Influence of sodium hyaluronate on dehydration and water distribution in soft contact lenses

The purpose of this investigation was to examine the influence of sodium hyaluronate (HA) solution on contact lens dehydration and the distribution of water in lens materials. These parameters were measured with gravimetry and differential scanning calorimetry. Five commercial soft contact lenses were used. They represented four FDA (Federal Drug Administration) groups: Air Optix Night&Day Aqua and Acuvue Oasys (I FDA group), Proclear 1-Day (II FDA group), PureVision (III FDA group) and 1-Day Acuvue Moist (IV FDA group). All materials were investigated with two preservative-free HA solutions 0.1% and 0.3%. HA solutions influenced the water content and the dehydration rate of some examined lenses. For three lenses (Oasys, Proclear, Moist) water content of HA lenses was greater than control. Significant slowdown of dehydration rate under HA during the first 20min was observed only for Proclear. PhaseI of dehydration increased significantly with HA solutions in case of Moist and Proclear. For Night&Day and Oasys phaseI appeared under HA solution while it was not present for control lenses. Duration of the phaseI was strongly correlated with water content of the lenses (R₂=0.844). The amount of freezable and non-freezable water depended strongly on characteristics of lens material and its interaction with HA molecules. Proclear seems to be the most prone to attach HA molecules which affect changes in dehydration characteristics and water behavior in the polymer. PureVision might be considered as the most resistant to HA in terms of dehydration dynamics and water distribution. All measured parameters seem to be dependent more on material properties than HA concentration.