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)
- Infection (bacteria and other organisms can invade the cornea through the epithelium causing epithelial defects or ulcers)
Refer to Etiology
Corneal abrasions can be prevented by wearing protective eyewear. Sunglasses can prevent UV light exposure. Safety glasses during risky activities (weed whacking, car repair, painting, playing with NERF toys, etc) can prevent foreign bodies from injuring the cornea. Good hygiene practices (not touching the eyes with unwashed fingers, not sleeping in contact lenses, etc) can prevent infections. Treatment of dry eye, trichiasis, lagophthalmos, and other conditions mentioned above can protect the corneal epithelium.
When visualizing corneal defects, fluorescein dye is instilled either as a liquid drop (mixed with a topical anesthetic) or via a fluorescein impregnated paper strip after the instillation of topical anesthetic. 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 defects 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 anesthetic. There may also be blurry vision, redness, 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 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 cause, size, and other characteristics of the defect as well as on patient compliance and provider preference. For small defects, observation is an acceptable treatment, with or without topical antibiotics to prevent possible infection. For large defects, management options may include lubricating or antibiotic drops or ointments, bandage contact lenses, or pressure patching. Persistent epithelial defects, as might occur with neurotrophic keratitis, can also be treated with lubrication, tarsorrhaphy, serum tears, amniotic membrane grafts, or Oxervate (approved by the FDA in 2018). The goal of treatment is to provide patient comfort and prevent infection as the limbal stem cells 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. Topical anesthetics also delay wound healing and can result in tragic outcomes such as permanent scarring or even perforation.
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
- 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].
- Lee, Driver, Seitzman, "Cornea Specialists Do Not Recommend Routine Usage of Topical Anesthetics for Corneal Abrasions," Annals of Emergency Medicine [correspondence]. Vol 74, No 3, Sept 2019, pp 463-466.