Topical Ocular Drug Delivery: Recent Developments and Future Challenges

Optimized Ophthalmic: Advances in the Treatment of Ocular Diseases in Animals

“…When an eyedrop is instilled, the cul-de-sac may momentarily contain a 30 µl volume, but the instilled solution is rapidly removed by spillage from the conjunctival sac or loss through the puncta to the lacrimal drainage system until the tears return to their normal volume. This rate decreases with viscosity and increases with larger eye drop volumes Lee & Robinson [8]. Ocular administration of irritating drugs or vehicles increases the drug loss from the precorneal area to a further extent due to induced lacrimation Lee & Robinson [6].…”

Minimally invasive microneedles for ocular drug delivery

“…Drug delivery research has significantly increased for other routes such as oral and transdermal routes, whereas progress in the area of ocular drug delivery has been gradual and relatively limited. Lee and Robinson in 1986 described the majority of ocular drug delivery systems as 'primitive and inefficient' [9], referring mainly to solutions, suspensions, and ointments. In 1995 around 90% of the ophthalmic formulations on the market were based on these three systems [10].…”

Soft Glucocorticoids: Eye-Targeted Chemical Delivery Systems (CDSs) and Retrometabolic Drug Design: A Review

“…The relatively lipophilic corneal epithelium tissue having low porosity and high tortuosity due to tight annular junctions, is the primary barrier for hydrophilic drugs, where as the middle stromal layer consisting mainly of water interspersed with collagen fibrils( major thickness of cornea), is the main barrier for the lipophilic drugs [38][39][40][41]. All these facts result not only in a low net eye drug delivery, but also in substantial systemic availability of ophthalmic drugs after topical administration giving systemic side effects [42]. Moreover as mentioned earlier, existing ophthalmic drugs are actually not developed for ocular applications, they were intended for other therapeutic areas which were later converted to ocular applications following their high efficacy.…”