PURPOSE: To compare the rheological characteristics of a viscoadaptive viscoelastic formulation with those of 2 standard ophthalmic viscosurgical devices (OVDs). SETTING: Department of Ophthalmology, Johannes Gutenberg-University, and Max Planck-Institute for Polymer Research, Mainz, Germany. METHODS: An independent comparative study of 3 OVDs of sodium hyaluronate (Healon(R), Healon GV(R), and Healon(R)5) was performed using the Advanced Rheometric Expansion System to analyze rheologic behavior (eg, dynamic frequency dependence of the complex viscosity) as well as rheological parameters (eg, viscosity at zero shear rate, pseudoplasticity, relaxation time, elastic and viscous modulus). RESULTS: Mean viscosity at zero shear rate was 243 Pas +/- 5 (SD) for Healon, 2451 +/- 12 Pas for Healon GV, and 5525 +/- 14 Pas for Healon5. Mean pseudoplasticity was 173 +/- 7, 754 +/- 10, and 591 +/- 6, respectively. Mean relaxation time was 21 +/- 3 sec, 83 +/- 4 sec, and 88 +/- 6 sec. At low shear rates, viscosity and elasticity (elastic and viscous modulus) increased from Healon through Healon5. Healon5 exhibited a dynamic behavior of the complex viscosity dependent on the duration of the shear rate exposure: At low shear rates, it slowly built up a high viscosity. At higher shear rates, it demonstrated a lower viscosity that decreased further during constant exposure to a specific shear rate. CONCLUSIONS: Healon5 had the highest viscosity and elasticity when exposed to low and high shear rates. These characteristics maintain anterior chamber depth. Also, the high viscosity of Healon5 exhibited a dynamic frequency dependence. In the presence of turbulence and phaco power (continuous high shear rates), it became dispersive by fragmentation and formed a cavity with an outer retentive shell. The cohesive and dispersive properties of Healon5 make it the best of the 3 OVDs evaluated for use at all stages of phacoemulsification.
PURPOSE: To compare the rheological characteristics of a viscoadaptive viscoelastic formulation with those of 2 standard ophthalmic viscosurgical devices (OVDs). SETTING: Department of Ophthalmology, Johannes Gutenberg-University, and Max Planck-Institute for Polymer Research, Mainz, Germany. METHODS: An independent comparative study of 3 OVDs of sodium hyaluronate (Healon(R), Healon GV(R), and Healon(R)5) was performed using the Advanced Rheometric Expansion System to analyze rheologic behavior (eg, dynamic frequency dependence of the complex viscosity) as well as rheological parameters (eg, viscosity at zero shear rate, pseudoplasticity, relaxation time, elastic and viscous modulus). RESULTS: Mean viscosity at zero shear rate was 243 Pas +/- 5 (SD) for Healon, 2451 +/- 12 Pas for Healon GV, and 5525 +/- 14 Pas for Healon5. Mean pseudoplasticity was 173 +/- 7, 754 +/- 10, and 591 +/- 6, respectively. Mean relaxation time was 21 +/- 3 sec, 83 +/- 4 sec, and 88 +/- 6 sec. At low shear rates, viscosity and elasticity (elastic and viscous modulus) increased from Healon through Healon5. Healon5 exhibited a dynamic behavior of the complex viscosity dependent on the duration of the shear rate exposure: At low shear rates, it slowly built up a high viscosity. At higher shear rates, it demonstrated a lower viscosity that decreased further during constant exposure to a specific shear rate. CONCLUSIONS: Healon5 had the highest viscosity and elasticity when exposed to low and high shear rates. These characteristics maintain anterior chamber depth. Also, the high viscosity of Healon5 exhibited a dynamic frequency dependence. In the presence of turbulence and phaco power (continuous high shear rates), it became dispersive by fragmentation and formed a cavity with an outer retentive shell. The cohesive and dispersive properties of Healon5 make it the best of the 3 OVDs evaluated for use at all stages of phacoemulsification.