Corneal Epithelial Defect
Corneal epithelial defects are focal areas of epithelial (outermost corneal layer) loss; they can be due to mechanical trauma, corneal dryness, neurotrophic disease, post surgical changes, infection, or any other of a variety of etiologies. Corneal epithelial defects are one of the most commonly seen ocular pathologies in the general patient population.
Corneal epithelial defects can occur by a variety of means.
- Mechanical trauma ( e.g. fingernail scratch, edge of contact lens, foreign body in the lid/fornices, trichiasis/distichiasis, chemical exposure, etc)
- Exposure ( e.g. neurotrophic diseases causing incomplete lid closure (such as palsy of the 7th cranial nerve or Bell's palsy), restrictive eyelid diseases, proptosis / exophthalmos, decreased consciousness in drug abuse or comatose state, blepharoplasty that overcorrects ptosis, lagophthalmos, etc)
- Ultraviolet burns (e.g. welding, prolonged sun exposure off reflective surfaces)
- Decreased tear production (due to side effects of topical or systemic medications, Sjogren’s syndrome, vitamin A deficiency, etc)
- Limbal stem cell deficiency (failure to regenerate epithelial cells may be due to chronic contact lens wear, chemical burns, a history of ocular surgery, ocular autoimmune degenerations, etc)
- Topical anesthetic abuse
- Neurotrophic keratopathy (e.g. corneal hypoesthesia or anesthesia caused by damage to the trigeminal nerve, HSV, VZV, diabetes, topical drop toxicity, etc)
Refer to Etiology
Modification of risk factors for corneal abrasions including protective eye wear for UV exposure and foreign bodies, treatment of pre-existing corneal dryness/dry eye syndrome, abstaining from eye rubbing, etc.
When visualizing corneal defects, fluorescein dye is instilled either as a liquid drop (mixed with a topical anaesthetic) or via a fluorescein impregnated paper strip after the instillation of topical anaesthetic. The dye is visualized using a cobalt-blue filter which causes the dye to fluoresce a bright green color. Fluorescein does not stain intact corneal epithelium but does stain corneal stroma, thus demarcating the area of the epithelial loss. The distribution, size and shape of the corneal defect will vary depending on the etiology (e.g. thin, linear defect for fingernail scratch, whole corneal surface defect for an extensive chemical burn, inferior corneal irregular defect for lid abnormalities/lagophthalmos).
A focal area of corneal fluorescein uptake is an obligatory sign. Conjunctival injection is frequently present on the ipsilateral side of the corneal defect. Periorbital skin or lid changes are present variably given the etiology of the defect (e.g. skin burns with chemical exposures, periorbital trauma in post-motor vehicle collision defects, poor lid closure in exposure defects).
Symptoms include pain, tearing and foreign body sensation of the affected eye (the exception being neurotrophic keratopathy) which are commonly alleviated by the instillation of topical anaesthetic. They can also be accompanied by photophobia, pain with blinking and pain with eye movement.
Corneal epithelial defects accounted for 10% of all eye-related emergency room visits in the early 1990s. They are a common, and frequently overlooked, ocular pathology. Specific occurrences vary by etiology of epithelial defect.
A thorough history is required to determine the etiology of the corneal defect. Similarly, a thorough exam of both eyes is needed because in many cases of systemic diseases or trauma both eyes can be affected.
Several techniques exist for the management of corneal epithelial defects. Which technique is utilized depends on the defect's extent, patient compliance and provider preference. For small defects, observation is an acceptable treatment, with or without topical antibiotics to prevent infection given the mechanism of injury or provider suspicion. For large defects, bandage contact lenses and pressure patching can be administered in patients with history of good follow up. The goal of treatment is to provide patient comfort and prevent infection as the limbal stem cell regenerate the corneal epithelium.
Topical anesthetics are not considered to be helpful in the treatment of corneal epithelial defects due to the concern for topical anesthetic abuse and masking of worsening pain/symptoms/infection by continuous anesthesia.
Medical follow up
Patients should be followed closely in the clinic to ensure resolution of the defect and to monitor for signs of infection.
- External Disease and Cornea. Basic and Clinical Science Course, Section 8. San Francisco: American Academy of Ophthalmology. 2017-2018
- American Academy of Ophthalmology. Persistent corneal epithelial defect. Practicing Ophthalmologists Learning System, 2017–2019 San Francisco: American Academy of Ophthalmology, 2017.
- Practical Ophthalmology, 6th Edition. San Francisco: American Academy of Ophthalmology. 2009
- Shields T, Sloane PD. A comparison of eye problems in primary care and ophthalmology practices. Fam Med. Sep-Oct 1991;23(7):544-6. [Medline].