Although headaches may occur for no obvious reason, they are sometimes a symptom of a health problem. Headaches over just one eye -- either the right or the left -- may be due to an infection in the eye or surrounding area, such as the sinuses. Glaucoma and cluster headaches are other causes of headaches over just one eye. Less commonly, headaches over one eye are due to blood vessel problems, such as temporal arteritis or an aneurysm, or a problem within the skull that causes increased intracranial pressure.
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An infection in or around the eye may cause a headache over that eye. Most commonly, the infection occurs in a sinus -- a hollow space within a skull bone. The frontal, maxillary, sphenoid and ethmoid sinuses are all located near the eye. They can become infected with a bacteria, virus or even fungus, producing sinusitis. Other symptoms of sinusitis may include a runny or stuffy nose, cough, fatigue or fever. Less often, an infection inside the eye or in the tissues behind and around the eye will produce a headache over the eye. In these conditions, the eye or surrounding tissue may appear red or swollen.
Cluster headaches are also known as ice-pick headaches, as they are usually sharp and extremely painful. The pain is centered in or around one eye but may sometimes extend to other parts of the head. Other symptoms are typically present as well, such as redness and tearing of the affected eye and a runny or stuffy nose on the affected side. Cluster headaches tend to occur several times a day for weeks to months and then disappear completely for a period of time before they return. Cluster headaches are more common in men than women and are more common during adolescence and middle age. They may be triggered by alcohol and cigarettes, bright light, heat, exertion or certain foods and medications.
In glaucoma, the pressure inside the eye is increased, often because of a build-up of fluid within the eye. Glaucoma can cause a headache over the eye, as well as eye pain. Over time glaucoma can damage the optic nerve, which connects the eye to the brain, reducing the ability to see and eventually causing blindness. Regular eye examinations will help detect glaucoma at an early stage so appropriate treatment can be started.
Blood Vessel Problems
Blood vessel problems near the eye or the nerves supplying the eye may also cause headaches. Temporal arteritis occurs when the temporal artery -- which runs just under the skin along the side of the head near the eye -- becomes inflamed. This condition primarily occurs in older people and can also cause jaw pain, vision changes or a stroke.
An aneurysm near the nerves serving the eye may cause a headache over the eye. In an aneurysm, the wall of the artery becomes weak, causing it to balloon out. Pain occurs when an aneurysm presses on a nerve. Blurred or double vision or a drooping eyelid may occur as well. Because the blood vessel wall is weakened, an aneurysm can burst, producing a severe headache and life-threatening bleeding within the skull.
Increased Intracranial Pressure
Excessive pressure within the skull -- known as increased intracranial pressure -- most commonly produces pain throughout the head. But it can sometimes cause pain over just one eye. Because the skull is made of bones, it is a rigid container so anything that takes up space within the skull can increase the pressure inside it. Bleeding in or around the brain, brain tumors or an infection within the brain or surrounding tissue are among the various causes of increased intracranial pressure. In addition to a headache, increased intracranial pressure may produce nausea, vomiting, confusion, double vision and decreased level of consciousness. Other neurologic symptoms may also be present, either due to the increased pressure or the underlying cause.
Seeking Medical Attention
See your doctor to determine the cause if you have headaches that usually occur over just one eye. Seek immediate medical attention if you have a sudden severe headache, any changes in vision, sudden drooping of an eyelid or significant redness or swelling of the eye or surrounding area. Also obtain immediate medical care if you have symptoms of increased intracranial pressure or any other neurologic symptoms, such as weakness, numbness, a seizure or difficulty speaking or swallowing.
Reviewed by: Mary D. Daley, MD