Eye pain can originate from the surface of the eye, deeper ocular structures, tissues around the eye or nerves carrying facial sensation. Common causes include dry-eye disease, corneal abrasions, corneal infections, conjunctival inflammation, contact-lens-related problems, foreign bodies, uveitis, glaucoma and trauma. Pain can also be referred from the sinuses, teeth or neurological structures, and conditions such as migraine or cluster headache can produce pain around the eye without primary damage to the eyeball. The character of pain matters: superficial burning or gritty discomfort often suggests an ocular-surface disorder, while deep aching pain with light sensitivity can occur with intraocular inflammation. Severe pain accompanied by reduced vision, marked redness, nausea, halos or trauma can indicate an urgent condition.
The cornea is highly innervated and is therefore particularly sensitive to injury. A corneal abrasion can occur when the surface epithelium is scratched by a fingernail, foreign object, contact lens or other trauma. Symptoms can include sharp pain, tearing, redness, light sensitivity and a sensation that something is trapped in the eye. Corneal infections, including microbial keratitis, can be much more serious and may threaten vision if treatment is delayed. Contact-lens wear increases the risk of certain corneal infections, especially when lenses are worn incorrectly or hygiene is inadequate. Persistent pain in a contact-lens wearer should therefore not automatically be treated as simple irritation.
Dry-eye disease can produce burning, stinging, grittiness, fluctuating vision and sometimes significant discomfort. The problem arises from instability or deficiency of the tear film and associated inflammation of the ocular surface. Evaporative dry eye, in which tears evaporate too quickly, is common and can be associated with meibomian-gland dysfunction. Reduced tear production can occur with ageing, autoimmune disorders, certain medications and other conditions. Although dry eye usually causes discomfort rather than severe deep ocular pain, significant ocular-surface inflammation can make symptoms substantial. Pain that persists despite routine lubrication or that is accompanied by reduced vision should prompt further assessment.
Intraocular inflammation, particularly anterior uveitis, can cause deep eye pain, redness and photophobia, meaning discomfort when exposed to light. The inflammation can involve the iris and ciliary body and may cause blurred vision or floaters. Uveitis can be associated with autoimmune or inflammatory diseases, infections, trauma or other causes, although sometimes no systemic cause is identified. Because untreated intraocular inflammation can lead to complications such as synechiae, cataract, glaucoma or macular oedema, suspected uveitis requires professional assessment. It should not be confused with ordinary conjunctivitis, which usually causes more superficial irritation and discharge and generally does not cause severe deep pain or major loss of vision.
Glaucoma can cause eye pain in particular circumstances. Chronic open-angle glaucoma commonly progresses without pain, making routine eye examinations important for detecting optic-nerve damage. Acute angle-closure glaucoma, by contrast, can cause sudden severe eye pain, marked redness, blurred vision or halos around lights, headache, nausea and vomiting. It occurs when the drainage angle becomes critically obstructed and intraocular pressure rises rapidly. This is an ophthalmic emergency because sustained high pressure can damage the optic nerve. Eye pain with a red eye and reduced vision should therefore never be assumed to be conjunctivitis without appropriate assessment.
Trauma and foreign bodies can cause ocular pain through mechanical injury. Chemical splashes can rapidly damage the ocular surface and require immediate prolonged irrigation, followed by medical assessment, while penetrating injuries can threaten the integrity of the globe. A retained foreign body under an eyelid can repeatedly abrade the cornea and cause persistent symptoms. Orbital inflammation, infection or trauma can produce pain with eye movement and swelling around the eye. Pain on moving the eye is also an important feature of optic neuritis, which can cause reduced vision and impaired colour perception, although not every episode of pain with eye movement is caused by optic neuritis.
Neurological conditions can produce severe pain around or behind the eye without primary ocular pathology. Migraine can cause unilateral head or orbital pain and may be accompanied by visual aura, nausea and sensitivity to light. Cluster headache can cause very severe unilateral orbital or temporal pain accompanied by autonomic signs such as tearing, nasal congestion or eyelid changes. Trigeminal neuralgia can produce brief electric-shock-like facial pain. Sinus inflammation can produce facial or orbital pressure, although sinus symptoms are often misattributed as the cause of eye pain. These conditions demonstrate why examination of the eye and assessment of associated neurological and systemic symptoms are important when the source is uncertain.
Evaluation depends on the symptoms and examination findings. An eye examination can assess the cornea, conjunctiva, anterior chamber, pupils, intraocular pressure, lens, retina and optic nerve, with imaging used when orbital or neurological disease is suspected. Urgent assessment is warranted for severe or rapidly worsening pain, sudden visual loss, significant light sensitivity, a markedly red eye, chemical or penetrating injury, a painful eye after contact-lens use, severe headache with visual symptoms, nausea and vomiting with eye pain, or new neurological abnormalities. Treatment ranges from lubricating drops and removal of a superficial foreign body to antimicrobial therapy, anti-inflammatory treatment, pressure-lowering medication or surgery depending on the diagnosis.
