pharmaceutics Review Advanced Formulation Approaches for Ocular Drug Delivery: State-Of-The-Art and Recent Patents Eliana B. Souto 1,2,*, João Dias-Ferreira 1 , Ana López-Machado 3,4, Miren Ettcheto 5,6, Amanda Cano 3,4,5, Antonio Camins Espuny 5,6 , Marta Espina 3,4 , Maria Luisa Garcia 3,4,5 and Elena Sánchez-López 1,3,4,5,* 1 Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra, 3000-458 Coimbra, Portugal 2 CEB—Centre of Biological Engineering, University of Minho, Campus de Gualtar 4710-057 Braga, Portugal 3 Department of Pharmacy, Pharmaceutical Technology and Physical Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain 4 Institute of Nanoscience and Nanotechnology (IN2UB), University of Barcelona, 08028 Barcelona, Spain 5 Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), University of Barcelona, 08028 Barcelona, Spain 6 Department of Pharmacology, Toxicology and Therapeutic Chemistry, Faculty of Pharmacy and Food Sciences, University of Barcelona, 08028 Barcelona, Spain * Correspondence: ebsouto@ff.uc.pt (E.B.S.);
[email protected] (E.S.-L.); Tel.: +351-239-488-400 (E.B.S.); +34-696-793-679 (E.S.-L.) Received: 6 August 2019; Accepted: 26 August 2019; Published: 6 September 2019 Abstract: The eye presents extensive perspectives and challenges for drug delivery, mainly because of the extraordinary capacity, intrinsic to this path, for drugs to permeate into the main circulatory system and also for the restrictions of the ocular barriers. Depending on the target segment of the eye, anterior or posterior, the specifications are different. The ocular route experienced in the last decades a lot of progresses related with the development of new drugs, improved formulations, specific-designed delivery and even new routes to administer a drug.