Corneal Abrasions and Corneal Foreign Bodies
(Ocular Foreign Body)
The most common injuries involving the surface of the transparent dome on the front surface of the eye (cornea) are
Foreign bodies in the cornea leave abrasions behind after they are removed. Most of these injuries are minor.
Particles are common causes of corneal abrasions. Particles can be dispersed via explosions, wind, or working with tools (for example, grinding, hammering, or drilling). Tree branches or falling debris can also cause corneal abrasions. Other common sources of abrasions are
Poorly fitting lenses, lenses worn when the eyes are dry, lenses that have been incompletely cleaned and that have particles attached to them, lenses left in the eyes too long, lenses left in inappropriately during sleep, and forceful or inept removal of lenses can result in scratches on the surface of the eyes. Most corneal abrasions heal without developing infections (such as conjunctivitis and corneal ulcers), but those contaminated with soil or vegetable matter (for example, an injury caused by a tree branch) are more likely to become infected.
Corneal abrasions and foreign bodies usually cause pain, tearing, and a feeling that there is something in the eye. They may also cause redness (due to dilated blood vessels on the surface of the eye) or, occasionally, swelling of the eye and eyelid. Vision may become blurred. Light may cause the muscle that constricts the pupil to undergo a painful spasm.
Injuries that penetrate the eye may cause similar symptoms. If a foreign object penetrates the inside of the eye, fluid may leak out.
The surface of the eye is usually numbed with an anesthetic drop (such as proparacaine). An eye drop containing a dye (fluorescein) that glows under special lighting makes surface objects more visible and reveals abrasions. Using a slit lamp or other magnifying instrument, the doctor then removes any remaining foreign objects. Often the foreign object can be lifted out with a moist sterile cotton swab or flushed out with sterile water (irrigation). If the person is able to stare without moving the eye, foreign objects that cannot be dislodged easily with a swab can often be removed painlessly with a sterile hypodermic needle or a special instrument.
When iron or steel foreign bodies are removed, they can leave a ring of rust, which may need to be removed with a sterile hypodermic needle or a low-speed rotary sterile burr (a small surgical tool with a tiny, rotating, grinding, and drilling surface).
Sometimes a foreign body is trapped under the upper eyelid. The eyelid must be flipped over (a painless procedure) to remove the foreign body. Doctors may also gently rub a sterile cotton swab over the inside of the eyelid to remove any tiny particles that may not be visible.
Corneal abrasions are treated similarly whether or not a foreign body was removed. Usually, an antibiotic ointment (for example, bacitracin with polymyxin B) is given for a few days to prevent infection. Large abrasions may require additional treatment: The pupil is kept dilated with cycloplegic eye drops (such as cyclopentolate or homatropine). These drops prevent painful spasm of the muscles that constrict the pupil.
Pain can be treated with oral drugs such as acetaminophen or occasionally with acetaminophen with oxycodone. Some doctors give diclofenac or ketorolac eye drops to help relieve pain, but care must be taken because these drugs could rarely cause complications such as a type of corneal scarring (called corneal melting). Anesthetics that are applied directly to the eye, although they relieve pain effectively, should not be used after evaluation and treatment because they can impair healing.
Eye patches may increase the risk of infection and usually are not used, particularly for abrasions that result from a contact lens or an object that may be contaminated with soil or vegetable matter.