What do you think about Acuvue Advance and the newer Acuvue Oasys? They seem to have relatively high dk/t stats but perhaps without as much stiffness as Pure Vision or Night and Day. The stats I saw were: traditional Acuvues dk/t: 28, Acuvue Advance: 60, Acuvue Oasys: 103, Pure Vision: 101, and Night and Day: 140+. What I'm wondering is: what's the tradeoff between the problems of low oxygen permeability vs. extra material stiffness, especially for someone who will use any of the lenses as daily wear rather than extended wear.

There are a number of differences between the current silicone hydrogel lenses, as you point out. Most of these are described in the previous editorials section of the Silicone Hydrogels website. The link below gives an overview of the lenses, excluding Oasys which was not available at the time. Its internal wetting agent is similar to Acuvue Advance, being based on PVP, but is termed “HydraClear™ Plus”, as it has approximately 30% more “HydraClear™” than Acuvue Advance. According to the manufacturer, the lens is softer and more wettable.

http://www.siliconehydrogels.com/editorials/index_august.asp

In the clinical situation, PureVision and Advance lenses have been reported to build up more lipid in lipid prone patients. Focus Night & Day and PureVision lenses are somewhat stiffer and therefore lens fit may be more critical with these lenses. There is no single lens that is the best choice for all patients. The ‘best’ lens is the one which works the best for each individual patient.