Nanoparticles are perfectly suited as drug delivery systems due to their size and the diversity of materials used. They are able to penetrate biological barriers, can directly deliver drugs to the target site and provide a sustained release profile. Having long been established in oncology, in the last decade research has started to take a closer look at the potential of nanoparticles for ocular drug delivery. Obstacles, such as poor delivery of drugs via eye drops and the side effects of invasive methods, such as placing implants as drug depots could be overcome. Among the most relevant investigated structures are polymeric nanoparticles, micelles, liposomes, solid lipid nanoparticles, dendrimers and cyclodextrins. Besides the composition of the nanoparticle itself, its efficacy and stability can be optimized through coatings; however, long-term stability, standardization of production and toxicity remain the major challenges. The preclinical and partly clinical results obtained so far will hopefully give impulse to the idea of applying nanoparticles for optimized ocular drug delivery in the near future.
