Small particles of grit or dust commonly become embedded in the cornea and every casualty officer is aware of the increasing inci dence of this occurrence on windy, dry days. Small foreign bodies also become embedded as the result of using high-speed grinding tools without adequate protection of the eyes. The dentist's drill can also be a source of foreign bodies, but the most troublesome are those particles that have been heated by grinding or chiselling. It is important to have some understanding of the anatomy of the cornea if one is attempting to remove a corneal foreign body. One must realise, for example, that the surface epithelium can be stripped off from the underlying layer and can regrow and fill raw areas with extreme rapidity. Under suitable conditions the whole surface epithelium can reform in about 48 h. The layer underlying, or posterior, to the surface epithelium is known as Bowman's membrane and if this layer is damaged by the injury or cut into unnecessarily by overzealous use of surgical instruments, a permanent scar might be left in the cornea. When the epithelium alone is involved, there is usually no scar, and healing results in perfect restoration of the optical properties of the surface.
The stroma of the cornea is surprisingly tough, permitting some degree of boldness when removing deeply embedded foreign bodies. It should be remembered that if the cornea has been perforated, the risk of intraocular infection or loss of aqueous dictates that the wound should be repaired under full sterile conditions in the operating theatre.
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