Drug delivery to the eye is highly challenging due to the existence of
protective anatomical barriers. Numerous vision threatening diseases affect the anterior
and posterior segments of the eye. The topical route is the most common mode of drug
administration for the treatment of eye diseases. Following topical administration, less
than 5% of instilled dose may be absorbed primarily by corneal and secondarily by
conjunctival pathway. However, the remaining portion of the drug is washed out by precorneal
mechanisms such as tear turnover, nasolachrymal drainage and blink reflex. In
addition, the physicochemical properties of the drug and lipoidal nature of the cornea
limit ocular absorption. Various therapeutic strategies such as ultrasound, microneedle
and prodrug modification are known to enhance drug concentrations at the target
tissues. In this chapter, we made an attempt to discuss briefly these strategies and their
role in enhancing bioavailability in the anterior and posterior ocular segments.
Keywords: Eye, bioavailability, efflux transporter, prodrugs, microneedles.
