Drainage pattern of commercial ophthalmic gels: an innovative method of evaluation

The feasibility of an innovative in vitro technique for providing information about the drainage pattern of certain commercially available ophthalmic gels has been investigated. The samples showed qualitatively and/or quantitatively different formulations in terms of either the gelforming agents or the other auxiliary substances. Both torsional oscillation and sine-wave vibro viscometers have been employed during the experiments. The drainage behavior of the gels in systems that essentially differ in both probe adhesiveness and tonicity level of the dispersing media have been estimated. The results obtained revealed different patterns of drainage over time among the various samples. In conclusion, the technique developed offers a viable means of characterizing gels in terms of consistency, adhesion and clearance and it appears to be a useful tool for estimating the surface residence times of gels.