Corneal Abrasions and Foreign Bodies
Corneal abrasions are self-limited, superficial epithelial defects.
The most common conjunctival and corneal injuries are foreign bodies and abrasions. Improper use of contact lenses can damage the cornea. Although superficial foreign bodies often spontaneously exit the cornea in the tear film, occasionally leaving a residual abrasion, other foreign bodies remain on or within the cornea. Sometimes, a foreign body trapped under the upper lid causes one or more vertical corneal abrasions that worsen as a result of blinking. Intraocular penetration can occur with seemingly minor trauma, particularly when foreign bodies result from high-speed machines (eg, drills, saws, anything with a metal-on-metal mechanism), hammering, or explosions.
With a corneal injury, infection generally does not develop from a metallic foreign body. However, corneal scarring and rust deposits can develop. Also, if a corneal foreign body is organic material, infection can develop.
If intraocular penetration is not recognized, regardless of foreign body composition, infection within the eye (endophthalmitis) may develop.
After an anesthetic (eg, 2 drops of proparacaine 0.5%) is instilled into the inferior fornix, each lid is everted, and the entire conjunctiva and cornea are inspected with a binocular lens (loupe) or a slit lamp. Fluorescein staining with cobalt light illumination renders abrasions and nonmetallic foreign bodies more apparent. Seidel sign is streaming of fluorescein away from a corneal laceration, visible during slit-lamp examination. A positive Seidel sign indicates leakage of aqueous fluid through a corneal perforation. Patients with multiple vertical linear abrasions should have their eyelids everted to search for a foreign body under the upper lid. Patients with a high-risk intraocular injury or (more rarely) visible globe perforation, or a teardrop-shaped pupil should undergo CT to rule out intraocular foreign body and be seen by an ophthalmologist as soon as possible. MRI should not be ordered if a metallic foreign body is suspected due to the possibility of the metal moving and causing further injury.
After an anesthetic is instilled into the conjunctiva, clinicians can remove conjunctival foreign bodies by irrigation or lift them out with a moist sterile cotton applicator. A corneal foreign body that cannot be dislodged by irrigation may be lifted out carefully on the point of a sterile spud (an instrument designed to remove ocular foreign bodies) or of a 25- or 27-gauge hypodermic needle under loupe or, preferably, slit-lamp magnification; the patient must be able to stare without moving the eye during removal.
Steel or iron foreign bodies remaining on the cornea for more than a few hours may leave a rust ring on the cornea that also requires removal under slit-lamp magnification by scraping or using a low-speed rotary burr; removal is usually done by an ophthalmologist.
An ophthalmic antibiotic ointment (eg, bacitracin/polymyxin B or ciprofloxacin 0.3% qid for 3 to 5 days) is used for most abrasions until the epithelial defect is healed. Contact lens wearers with corneal abrasions require an antibiotic with optimal antipseudomonal coverage (eg, ciprofloxacin 0.3% ointment qid). For symptomatic relief of larger abrasions (eg, area > 10 mm2), the pupil is also dilated once with a short-acting cycloplegic (eg, one drop cyclopentolate 1% or homatropine 5%).
Eye patches may increase risk of infection and are usually not used, particularly for an abrasion caused by a contact lens or an object that may be contaminated with soil or vegetation. Ophthalmic corticosteroids tend to promote the growth of fungi and reactivation of herpes simplex virus and are contraindicated. Continued use of topical anesthetics can impair healing and is thus contraindicated. Pain can be managed with oral analgesics.
The corneal epithelium regenerates rapidly; even large abrasions heal within 1 to 3 days. A contact lens should not be worn until the injury is healed. Follow-up examination by an ophthalmologist 1 or 2 days after injury is wise, especially if a foreign body was removed.
Intraocular foreign bodies require immediate surgical removal by an ophthalmologist. Systemic and topical antimicrobials (effective against Bacillus cereus if the injury involved contamination with soil or vegetation) are indicated; they include ceftazidime 1 g IV q 12 h, in combination with vancomycin 15 mg/kg IV q 12 h and moxifloxacin 0.5% ophthalmic solution q 1 to 2 h. Ointment should be avoided if the globe is lacerated. A protective shield (such as a Fox shield or the bottom third of a paper cup) is placed and taped over the eye to avoid inadvertent pressure that could extrude ocular contents through the penetration site. Patches should be avoided. Tetanus prophylaxis is indicated after open globe injuries. As with any laceration of the globe, vomiting (eg, due to pain), which can increase intraocular pressure, should be prevented. If nausea occurs, an antiemetic is given.
Symptoms of corneal abrasion or foreign body include foreign body sensation, tearing, and redness; visual acuity is typically unchanged.
Diagnosis is usually by slit-lamp examination with fluorescein staining.
Suspect an intraocular foreign body if fluorescein streams away from a corneal defect, if the pupil is teardrop shaped, or if the mechanism of injury involves a high-speed machine (eg, drill, saw, anything with a metal-on-metal mechanism), hammering, or explosion.
Treat corneal abrasions and foreign bodies by removing foreign material, prescribing a topical antibiotic, and sometimes instilling a cycloplegic.
For intraocular foreign bodies, give systemic and topical antibiotics, apply a shield, control pain and nausea, and consult an ophthalmologist for surgical removal.