A review.The design of a drug delivery system for the eye requires a balance between the limitations imposed by the physicochem. properties of the drugs, the limitations imposed by the anatomy and disease state of the eye, and the dosing requirements of the drug the a particular disease.Some general concepts and tactics in drug delivery, barriers to getting drugs into the vitreous and retina, mechanisms by which drugs are cleared, and drug delivery for some specific ophthalmic problems are discussed.