contact lenses
A Year of Continuous Wear Success
Continuous wear silicone hydrogels have changed the contact lens field.
DAVID W. HANSEN, O.D., F.A.A.O., Des Moines, Iowa

The scare is almost over, and continuous wear silicone hydrogel contact lenses are a refractive reality. As our daily lives change with the advancements in technology, so too has the practice of contact lens care changed with the introduction of the third contact lens modality material -- silicone hydrogels. At last contact lens wearers can safely and comfortably wear their lenses for up to 30 days.

ILLUSTRATION BY JOHN SCHREINER

Looking back

For the last 20 years, we've walked a tight rope to eliminate and prevent complications of overnight contact lens wear. In 1978, I had the opportunity to investigate the clinical implications of extended contact lens wear with the Swedish Scanlens.

It was strange to tell patients that we endorsed the concept of sleeping with their contact lenses up to one week. Sterilization consisted of weekly thermal disinfection with these 75% water lenses. The patient's enthusiasm for "seeing 24 hours a day" and only caring for their contact lenses on a minimal basis was exciting. In one case, after the study was completed and the contact lenses were discontinued, an entrepreneur patient wanted to buy the contact lens company because he didn't want to cease wearing this lens that gave him excellent clarity and comfort!

The Food and Drug Administration, in the interim years, was given data indicating that materials considered acceptable for overnight wear compromised corneal physiology. This information and the early introduction of certain materials that weren't meant for extended wear put the contact lens industry in jeopardy. Optometrists warned their patients of the potential adverse complications of the overnight modality. Our concern made it difficult for us to believe the new science of silicone hydrogels was safe and effective. Were we going to be fools again? Were there other corneal complications producing dangerous, if not sight-threatening, situations in our litigious society?

Looking out for the cornea

Here's what I have learned in the last five years: Silicone hydrogel (and for the time being, CIBA Vision's Focus Night and Day contact lens, specifically) along with the Menicon Z material, is the best material the contact lens industry has experienced! These hyper Dk materials are the only ones that physiologically protect the integrity of the cornea and adnexa for overnight wear. These are strong statements, but they're supported with the independent research of H. Dwight Cavanagh, M.D., Ph.D.; William J. Benjamin, O.D., Ph.D.; Desmond Fonn, Dip Optom; Brien Holden, Ph.D., and others internationally.

The data supports overnight contact lens wear beyond the minimum limits because silicone hydrogel lenses exceed the oxygen transmissibility required to provide sufficient oxygen to the cornea during sleep. Clinical trials and market experience demonstrate that hypoxia-associated complications occur even with conventional daily wear or disposable soft contact lenses of lower Dk. Silicone hydrogels have overcome these problems. They can be worn for hours, days, months, and years without metabolic stress caused by hypoxic conditions.

So far, the incidence of microbial keratitis is significantly reduced. Holden, et al., reported that microbial keratitis was prevalent in one in 7,000 silicone hydrogel wearers (7,000 study population) in Australia. These findings compare to one in 500 in the low Dk extended-wear population and one in 2,500 for the low Dk daily wear group.

Oxygen demand was not the only criteria needed for success. The wettability, comfort, optical quality, material stability and durability of silicone hydrogels were improved. The surfaces create a permanent, ultrathin (25mm) continuous hydrophilic surface.

What is continuous wear?

Continuous wear is not "extended wear" or "disposable wear." Continuous breaks the barrier; it means wear of longer than a week, but it also means that if the lens is worn a few days overnight and then disinfected, it can be reapplied to wear up to 30 days total. Maybe they can be worn longer, but why put yourself in the same position as the previous extended wear-fitting community?

If removal and frequent replacement of contact lenses is healthier for the eye, why do we prescribe outside the FDA indications? Quit trying to beat the system. After all, isn't our goal to promote healthy eye care? As Glenda Secor, O.D., says, "It's not a race!"

Brush up on fitting

Silicone hydrogel gives the patient the best acuity and comfort with optimum design selection -- but the lens material and design require accurate fitting. Choosing the correct base curve from corneal topographic measurements or diagnostic lens comparisons is important. I usually select a diagnostic lens .6mm flatter than the flattest K reading to calculate the initial base curve. The 8.4 and 8.6 base curve options fit the majority of the patients. These lenses are not "one-size-fits-all"; they bring the art and science of fitting contact lenses to the profession again.

Embracing "the third option"

In the year since the FDA approved CIBA's Focus Night and Day, our office has enthusiastically embraced what I call the "third option." This "third option" is not a GP lens, nor is it a soft contact lens -- it's a silicone hydrogel lens. We've positioned this modality as something different, and it is. It's a very special contact lens, especially for those who were previously unsuccessful with contact lenses or who struggled with limited wearing time. It may even upgrade regular soft contact lens patients to a "continuous wear" system.

Our office experience appears to be consistent with that of the majority of contact lens practitioners in the United States as presented in a recent CIBA Vision survey. The company contacted 200 eye care professionals and 80% said they believe that silicone hydrogels are the most significant contact development since disposable lenses.

They (78%) also said that approval of this product increased the more patients they fit. I've noticed that the energy level of our staff surges when patients arrive for their follow up appointments saying, "I love these! They're awesome!" This enthusiasm builds staff confidence and is transferred to other potential candidates without coaxing.

Educate, then listen

As these lenses become the workhorse of the practice, it's important to prepare your staff for possible concerns, and systematically educate all patients to this "third option," even if they have worn contact lenses previously.

Listening to the patient and problem solving are the keys to success. I've found that if the patient returns for a follow up visit without resounding enthusiasm, it's time to review the fit, change the base curve, check the care system (which may not be compatible), investigate the systemic and over-the-counter medications, review the possible allergies, sinus infections, systemic diseases, and other health issues, and inquire about environmental habits, including swimming, chemicals, etc. Then practice good clinical investigation of acuities and biomicroscopic examination.

Remember, silicone hydrogel lenses usually don't leave deposits unless the surface has been altered and "mucin balls," when present, usually don't implicate corneal hypoxia or infectious complications. Never forget that silicone hydrogel lenses are medical devices and need professional supervision.

Conclusion

Patient compliance is our responsibility, so educate them about silicone hydrogels. We usually give the patient too much information at once, so do what the public relations experts do -- give it to them three times. Remember, it's a privilege to wear contact lenses overnight with continuous wear and not the patient's right! This is a wonderful material and we must carefully prescribe these lenses and educate our staffs and patients in order to prevent another "black eye" to the contact lens field.

Dr. Hansen, a diplomate and fellow of the American Academy of Optometry, is in private practice. Contact him at (515) 243-1667.