Abstract
Purpose: :
1–Day Acuvue® MoistTM contact lenses (J&J Vision Care, USA) combine a pHEMA–methacrylic acid material (etafilcon A) with a moisture–rich ingredient based on polyvinyl pyrrolidone (PVP), using the proprietary LACREONTM technology. The purpose of this study was to compare the surface properties of etafilcon (1–Day Acuvue – AV) with that of etafilcon with LACREONTM or an internal wetting agent(1–Day Acuvue Moist – AVM), to assess whether the embedded wetting agent remains in the lens or is released into the surrounding ocular environment. Surface properties data provided important insight into the clinical observation of improved end of day comfort with AVM compared with AV.
Methods: :
Lenses were removed from their packaging solutions and placed in PBS at 35oC. Releasate was collected at regular intervals. The release solutions were analyzed for PVP using a variety of methods, including UV spectrophotometry, gel permeation chromatography, FTIR and mass spectroscopy to assess whether the wetting agent was released and to quantify any such release. Analyses of the packing solutions were also performed for comparison. The lens surfaces were examined by measuring water contact angles (CA) and XPS to determine whether there were changes in the surface hydrophilicity and surface chemistry, as a function of PBS exposure.
Results: :
All analytical results for the releasates demonstrate that there were no high molecular components that came out of either lens during the simulated wear period of 15 hours. The FTIR spectrum showed no peak consistent with the molecular fingerprint of the wetting agent. These results suggest that the wetting agent is "embedded" into the lens and does not leach out of the lens material. All results for AVM were consistent to those obtained for the AV lenses, providing additional evidence that the wetting agent remained in the AVM lenses. Both CA and XPS results changed as a function of time for the AV lenses (p<0.05), but showed little or no time variation over 15 hours for the AVM lenses (p>0.05), suggesting that the surface of the AVM lenses is not altered by PBS exposure.
Conclusions: :
AVM lenses contain an internal wetting agent that is not released in measurable quantities in PBS over a simulated wear period of 15 hours. Compared with an identical etafilcon material without the wetting agent, there were fewer changes in the surfaces of AVM lenses, suggesting that the PVP–based wetting agent provides a surface to etafilcon that changes less throughout the wear period, a finding that may explain the clinical observation of improved end of day comfort with AVM lenses.
Keywords: contact lens • topography • detection