contact lens materials
Battling the Misconceptions of Silicone Hydrogel Lenses
BY N. REX GHORMLEY, OD, FAAO

I've participated in numerous silicone hydrogel symposiums across the United States in the last year. At the events, we asked participants, "Do you still fit PMMA lenses on your new contact lens patients?" The surprising result: 25 percent to 30 percent in several cities answered "yes." In addition, 50 percent had fit fewer than 50 patients with silicone hydrogel contact lenses.

Currently, four spherical silicone hydrogel contact lenses (Acuvue Advance [Vistakon], Night & Day and O₂Optix [CIBA Vision] and PureVision [Bausch & Lomb]) are available in the United States. Later this year, Vistakon will introduce the Acuvue Oasys in the United States. The major lens companies are currently doing almost all research with silicone hydrogel technology. I believe the future of contact lenses is definitely with these new materials.

So why are many practitioners slow to adapt to them? Let me address some of the most common "excuses" for not fitting silicone hydrogel lenses.

1. If it's Not Broken, Don't Fix it

Chronic hypoxia can cause corneal edema, neovascularization, ocular redness, endothelial polymegethism, changes in corneal topography, myopic creep and reduced contact lens wearing time. It's our responsibility to be proactive and prescribe the "best" lenses for our patients.

Primary care physicians discuss the serious complications of smoking with all patients who smoke — even when these patients don't yet have complications from smoking. Why should we avoid treating our patients who similarly may develop serious complications from wearing a low-Dk contact lens?

2. They're too Expensive

The most expensive silicone hydrogel lens is less expensive than a toric or a bifocal soft contact lens. In my practice, specialty lens patients don't complain about costs because they know and appreciate the benefits of these lenses. If you educate your patients about the many benefits of these lenses, then price isn't an issue.

3. They're Uncomfortable

When silicone hydrogel lenses first entered the US market, only one base curve was available and the lens materials had a "stiff" modulus. We now have several base curves, diameters and lens materials of differing modulus available. With proper fitting, patients should find the lenses comfortable. In addition, patients may experience a "rebound effect" resulting from an end to chronic hypoxia, in which for a short time patients may have more sensitive corneas because of the additional oxygen. Again, educate your patients that they may have some adaptation to these new materials, and comfort won't be an issue.

4. Parameters are Limited

We now have silicone hydrogel lens powers from +8.00D to –12.00D, several different diameters and base curves and materials with different modulus. In addition, by this summer we'll have three toric silicone hydrogel lenses. At least one manufacturer plans to release a bifocal silicone hydrogel in the United States. So, are parameters a problem? No! By the end of this decade, I predict that we'll have color silicone hydrogel lenses, numerous bifocal lens designs and single-use silicone hydrogel lenses.

No More Excuses

When Canadians at a symposium responded to that same question, no one answered "yes."  Maybe Canadians "get it" because they have had this technology longer.

I do hope my US colleagues "wake up" and start using this new technology soon!

Dr. Ghormley is in private practice in St. Louis, MO. He is a past president of the American Academy of Optometry and is a Diplomate of its Cornea & Contact Lens Section. He is also a consultant to CIBA Vision.