Drop it like it’s Hot- A case presentation and critical appraisal on the use of tetracaine eye drops following corneal abrasion: A Medical Student Pearl
Claudia Cullinan
DMNB, Med 3
Case:
It’s a sunny July afternoon and you are just starting your shift in the ED when a 25-year-old male presents with sudden onset of severe right eye pain. You bring him into the exam room, and he explains he ran into a tree branch. He is reluctant to open his eye due to the pain and his eye is watering uncontrollably. He also keeps his sunglasses on while you talk because his eye is now extremely sensitive to the bright ED lights.
The patient is visibly in a lot of distress, so you do a quick penlight exam and attempt to assess visual acuity to confirm there is no evidence of penetrating trauma.
At this point you suspect a corneal abrasion, so you move onto a slit lamp and fluorescein examination and add a tetracaine 0.5% (topical anesthetic) to the affected eye. The patient appears more comfortable within seconds. You are able to complete the exam with the patient sitting comfortably in the exam chair. There is no evidence of Seidel sign (streaming fluorescein caused by leaking aqueous humor) and no visible foreign body in the eye. You can visualise a linear yellow lesion along the lateral cornea when viewed with fluorescein under cobalt blue light and you are confident this is a simple corneal abrasion.
Figure 1. Corneal abrasion viewed with cobalt blue light after fluorescein staining. Accessed from DFOptometrists.com
You explain to the patient that he has a corneal abrasion, prescribe him erythromycin 0.5% ophthalmic ointment to be inserted into the affected eye QID for 5 days and encourage him to avoid rubbing his eyes. He can also take PRN ibuprofen if needed. He asks “That one eye drop made my eye feel so much better, can I have a bottle of that to bring home?”
You know he is talking about Tetracaine, and you remember learning about the controversy of using topical anesthetics for the outpatient treatment of corneal abrasions….what do you tell him?
Critical Appraisal : Short-term topical tetracaine is highly efficacious for the treatment of pain caused by corneal abrasions: a double-blind, randomized clinical trial. (2020)
Background:
Corneal abrasions are among the most common ophthalmic presentations to the emergency department (ED). They occur when the corneal epithermal becomes disrupted, such as when tiny foreign bodies land in your eye or when your new puppy accidentally scratches the surface of your eye. Although corneal abrasions typically heal rapidly with minimal risk of complication, they are often VERY painful and can be extremely debilitating. There has been controversy on whether patients should be discharged home with topical anesthetics for short term management of corneal abrasions because of previously described safety concerns regarding toxicity. However, recent literature is beginning to surface suggesting there may be a role for short term topical analgesia following simple corneal abrasion, with appropriate follow up.
Figure 2. Anatomy of the cornea. Accessed form AAFP.org
Clinical Question:
How effective is the home use of topical tetracaine every 30 minutes PRN pain for 24 hours following corneal abrasion?
Reference
Shipman, S., Painter, K., Keuchel, M., & Bogie, C. (2021). Short-Term Topical Tetracaine Is Highly Efficacious for the Treatment of Pain Caused by Corneal Abrasions: A Double-Blind, Randomized Clinical Trial. Annals of Emergency Medicine, 77(3), 338–344. https://doi.org/10.1016/j.annemergmed.2020.08.036
Study Overview:
Population: Patients 18-80 years old presenting to an urban ED in Oklahoma City with suspected acute corneal abrasion.
Intervention: 2mL bottle of Tetracaine 0.5% one drop applied q30 minutes PRN pain for a maximum of 24 hours + antibiotic ophthalmic solution (polymyxin B sulfate/ trimethoprim sulfate) 2 drops to affected eye q4h.
Control: 4 separate 0.5mL ampules of artificial tears (Systane) one drop applied q30 minutes PRN pain for a maximum of 24 hours + antibiotic ophthalmic solution (polymyxin B sulfate/ trimethoprim sulfate) 2 drops to affected eye q4h.
Outcome: Pain rating at 24-48h follow up.
Methods:
- Prospective, double blind, randomised control trial of topical tetracaine vs control (artificial tears) in the ED following diagnosis of corneal abrasion in the ED.
- Took place in an urban Oklahoma ED from 2015 to 2017.
