Ocular Drug Delivery Systems: Traditional Review

Polat H. K., Ünal S., Aytekin E., Gözcü S.

Literatür Eczacılık Bilimleri Dergisi, vol.11, no.3, pp.189-200, 2022 (Peer-Reviewed Journal)


Ocular drug applications are a challenging area for ophthalmologists and scientists developing drug delivery systems due to the structural and barrier complexity of the eye. Obstacles such as different corneal layers, sclera, conjunctival blood flow, tear dilution, and blood retinal barrier limit the effectiveness of drug administration to the anterior and posterior parts of the eye. Among the conventional ocular drug administration forms, ocular eye drops are widely preferred by patients. However, these eye drops have low bioavailability due to the ocular barrier and therefore require frequent application. This situation reduces patient compliance. In addition, in some cases, it isn’t possible to prepare the active substance in solution form. For this reason, different dosage forms such as suspension and emulsion, which can be used in drops form, are also being developed. However, such formulations also have serious problems such as formulation-related stability and high viscosity. Both the structural problems of the eye and the inability to achieve the desired effects in dosage forms push researchers to different studies. For this reason, scientists have designed and studied various drug delivery systems to increase the drug delivery potential to the eye and thus the treatment efficacy. New drug delivery systems such as nanoparticles, liposomes, microemulsions, inserts, and drug-loaded contact lenses have recently been investigated as an alternative to conventional drug delivery systems. Although such new drug delivery systems provide a glimmer of hope for ocular drug delivery, there are still problems to be overcome. In this review, various traditional and new drug delivery formulations have been tried to be summarized.