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INTRODUCTION

Corneal rust rings occur commonly when metallic foreign bodies become embedded in the cornea (Figure 192-1). Removal of the rust ring is imperative to avoid permanent staining of the cornea, persistent inflammation, or disruption of corneal integrity (i.e., necrosis) with loss of stromal substance.1-3 Two techniques for the removal of rust rings are discussed. Topical deferoxamine as a chemical chelator should only be used by an Ophthalmologist and is mentioned only for the sake of completeness.

FIGURE 192-1.

The corneal rust ring. (Knoop KJ, Stack LB, Storrow AB (eds): Atlas of Emergency Medicine, 2nd ed. New York: McGraw-Hill; 2002. Courtesy of Kevin J. Knoop, MD.)

ANATOMY AND PATHOPHYSIOLOGY

The cornea is approximately 0.5 mm thick and is composed of five layers. From the outer to inner layer is the corneal epithelium, Bowman’s membrane, stroma (largest layer), Descemet’s membrane, an endothelial layer, lies directly over the anterior chamber. Corneal rust rings are formed from the oxidation of iron present in metallic foreign bodies.4 As little as 3 hours of corneal contact are required to form the brown stain of a rust ring.1

INDICATIONS

All corneal metallic foreign bodies require prompt removal to avoid the possibility of rust ring formation. A rust ring requires complete removal in a timely fashion in order to avoid the damaging effects of rust on the cornea. While foreign bodies should be removed in the Emergency Department, the rust ring can be left for the Ophthalmologist to remove within 24 to 48 hours if the Emergency Physician does not feel comfortable removing the rust ring.

CONTRAINDICATIONS

Corneal foreign bodies and rust rings that are located in the direct axis of vision can cause permanent visual disturbances if improperly removed.2 Consult an Ophthalmologist before removing these as they often prefer to remove them. Do not attempt to extract a rust ring if the patient is a young child, confused, or uncooperative as this can result in a perforated globe. These patients may require the use of intravenous sedation, procedural sedation (Chapter 159), or general anesthesia to extract the rust ring.

EQUIPMENT

  • Slit lamp

  • 25 or 27 gauge needle

  • Tuberculin syringe with a needle

  • Burr drill

  • Burr bits

  • Topical ocular anesthetic agent (e.g., proparacaine or tetracaine)

  • Topical ophthalmic antibiotic

  • Cycloplegic agents (e.g., cyclopentolate, homatropine, or tropicamide)

  • Ringer’s lactate solution or normal saline

  • Fluorescein strips or liquid

  • Wood’s lamp, if a slit lamp is not available

  • Eidolon Bluminator, if a slit lamp is not available

  • Ophthalmic foreign body instruments, optional5

Having the availability of a slit lamp is preferred when removing a corneal rust ring.6 There are alternatives if a slit lamp is not available ...

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