Washington University Emergency Medicine Journal Club- February 18, 2021
This month’s journal club will look at the short-term use of topical anesthetics for the pain associated with corneal abrasions. Traditional teaching warns against the use of these agents due to a reported risk of worsening corneal injury, but there is scant evidence to support this. We will look at four fairly recent articles that compared treatment with and without topical anesthetics to try to come to a more evidence-based conclusion.
All four articles will be appraised using the Therapy form.
You are working an EM-2 shift one evening when you encounter Mr. M, a 30-year-old male with no past medical history who was playing with his 2-year-old son that afternoon when his son reached out and poked him in the right eye. He has since had significant pain, tearing, and a foreign body sensation in the eye with no change in vision. He does not wear contact lenses. His visual acuity is 20/20 in each eye and in both eyes together. You get ready to perform a slit-lamp exam, and seconds after instilling tetracaine eye drops the patient lets out a huge sigh and proclaims that the pain in his eye is finally gone. You proceed with the exam, during which you see a small linear area of fluorescein uptake on the cornea, just lateral to the pupil. Seidel’s sign is negative.
You diagnose the patient with a corneal abrasion and are getting ready to discharge him on antibiotic drops when your attending reminds you that corneal abrasions can be quite painful. She mentions sending the patient out with a small number of hydrocodone/acetaminophen tablets when you start thinking about the relief the patient felt upon getting anesthetic eye drops. You ask about sending the patient home with the bottle of tetracaine when your attending starts laughing and says, “Sure, if you want his eyeball to explode!!!” Assuming that your attending must be exaggerating, you look on UpToDate and find that while they make no mention of spontaneous ophthalmic combustion, they do “discourage the prescribing or dispensing of topical anesthetic agents and favor other means of pain control.” Seeing no evidence to support this recommendation, you decide to do your own literature search to see if there really is any harm in providing topical anesthetics for corneal abrasions…
Population: Adult patients with simple cornel abrasions and no immunosuppression
Intervention: Topical tetracaine/ proparacaine drops upon discharge home
Comparison: Standard care.
Outcome: Pain reduction, patient satisfaction, delayed healing, corneal complication, vision loss.
PubMed was searched using the terms “corneal abrasions (tetracaine OR
proparacaine)” with no limits (tinyurl.com/2r1af4qo). Out of 28 results, four
relevant articles were chosen.
Article 1: 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
Apr;21(4):374-82. Answer Key.
Article 2: Waldman N, Winrow B, Densie I, Gray A, McMaster S, Giddings G, Meanley
J. 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. 2018 Jun;71(6):
767-778. Answer Key.
Article 3: Shipman S, Painter K, Keuchel M, Bogie C. Short-Term Topical Tetracaine Is
Highly EfCicacious for the Treatment of Pain Caused by Corneal Abrasions: A Double Blind , Randomized Clinical Trial. Ann Emerg Med. 2020Oct27:S0196-0644(20)30739-3. Answer Key.
Dogma has long held that topical anesthetics should not be given to patients with corneal abrasions outside of the ED or clinic setting due to a theoretical risk of toxicity, leading to delayed corneal healing and ocular complications. These concerns, however, are based on case reports and case series rather than clinical trials (Epstein 1968, Willis 1970, Duffin 1984, Chern 1996, Wasserman 2002), and persisted despite lack of causative evidence between tetracaine use and complications. Over the last decade, a handful of studies have sought to compare complication rates in patients using topical tetracaine outside of the acute setting to similar patients who did not receive tetracaine. We reviewed four of these articles, including three randomized controlled trials.
An early randomized controlled trial from 2010, conducted at 2 tertiary care EDs in London, Ontario found that patients with corneal injuries treated with dilute proparacaine (0.05%) had better pain reduction after taking the study medication than those who received placebo (improvement 3.9 cm vs. 0.6 cm on a visual analogue scale [VAS], p = 0.007). Patient satisfaction was also higher and there were no ocular complications or signs of delayed healing in either group.
