The present invention relates to a colloidal anionic oil-in-water emulsion comprising a prostaglandin, an oil having a iodine value ‰¤ 2, a surfactant and water, provided the anionic oil-in-water emulsion does not contain polyvinyl alcohol. The present invention also pertains to the use of said anionic 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.
