A new generation of "super-permeable" contact lenses can transmit unprecedented amounts of oxygen to your cornea and, in some cases, enable 30 consecutive days of wear without removal.

Silicone hydrogel contact lenses represent a breakthrough over traditional hydrogel soft contact lenses, because silicone lets so much oxygen pass through the lens. These lenses allow six to seven times more oxygen through than previous lenses.

Silicone hydrogel contact lenses have caught on with both wearers and eye care practitioners. By 2009, silicone hydrogel lenses were expected to account for 60 percent of U.S. soft contact lens sales.

How Silicone Hydrogel Lenses Work

Traditional soft contact lenses are made from hydrogel polymers (soft, water-containing plastics). The plastic itself is not oxygen permeable, so the water content performs the job of carrying oxygen through the lens to the eye. But water can carry only so much oxygen - and the more water a lens contains, the greater its tendency to dehydrate after long periods of wear.

Silicone is oxygen permeable. So silicone hydrogel lenses use both their water and polymer content to transmit oxygen to the eye.

The benefits to wearers include comfort and convenience:

• Silicone hydrogel contact lenses contain less water than traditional hydrogel lenses. As a result, they aren't as prone to dehydration while you're wearing them. For some people who wear their lenses for long days, this can mean better end-of-day comfort.
   
• Silicone hydrogels also have made 30-day contact lens wear - sometimes called "continuous wear" - available once again.

30-Day Contact Lens Wear

The initial heyday of 30-day wear was in the 1980s, but that ended due to health and safety concerns.

Want to wear your contact lenses for up to 30 days without removing them? Silicone hydrogel contact lenses could make that possible, if you're a good candidate.

Today's new silicone hydrogel contact lenses provide much more oxygen to the eye than most conventional soft contact lenses, making 30-day extended wear a safer option than before. As well, the lenses are discarded and replaced monthly, preventing long-term buildup of deposits on the lens surface.

Different Flavors of Silicone Hydrogel

Because silicone hydrogel lenses provide increased oxygen to your eyes, 30-day wear isn't the only reason to consider using them.

And in fact, not all silicone hydrogel brands are approved for 30 days of wear. Currently two brands - Night & Day by CIBA Vision, and PureVision from Bausch & Lomb - can be worn for 30 days.

Four other silicone hydrogels - Acuvue Oasys from Johnson and Johnson, O2Optix and AirOptix from CIBA Vision, and CooperVision's Biofinity - are approved for overnight wear of six nights consecutively. Acuvue Advance and CooperVision's Avaira are approved for daily wear only.

Silicone hydrogel lenses generally have a replacement schedule of two to four weeks. But daily disposable silicone hydrogel contact lenses are on the horizon: 1-Day Acuvue TruEye was launched in the UK in 2008.

Should Everyone Be Wearing Silicone Hydrogels?

If you regularly sleep in your lenses, the case for silicone hydrogels is compelling. For daily wear, it's less so.  In terms of comfort, some people will find that silicone hydrogel lenses address their dryness and discomfort issues, and others won't see a difference.

30-Day Wear: Not for Everyone

Do you like the idea of dealing with your contact lenses only once a month? Before you become too attached to that thought, it's good to be evaluated by an eye care practitioner. Today just about everyone is a candidate for daytime contact lens wear, but not everyone's eyes can adapt to sleeping in contacts. Further, your eyes may be suited for some overnight wear, but perhaps not for 30 consecutive nights. For example, people who have had previous problems with contacts may not be good candidates for 30-day wear.

Dr. Ellerbrock can help you evaluate the opportunities and risks of 30-day wear, and extended wear in general. If it's not for you, silicone hydrogel lenses for daily wear may be a good option, or you might consider other ultra-convenient options such as daily disposables.