Sodium hyaluronate is the sodium salt of hyaluronic acid. It is a glycosaminoglycan and long-chain polymer of disaccharide units of Na-glucuronate-N-acetylglucosamine. It can bind to specific receptors for which it has a high affinity. The polyanionic form, commonly referred to as hyaluronan, is a visco-elastic polymer found in the aqueous and vitreous humour of the eye and in the fluid of articulating joints. Sodium hyaluronate, as hyaluronic acid, is distributed widely in the extracellular matrix of mammalian connective, epithelial, and neural tissues, as well as the corneal endothelium. Sodium hyaluronate functions as a tissue lubricant and is thought to play an important role in modulating the interactions between adjacent tissues. It forms a viscoelastic solution in water. Mechanical protection for tissues (iris, retina) and cell layers (corneal, endothelium, and epithelium) are provided by the high viscosity of the solution. Elasticity of the solution assists in absorbing mechanical stress and providing a protective buffer for tissues. In facilitating wound healing, it is thought that it acts as a protective transport vehicle, taking peptide growth factors and other structural proteins to a site of action. It is then enzymatically degraded and active proteins are released to promote tissue repair.