A comparison of proparacaine and tetracaine eye anesthetics

To compare two topical eye anesthetics, proparacaine and tetracaine, for pain of instillation and duration of activity.

Volunteers received both anesthetics in a prospective, randomized, double-masked protocol. The subjects were given one drop of a study solution in the lower lid fornix of the left eye. Immediately after receiving the medication, they rated the pain of instillation on a previously validated visual-analog pain scale. This procedure was then repeated in the right eye with the other study solution. Pain scales were quantified by making measurements to the nearest millimeter from the point of scale origin to the point marked by the patient. The time interval until return of the corneal blink reflex was determined using a cotton wisp. Pain scores and the time to return of corneal reflex were analyzed by the Sign test and Wilcoxon rank-sum test, respectively, with significance defined as p < 0.05.

Twenty-three subjects were available for analysis. Twenty subjects reported proparacaine hurt less than tetracaine, two felt the pain was the same for the two agents, and only one reported that proparacaine was more painful. The mean pain score for tetracaine was 24 mm (100 mm maximum) higher than that for proparacaine (p < 0.0002). Proparacaine lasted 1.3 minutes longer than tetracaine, 10.7 minutes versus 9.4 minutes (p = 0.0001).

Proparacaine eye drops cause less pain than tetracaine eye drops upon instillation. Anesthesia from proparacaine last slightly longer. These properties make proparacaine preferable to tetracaine.