P Piccerelle, M Frojo, C Orneto, A Garnier, C Gard and M Claret
UMR : IMBE 7263 CNRS, IRD 237 Aix-Marseille Universit├?┬ę, France
Horus Pharma, France
Posters & Accepted Abstracts: J Clin Exp Ophthalmol
The aim of this study was to compare the rheological behaviours of different tear substitutes and to provide information about in vivo performance. Our rheological study included: flow behavior, oscillatory measurements, rheological characterization of a mixture tear substitute/mucin. Data analysis confirmed two types of rheological behaviours, shear-thinning (pseudoplastic) properties and dilatant flow, close to Newtonian behavior. We showed that Vismed Multi and Optive fusion had a similar pseudoplastic index (0.78), also Hylo Confort Plus had a pseudoplastic index of 0.57. A Viscosity value of 6-12 mPas is considered as relevant and adapted for dry eye syndrome. The Non-Newtonian behavior of sodium hyaluronate, combines the advantages of high viscosity at rest between blinks, with lower viscosity during blinking. The rheological thinning provides improved lubrification of the ocular surface. Dynamic tests confirmed the viscous properties of tear substitutes. A synergistic increase in viscosity was observed when the formulations and mucin were mixed together. Mucin did not change the profile of the system. This change suggested the formation of a chemically cross-linked structure between polymer in formulation and mucin chains in addition to physically entanglement. In fact, when we compare Vismed versus Thealose, Vismed presents advantages: A pseudoplastic behavior related to better coverage and spreading on the ocular surface. Apparent viscosity of 12 mPas is considered as adapted for dry eye syndrome. The difference of rheological behavior and apparent viscosity came for apart from the molecular weight of hyaluronic acid: 1621 kDa for Vismed and 488 kDa for Thealose. An increase of viscosity for the mixture Vismed/mucin showed a synergistic effect, explained by bioadhesive properties. Due to the interaction with the precorneal mucin layer via non-covalent bonds, these mucoadhesive polymers increased the residence time of the formulation on the ocular surface and decreased the product loss.