Division of viscoelastic substances for ophthalmological surgery

Individual properties of a viscoelastic substance for ophthalmologic applic ations are intimately tied to its chemical and rheologic characteristics. I ndependent comparative data for vicoelastic substances are not readily avai lable or interpretable. Material and methods: Twenty-six different commerci ally available viscoelastic substances were investigated using the Advanced Rheometric Expansion System and the Rheometric Scientific 800 device to an alyze elastic and viscous modulus, complex viscosity (dynamic frequency dep endance) and viscosity at the zero shear rate by extrapolation using the El lis fit. Results: Viscosity (cps) at zero shear rate (s(-1), mean of six di fferent samples): Sodium hyaluronate products: Amivisc Plus: 128; AMO Vitra x: 41; Biolon: 243; Dispasan: 130;Dispasan Plus:782;Healon:243;Healon GV: 2 451; Healon 5: 5525; Microvisc (Morcher Oil): 1162; Microvisc Plus: 3663; M orcher Oil: 1253;Provisc:207;Rayvisc:78;Viscoat:58; Viscorneal (Allervisc): 733;Viscorneal Plus (Allervisc Plus): 1176; Visko: 206; Visko Plus: 1683. Hydroxypropylmethylcellulose (HPMC) products: Acrivisc: 7; Adatocel: 8; Coa tel: 6; HPMC Ophthal H: 94; HPMC Ophthal L: 7; Ocucoat: 6; PeHa-Visko: 5; V isco Shield: 60. Conclusion: Sodium hyaluronate as well as HPMC viscoelasti c substances demonstrated remarkable differences in theological properties from each other. In some cases, the results of this independent investigati on differed from the Values provided by the companies. A new division of co mmercially available viscoelastic substances into subgroups is presented, w hich provides a scientific base for Various practical viscosurgical aspects . These real theologic properties of each substance allow the ophthalmic su rgeon to choose the viscoelastic substance that is most suitable for the su rgical situation.