Causes of eye pain fall into 2 broad categories: ocular pain and orbital pain.

Ocular pain is eye pain coming from the outer structures of the surface of the eye.

Conjunctivitis is one of the most common eye problems. Conjunctivitis can be an allergic, bacterial, chemical, or viral inflammation of the conjunctiva (the delicate membrane lining the eyelid and covering the eyeball). Pinkeye is a nonmedical term usually referring to a viral conjunctivitis. Pain is usually mild, or there is no pain. Itching, redness, and drainage may be seen.

Corneal abrasions and corneal ulcerations are also common causes of eye pain. The cornea is the transparent surface of the eye. Abrasions occur from scratches to the surface of the cornea, such as a foreign body in the eye or overuse of contact lenses. Ulcerations occur from infections or abrasions.

Foreign bodies, usually located on the cornea or in the conjunctiva, are objects or material that give you the sensation that something is in your eye. Foreign bodies produce eye pain similar to that of corneal abrasions.

Chemical burns and flash burns are significant causes of eye pain. Chemical burns come from eye exposure to acid or alkali substances. Flash burns occur from intense light sources, such as arc welding or tanning booths, when improper eye protection is worn.

Blepharitis causes eye pain when an inflammation of the eyelid is caused by plugged oil glands at the eyelid edges.

A sty or a chalazion causes eye pain because of local irritation. Both cause a lump you can see or feel within the eyelid formed by a blocked oil gland. This lump causes irritation to the eye.

Orbital pain is described as a deep, dull ache behind or in the eye. This pain is often caused by diseases of the eye.

Severe glaucoma can cause orbital pain, although most glaucoma is painless. Glaucoma is caused by an increase in intraocular pressure (pressure inside the eye), which can ultimately lead to defects in vision and blindness if left untreated. Intraocular pressure can increase because of a blockage of outflow or increased production of aqueous humor (fluid that bathes the inner eye).

Iritis is an inflammation of the iris (the colored part of the eye) that causes deep eye pain.

Optic neuritis is an inflammation of the optic nerve. The optic nerve connects to the back of the eye. The cause of this inflammation can be from multiple sclerosis, viral infections, or bacterial infections.

Sinusitis, which is a bacterial or viral infection of the sinuses, can cause a sensation of orbital pain.

Migraines are also a very common cause of orbital eye pain associated with headaches.

Traumatic events, such as a penetrating injury to the eye, a blow to the eye with a foreign object, and motor vehicle collisions, are causes of significant eye pain and injury.

Pain is a variable measure. Each person may interpret pain differently.