While topical administration is effective in the treatment of anterior chamber diseases, it is ineffective in the treatment of diseases afflicting the posterior segments of the eye. Major problems include washing away of the drug by tears and the inefficient diffusion of drug from the corneal side to the posterior. Systemic injection does deliver drugs to the posterior of the eye but is also associated with non-specific accumulation of drug in other organs. In addition the blood retinal barrier also hinders the diffusion of drug into the posterior chamber. In light of this information, intraocular drug injections have gained in importance. However, although they achieve therapeutic drug levels, they are associated with high vitreal clearance which necessitates multiple injections. Many therapeutic strategies have been developed in recent years. One such method is the use of biomaterial drug delivery devices either in the form of implants or as micro or nanoparticles. Despite of their ability to release therapeutic agents for a prolonged period of time, ocular rod implants have been found to be responsible for causing retinal detachment and endophthalmitis. With the expansion of nanotechnology in medicine, a wide variety of nanoparticle drug releasing devices have been fabricated and tested for their ability to treat a wide range of diseases. Many studies have been done to explore the possibility of using polymeric micro and EX 527 nanoparticles for anterior and posterior chamber drug delivery. Although microparticles have better drug loading capacity than nanoparticles, the latter is recognized as favorable drug carrier due to its low risk on hampering normal vision. Although different types of nanoparticles have been investigated for their ability to target different cells, tissues and to cure different ocular diseases. very limited studies have been done to systematically evaluate the effect of material physical and chemical properties on their ocular tissue and cell compatibility. It is well established that the physical and chemical properties of materials affect their cell and tissue compatibility. We thus assumed that nanoparticles made of different materials are likely to cause different extents of acute tissue responses in the eye. To test this hypothesis, nanoparticles made of different materials were included in this study. Specifically, nanoparticles were made out of degradable polymers like poly, hydrogels like poly N-isopropyl acrylamide, non-degradable materials like polystyrene, and biological materials like hyaluronic acid. The ocular compatibility of these nanoparticles was evaluated using rabbit intravitreous implantation model. After implantation for different periods of time, we measured the changes in intraocular pressure. At the end of the studies, animals were sacrificed and ocular tissues were histologically evaluated. The effect of material properties on the ocular tissue responses was then determined to show that it can play a key role in determining the fate of nanoparticles in the eye. Drug delivery to the back of the eye, especially the posterior segments, is a key research area and important considering numerous ocular diseases that afflict that region.