Learn about the nerve that is involved in many causes of eye pain and discomfort.
Understanding what causes eye pain begins with learning about how pain around the eye is sensed. All sensation from the head and face (such as pain, temperature, touch) is transmitted to the brain by the trigeminal, or fifth cranial nerve. Pain sensory fibers from all parts of the head and face feed into nerve endings of this nerve. These nerve fibers then converge into three branches, with the first being the ophthalmic branch – related to the eyes and the orbit, the socket that holds the eye. The maxillary branch is connected to the cheek and sinuses, and the mandibular branch is associated with the jaw and mouth. These three branches combine into a single nerve bundle behind the ear and then connect to the brain. When these fibers are activated, such as by sharp objects, we sense “pain.”
The following are common causes of pain in the eye:
- Foreign Body
The cornea, or the window into the eye, has the most number of sensory nerves per area of any part of the body. For this reason, when we get something in our eye such as dust, we immediately tear and shut our eyes to try to expel the object and prevent more dust from getting in. Drying of the cornea and sudden exposure to bright light can also activate the trigeminal nerve and cause eye pain.
- Eye Strain
The exact mechanisms of how eye strain and double vision lead to eye pain is not well understood. As these are common causes of eye pain, brow ache and headache, it is important to assure that you have an updated eye glass prescription and you are seen by an eye provider if you have double vision.
- Inflammation
Aside from the cornea, the uvea, which includes the iris and the layer of tissue under the retina, are the only parts of the eye that have sensory fibers. When these tissues are irritated such as by inflammation, we sense pain. Medical conditions that can lead to inflammation of the eye include rheumatoid arthritis, sarcoidosis, lupus, Crohn’s disease, Behcet’s disease, granulomatosis polyangiitis, ankylosing spondylitis, IgG4 disease, and infection such as from herpes zoster virus, syphilis, varicella zoster virus, and tuberculosis. Inflammation and infection behind the eye can also lead to pain by activation of the trigeminal nerve. Optic neuritis, Grave’s disease, sarcoidosis, and IgG4 disease are common conditions that can cause inflammation behind in the eye socket
- Elevated Pressure
The eyeball has mechanosensory or pressure sensing cells that are sensitive to touch and stretch. When the pressure in the eye is markedly elevated, such as in acute angle-closure glaucoma, the trigeminal is activated and we sense pain.
- Migraine
Because the sensory fibers of the dura, the tissue that wraps the brain, also feed into the trigeminal nerve, irritation of trigeminal fibers on the cornea, such as from dry eye, can irritate the trigeminal nerve and lead to activation of dural sensory fibers, inducing a migraine. In some patients, treating dry eyes will decrease the occurrence of migraines.
- Referred Pain
Because the trigeminal fibers of the eye (the ophthalmic branch) converge with sensory fibers of the sinuses and teeth (the maxillary and mandibular branches), sometimes sinusitis or tooth infections are confused by the brain and perceived as eye pain.
