Corneal Foreign Bodies and Rust Rings

Following instillation of local anaesthetic, small loose conjunctival foreign bodies can be washed out with water or removed with a cotton bud.

If the foreign body is adherent or embedded in the cornea, a needle may be used to lift it out of the cornea. This must be done either using a slit lamp or loupes to ensure accuracy and minimal damage to the cornea. Once the foreign body has been removed, any remaining epithelial defect can be treated as an abrasion.

Rust rings can be removed either by a needle or by ophthalmic burr. Studies have shown that it can take up to twice as long to remove a rust ring with a needle as it does with a burr [34]. It may be easier to remove rust rings 2-3 days after presentation, as local necrosis will separate the rust ring from the corneal epithelium [34].

This video shows the use of both a needle and a burr to remove both a foreign body and a rust ring. In practice this must be performed using a slit lamp. For safety, always warn the patient to sit with their chin and forehead pressed against the bars of the slit lamp so that any movement will be away from the needle/burr, rather than towards it.

Learning bite

Great care must be taken when trying to remove a rust ring as the eye may easily be damaged. If there is any doubt, these patients should be referred to an ophthalmologist.