Modified low molecular weight poly-vinyl alcohol as viscosity enhancer

Dry Eye Disease (DED) is a multifactorial disease that provokes a reduced vision quality and eye fatigue. It is often treated with artificial tears that must have enhanced viscosity in comparison with human tears. Phosphorylated low molecular weight PVA was synthesized to obtain a viscosity enhancer for the production of artificial tears. Three different concentrations were analyzed, verifying that, thanks to the combined action of low molecular weight and presence of anionic groups inserted along the chains, formulations can be sterilized by filtration without losing their viscosity properties, stability and transparency (light trasmittance > 85%). Formulations were characterized by Infrared and UV spectroscopy, thermal analyses and rheology. The developed viscosity enhancer shows adequate viscosity values for the foreseen application. Indeed, its viscosity is higher than natural tears (1.5 mPa.s) but lower than 30 mPa.s (sticky sensation) at the shear stress values the eye is subjected. It shows a mean viscosity value of 20 mPa.s at shear rate 1 s−1 (interblinking phase: open eye), and 10.5 mPa.s at 10,000 s-1 (blinking phase).