Administration of drug directly into the vitreous is also associated with a lot of problems; clearance of the drug being one of the main drawbacks. In light of this fact, nanotechnology has come to the forefront of ocular drug delivery and as such, understanding ocular tissue response to implanted nano-biomaterials is of paramount significance. Our selection of materials to synthesize various nanoparticles was based on the SP600125 following facts. First, a vast majority of drug releasing nanodevices are made out of FDA approved polymers like PLLA and PLGA and are usually in the range of 10 nm to 1000 nm. In fact, previous studies have shown that particles in the range of 20 nm to 200 nm have the highest affinity to tissue. Second, hydrogels like PNIPAM have been extensively researched for drug delivery applications. Thirdly, HA is a major component of the vitreous and as such, their presence in the eye should be tolerable. HA makes up a sizeable proportion in the retinal pigment epithelium and interphotoreceptor matrix. Considering this information, we selected nanoparticles made out of PLLA, PS, HA and PNIPAM in the size range of 100 to 200 nm. It is well established that material properties trigger different extent of soft tissue responses. We thus assumed that material properties would exert some influence on ocular tissue reactions. Very few studies have been done to assess the effect of material properties on ocular compatibility of particles. Nevertheless, studies have found that PLLA and PLGA nanoparticles can be used for delivery of high molecular weight drugs to the retina, and poly is well tolerated by retinal tissue for at least 4 weeks. Non-toxic chitosan and hyaluronic acid have been found to be good drug carriers, and carbodiimide crosslinked hyaluronic acid has been shown to have good ocular compatibility in the anterior chamber. PNIPAM hydrogel grafted with chitosan has also been applied as a thermally responsive ophthalmic drug delivery device. Also most of the studies until now have mainly focused on visual signs of inflammation to suggest lack of biocompatibility. To determine the ocular tissue responses to particle implants, we first measured the IOP changes following intravitreous implantation of particle. The fluctuation of IOP indicates the balance between production and drainage of aqueous humor and hence it was measured to determine the impact of various nanoparticle injections on aqueous humor drainage. In addition, it has been documented that ocular inflammation strongly influences the IOP. Diseases like glaucoma have been shown to increase IOP while inflammatory conditions produced by anterior uveitis and iritis were found to reduce IOP. Substantial studies in glaucoma research have focused on using various pharmacological approaches to reduce IOP for prolonged period of time. Interestingly, our studies have found that the intravitreous implantation of particles prompted different extent of IOP reduction. Specifically, we found that PNIPAM and PS particles triggered the maximum reduction in IOP, while PLLA particles caused a rather mild reduction in IOP. Most interestingly, our results show that the implantation of HA particles trigger minimal or no IOP reduction.