Overview
A corneal foreign body is an object (eg, metal, glass, wood, plastic, sand) either superficially adherent to or embedded in the cornea of the eye (see the image below). The removal of a corneal foreign body is a procedure commonly performed in the clinic or emergency department setting. [1, 2] If corneal foreign bodies are not removed in a timely manner, they can cause prolonged pain and lead to complications such as infection and ocular necrosis.
See Foreign Bodies in the Head, Neck, Airways, and Extremities: Curious Findings, a Critical Images slideshow, to help identify various foreign objects and determine appropriate interventions and treatment options.
An intraocular foreign body penetrates into the anterior chamber of the eye or into the globe itself. It is likely to cause significant morbidity and, thus, necessitates a thorough workup, including, in many instances, a detailed ophthalmologic evaluation with imaging such as plain radiography or CT scan of the orbits. [1, 3] Though MRI is occasionally used, it is contraindicated if a metal foreign body is suspected. The patient’s description of the circumstances of the injury is the most crucial element in determining the likelihood of globe penetration, which would necessitate referral to an ophthalmologist. [1, 4, 5] An intraocular foreign body does not necessarily change visual acuity.
Indications
Corneal foreign body removal is indicated when a foreign body is on the cornea.
Contraindications
Patients who present to the emergency department with emergent conditions should be referred to an ophthalmologist on the day of presentation. Patients with urgent conditions can be seen the following day.
Emergent conditions include the following:
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Hyphema (blood in the anterior chamber)
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Diffuse corneal defect or opacity
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Laceration of the cornea or sclera
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Single dilated pupil or an abnormally shaped pupil
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A more deep or shallow anterior chamber (when compared to the other eye)
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Possible penetration of the globe
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Multiple foreign bodies
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Extremely uncooperative patient (eg, young child, intoxicated individual, patient with mental disability)
Urgent conditions include the following:
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Significant lid edema
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Diffuse subconjunctival hemorrhage
Anesthesia
Anesthesia is necessary prior to foreign body removal and usually facilitates the initial eye examination.
Instill a topical anesthetic ophthalmic solution (eg, proparacaine 0.5% [Alcaine, Ophthetic]).
Equipment
Equipment used for corneal foreign body removal includes the following:
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Topical anesthetic ophthalmic solution (eg, proparacaine 0.5% [Alcaine, Ophthetic])
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Fluorescein strips
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Cotton-tipped applicator
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Irrigation fluid with plastic syringe
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Device to remove the foreign body
Eye spud (specialized equipment designed for the removal of corneal foreign bodies). The tip is less sharp than a needle, so iatrogenic injury is less likely to occur during the procedure.
A sterile 25-gauge needle, placed onto a syringe (1-3 mm), can be used. Some clinicians like to bend the needle at a slight angle.
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Loupes or a slit lamp (See image below.)
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Topical antibiotic ophthalmic ointment (eg, erythromycin) or ophthalmic drops (See Pearls section for further discussion.)
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Eye patch (See Pearls section for further discussion. See image below.)
Positioning
Have the patient press their face against the forehead strap and chin rest as demonstrated below so that the patient cannot move his head (and, hence, eye) forward toward the eye spud or needle during removal of the foreign body. This positioning is critically important.
The clinician’s hand should be similarly anchored, either against the patient's face or on part of the slit lamp itself. Again, this prevents the clinician from inadvertently penetrating the patient's cornea with the spud or needle during the procedure.
When removing an object from the left eye, place hand on the left maxillary bone.
When removing an object from the right eye, place hand against the bridge of the nose or the infranasal aspect of the face.
Technique
Technique is as follows:
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Explain the procedure, benefits, risks, and complications to the patient or the patient’s representative and obtain informed consent.
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Place 2 drops of anesthetic ophthalmic solution inside the lower eyelid. See image below.
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Wet the fluorescein strip. See image below.
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Apply a wet fluorescein strip inside the lower eyelid to instill fluorescein onto the cornea. Under ultraviolet light, examine the cornea to locate the foreign body. Document a negative Seidel sign. (A positive Seidel sign indicates corneal penetration with oozing aqueous humor; it appears under ultraviolet light as a "dark waterfall," clearing away excess fluorescein on the cornea.) See image below.
