continuous wear colloquy

Test Your Knowledge About Continuous Wear

continuous wear colloquy
Test Your Knowledge About Continuous Wear

All contact lens practitioners should educate themselves about continuous wear (CW) contact lenses. Take this test to see how informed you are about this new contact lens technology.


1. What were the first soft contact lenses that the FDA approved for extended wear (EW)?

2. In what year was the first contact lens FDA approved for 30 days of EW?

3. The FDA approved silicone hydrogel lenses for CW in 1999. True or False?

4. The FDA has approved three contact lenses for up to 30 days of CW. True or False?

5. Today, what Dk/t have vision scientists found necessary for CW?

6. Lotrafilcon A (CIBA Vision's Focus Night & Day) has a Dk/t of 165 and balafilcon A (Bausch & Lomb's PureVision) has a Dk/t of 100. True or False?

7. With a silicone hydrogel contact lens, if you increase the water content of the lens material, then you also increase the oxygen permeability. True or False?

8. The current CW silicone hydrogel contact lenses use a gas plasma treatment to increase the wettability of the lens surface. True or False?

9. Consumer studies show that 25 percent of our current contact lens patients have a strong interest in CW. True or False?

10. You can achieve continuous good vision today with refractive surgery, corneal refractive therapy and CW contact lenses. CW contact lenses offer what advantages?


1. The Permalens (Dk 34) and the Hydrocurve lens (Dk 16) were approved in 1982 by the FDA for two weeks of EW.

2. In 1983, the FDA approved B&L's 03-04 lenses (Dk 8.4) for 30 days of EW. EW grew rapidly in the 1980s -- at one time more than 30 percent of the US contact lens population wore their lenses EW. But a 1989 study by Poggio et al reported the risk of corneal ulcers as 10 to 15 times greater for patients wearing soft lenses EW than DW. The FDA then reduced the approved wearing time for EW lenses to seven days.

3. False. In 1999, the FDA approved PureVision for daily wear. In 2001, Night & Day received FDA approval for up to 30 days of CW.

4. True. The FDA has approved PureVision, Night & Day and the Menicon Z (Menicon Ltd.) GP lens for up to 30 days of CW. The PureVision lens is currently not available in the United States.

5. Today, most vision scientists agree that a minimum Dk/t of 125 is necessary for safe CW.

6. False. Lotrafilcon A has a manufacturer-reported Dk/t of 175 and balafilcon A has a manufacturer-reported Dk/t of 110.

7. False. When you decrease the water content of silicone hydrogel lenses, you increase the silicone, which increases the oxygen permeability of the material.

8. True. PureVision uses plasma oxidation, which creates silicate islands on the lens surface. Night & Day has a dense uniform coating (25nm). These lens treatments aren't removable.

9. False. Consumer studies show that 50 percent of current contact lens patients are interested in continuous wear. The interest increases to 69 percent if doctors recommend it.

10. The advantages of continuous wear silicone hydrogel contact lenses are:

  • Noninvasive method of providing continuous vision
  • Predictable vision outcome
  • Can correct myopia and hyperopia
  • Reversible
  • Low risk of losing best corrected visual acuity

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 the team optometrist for the St. Louis Rams (NFL) and the St. Louis Blues (NHL).