Another randomized controlled trial from Southland Hospital in Invercargill, New Zealand, published in 2014, compared 1% tetracaine use, instilled every 30 minutes for 24 hours, with saline placebo in patients with an uncomplicated corneal abrasion. Among 116 total patients, of whom 59 received tetracaine, there were no complications up to one month after ED presentation. Persistent fluroscein uptake at 48-hour ED follow-up was seen in 23.9% of patients receiving tetracaine and 21.3% of patients receiving saline (risk difference 2.6%, 95% CI -14% to 20%), and persistent symptoms were present with similar rates. At one week follow-up, persistent symptoms were present with similar rates and patients receiving tetracaine had lower overall pain scores on a 0-10 scale (7.7 vs. 3.8; difference = 3.9, 95% CI 2.5 to 5.3), though strangely there was no significant difference in self-recorded pain scores at any given time between the two groups.
A retrospective study conducted at the same ED in New Zealand between 2014 and 2015 looked at all patients with corneal abrasions seen in their ED. They then compared outcomes in those who were sent home with 1% tetracaine hydrochloride (to use every 30 minutes for up to 24 hours) with those who were not given tetracaine. In patients with simple corneal abrasions—defined as mechanical injuries that were not penetrating, not lacerating, with a “not large” area of fluorescin uptake—the risk of requiring an ED recheck was similar between the groups (RR 1.29, 95% CI 0.80 to 2.07). Both groups were at low risk of requiring ophthalmology follow-up (0.3% with tetracaine, 1.8% without; RR 0.18, 95% CI -0.02 to 1.64), and none of the 303 patients who received tetracaine had an ocular complication. The authors reported that the upper limit of the 95% CI for complications among SCA patients who received tetracaine was 1.19%. For patients with non-simple corneal abrasions, the upper limit of the 95% CI for complications among those who received tetracaine was 2.41%.
A more recent randomized controlled trial, published in 2020 and conducted in a large ED in Oklahoma City, Oklahoma, found that patients treated with tetracaine had lower overall pain score at 24-48 hour ED follow-up compared to the placebo group (median 1 on a numeric rating scale versus 8; difference = 7, 95% CI 6 to 8). Interestingly, the authors planned to report pain scores before and 2 minutes after each use of the study drops, but did not do so for unclear reasons. Patients in the placebo group took more hydrocodone tablets than those in the tetracaine group (median 7 vs. 1, difference 6; 95% CI 4 to 9). A larger number of patients was found to have a small residual corneal abrasion at ED follow-up in the tetracaine group, but this did not achieve statistical significance (18% vs. 11%, 95% CI -6.4% to 20.4%). Adverse event rates, however, were lower in the tetracaine group, though this also did not achieve statistical significance (3.6% vs. 11%; difference 7.4%, 95% CI -2.95 to 18.6%).
Interestingly, improved pain control was not universally seen with topical anesthetic use in these studies. In the initial study by Waldman et al, there was no significant difference in pain scores between those who did and did not receive tetracaine, despite a significantly higher drug effectiveness rating. Ball et al found that while proparocaine reduced pain scores, it did not reduce the number of acetaminophen/codeine tablets taken. Additionally, none of the patients in the study by Ting et al required any oral analgesics. Shipman et al found that pain scores were reduced at ED follow-up, but their failure to report changes in pain score after study drop use—a planned secondary outcome—limits our understanding of how quickly analgesia was achieved.
Despite these limitations, and despite the ophthalmologic risks of long-term topical anesthetic use, there does not appear to be any significant risk of delayed healing or ocular complications with short-term use. In the trials included here, no serious complications were observed in 458 patients who received topical tetracaine or proparacaine. It should be noted that these studies universally excluded contact lens wearers and those with a history of ocular surgery or signs of ocular infection, and topical anesthetics should not be provided in such patients. If they are to be prescribed, clinicians should only dispense enough drops to last a short period of time (e.g., 24 hours).