Laboratory Studies
Unless an infectious corneal infiltrate/ulcer or an intraocular foreign body is suspected, no laboratory work is indicated.
Infectious corneal infiltrates/ulcers generally require scrapings for smears and cultures.
Imaging Studies
To exclude intraocular or intraorbital foreign body, consider B-scan ultrasound, orbital CT scan (1-mm axial and coronal cuts), and/or ultrasound biomicroscopy (UBM). If the foreign body is metallic, the initial study may include orbital x-ray films. If plain films are negative and a high suspicion still exists for intraocular foreign body, the previously mentioned studies are indicated. These studies should be complemented by a full-dilated examination by an ophthalmologist.
Avoid MRI if a possible history of metallic foreign body exists.
UBM, with high-frequency ultrasound, is often useful to rule out a foreign body embedded in the anterior sclera. These foreign bodies may not be visible because of their nature (eg, glass) or overlying opacity (eg, conjunctival hemorrhage).
Laser in vivo confocal microscopy (IVCO) is particularly sensitive and useful in the diagnosis of hidden corneal foreign bodies. [2]
Other Tests
A Seidel test is performed to rule out corneal perforation in the setting of a deep corneal foreign body.
The lower and upper lids need to be everted to look for additional foreign bodies. If a superficial foreign body is suspected but not found, double eversion of the upper lid to search for a foreign body is required.
Procedures
Corneal foreign bodies are removed using a sterile foreign body spud or needle after topical anesthesia. Antibiotic is applied to the eye before and after the removal. Cotton-tipped applicators often are not appropriate because of the large surface area of cotton that touches the cornea, potentially creating a large epithelial defect. Because of the risk of corneal scarring and inadvertent globe perforation, this procedure should be completed using a slit lamp biomicroscope and performed by a clinician who is well trained and experienced in corneal foreign body removal.
Rust rings that remain in the cornea after removal of a metallic foreign body may require removal with a rust ring drill. This procedure also should be performed using a slit lamp biomicroscope by a clinician who is well trained and experienced in rust ring removal because of the risk of corneal scarring and inadvertent globe perforation.
