April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Surface and Bulk Properties of a Novel Inherently Wettable Silicone Hydrogel Material
Author Affiliations & Notes
  • Katarzyna A Wygladacz
    Vision Care, Bausch and Lomb, Rochester, NY
  • Anthony Taddei
    Vision Care, Bausch and Lomb, Rochester, NY
  • Daniel Hook
    Vision Care, Bausch and Lomb, Rochester, NY
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 4640. doi:
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      Katarzyna A Wygladacz, Anthony Taddei, Daniel Hook; Surface and Bulk Properties of a Novel Inherently Wettable Silicone Hydrogel Material. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4640.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

To demonstrate surface and bulk properties of samfilcon A that were designed to attain inherent wettability and elevated oxygen transmissibility of a novel silicone hydrogel (SiHy) material. Topography and chemical properties of samfilcon A were illustrated by Atomic Force Microscopy (AFM) imaging and were compared with comfilcon A material. Consistent surface chemistry - lens to lens, side to side and lot to lot was evaluated using X-ray Photoelectron Spectroscopy (XPS) for samfilcon A.

 
Methods
 

TEM images of 90nm thick sections of samfilcon A were recorded at 80kV using Hitachi7650 TEM. The AFM topography images of samfilcon A were recorded by tapping in air (Dimension ICON, Bruker). The lenses were rinsed for 24hrs in DI water, assembled on custom-made holders and dried. The surface chemistry of samfilcon A and comfilcon A were characterized by XPS using a Quantum XPS.

 
Results
 

TEM images visualized the presence of PVP surrounding a silicone network. AFM results showed a smooth surface of samfilcon A with an average roughness of RMS=2.6±0.5nm (RMS=2.6±0.3nm (anterior side); RMS=2.6±0.6nm (posterior side)). Topography of comfilcon A was variable with the presence of random domains (peak to valley 516.5nm) that locally elevated the RMS up to 30nm (RMS=9.0±6.7nm (anterior side); RMS=4.6±3.3nm (posterior side)). XPS detected uniform spatial distribution of species (carbon (C), oxygen (O), silicon (Si), nitrogen (N)) on the surface of samfilcon A, while the distribution of the detected elements (carbon (C), oxygen (O), silicon (Si), nitrogen (N), fluorine (F)) on the surface of comfilcon A varied. The ratio of silicon to nitrogen was well controlled in the case of samfilcon A (Si/N=2.1±0.2, n=14 lots) but it varied even within individual lenses in the case of comfilcon A (Si/N=3.5±1.1, n=14 lots).

 
Conclusions
 

TEM imaging demonstrated presence of PVP surrounding domains of silicone in samfilcon A. The surface properties of samfilcon A were well controlled compared to the characteristics of comfilcon A. Samfilcon A hydrogel was very smooth and uniform from lens to lens, side to side and lot to lot. Topography of comfilcon A was more erratic and rough. The ratio of Si/N (oxygen transmissibility and material wettability) was consistent form lens to lens and lot to lot of samfilcon A but it varied in the case of comfilcon A.

 
 
Figure 1. TEM (top) and AFM (bottom) images of anterior side of samfilcon A hydrogel
 
Figure 1. TEM (top) and AFM (bottom) images of anterior side of samfilcon A hydrogel
 
Keywords: 477 contact lens • 597 microscopy: electron microscopy • 733 topography  
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