Written by: Jonathan Hung, MD, (NUEM PGY-3) Edited by: Matt Klein, MD (NUEM ‘18) Expert commentary by: Dr. Glaucomflecken
Introduction
Corneal abrasions are a commonly encountered eye-related presentation in the emergency department (ED) [1]. Patients will often have a significant amount of pain from even minor abrasions. Topical anesthetics such as tetracaine have been found to be effective in treating the pain and are now routinely used in the ED [2]. However, the use of topical anesthetics for corneal abrasions in the outpatient setting is controversial due to concerns over safety and delayed healing. These traditional concerns over the prolonged use of topical anesthetics are based on early animal studies and case reports in humans [3]. The current literature suggests that topical anesthetics are, in fact, safe and effective if given as a short course with appropriate follow up, but further studies with larger patient populations are needed to support these findings [4]. A recent study published in Annals of Emergency Medicine is one of the largest studies to date that examines the safety of discharging patients home from the ED with a short supply of tetracaine for corneal abrasions.
Study
Waldman N, Winrow B, Densie I, et al. An Observational Study to Determine Whether Routinely Sending Patients Home With a 24-Hour Supply of Topical Tetracaine From the Emergency Department for Simple Corneal Abrasion Pain Is Potentially Safe. Ann Emerg Med. 2017.
Study Design
The study design was a single-center, retrospective cohort study with ethics approval given by the Human Ethics Committee at the University of Otago.
Population
The study was performed at the ED of Southland Hospital, Invercargill, New Zealand. A computer search of the hospital’s ED information system was conducted looking for all eye-related diagnoses and charts were reviewed between February 1, 2014 to October 31, 2015. Patients were initially selected if they were seen in the ED with an injury or illness involving the cornea.
Intervention protocol
Patients with simple corneal abrasions were discharged home with undiluted 1% tetracaine hydrochloride in addition to the standard treatment of acetaminophen and chloramphenicol eye ointment. Instructions were given to place tetracaine in the eye as often as every 30 minute over the first 24 hours.
Outcome Measures
ED rechecks
Persistent fluorescein uptake
Ophthalmology clinic referrals
Complications
Results
There was a total of 1,576 ED presentations of corneal abrasions of which 532 were simple corneal abrasions (SCA) and 1,044 were defined as nonsimple corneal abrasions (NSCA). Tetracaine was given to 57% (303) of SCA patients and 14% (141) of NSCA patients. Overall, there were no serious complications or uncommon adverse events in either the SCA or NSCA group (0/459). The relative risk of patients with SCA receiving tetracaine and returning to the ED, having fluorescein uptake, or requiring a referral to ophthalmology was low compared to the standard treatment group.
Interpretation
This study is one of the largest studies to examine the safety of outpatient tetracaine use in simple corneal abrasions. More importantly, it gives a robust conclusion similar to previous smaller studies in that there was no evidence that using topical tetracaine for a short duration caused harm. The strengths of this study include the large patient population and good patient follow-up. Furthermore, the physicians that administered tetracaine did not know that an observational study was planned, thus increasing the internal validity. However, the researchers were not blinded to the hypothesis which could have led to bias when collecting data. This was also a retrospective study and therefore due to the lack of randomization, those who received tetracaine may have differed from those who did not. Another limitation was that it was not known if all the patients administered the tetracaine as instructed after leaving the ED. Also, the diagnosis of simple corneal abrasion was limited to what the physician documented in the chart. The external validity is limited since this was a single-center study and about 71% of the patients were males. Overall, this study further strengthens the role of tetracaine in treating pain secondary to simple corneal abrasions and may gradually change practice patterns in the emergency department despite traditional teaching.
Take Home Points
Topical tetracaine is effective in treating pain due to corneal abrasions
Patients with simple corneal abrasions can benefit from a short course of topical tetracaine to treat pain
Topical tetracaine use over a 24-hour period is generally safe
Emergency medicine physicians should consider incorporating topical tetracaine in their practice for treating SCAs
Expert Commentary
This is an interesting observational study regarding the safety of prescribing a limited supply of topical tetracaine to patients who present to the emergency department with what the authors describe as “simple corneal abrasions.” It is well documented in the literature that long term use of topical anesthetics can lead to a variety of serious ophthalmic complications, including persistent epithelial defects, neurotrophic ulceration, secondary infectious keratitis, corneal scarring and perforation. However, many of these reports describe long term use of anesthetics ranging from 7 days to 6 months which have helped establish the long-held dogma that topical anesthetics are only appropriate for use during surgery or clinic examination. This study, as well as several smaller previous studies, has attempted to challenge that dogma in an effort to better treat the immense pain often associated with corneal abrasion.
