PURPOSE: To obtain the rod for damming up the tears which is less fluctuated in a dissolution speed by using a copolymer of one or ≥2 kinds of p-dioxanon and lactide.

CONSTITUTION: The lactide is more specifically exemplified by cyclic cliester consisting of two molecules of α oxyacid, such as glycolic acid, lactic acid and α hydroxy lactic acid, and the generally used lactide is lactide consisting of a glycolic acid unit and lactide consisting of a lactic acid unit. The copolymer is obtd. by successively polymerizing a p-dioxane monomer and a lactide monomer in the presence of a catalyst, such as stannous octanoate, etc. The resulted copolymer is melt spun by using a plunger extruder, etc., and is cooled to solidify; thereafter, the extruded polymer is cut to a desired length, by which the rod for preventing the outflow of the tears is obtd. A dry eye symptom is decreased by using such rod for preventing the outflow of the tears. Since the dissolution speed is uniform, the management of an insertion schedule is easy and in addition, the unstability as to bioaffinity is lessened.