Up until 2000 there were relatively few major advances in contact lenses. Mostly changes were a result of lenses that would not dry out as much or changes to the shape of the lens to make them more comfortable.
In 2000 contact lens companies started introducing silicone-hydrogel lenses which were able to provide much more oxygen permeability to contacts. We have know for the last 30-40 years that silicone is extremely permeable to oxygen, the problem is that lenses made out of silicone dry out very quickly and were very uncomfortable. Silicone-hydrogel lenses were able to combine the oxygen permeability of silicone with the comfort of traditionally hydrogel lenses.
Before the silicone-hydrogel lenses the 2 brands with the most permeability were Acuvue2 (25units of permeability) and Proclear(34 units of permeability). Currently there are 5 brands of silicone-hydrogel lenses on the market(In brackets are their oxygen permeability):
- O2 Optix (138)
- Focus Night & Day (175)
- Acuvue Advance (85)
- Acuvue Oasys (147)
- Purevision (101)
As can be seen, Silicone-hydrogel lenses can provide ~5X as much oxygen as even the best hydrogel lens. That’s a big improvement, which can significantly reduce the risk of corneal infiltrates. It just doesn’t make sense to not wear a silicone-hydrogel lens.
Michael Nelson, OD