A mydriatic medication produces mydriasis or dilation of the pupil. Mydriatic medications are used preoperatively in the cataract client. These medication act by dilating the pupils. They also constrict blood vessels. An osmotic diuretic may be used to decrease intraocular pressure. A miotic medication constricts the pupil. A thiazide diuretic is not likely to be prescribed for a client with a cataract.