[Distribution of radioactively labeled digitalis in the eye]

Twenty-four hours after instillation of radioactively labeled digoxin into the conjunctival sac the radioactivity is concentrated in the various ocular tissues. A fourfold enrichment was observed in highly vascularized tissues such as the iris, ciliary body, and retina, as opposed to tissues with minimal vascularization such as the sclera. No concentration of digoxin was observed in the untreated control eye. Only in the sclerae was there a slight enrichment, corresponding to that found in the blood. Values in the untreated control tissues (skeletal muscle and skin) were minimal. These experiments show that the retina, ciliary body, and iris have a selective affinity for locally administered digoxin.