contact lens materials
A New Silicone Hydrogel Lens Comes to Market
BY LYNDON JONES, PHD, FCOPTOM, FAAO
The continued dramatic growth in the use of silicone hydrogel contact lenses has prompted several companies to recently launch new siloxane-based materials. Lenses made in these materials include O2Optix Custom (CIBA Vision) and Biofinity (CooperVision), both of which I've recently reviewed in this column.
The newest in this category is the PremiO silicone hydrogel lens from Menicon. Table 1 summarizes the lens parameters and material characteristics. Menicon uses a patented polymerization system (MeniSilk) to combine the siloxane and hydrophilic monomers and uses a novel plasma surface treatment which, according to Menicon, combines the benefits of both plasma coating (as exemplified in the lotrafilcon A and lotrafilcon B materials from CIBA Vision) and plasma oxidation (as in the surface treatment process Bausch & Lomb uses with its balafilcon A material). This Nanogloss surface modification process ensures that the surface is very smooth and provides a low contact angle for silicone hydrogel lenses of 27 degrees (captive bubble method), according to the manufacturer.
PremiO is packaged in a unique heart-shaped blister and has an oxygen permeability that is higher than might be predicted from its water content (Figure 1).
Figure 1. Graph of oxygen permeability (Dk) versus water content (WC) for a variety of silicone hydrogels (green dots) and conventional HEMA-based lens materials (red dots). It's clear from the graph that both Biofinity and PremiO have a higher Dk than would be predicted from their WC.
To date, no clinical information is available on the material and all information reported here is derived directly from Menicon. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #143.
Dr. Jones is the associate director of the Centre for Contact Lens Research and a professor at the School of Optometry at the University of Waterloo, Ontario, Canada.