Abstract
Purpose :
To understand the modification of the Air Optix Aqua (lotrafilcon B) contact lens surface after exposure to commercial drops as a function of time with atomic force microscopy (AFM) measurements of sliding friction.
Methods :
The kinetic friction between lotrafilcon B lenses presoaked 24hrs in PBS and a 5 micron diameter colloidal silica probe was measured on the micron length scale and nanometer force scale. Employing a colloidal sphere for the counterface aimed to manage interfacial pressures, matching contact pressures found in the eye, and to avoid massive deformation of the soft lenses and corresponding displacement of adsorbates. Measurements were made again after lens exposure to 1 drop of Systane Ultra or Refresh Contacts at 10 min, 1 hr or 6 hrs post-drop to evaluate the persistence of any measured change in friction. All AFM measurements were measured under PBS solutions. Measured friction values for each drop were compared with results from the neat lotrafilcon B lenses prepared by a 24-hour PBS soak.
Results :
Systane Ultra produced a sustained measurable change in interfacial friction for the lotrafilcon B lenses; friction of neat lenses was significantly reduced 61% at 10 min, 81% at 1hr, and 73% at 6 hrs post-drop instillation (p<0.001 for all). In contrast to Systane Ultra, Refresh Contacts drops proved to have less effect on the frictional properties of the lotrafilcon B lenses, showing a smaller decrease in friction (26%) at only the 1 hr time point (p=0.008).
Conclusions :
These results depict the impact of polymer adsorption found within commercial drop solutions on the frictional response of lotrafilcon B lenses. They indicate the active ingredients in Systane Ultra can have a positive, sustained impact on lubrication properties of lotrafilcon B silicone hydrogel lenses.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.