Groups of rabbits were treated with a single drop of a topically administered carbon 14, ringlabeled solution of 0.1% dexamethasone sodium phosphate. The radioactive steroid preparation was compounded by the manufacturer of the comparable ophthalmic preparation in a manner identical to that used in the formulation of the commercial product. In the presence of an intact epithelium, no steroid could be detected, either in the cornea or the aqueous humor of the uninflamed eye. Removal of the epithelium prior to therapy permitted passage of detectable steroid into the cornea and penetration of the drug into the aqueous humor. A detectable level of dexamethasone was also demonstrable in the cornea and in the aqueous humor of the inflamed eye despite a structurally intact epithelium.
Cox WV, Kupferman A, Leibowitz HM. Topically Applied Steroids in Corneal DiseaseI. The Role of Inflammation in Stromal Absorption of Dexamethasone. Arch Ophthalmol. 1972;88(3):308-313. doi:10.1001/archopht.1972.01000030310017