I understand your confusion. My reference to using Latanoprost myself every other night was not to infer the Latanoprost was preservative free, but rather to indicate that maybe using less Latanoprost would lessen the degree of side effects. In my opinion the dispenser bottles do not limit the amount of Latanoprost administered to the eye to the one drop specified in my doctor's prescription. Therefore I was over medicating with way too much Latanoprost being applied. To me it was logical to simply use less by only applying it every other night. Doctor's may not agree, but they're not the ones suffering the side effects are they? The preservative may help protect against contaminations which could cause an eye infecton, so instead of preservative free I myself am sticking with the Latanoprost with just one drop per eye as prescribed. Now figure out how to dispense only one drop per eye!!