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Inspect the lower eyelid while the patient looks up. See image below.
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Inspect the upper eyelid by everting with an applicator while the patient looks down. Sweep the recesses of the upper conjunctival fornix. See image below.
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If the foreign body is superficial, irrigate the eye to moisten the cornea and attempt to remove the foreign body by using a gentle rolling motion with a wetted cotton-tipped applicator. Take care not to apply pressure, which may push the foreign body deeper into the cornea, or scrape, which may create a large corneal abrasion. See images below.
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An embedded foreign body cannot be removed with irrigation or with a cotton-tipped applicator. See image below.
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An embedded foreign body can be removed by using a gentle flicking motion with an eye spud, if available, or with a 25- or 27-gauge needle. Place the hub of the needle on the tip of a cotton swab or a 3-mL syringe. Approach the cornea from the side, with the needle in a plane tangent to the cornea and the bevel away from the corneal surface. This minimizes the chance of corneal perforation. Once dislodged from its embedded position on the cornea, remaining corneal debris can be removed with a wetted cotton-tipped applicator. See images below.
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Document a negative Seidel sign after the foreign body is removed.
Pearls
Topical ophthalmic antibiotics
Current practice leans toward their use to prevent superinfection. [6] However, no evidence supports their use in superficial corneal defects after foreign body removal. [7]
Ophthalmic antibiotic ointments (eg, bacitracin, ciprofloxacin) have an advantage by functioning as a lubricant. Be sure to choose a fluoroquinolone antibiotic if the patient wears contact lenses, as the risk of a Pseudomonas infection is higher.
Ophthalmic solutions (eg, sulfacetamide, ofloxacin) are easier to apply and, therefore, enhance patient compliance.
Corticosteroid ophthalmic solutions or ointments should be avoided because they increase the likelihood of superinfection and slow healing.
Pain control
Recent studies indicate that topical anesthetics do not prolong epithelial healing and can be prescribed for pain relief for the first 24-48 hours. [8, 9]
Opioid analgesic agents (eg, hydrocodone/acetaminophen [Vicodin], oxycodone/acetaminophen [Percocet]) can be used to relieve moderate to severe pain and have been found to allow patients to sleep more comfortably at night.
Nonsteroidal anti-inflammatory drug (NSAID) ophthalmic solutions (eg, ketorolac) can provide significant pain relief and have not been found to slow healing. [10]
Patching
The use of patching has been controversial. Most recently, studies have shown that corneal abrasions due to a foreign body are best treated without eye patching. [11, 12, 13] Patients note faster healing, less blurred vision, and even less pain without an eye patch. Add this lack of proven benefit to patient inconvenience, and the only possible reason to use an eye patch is to protect abrasions that cover greater than 50% of the cornea.
Tetanus vaccination
This should be given to any patient with an intraocular foreign body or any injury that penetrates the cornea or sclera. [7]
Seidel sign
Use the Seidel test to look for hidden globe penetration when it is not obvious. [14] In the case of a positive Seidel sign, the oozing aqueous humor at the site of penetration through the cornea appears under ultraviolet light as a "dark waterfall," clearing away excess fluorescein on the cornea.
A positive Seidel sign indicates globe penetration and requires emergent ophthalmological consultation.
Documenting a negative Seidel sign after the removal of a corneal foreign body is good practice, especially after using a sharp instrument, to confirm that no iatrogenic penetration of the cornea occurred during the procedure.
Complications
Potential complications of corneal foreign body removal include the following:
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Incomplete foreign body removal or rust ring
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Perforation of the cornea
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Epithelial injury
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Equipment needed for corneal foreign body removal.
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Slit lamp needed for corneal foreign body removal.
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Positioning.
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Application of anesthetic ophthalmic solution.
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Wetting the fluorescein strip.
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Instilling fluorescein onto the cornea.
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Lower eyelid inspection.
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Upper eyelid inspection.
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Removal of foreign body with wetted cotton-tipped applicator.
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Irrigation of eye.
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An embedded foreign body.
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Removal of embedded foreign body with needle.
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Removal of embedded foreign body.
