In rabbits, topical application of tritium-labelled 0.1% dexamethasone sodium phosphate (Decadron) with a high specific activity resulted in easily detectable corneal and aqueous humor levels of this corticosteroid. Thin-layer chromatography (TLC) on aqueous humor samples demonstrated the tritium label on the dexamethasone molecule. Differential staining after TLC confirmed the presence of dexamethasone sodium phosphate in the aqueous humor samples. Using application of lower specific activity, dexamethasone resulted in an apparent lack of penetration because of the limits of this method.
Krupin T, Waltman SR, Becker B. Ocular Penetration in Rabbits of Topically Applied Dexamethasone. Arch Ophthalmol. 1974;92(4):312-314. doi:10.1001/archopht.1974.01010010322012