Subjective daily wear performance of two silicone hydrogel lenses

Ian Davies and Jane Veys report on the findings of a large controlled study recording the subjective response to two relatively new silicone hydrogel contact lenses worn on a daily wear basis by increasing numbers of patients

Silicone hydrogel lenses were introduced in Europe in 1999. The first two products: PureVision (Bausch and Lomb) and Night & Day (Ciba Vision) were launched with a recommended wearing regime of 30 nights' continuous wear. This indication was driven by the high oxygen flux that both products have; each providing 98-99 per cent of the oxygen that would be available to the cornea with no lens wear for the open eye.^1,2
Although both products soon took the major share of extended wear fits, the extended wear market was slow to establish, with both lenses representing less than 2 per cent of new fits in the UK in 2004 and 7.5 per cent of contact lens sales.³

A factor holding back the wider adoption of first-generation silicone hydrogels was the relatively high modulus of the materials, resulting in some levels of discomfort and signs of corneal trauma such as superior epithelial arcuate lesions (SEALs).⁴ Concern also persisted over extended wear. While recent research suggests silicone hydrogels might reduce the incidence of adverse reactions in extended wear compared to conventional hydrogel extended wear^,5 the same research supports that of others over the years that shows daily wear of contact lenses results in fewer adverse reactions.^6-8 These factors contributed to the increasing use of these first-generation silicone hydrogel lenses as daily wear products.

In 2004 two new silicone hydrogels were launched: Acuvue Advance with Hydraclear (Johnson & Johnson Vision Care) and O2Optix (Ciba Vision). Both lenses are primarily intended for daily wear, although O2Optix also has an extended wear indication. Acuvue Advance is recommended for two-weekly replacement; O2Optix is recommended for monthly replacement in Europe although in the US the recommendation is for two-weekly replacement (Table 1).

Although some clinical data has been published on the products individually,^9-11 to date no data has been published on the comparative performance of the lenses. This paper will report on the short-term subjective response.

Both lenses rely on a silicone hydrogel polymer backbone to deliver high oxygen levels to the eye; both provide the eye with 97-98 per cent of the oxygen that would be available if no lens was worn at all in the open eye situation (Figure 1). The moduli of both lenses are significantly lower than the first-generation silicone hydrogels (Figure 2), Acuvue Advance having a modulus similar to traditional hydrogel lenses.⁹

Wettability is achieved by a plasma surface treatment with the O2Optix, and by Hydraclear patented technology with Acuvue Advance, combining the lens material with a moisture rich wetting agent.