Sodium hyaluronate viscoelastic properties

The beneficial effects of sodimn hyaluronate follow from its viscoelastic properties, which lubricate as well as protect the ocular surface. A study foimd a 0.2% solution of sodium hyaluronate had a significantly longer ocular residence time than did 0.3% HPMC or 1.4% PVA. Most patients achieve control of symptoms with topical instillation up to four times daily. Subjective relief of symptoms such as burning and grittiness usually occurs immediately after drug instillation, and these effects can last 60 minutes or longer. 

Patients suffering from dry eye s3mdrome complain about tear film instability. Stability can be improved by increasing the viscosity of the tear film (see also Sect. 10.4.4) [34]. Viscoelastic polymers increase viscosity but also possess elastic properties. During blinking sodium hyaluronate (Na-HA) exhibits a kind of cushioning action and induces improved protection of the ocular surface compared to classical pseudoplastic viscosity enhancing polymers. 

---