Travatan Z (Travoprost) is a prostaglandin used to treat glaucoma. It is different from Travatan because it does not contain Benzalkonium as a preservative.Travatan is used to treat high pressure inside the eye due to glaucoma (open-angle type) or other eye diseases (e.g., ocular hypertension). Lowering high pressure inside the eye can help prevent blindness. This medication works by regulating the flow of fluid within the eye to maintain a normal pressure. Bimatoprost is used after other medicines either caused very bothersome side effects or did not fully work to lower the pressure in the eye. Travatan may slowly (over months to years) cause brown discoloration of the colored portion of the eye (iris). If you are using bimatoprost in only one eye, only that iris may change color. An increase in eyelash number/length/thickness and darkening of the eyelashes/eyelids may also occur in the treated eye.