Special Feature
Corneal Abrasions: Controversies in Management
By Jacob W. Ufberg, MD David J. Karras, MD, FAAEM, FACEP
Ocular emergencies are a common cause for emergency department (ED) visits, accounting for 2-3% of all ED presentations. Most of these emergencies may be treated by emergency physicians and will not require a consulting ophthalmologist.1 The majority of these ocular emergencies consist of patients with uncomplicated corneal abrasions. For many years, the treatment of corneal abrasions was fairly standard. However, the recent trend toward evidence-based emergency medicine has called some of these "standard" treatments into question.
Background
The cornea, a specialized layer of transparent tissue that is able to refract and transmit light, consists of five layers. The epithelium is the most exterior 10%, and is 5-6 cells deep. Bowman’s membrane is below the epithelium, and is a strong protective layer of the cornea. The stroma, an ordered layer of lamellar keratocytes, makes up 90% of the corneal thickness. The stroma is separated from underlying endothelium by Descemet’s membrane. Despite being remarkably thin (0.5 mm thick centrally), the cornea is highly resilient. It is well protected by barriers such as the eyelids, the conjunctiva, and a film of tears.
Corneal abrasions result from the loss of several cell layers of the corneal epithelium, and usually remain superficial to Bowman’s membrane. They can result from chemical or thermal burns or radiation exposure. Most injuries are mechanical corneal abrasions secondary to trauma and foreign bodies. This discussion will focus on the presentation, diagnosis, and management of mechanical corneal abrasions.
Diagnosis
Patients with corneal abrasions often present to the ED with pain, photophobia, lacrimation, foreign body sensation, and usually a history of minor trauma to the eye. Clinical examination may reveal injected conjunctiva, decreased visual acuity (with large or central abrasions), lacrimation, and an epithelial defect that appears as a bright yellow-green area during fluorescein examination with a cobalt blue light. It is essential to document visual acuity and to check the conjunctiva (including upper lid eversion) to exclude the presence of a foreign body. The degree of relief after administration of topical anesthesia can help differentiate corneal injuries from more serious causes of ocular pain.2 However, it is important that the patient is not dispensed topical anesthetic on discharge, as prolonged use of these agents results in epithelial toxicity with an increased risk of corneal infection.
Management
Traditional management of corneal abrasions included: 1) pressure patching, which was believed to reduce pain and speed healing; 2) pain control with oral pain medicines; 3) administration of topical antibiotic drops or ointment for infection control; 4) tetanus prophylaxis; and 5) topical cycloplegic agents to reduce ciliary spasm and to prevent posterior synechiae formation. However, a number of studies published in the past decade have caused us to question these practices.
Pressure patching. The use of pressure patches was originally based on anecdotal evidence and the theory that patching would speed healing or lessen pain related to corneal abrasions. This practice was recently evaluated in a meta-analysis that compared the rate of healing and degree of pain relief in patched patients to those not patched for mechanical corneal abrasions.3 The authors found no difference in healing rates on the first and second days following injury. In addition, of the six studies that evaluated pain, four found no difference in reported pain, and two showed decreased pain in the non-patched group. The authors concluded that patients with corneal abrasions should not be patched, as healing was not slowed, pain may have been decreased, and patients were able to retain binocular vision.
Pain control. Traditional pain management for corneal abrasions centered on the use of oral agents such as nonsteroidal anti-inflammatory drugs (NSAIDs), narcotics, or acetaminophen. Several studies over the last five years have shown that topically applied sterile NSAID solutions may also provide significant pain relief in patients with mechanical corneal abrasions.
A study by Jayamanne and colleagues yielded a significant decrease in pain scores using topical diclofenac 0.1% solution compared to placebo.4 In addition, diclofenac reduced reports of photophobia and foreign body sensation. A similar study compared topical ketorolac 0.5% to placebo.5 This study also found significant pain relief and decreased reports of photophobia and foreign body sensation in the NSAID group. The authors found no difference in rate of healing, and no systemic side effects or allergic reactions occurred in the NSAID group. However, each study permitted additional oral analgesia in the placebo and NSAID groups, and neither reported the amount of additional analgesia needed by the placebo or NSAID groups. Thus, the treatment effect is difficult to quantify in these two studies.
