ABSTRACT
Different pharmaceutical approaches are available to control intraocular pathologies, such as diabetic retinopathy, uveitis, age-related macular degeneration, and cytomegalovirus (CMV) retinitis. Nevertheless, it is still difficult to achieve effective drug levels in the posterior segment tissues of the eye including the retina and vitreous without undesirable side effects. Among these approaches, topical and/or systemic administration of drugs have been widely used due to the advantage of being noninvasive. However, drugs administered orally or topically have limited penetration to ocular tissues such as retina and vitreous and therefore have little therapeutic effect on posterior structures in the eye. Topical applications of drugs at the surface of the eye result in poor intravitreal penetration due to several diffusion barriers preventing the entry of xenobiotics. These barriers are lacrimation, humor turnover, and length of diffusion path (1). Systemically administered drugs penetrate poorly into the eye due to the blood-retinal barrier (2) and require large doses of drug, resulting in potential systemic side effects. Both topical
and oral treatments require rigorous patient compliance over an extended period of time to effectively deliver active drugs.
