The effect of cold tetracaine on the severity of burning sensation upon instillation

PURPOSE: Tetracaine is one of the most common eye drops that are used for analgesia in clinical practice. However, it causes ocular burning sensation when instilled. This study aimed to compare the effects of the cold and room temperature tetracaine on burning sensation. PATIENTS AND METHODS: We conducted a prospective, double-blinded, randomized controlled trial at the ophthalmology outpatient clinic, Phramongkutklao Hospital during January 2016–February 2017. In this study, 424 consecutive patients (those with a history of keratopathy or neuropathy were excluded) who received dilated fundus examination were randomized to receive cold tetracaine (4°C) in one eye and room temperature tetracaine (22.5°C) in the other eye. Each patient was asked to answer the questionnaire on the severity of burning sensation using 100 mm visual analog scale. RESULTS: Patients reported less burning sensation on the eye that received cold tetracaine (visual analog scale 20.50±18.8 vs 22.70±20 mm; P=0.025). In the subgroup analysis, young patients (≤40 years old), female subjects, patients who received tetracaine for the first-time and those who had no previous ocular surgery reported more benefit from cold tetracaine. The subgroup of patients who had normal corneal sensation, identified by using a Cochet–Bonnet esthesiometer, also showed greater benefit from cold tetracaine compared to those with impaired corneal sensation. CONCLUSION: Cold tetracaine caused less burning sensation than room temperature solution. Its benefit was greater in the subgroup of patients who reported more severe burning sensation. We recommend using cold tetracaine in routine practice, especially in those who are anticipated to have this common side effect.