The administration of drugs to treat ocular disorders still remains a technological
challenge in this XXI century. Although there is an important arsenal of active molecules useful
to treat ocular diseases, ranging from classical compounds to biotechnological products,
currenty, no ideal delivery system is able to profit all their therapeutic potential. Among the
Intraocular Drug Delivery Systems (IODDS) proposed to overcome some of the most important
limitations, microsystems and nanosystems have raised high attention. While microsystems
are able to offer long-term release after intravitreal injection, nanosystems can protect
the active compound from external environment (reducing their clearance) and direct it to its
target tissues. In recent years, some researchers have explored the possibility of combining
micro and nanosystems in “Nanoparticle-in-Microparticle (NiMs)” systems or “trojan systems”.
This excellent idea is not exempt of technological problems, remains partially unsolved,
especially in the case of IODDS. The objective of the present review is to show the
state of art concerning the design, preparation and characterization of trojan microparticles for
drug delivery and to remark their potential and limitations as IODDS, one of the most important
challenges faced by pharmaceutical technology at the moment.