- One hundred and eleven patients were included and were randomly assigned to the treatment or control group.
- The patients in both groups had similar baseline characteristics and baseline numeric rating scale (NRS) pain scores (0-10, 10 being the most pain).
Inclusion criteria:
Patients 18 to 80 years old, presenting to the ED with suspected acute corneal abrasion, and gave written informed consent.
Exclusion criteria:
Contact lens wearers, previous corneal surgery or transplant in the affected eye, presented more than 36 hours after their injury, had a grossly contaminated foreign body, had coexisting ocular infection, currently pregnant, retained foreign body, penetrating eye injury, receiving immunosuppression, allergy to study medication, unable to attend follow-up, unable to fluently read and speak English or Spanish, and any injury requiring urgent ophthalmologic evaluation.
Results:
Main outcomes at the 24-48hr follow up appointment:
- The overall numeric rating scale (NRS) pain score was significantly lower in the tetracaine group compared to the control group (1 versus 8, P<0.001).
- The number of patients found to have a small residual corneal abrasion on their follow up slit-lamp examination was similar between groups (18% in the tetracaine group and 11% in the control group).
- There were only two complications in the tetracaine group (versus 6 in the control group), with similar rates of worsening corneal abrasions in both groups. All patients had normal healing after 10 days. No serious adverse outcomes were encountered.
Table 1. Patient baseline demographics and 24-48hr follow up data points.
| Group |
Tetracaine (n=59) |
Control (n=59) |
| Age, y |
35 (28-43) |
38 (27-47) |
| Male patients, No. (%) |
36 (61) |
34 (58) |
| Baseline pain rating |
7 (6-7.5) |
7 (6-8) |
| 24-48hr pain rating |
1 (1-2) |
8 (7-8) |
| No. of hydrocodone tablets recorded |
1 |
7 |
| Adverse Events, No (%) |
2 (3.6) |
6 (11) |
Limitations and suggestions for future studies:
- Although this was a double-blind study, there are two things that could have made patients aware of their treatment group. First, the control was packaged in 4 ampules and the treatment was packaged in a single bottle. Second, Tetracaine burns when administered to the eye and Systane (control) does not.
- The study was slightly underpowered for the primary outcome of efficacy and certainly not powered to determine safety for rare adverse events associated with topical anesthetics. That being said, there are more patients in this trial demonstrating short term safety than previous care reports and series demonstrating tetracaine harm.
- There was an extensive exclusion criterion, including patients who wear contacts (which are a common cause of corneal abrasions). By broadening the inclusion criteria, the results could be applied to a greater number of patients.
- Patients were required to return for follow up at which time they were required to return their “study drops” so the drops cannot be abused. It would be more feasible to limit the amount of eye drops in the bottle so the patient does not have to return to the ED for bottle disposal.
Our conclusions:
Short term topical tetracaine is an efficacious analgesic for acute corneal abrasions, is associated with less hydrocodone use compared to control, and appears to be safe.
Case
Back to our original question…what do we tell our patient?
Provide him with a limited number of tetracaine drops and administer one drop in affected eye q30 minutes PRN pain for a maximum of 24 hours. Advise him to return to ED if his symptoms persist beyond 48 hours or get worse.
References
McGee, H. T., & Fraunfelder, F. (2007). Toxicities of topical ophthalmic anesthetics. Expert Opinion on Drug Safety, 6(6), 637–640. https://doi.org/10.1517/14740338.6.6.637
Shipman, S., Painter, K., Keuchel, M., & Bogie, C. (2021). Short-Term Topical Tetracaine Is Highly Efficacious for the Treatment of Pain Caused by Corneal Abrasions: A Double-Blind, Randomized Clinical Trial. Annals of Emergency Medicine, 77(3), 338–344. https://doi.org/10.1016/j.annemergmed.2020.08.036
Wipperman, J. L., & Dorsch, J. N. (2013). Evaluation and management of corneal abrasions. American Family Physician, 87(2), 114–120.
Yu, C. W., Kirubarajan, A., Yau, M., Armstrong, D., & Johnson, D. E. (2021). Topical pain control for corneal abrasions: A systematic review and meta-analysis. Academic Emergency Medicine, 28(8), 890–908. https://doi.org/10.1111/acem.14222