The authors did a great job trying to distinguish between simple and non-simple corneal abrasions. This can be very difficult, even for an ophthalmologist. What may look like a simple corneal abrasion can easily turn out to be a different diagnosis altogether. Herpes simplex keratitis can present as a geographic ulcer, lighting up with fluorescein much like a corneal abrasion without the tell-tale sign of dendritic lesions to accompany it. Dry eye disease can result in confluent, punctate epithelial defects which can look like a corneal abrasion without the magnification afforded by a slit lamp. These conditions should not be treated with topical anesthetics and will only delay the patient in receiving appropriate care. Stating that topical anesthetics are safe for simple corneal abrasions assumes that the examiner is able to accurately diagnose a simple abrasion. In this study, several patients were misdiagnosed as simple abrasions and ultimately required follow up with ophthalmology. Patients who need to see ophthalmology for a non-simple abrasion may be less likely to follow up in a timely manner if they are given topical anesthetic that will effectively mask the pain. This can result in more extensive corneal scarring from a variety of diagnoses such as delayed rust ring removal or treatment of infectious keratitis.
The authors make a compelling point that a limited supply of tetracaine in a subset of corneal abrasions intended to last no more than 24 hours is safe with no significant difference in the number of ED rechecks, ophthalmology clinic referrals, persistent fluorescein uptake, or complications. If this is indeed true, is treating with topical anesthetic worth it? At best, you are providing a minimally-painful healing process which will be complete in 48-72 hours regardless of topical anesthetic use. At worst, you are masking pain of a potentially vision-threatening process that may have been misdiagnosed as a simple abrasion. I contend that setting patient expectations regarding pain (very severe for first 24 hours, then rapid improvement) and discussing more conservative comfort measures like icing and patching are sufficient.
Lastly, I want to discuss the treatment for simple and non-simple corneal abrasions. It is unclear whether or not the patients in this study were treated with topical antibiotics. It is possible that patients with simple corneal abrasions were sent home with a 24 hour supply of tetracaine and no topical antibiotics. Without an epithelial barrier, the underlying corneal stromal is prone to infection. Topical antibiotics act as a preventive measure and are particularly important if a patient is using topical anesthetic, which could mask the pain of infectious keratitis. Although not all sources agree, there is general consensus among ophthalmologists that all corneal abrasions require topical antibiotics at the time of diagnosis.
In conclusion, I agree that a 24 hour prescription of topical anesthetic in a simple corneal abrasion is likely safe. However, given the rapid healing time, consideration should be made to counseling patients on pain expectation and comfort measures in place of topical anesthetic. Lastly, prescribing more than a 1 day supply of topical anesthetic is unnecessary given the rapid improvement in pain after the first 24 hours
Dr. Glaucomflecken, MD
https://www.drgcomedy.com/
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How To Cite This Post
[Peer-Reviewed, Web Publication] Hung J, Klein M. (2019, July 8). Tetracaine. [NUEM Blog. Expert Commentary by Dr. Glaucomflecken]. Retrieved from http://www.nuemblog.com/blog/tetracaine.
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References
Verma A, Khan FH. Corneal abrasion. MedscapeAvailable at: http://emedicine.medscape.com/article/1195402-overview. Accessed November 1, 2017.
Waldman N, Densie IK, Herbison P. Topical tetracaine used for 24 hours is safe and rated highly effective by patients for the treatment of pain caused by corneal abrasions: a double-blind, randomized clinical trial. Acad Emerg Med 2014;21:374–82.
Chang YS, Tseng SY, Tseng SH, et al. Cytotoxicity of lidocaine or bupivacaine on corneal endothelial cells in a rabbit model. Cornea 2006;25:590–6.
Swaminathan A, Otterness K, Milne K, Rezaie S. The Safety of Topical Anesthetics in the Treatment of Corneal Abrasions: A Review. J Emerg Med. 2015;49(5):810-815.