Aqueous liquid bromfenac composition having preservative efficacy

A method for enhancing the preservative efficacy of an aqueous solution, the method comprising adding bromfenac or a salt thereof to the aqueous solution, wherein the aqueous solution is an aqueous base which contains (a) 0.001 to 0.002% of benzalkonium chloride and (b) 0.025% or higher and lower than 0.25% of a non-ionic surfactant, but does not have sufficient preservative efficacy.