Topical Tetracaine for Home Use Not Associated With Delayed Corneal Healing or Increased Symptom Rates at 48 Hours in Patients With Corneal Abrasion
EBM Focus - Volume 9, Issue 22
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Reference: Acad Emerg Med 2014 Apr;21(4):374 (level 2 [mid-level] evidence)
Pain from corneal abrasion is a common complaint in the emergency department. Topical anesthetics such as tetracaine are known to be effective at reducing ocular pain, with rapid onset and short duration of action. However, the use of topical anesthetics at home after discharge from the acute care setting has been discouraged because of concerns about complications, including delayed healing of the abrasion, based on case reports, studies of tissue samples, and animal studies. A recent randomized trial compared the safety and efficacy of topical tetracaine to saline drops in 122 patients presenting to the emergency department with a corneal abrasion.
All patients had an uncomplicated corneal abrasion and were randomized to topical tetracaine hydrochloride 1% vs. saline and followed for up to 1 month. The interventions were applied by patients at home every 30 minutes while awake as needed, for 24 hours total. All patients received acetaminophen (paracetamol) 1,000 mg orally every 4 hours for 4 doses and chloramphenicol 1% eye ointment. Patients recorded their pain scores every 30 minutes for the first 2 hours after leaving the emergency department, and then every 2 hours while awake for the next 48 hours. The safety of tetracaine was assessed by evaluating corneal healing by slit-lamp exam and fluorescein uptake at 48 hours from discharge, and by comparing persistent symptoms at 48 hours and 1 month. Patients were also asked to rate how well the intervention had worked on a 0-10 numeric rating scale (higher being more effective), after being contacted by telephone at 1 week and/or 1 month.
There were no significant between-group differences in pain scores at any time point evaluated. Fluorescein uptake at 48 hours occurred in 24% with tetracaine vs. 21% with placebo (not significant). Similarly, persistent symptoms at 48 hours occurred in 17% with tetracaine vs. 18% with placebo (not significant. The self-reported effectiveness score among patients responding at 1 week was 7.7 with tetracaine vs. 3.9 with placebo (p < 0.0005) among 80 patients (66% of those randomized) with data available. Results for persistent symptoms and self-reported effectiveness were consistent at 1 month. In addition, no other complications attributed to topical anesthetic were reported. A total of 29 patients (24%) were excluded from the analyses for incorrect enrolment (5%) or for retained rust rings (19%). Patients with retained rust rings were excluded because their persistent symptoms were thought to be mainly attributed to the rust rings themselves and repeated attempts to remove them, rather than any effect of study medication.
In this study, patients rated the overall effectiveness of topical tetracaine significantly higher than placebo when recalling their experience at 1 week or 1 month after presenting with a corneal abrasion. However, the pain scores recorded during the first 48 hours did not significantly favor tetracaine over saline. The reasons for this apparent discrepancy are not clear, but the large variation in pain scores and the fact that pain scores quickly decreased to nearly zero in both groups after 12 hours are likely contributing factors. Importantly, this study found that patients receiving tetracaine had no evidence of delayed corneal healing, persistent symptoms, or any other complications traditionally attributed to topical anesthetics. These findings highlight the fact that laboratory studies evaluating surrogate outcomes, while useful for elucidating pathophysiologic processes, have limited value in determining the efficacy of an intervention in a clinical setting. The use of chloramphenicol may limit the generalizability of these findings, since antibiotic use for corneal abrasion has limited supporting evidence and may not be routinely used in many practices. It’s also possible that the ointment itself provided relief irrespective of the antibiotic, which may explain the steep drop in pain scores in both groups. Further studies are warranted, but in the meantime these results suggest that topical anesthetics used for 24 hours are safe and may be an option for selected patients presenting to the emergency department with a corneal abrasion.
For more information see the Corneal abrasion topic in DynaMed.