Siamak Khavandi, - Nikookari Ophthalmology Hospital, Tabriz university of Medical Sciences, Tabriz, Iran
Mozhdeh Mirahadi - Nikookari Ophthalmology Hospital, Tabriz university of Medical Sciences, Tabriz, Iran

Purpose: Ocular drug delivery is challenging in terms of achieving optimum drug concentration due to exclusive protective mechanisms of the eye. Many of barriers in eye are inherent and unique to ocular anatomy and physiology, creating it a challenging mission for drug delivery innovations. Corneal and conjunctival epithelium, bloodaqueous barriers and blood-retinal barriers are the fundamental structures that restrict the passage of molecules and fluids to the retina and impede drug penetration. Moreover, various elimination mechanisms, such as tear turnover, Nasolacrimal drainage, protein binding, systemic absorption, and enzymatic degradation, limit the ocular bioavailability of drugs, emphasizing the leading role of liposomes. Methods: In this article, we will review the promising nanocarrier for drug delivery into the posterior segment of the eye, emphasizing the use of liposomes Results: Nanostructured carriers have proven to be an effective and slightly invasive drug delivery system to keepdrug concentrations in the posterior segment of the eyeball. The advantage of using nanocarriers is their ability to increase the biopharmaceutical properties of the incorporated drug: solubility, stability, permeability, and retention at the site of application. Liposomes have been investigated for ophthalmic drug delivery since it offersadvantages as a carrier system. It is a biodegradable and biocompatible nanocarrier. In the case of posterior segment disorders, improvement of intravitreal half-life and targeted drug delivery to the retina is necessary. Liposomes was proven successful in enhancing the intravitreal half-life and targeted delivery to the inner retinal cells. It can enhance the permeation of poorly absorbed drug molecules by binding to the corneal surface and improving residence time. Conclusion: Considering that liposomes accumulate the main characteristics of an optimal drug delivery system, we consider that liposomes are hopeful nanoparticles for the therapy of multiple intraocular illnesses.