Retinal barriers ocular drug delivery

Consequently, frequent instillation of eye drops is required, resulting in pulsed administration and patient noncompliance. Clearly, the main prerequisite for absorption of drugs into the eye is good corneal penetration and prolonged contact time with the corneal epithelium. Many intrinsic barriers, such as the cornea barrier, blood-aqueous barrier (BAB), and blood-retinal barrier (BRB), restrict ocular drug delivery (Figure 51.2). The barriers related to topical drug administration route are as follows. 

The ocular endotamponades of the future could be a combination of tampo-nading and drug delivery device. Vitrectomy removes the natural vitreous after it has become opaque, inflamed, or unable to keep the retina in place. In many cases, the necessity to remove it is the result of retinal disorders, which are still existent after vitrectomy [50]. In equivalence to the blood-brain barrier, there is also a blood-retina barrier, with the effect that it is difficult to treat retinal disorders systemically. Therefore, the delivery of appropriate drugs via the vitreous cavity would open new treatment options. 

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