Why do you get a headache after reading for a long time? What is the biological explanation that occurs within the brain?

Eye-related headaches typically occur after extended periods of reading, watching television, computer work, or other close work that requires intense concentration. This type of headache usually disappears after a period of rest. In some cases, headaches may be caused by eyestrain related to eyeglasses. A tendency for the eyes to cross or drift outward may also bring on headaches. One eye problem known to cause an intense headache is angle-closure glaucoma. With this type of glaucoma, the headache is only part of the problem. Patients suffering from an angle-closure attack also may experience nausea, intense pain around the eye, blurred vision, and haloes around lights. Headaches caused by eye disease are unique in their symptoms and types of pain. It is important to make detailed notes of your symptoms, type of pain, lifestyle and what you were doing when the headache began. This information is very helpful to the physician to diagnose the type and cause of the headache you are experiencing.