2.05 Corneal Foreign Body

agk’s Library of Common Simple Emergencies

Presentation

The eye has been struck by a falling or blowing particle, often a fleck of rust while working under a car, or a loose foreign body has become embedded by rubbing, thereby producing intense pain. Moderate to high-velocity foreign bodies (fragments chipped off a chisel by a hammer or spray from a grinding wheel) can be superficially embedded or lodged deep in the vitreous. Superficial foreign bodies may be visible during simple sidelighting of the cornea or by slit lamp examination. Deep foreign bodies may be visible only as moving shadows on funduscopy, with a trivial-appearing or invisible puncture in the sclera.

What to do:

Instill topical anesthetic drops.
Perform visual acuity and funduscopy (look for shadows), bright light anterior chamber (slit lamp is best), and check pupillary reflexes (for iritis) and conjunctivae (for loose foreign bodies).
If there is any suspicion of a penetrating intraocular foreign body, then get special orbital x rays or CT scans to locate it or rule it out.
A barely embedded foreign body might be touched out with a moistened swab as shown in the section on the conjunctival foreign body, but if firmly embedded, it will have to be scraped off (under magnification) with an ophthalmic spud or an 18 gauge needle. Give the patient an object to fixate upon to keep his eye still, brace your hand on his forehead or cheek, and approach the eye tangentially so no sudden motion can cause a perforation of the anterior chamber. Removal of the foreign body leaves a defect which is treated as a corneal abrasion. If a rust ring is present, it will appear that a foreign body remains adherent to the cornea. Use the needle to continue to scrape away this rust-impregnated corneal epithelium. A corneal burr is preferable for this task, if available.
If unclear, perform a fluorescein exam to document the extent of the corneal defect.
Finish with further irrigation for possible fragments, instill drops of a mydriatic like homatropine, antibiotic ointment, eye patch, and analgesic medication (Percocet, ibuprofen, etc.), the first dose given before leaving the ED.
Make an appointment for ophthalmologic followup the next day, to evaluate healing and any residual foreign bodies.

What not to do:

Do not overlook a foreign body deep inside the globe: the delayed inflammatory response can lead to blindness.
Do not leave an iron foreign body in place without arranging early ophthalmic followup.
Do not be stingy wuth pain medication. Large corneal abrasions following foreign body removal can be quite painful despite patching the eye.
Do not forget to thell the patient, if homatropine was instilled, that he will have blurred near vision and an enlarged pupil for 12-24 hours.

Discussion

Decide beforehand how much time you will spend (and how much trauma you will inflict on the cornea) before giving up on removing a corneal foreign body and calling your ophthalmologic consultant. Some emergency physicians recommend using a small needle for scraping, to minimize the possibility of a corneal perforation, but with a tangential approach the larger needle is less likely to cause harm.

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