Chapter 191: Corneal Foreign Body Removal

INTRODUCTION

Corneal foreign bodies are a common complaint confronting Emergency Physicians and account for approximately 35% of all eye injuries seen.^1-3 Many objects have been implicated as a source of corneal foreign bodies (e.g., dirt, dust, glass, insects, metal, plant particles, and wood) (Figure 191-1).¹ Metal is the most frequently encountered ocular foreign body, often from hammering.⁴ Most ocular foreign bodies require prompt removal. More than 75% of retained foreign bodies presenting on the eye surface are corneal in nature and result in a keratitis if left in place for more than 3 days.⁵

The prevailing symptom that forces patients to seek treatment is the sensation of an ocular foreign body or 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.

ANATOMY AND PATHOPHYSIOLOGY

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 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 and into the nose.⁵ Objects 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.⁵ Foreign bodies may travel deeper into the respected fornices where they may be difficult to find. Foreign bodies may be lodged into the surface of the conjunctiva overlying the sclera or the cornea. Foreign bodies in the cornea carry the most risk of serious injury or permanent scarring.

The cornea is only millimeters thick. It is composed 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.⁶ The surface epithelium 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, scarring and permanent injury can ...