Herps zoster is a viral infection and a common disorder of the eyes. It is caused by herpes simplex virus: herpes virus type 1(HSV-1) & herpes virus type 2 (HSV-2). Topical acyclovir is currently the only and safe pharmacologic treatment of severe viral infection of the eyes. Nanoparticulate formulations have advantage of improving residence time over ocular surface, reduced size increasing permeation across corneal surface for intraocular activity. The objective of this study was to prepare and evaluate Acyclovir (Acy)  nanoparticles (NPs) for the treatment of Herps zoster infection of the eyes. So, the present study was designed with the primary aim to prepare nanoparticles by nanoprecipitation method using cationic polymer Eudragit E100 and secondly to study the effect of variables on the behaviour of nanoparticles. Preliminary study showed the compatibility of the drug with the formulation. Optimization was done using full factorial design with independent variables such as Drug to polymer ratio, Organic: aqueous phase ratio and effect of type and concentration of stabilizer. The dependent variables were determined such as particle size, drug entrapment, % drug release selected as the levels. F21 formulation was selected as the final optimized formulation.