New Data Haven’t Changed Ophthalmology’s Myopic View of Topical Anesthetics for Corneal Abrasions

For decades, emergency physicians have challenged the premise that topical anesthetics used for a short duration of time (eg, hours to days) couldn’t possibly harm patients. This seems like a reasonable, common-sense argument, which should prompt widespread adoption. However, emergency physicians who were bold enough to go rogue on this topic were met with great resistance. Apparently, commonsense is no match for the myopic dogma about this topic in the ophthalmological community.

Perhaps, randomized controlled trials would be necessary to unequivocally demonstrate that the safety of the short-term use of topical anesthetics (eg, tetracaine) for corneal abrasions.

The Data

The roots of dogmatism and myth propagation run deep—in this case, very deep. Three credible studies, which were published in 2014, more than adequately reflect the safety of the short-term use of tetracaine for corneal abrasions. The first, was published by Waldman et al in 2014.¹ This prospective, randomized, double-blind study of 116 patients compared undiluted tetracaine (1%) to saline in patients presenting with uncomplicated corneal abrasions during a 12-month period. The drops could be applied every 30 minutes while the patient was awake for a maximum of 24 hours. No tetracaine-attributable complications were noted in the treatment group, and there was no statistically significant difference in delayed corneal healing (defined as fluorescein update at 48 hours) between the two groups (23.9 percent for tetracaine versus 21.3 percent for saline).

In 2015, Puls et al performed a systemic review and meta-analysis that included two randomized trials.² They reported no significant differences in pain, persistent symptoms, or corneal healing. Although their data reflected an odds ratio for delayed healing of 1.31 for those receiving topical anesthetics for 72 hours or less, suggesting 31 percent greater odds for delayed healing with topical anesthetics, the bottom line is that no complications from treatment were noted. Also published in 2015 was a systematic review that included the two randomized trials Puls identified, as well as four additional studies evaluating topical anesthetic use in patients following photorefractive keratectomy.³ They reached similar conclusions: “Our literature search produced two emergency department-based, randomized, double-blind, placebo-controlled studies on human patients with corneal abrasions. Additionally, we found four studies that investigated the application of topical anesthetics in patients who underwent photorefractive keratectomy. All six studies demonstrated that a short course of dilute topical anesthetic provided efficacious analgesia without adverse effects or delayed epithelial healing.”

Finally, this year Waldman published a study larger than the prior work in 2014.⁴ This was a well-done study of 1,576 patients with corneal abrasions, of which 532 were determined to be “simple” as opposed to “complicated.” The relative risks for ED return visit and fluorescein staining (both indications of persistent symptoms) were 1.67 and 2.53, respectively. However, when considering only simple corneal abrasions, the numbers neutralized to 1.16 and 0.77. Most important, the complications were too rare to model, and thus there was no evidence that the short-term use (24 hours) of non-dilute tetracaine was unsafe. Will our ophthalmology colleagues be satisfied? Past experience predicts future expectations.

A Change in Practice?

These data should suffice to put this question to rest. Unfortunately, dogma may create an irrational conviction to unfounded “facts.” For example, three ophthalmologists wrote a very critical rebuttal to Waldman’s 2014 study.⁵ “While tetracaine temporarily anesthetizes pain, its routine usage to treat traumatic corneal abrasions in an emergency department is dangerous and can lead to blinding ocular complications.”

What evidence did they offer to support this hysteria? None, except for one study about chloramphenicol ointment, which was used to establish a low rate of corneal ulcer (0.26 percent) from corneal abrasions in Nepal, reporting more complications in Waldman’s tetracaine group.⁶ However, none of Waldman’s patients ever developed corneal ulcers. The ophthalmologists also cited a case report of eight patients who developed corneal defects, stromal opacity, or ring-shaped infiltrates. However, only one patient was treated for a corneal abrasion while the others had more severe pathology and the mean duration of topical anesthetic use was 14.8 days ± 7.78 days.⁷

Their final evidence was from a 1990 article titled, “Topical Anesthetic Abuse.” Really? Is tetracaine a drug of abuse? This was a case report of six patients with complications, reportedly secondary to prolonged anesthetic use.⁸ Finally, perhaps their greatest criticism reflects a negative bias about emergency physicians. “The methodology used to diagnose corneal abrasions is ambiguous. None of the corneal evaluations were performed by an ophthalmologist, and some of the evaluations were not even done by a physician.”⁵ It is maddening to consider that in 2014, some ophthalmologists didn’t feel emergency physicians were qualified to diagnose corneal abrasions. Clearly, the evidence they were challenging was far superior to anything they presented.

With dogma as thick as fog, the only answer must be that the duration and volume of “evidence” must have shaped generations of ophthalmologists, resulting in the indiscriminate and irrational challenge of alternative perspectives, despite evidence supporting new thinking.

Anesthetic keratopathy from prolonged and uncontrolled use has been reported as far back as 1956.^9,10 Since that time, many articles have been published but were editorials based on historical opinion as opposed to evidence, studies using mouse and rabbit corneas, and an impressively long list of case reports. The volume is nearly as impressive as the 60-plus years of poor-quality or nonexistent evidence used to perpetuate this myth.

Emergency physicians are efficient in our work and our thinking. Four years and a small number of good-quality studies, and we have our answer. Short-term topical anesthetics have never been proven to cause injury or delay healing, and 24-hour use in simple corneal abrasions is certainly safe, particularly with dilution.³ It’s time to open the eyes of some ophthalmologists who believe that years of dogma and reams of poor evidence is a substitute for common sense and a small number of good-quality studies.

References

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;21(4):374-382.
2. Puls HA, Cabrera D, Murad MH, et al. Safety and effectiveness of topical anesthetics in corneal abrasions: systematic review and meta-analysis. J Emerg Med. 2015;49(5):816-824.
3. Swaminathan A, Otterness K, Milne K, et al. The safety of topical anesthetics in the treatment of corneal abrasions: a review. J Emerg Med. 2015;49(5):810-815.
4. 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. 2018;71(6):767-778.
5. Pruet CM, Feldman RM, Kim G. Re: “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(9):1062-1063.
6. Upadhyay MP, Karmacharya PC, Koirala S, et al. The Bhaktapur eye study: ocular trauma and antibiotic prophylaxis for the prevention of corneal ulceration in Nepal. Br J Ophthalmol. 2001;85(4):388-392.
7. Erdem E, Undar IH, Esen E, et al. Topical anesthetic eye drops abuse: are we aware of the danger? Cutan Ocul Toxicol. 2013;32(3):189-193.
8. Rosenwasser GO, Holland S, Pflugfelder SC, et al. Topical anesthetic abuse. Ophthalmology. 1990;97(8):967-972.
9. Behrendt T. Experimental study of corneal lesions produced by topical anesthesia. Am J Ophthalmol. 1956;41(1):99-105.
10. Marr WG, Wood R, Senterfit L, et al. Effect of topical anesthetics on regeneration of corneal epithelium. Am J Ophthalmol. 1957;43(4 Part 1):606-610.