Blurred eyes with headache may be caused by insufficient blood supply to the cerebral arteries, cluster headache, glaucoma and so on. 1. Insufficient blood supply of cerebral arteries: Insufficient blood supply of cerebral arteries is often due to atherosclerosis of the internal carotid artery, which leads to narrowing or occlusion of the internal carotid artery. Since the ophthalmic artery emanates from the internal carotid artery, when the blood supply of the ophthalmic artery is insufficient, symptoms of blurred vision will appear, followed by headache, dizziness and other uncomfortable symptoms. 2. Cluster headache: Cluster headache is one of the more serious types of headache, which mainly manifests as migraine. The headache is usually fixed in the distribution area of the first branch of the trigeminal nerve, accompanied by unilateral pain in the deep part of the eyeball and the periorbital area, which is followed by symptoms such as dizziness, nausea and sweating. 3. Glaucoma: Glaucoma patients with elevated intraocular pressure, causing damage to the optic nerve, increasing the eye nerve reactivity, leading to symptoms of blurred vision, eye swelling and pain. When the intraocular pressure continues to rise, it will cause nerve radiating pain, followed by headache, dizziness, nausea and other uncomfortable symptoms. It is recommended that patients with blurred eyes and significant headaches seek prompt medical attention to assess their condition and follow doctor’s instructions for treatment.