Quantitative method to determine the cohesion of viscoelastic agents by dynamic aspiration

Abstract

The method provided a quantitative basis for the clinical classification of viscoelastic materials as cohesive or dispersive. The aspiration kinetics profile (curve shape), maximum rate of removal, and vacuum levels at which the bolus removal of the viscoelastic agent started (break point) were useful in characterizing the viscoelastic agents. Because the results agree with the clinical impression of cohesion/dispersion, this method may be used to predict the surgical performance of viscoelastic agents.

Rheological and cohesive properties of hyaluronic acid

“…The method developed by Poyer et al 10 is useful in measuring the cohesive properties of HA, as it is fast and simple. The purpose of our study was to determine the effect of concentration and molecular weight on the cohesive properties of HA and to determine which dynamic rheological parameters (commonly measured theological parameters) correlate best with the cohesion of HA solutions as measured using the method of Poyer.…”

“…The cohesion-dispersion index (CDI) was measured by using an apparatus built according to the description in a paper by Poyer et al 10 A schematic of the apparatus used is shown in Figure 1. The principle of the technique is to measure the amount of sample aspirated with increasing vacuum applied to the sample; vacuum levels of 127, 254, 381, 533, and 711 mmHg were used.…”

“…The solution concentrations and viscosity ranges chosen for this study were purposely kept very broad. Since the application of HA solutions through a cannula should be related to the viscosity of solution and the cohesiveness, 10 both the solution cohesivedispersive properties, the CDI, as described by Poyer, and the solution rheology were measured. This study directly relates to the use of HA solutions for clinical application because HA is generally delivered by injection through a cannula.…”

“…One attempt at characterization of the effectiveness of HA formulations, for ophthalmology, has been to measure their cohesiveness. 10 The authors of this study attempted to relate the cohesiveness of the viscoelastic adjunct to the viscosity ( 0 ), but in these studies the effect of molecular weight and polymer concentration was not taken into account. 10 A more detailed study of HA and its cohesive properties was warranted to determine the effect of molecular weight and concentration on its cohesive characteristics, and to determine which rheological parameter relates more closely to the cohesive nature of the viscoelastic material.…”

“…Recently, a semiquantitative method was developed to estimate the cohesiveness of HA solutions of different zero shear viscosities by vacuum aspiration through a small-bore cannula, by Poyer et al 10 Using this technique, we noticed that the cohesiveness of HA was dependent on molecular weight. We examined the cohesive and rheological properties of HA, as a function of molecular weight and concentration, so as to determine which physical properties and viscoelastic measurements can be used to predict the cohesive properties of HA that were demonstrated by this dynamic aspiration technique.…”