The present invention relates to a colloidal cationic oil-in-water emulsion comprising: -a prostaglandin, -an oil having a iodine value ≤ 2, -one or more surfactants including at least one quaternary ammonium compound, -water, wherein the prostaglandin/total sum of surfactants mass ratio is comprised between 0.5 and 5. The present invention also pertains to the use of said cationic oil-in- water emulsions for enhancing the stability of said prostaglandins, for the treatment of ocular hypertension and/or glaucoma, for promoting growth of eyelashes and/or for treating eyelash hypotrichosis.
