Provided is a drug therapy for preventing glaucoma or preventing or treating ocular hypertension, in which the ocular hypotensive effect is strong and the effect is more durable. A combination for preventing or treating glaucoma, the composition being obtained by combining (S)-(-)-1-(4-fluoro-5-isoquinoline sulfonyl)-2-methyl-1,4-homopiperazine or a salt or solvate thereof, and a prostaglandin.