No studies were located on a MEDLINE search that compared topical NSAIDs to oral NSAIDs or narcotics. Therefore, until a definitive study is published, decisions on pain control must center on the increased cost of topical NSAIDs and the side effects associated with oral narcotics and oral NSAIDs.
Topical antibiotics. While topical antibiotics are routinely given to patients with corneal abrasions, it is unknown whether the low infection rate of corneal abrasions can be attributed to their use. In a study of 351 consecutive patients with corneal abrasions in which no one was given topical antibiotics, only 0.7% developed a secondary infection that required antibiotic therapy.6 Another study examined patient symptoms and rate of healing in patients randomized to topical antibiotics or placebo, and found no difference between the groups.7 Of note, patients with corneal abrasions secondary to contact lens use were excluded. As this study shows, the baseline rate of infection in corneal abrasions is so low as to make a definitive study regarding the utility of topical antibiotic therapy nearly impossible. To date, there is no evidence in the literature to support the use of topical antibiotics for patients with simple mechanical corneal abrasions.
Tetanus prophylaxis. Whereas most physicians routinely administer prophylaxis against tetanus following a simple traumatic corneal abrasion, the existing literature does not specifically support this practice. An animal study showed that no mice developed tetanus after the topical innoculation of live Clostridium tetani or toxin following corneal debridement.8 No human studies have been done to date regarding the need for tetanus prophylaxis after corneal abrasions. Nevertheless, tetanus prophylaxis is essentially innocuous and is routinely recommended as a public health measure. Therefore, most authorities continue to advocate the use of tetanus prophylaxis in simple corneal abrasions.
Cycloplegics. Many leading textbooks recommend that physicians use topical cycloplegic agents to relieve ciliary spasm and reduce pain caused by corneal abrasions. Cycloplegics also have the added theoretical benefit of preventing the formation of posterior synechiae. A MEDLINE search did not reveal any placebo-controlled trials examining their use. Therefore, no specific recommendations can be made regarding the utility of cycloplegic agents for corneal abrasions.
Summary
The treatment of uncomplicated corneal abrasions has changed significantly in the last decade. The literature has shown us that pressure patching is no longer necessary. Greater flexibility now exists in our selection of pain medication. The utility of topical antibiotics has been called into question, although this argument may never be resolved. Textbooks often recommend the use of cycloplegics, with no research upon which to base this practice. Tetanus prophylaxis remains the standard of care.
References
1. Brunette DD, et al. Ophthalmologic Disorders. In: Rosen P, et al, eds. Emergency Medicine: Concepts and Clinical Practice. 4th ed. St. Louis: Mosby-Year Book; 1998.
2. Sklar DP, et al. Topical anesthesia of the eye as a diagnostic test. Ann Emerg Med 1989;18:1209.
3. Flynn CA, et al. Should we patch corneal abrasions? A meta-analysis. J Fam Pract 1998;47:264-270.
4. Jayamanne DG, et al. The effectiveness of topical diclofenac in relieving discomfort following traumatic corneal abrasions. Eye 1997;11:79-83.
5. Kaiser PK, Pineda R. A study of topical nonsteroidal anti-inflammatory drops and no pressure patching in the treatment of corneal abrasions. Corneal Abrasion Patching Study Group. Ophthalmology 1997;104:1353-1359.
6. King JWR, Brison RJ. Do topical antibiotics help corneal epithelial trauma? Can Fam Physician 1993; 39:2349-2352.
7. Kruger RA, et al. Emergency eye injuries. Austral Fam Physician 1990;19:934-938.
8. Benson WH, et al. Tetanus prophylaxis following ocular injuries. J Emerg Med 1993;11:677-683.
28. Which of the following is no longer a standard evaluation procedure or literature-supported treatment for corneal abrasion?
a. Pressure patching the affected eye
b. Pain medication
c. Evaluation with fluoroscein stain
d. Evaluation of visual acuity
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