In recent years, several colloidal preparations for ophthalmic use have been investigated, based on nanoparticles or liposomes. However, no evidence could be found in most cases of any considerable advantage over conventional formulations. In contrast, the introduction in the early eighties of the concept of in situ gel formation by means of highly concentrated latex systems demonstrated that a considerable prolongation in duration of action could be obtained. This had previously been achieved only with inserts. In the past 15 years, the coating technology developed in the paint industry has been the driving force for the very rapid evolution in the field of aqueous dispersions. Polymers with solubility properties depending on the pH, such as cellulose derivatives, cannot be prepared by emulsion polymerization techniques. An alternative method for the preparation of polymeric dispersions in the nanometer size range is the emulsification of the polymers, their solutions or melts into water, using conventional emulsifiers, stabilizer and emulsification techniques. Different approaches for the preparation of these so-called “latex formulation” are possible, e.g., solution emulsification, phase inversion, self-emulsification, etc. Recent advances in our knowledge of in situ gel forming systems used via the ocular route by drug-carrying nanoparticles will be discussed. These systems are based on the mechanism of drug adsorption onto the surface of colloidal particles (0.3 μm average particle size) which show a good biocompatibility. These colloidal or near colloidal dosage forms have low viscosity and can accommodate solid content up to 40% w/w. The features are that these systems provide a prolonged therapeutic effect, that they can be applied as easily as existing eye drops and that they show a good tolerance, which should result in improved patient compliance.