The present invention relates to cationic ophthalmic oil-in- water type emulsions, which comprise colloid particles having an oily core surrounded by an interfacial film, said emulsion comprising at least one cationic agent and at least one non ionic surfactant, said oily core comprising a prostaglandin selected from the group comprising in particular latanoprost, unoprostone isopropyl, travoprost, bimatoprost, tafluprost, 8-isoprostaglandinE2, or a mixture thereof, for treating ocular hypertension and/or glaucoma. These emulsions have the property to increase the chemical stability of prostaglandins.
