Simmons PA, et al. - This study probed the potential advantages of combining carboxymethylcellulose (CMC) and hyaluronic acid (HA) polymers in a single formulation. The combination of CMC and HA polymers yielded a synergistic rise in low-shear viscosity (which cannot be fully explained by simple molecular entanglement). The high-shear viscoelasticity of the combined solution was unaffected. CMC–HA combinations encompassed properties useful in formulating artificial tears that optimized ocular retention (through higher low-shear viscosity), while minimizing blur and stickiness during blinking (through lower high-shear viscosity).