Groups of rabbits were treated with a single standard dose of topically administered carbon14, ring-labeled ointment of 0.1% dexamethasone sodium phosphate. In the presence of an intact epithelium, no steroid could be detected either in cornea or in aqueous humor of the uninflamed eye. Removal of epithelium prior to therapy permitted passage of detectable steroid into cornea and penetration of the drug into the aqueous humor. Only a barely detectable corticosteroid level could be demonstrated in cornea and aqueous humor of the inflamed eye in the face of a structurally intact epithelium. Comparison of data obtained after administration of dexamethasone phosphate ointment with that previously obtained after administration of dexamethasone phosphate in solution reveals that the drug in ointment form produces lower steroid concentration in both cornea and aqueous humor than does solution form.
Cox WV, Kupferman A, Leibowitz HM. Topically Applied Steroids in Corneal DiseaseII. The Role of Drug Vehicle in Stromal Absorption of Dexamethasone. Arch Ophthalmol. 1972;88(5):549-552. doi:10.1001/archopht.1972.01000030551017