Corneal foreign bodies are a common complaint confronting Emergency Physicians and account for approximately 35% of all eye injuries seen.1 Many objects have been implicated as a source of corneal foreign bodies including, but not limited to glass, metal, wood, dirt, dust, insects, and plant particles.1 The majority of ocular foreign bodies require prompt removal. More than 75% of retained foreign bodies present on the eye surface are corneal in nature, and if left in place for more than 3 days will result in a keratitis.2
The prevailing symptom that forces patients to seek treatment is the sensation of an ocular foreign body or simply the pain associated with the foreign body. A variety of techniques exist for removal of ocular foreign bodies. A discussion of each of these techniques is necessary to determine the proper technique for a given situation.
Many foreign bodies are diverted from the surface of the eye by the rapid blinking action of the eyelids and the eyelashes. A foreign body may not necessarily lodge itself into the cornea or the surrounding scleral surface if it is able to get past the eyelids and eyelashes. It may be washed to the inner canthus by a combination of blinking and tear flow. The foreign body may occasionally be carried away via drainage through the lacrimal ducts.2 Objects that resist these means of diversion may be found in the upper or lower fornices, the channels created by the fold of the inner surfaces of the eyelids in communication with the conjunctival surface of the eye. The foreign body in the upper fornix is typically found lodged in the subtarsal groove on the inner surface of the upper eyelid, inferior to the tarsal plate.2 Foreign bodies may also travel deeper into the respected fornices where they may be difficult to find. Foreign bodies may lodge themselves into the surface of the conjunctiva overlying the sclera or into the cornea itself, which obviously carries the most risk of serious injury or permanent scarring.
The cornea is <1 mm thick. It is comprised of five layers (from outer to inner layer): epithelium, Bowman's membrane, stroma, Descemet's membrane, and the endothelial layer that lies directly over the anterior chamber.3 The surface epithelium itself has five layers of squamous cells. Most superficial corneal foreign bodies become embedded in this layer and do not result in scarring. Bowman's membrane has no regenerative capacity, and if injured, may result in scarring and permanent injury.4 Foreign bodies that violate Bowman's membrane are considered deep corneal injuries. The stroma is composed of collagen and accounts for the largest portion of the cornea. Descemet's membrane is a basement membrane that can be regenerated if injured. The final component of the cornea is the endothelial layer that is composed of a single row of cuboidal cells that can regenerate if damaged.
Healthy cells adjacent to the injury slide over the damaged site and eventually replicate to the previous number of cells present when the corneal epithelium is injured.3 Conjunctival epithelium migrates over the cornea to aid ...