Approach Considerations
Strongly consider use of a slit lamp examination with fluorescein to diagnose a corneal abrasion in ambulatory patients. Without the magnification of the slit lamp, small abrasions can be missed.
If ocular penetration with a retained foreign body is suspected, such as in a high-velocity injury (eg, lawn mower, string trimmer, hammering metal), then an ocular CT scan, ocular MRI (if the object is nonmetallic), or both are indicated.
If a corneal ulcer (eg, microbial keratitis) is suspected (because of prolonged symptoms and/or risk factors such as contact lens wear), consider obtaining bacterial cultures before instilling antibiotics.
Slit Lamp Examination
A topical anesthetic (ie, proparacaine, tetracaine) may facilitate the slit-lamp examination. Severe photophobia that causes blepharospasm may require instillation of a cycloplegic agent (ie, cyclopentolate [Cyclogyl], homatropine) 20-30 minutes prior to examination.
Perform fluorescein instillation and examination with a cobalt blue light. Fluorescein can permanently stain soft contact lenses. Do not forget to remove any contact lenses before applying the stain.
Fluorescein is applied using a paper strip applicator that is wet with saline and is gently placed over the inferior cul-de-sac of the eye. Once the patient blinks, the dye is spread over the cornea.
Fluorescein stains basement membrane that has been exposed by damage to the corneal epithelium. This causes the abrasion to appear green-yellow using cobalt blue light or a Wood's lamp.(See the images below.) Corneal abrasions associated with contact lenses tend to be punctate or can be larger in a round shape.
This corneal abrasion appears as a yellow-green area when stained with fluorescein and viewed with a blue light.
Multiple linear, vertical abrasions suggest a foreign body under the upper eyelid. See the image below. Evert the eyelid to look for blepharoconjunctival foreign bodies.
If the patient has suffered penetrating ocular trauma, leaking aqueous humor may be seen (Seidel sign). Examine the anterior chamber for evidence of iritis (cells and flare).
Histologic Findings
On histopathologic examination, intercellular and intracellular epithelial edema is associated with intraepithelial cysts, cellular debris, and intermittent pyknotic nuclei. Intraepithelial basement membrane formation may be present. Basement membrane under regenerating epithelium may appear thickened and multilaminar. Hemidesmosomes tend to be absent or form late in the course of epithelial healing.
Corneal abrasion and inflammation, paracentesis, intraocular infection, and uveal inflammation all cause a breakdown of the blood-aqueous barrier so that plasma proteins and inflammatory cells pour into the anterior chamber. As a result, inflamed aqueous humor has increased levels of serum proteins, including immunoglobulins and complement components C1-C7.
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This corneal abrasion appears as a yellow-green area when stained with fluorescein and viewed with a blue light.
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Corneal abrasion.
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Large corneal abrasion.
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Corneal keratitis and staining.
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Corneal foreign body.
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Corneal foreign body after removal.
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Corneal foreign body with cobalt blue lighting showing abrasion.
