Eye irrigation is more comfortable with a lidocaine: containing irrigation solution compared with normal saline

Background:  Is eye irrigation with a Morgan lens more comfortable with a lidocaine-containing solution compared with standard saline?

Methods:  Prospective randomized double-blind volunteer placebo controlled study. Subjects received two drops of 2% tetracaine in each eye. Morgan lenses were applied to each eye and connected to separate 1-L bags of room temperature 0.9% saline. Subjects were randomized to continuous irrigation with 0.01% lidocaine solution (10 mL of 1% lidocaine [100 mg] in 1 L saline) in either the right or left eye with the opposite eye serving as control. pH was measured and fluid flow rate set at 35 mL/min. Blinded interviewers asked the subjects at 5 minutes intervals to rate their discomfort on a five-point Likert scale. Differences in mean Likert scores and standard deviation at 5, 10, 15, 20, and 25 minutes in each eye were calculated. Data were analyzed using one-way analysis of variance and the Bonferroni (BON) multiple comparison test (paired sample t test).

Results:  One-way analysis of variance p value for the combined time sets was very significant (<0.0001). The difference in mean Likert scores for 5 minutes was not statistically significant; approached statistical significance at 10 minutes and were very significant at 15 minutes {1.22 [95% confidence interval (CI) 0.16-2.28]; BON 3.02}, 20 minutes [1.44 (95% CI 0.38-2.5); BON 3.57], and 25 minutes [1.55 (95% CI 0.62-2.88); BON 4.09]. There were no reported long-term adverse effects.

Conclusions:  Continuous irrigation of the eye with a lidocaine-saline solution and a Morgan lens causes less discomfort than saline alone in healthy volunteers.