Abstract
Purpose :
A new surface modified silicone hydrogel (SiHy) material, verofilcon A, was recently developed with superior surface lubricity and exceptional on-eye comfort. This study was conducted to characterize its surface treatment in fully hydrated conditions for better understanding the structure-property correlation of this novel contact lens material compared to other SiHy materials.
Methods :
Environmental Scanning Electron Microscopy (ESEM) and quantitative nanomechanical analysis with Atomic Force Microscopy (AFM) were utilized to image and assess both the surface and cross-section of different SiHy contact lenses in either 100% humidity environment or immersed in aqueous solutions for complementary characterization of the surface and core of the materials.
Results :
A unique surface gel was observed on the top of this surface modified contact lens core material in 100% relative humidity under ESEM. In addition, an ultra-soft surface layer on the top of verofilcon A material was visible using liquid AFM technique. AFM nanoindentation testing demonstrated a different modulus at the core (0.6 MPa) compared to the lens surface (<20 kPa), resulting from the special, high water surface material. Such distinctive surface structures and properties were not seen on any other SiHy contact lenses except delefilcon A, which is a water gradient contact lens.
Conclusions :
Surface modification techniques can create novel, ultra-soft surface gels on silicone hydrogel core materials. Such unique structures and properties have been successfully characterized by ESEM and AFM in fully hydrated conditions.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.