few people can also have diarrhea symptoms. In acute attacks of closed-angle glaucoma, intraocular pressure increases sharply in a short period of time, exceeding the normal limit, causing the eye to harden. Increased intraocular pressure can cause headache, eye pain and a series of systemic symptoms mentioned above. Persistent increased intraocular pressure can cause irreversible damage to the optic nerve in the fundus. Because the optic nerve tolerates high intraocular pressure very poorly, damage can occur in as little as 16 hours, so an acute attack of closed-angle glaucoma is an ophthalmic emergency and immediate measures must be taken to lower the intraocular pressure to a normal range. When the headache, ocular and systemic symptoms are relieved or disappear, surgical treatment should be considered. Once the opportunity for resuscitation is missed, permanent damage to vision can result, and in severe cases, complete blindness can occur. Generally speaking, headache caused by eye disease has two characteristics: first, there is eye pain first, and it radiates to the head only when the condition is aggravated, mostly caused by acute inflammation of the eye or glaucoma; second, there is no pain when the eye is not used, and the pain appears after looking at near or distant objects, and the pain can be relieved after closing the eye and taking a nap. In short, if you suffer from headache and have the above characteristics or do not get better after multifaceted treatment, you should think of going to the ophthalmology department to check your eyes.