Glaucoma is a progressive optic neuropathy characterised by increased ocular pressure and loss of retinal ganglion cells. Conventional drug therapy with eye drops to reduce intraocular pressure (IOP) has variable bioavailability and can lead to ocular surface disease. In this study poly(lactide)/monomethoxy-poly(ethyleneglycol) (PLA-PEG) nanoparticles (NP) were developed as a controlled drug delivery system. Latanoprost-loaded NP was administered to the subconjunctival space in rabbits with free LA and empty NP were given to two other groups of animals as controls. Aqueous humour levels of LA were measured by HPLC, and showed the drug released from NP was sustained over 14 day period. LA release from NP induced a significant hypotensive effect while the IOP remained the same in the other groups. No ocular inflammation was seen in the NP treated group. Nanoparticle technology is advancing at a significant rate targeting tumour and immune cells. The use of such systems for slow and controlled release of drug in ocular conditions is a potentially important step forward in treatment of disease.