Article Date: 2/1/2006

Scoring With Silicone Hydrogels
These contact lenses make for a patient — and a practice — success story.

Silicone hydrogel lenses, which have been on the market for about five years, are proving to be an all-around success story. Today, many eye care professionals make lenses with this hyper-oxygen transmissible material their preferred choice for patients of all sorts — for good reason. Silicone hydrogel lens materials offer distinct health advantages to the patient, while presenting eyecare practices with an opportunity to benefit financially. It's a win-win situation.

Counting down the benefits

Silicone hydrogel lenses are distinct in their ability to transmit more oxygen to the cornea than conventional HEMA-based lenses. This affords numerous health benefits to the patient. There are six types of silicone hydrogel lens materials currently on the market, with Dk values that vary from 60 to 140, as well as Dk/t values that range from 86 to 175 for a -3.00D lens.

As a group, silicone hydrogel lenses deliver 97% or more of available oxygen to the cornea (according to individual manufacturer's reports to the FDA). No one lens material really holds a significant edge in oxygen availability, so practitioners must evaluate the lenses based on criteria about wettability, modulus, UV protection, long-term comfort and other attributes.

Ask the right questions

As practitioners, the ability to offer patients the many benefits of silicone hydrogel lenses requires that we ask the right questions ... the right way.

In the screening stage, even before the patient sees a doctor, a staff member asks, "How many hours a day do you wear your contact lenses?" They then ask, "How does that compare with a year ago?" and, "Are your lenses still comfortable late in the day?" These three questions tell us a great deal about the patient's needs and whether silicone hydrogels might offer improvements. These questions also prompt patients to think about their contact lens-wearing experience. This opens them up to sharing their concerns.

When that patient reaches one of our doctors for the exam, their chart will bear a short note: "Eyes get dry late in day ...," so we can address that.

Trends in lens wear

We prescribe silicone hydrogel lenses to about 85% of all new contact lens fits. This is up from approximately 15% just a year ago. We firmly believe that patients in silicone hydrogel lenses will do better in the long run.

In our large practice, we see more than 200 patients each day. With this kind of volume we spot trends as they emerge and track them for the benefit of patients and the growth of our practice.

First and foremost, we've seen a dramatic reduction in the incidence of red eyes among silicone hydrogel patients. Many of our patients who still are in conventional lenses recognize that these past-generation lenses make their eyes appear red and irritated. "People ask me what I've been drinking," patients tell us.

The reduction in redness is also a great comfort to practitioners. Many doctors believe that limbal redness is a precursor to neovascularization. That may well be the case, as some recent articles indicate, though we don't know that definitively at this time.

Another trend we see with silicone hydrogel lenses is a decrease in myopic creep. With conventional HEMA lenses, patients often require a small amount of over-correction in their distance every time they come in for an annual exam. It might be only 0.25D, but over years it adds up. We see this with patients even in their 20s, a time when myopic creep generally stabilizes. With silicone hydrogel lenses, we hardly ever see it.

The discomfort factor

According to a recent study (sponsored by Vistakon) involving 40 doctors across the United States, discomfort due to dryness affects 67% of the more than 36 million contact lens wearers in the United States. Many patients complain that their eyes feel tired and dry during certain activities and in select environments (e.g., long hours of computer use, frequent ground or air travel, or everyday exposure to heated or air-conditioned surroundings).

In the same study, researchers examined clinical data taken from 1,092 wearers of soft contact lenses. Nearly half (48%) met at least one of six criteria for frequent or constant discomfort or dryness. The most commonly reported problems were: uncomfortable wear at the end of the day (31%), frequent or constant dryness (28%) and discomfort (17%). In my practice, patients who have switched to silicone hydrogel lenses report being able to wear their lenses longer into the evening.

How to compare lenses

When prescribing silicone hydrogel lenses, be aware of a number of patient benefits that may take some getting used to. The lenses typically have a higher modulus than traditional hydrogel lenses. Therefore, counsel patients on initial comfort issues relative to other types of lenses they may wear. We always inform the patient not to make any initial judgments of lens comfort relative to his or her current lens design until about 72 hours have passed.

The following points are useful in comparing the various silicone hydrogel lenses.

Consider Your Options
We now have at our disposal a variety of silicone hydrogel lenses from several manufacturers, some with designs to address astigmatism, which greatly extends the application of this lens material. And we will see future generations of silicone hydrogel materials with additional patient health benefits in the future.

The following are on the market today:

Lens & Manufacturer Dk/t value Material Wear schedule
AcuVue Oasys (Vistakon) 147 senofilcon A Daily wear; Extended wear up to seven days  
AcuVue Advance
with Hydraclear (Vistakon)
86 galyfilcon A Daily wear
AcuVue Advance for
Astigmatism (Vistakon)
86 galyfilcon A Daily wear
Biomedics XC (CooperVision) 44 omafilcon A Two-week replacement
Night & Day (CIBA Vision) 175 lotrafilcon A Extended wear up to 30 nights
O2Optix (CIBA Vision) 138 lotrafilcon B Daily or extended wear up to six nights
PureVision (Bausch & Lomb) 112 balafilcon A Extended wear up to 30 days

Flexible wearing schedules. Silicone hydrogel lenses are approved for varied wearing schedules and can meet different patient needs and preferences. In our practice, we believe that two-week daily wear is optimal, and that's what we prescribe most often. Many practitioners agree with this "shorter is better" philosophy, though attitudes may change as enhanced, next-generation materials emerge. However, some patients want seven-day or 30-day continuous wear, and we can fill that need with silicone hydrogel lenses that are approved for a longer wear schedule.

Silicone hydrogel lenses deliver greater comfort over long periods. In fact, most patients are able to wear their lenses for more hours each day than with traditional soft contact lenses. Very few patients now tell me, "I can't wait to get home and get these lenses out." That was commonly heard with previous lens materials.

Furthermore, silicone hydrogel lenses will likely become even more comfortable in the future. The goal of manufacturers has always been to make contact lenses feel as natural as the cornea itself. The dynamic contact angle (DCA) of a lens is a measure of its wettability, and manufacturers are adjusting lens materials to increase this. Lens designs with a higher DCA seem to be more comfortable on the patient's eyes.

Also, manufacturers use different surface treatments or internal wetting agents that can affect lens comfort. These are proprietary, but clinicians are aware that differences exist. This allows us to monitor patient symptoms relative to each lens.

UV blocking. Finally, the inclusion of a good UV blocker in silicone hydrogel lenses is also an important patient benefit that we should discuss with them. The only silicone hydrogel contact lenses now on the market with a Class I UV blocker are those in the Vistakon Ultra Comfort Series: AcuVue Oasys, AcuVue Advance, and AcuVue Advance for Astigmatism. These contact lenses block more than 90% of UVA rays and 99% of UVB rays, more than other contact lenses currently on the market. (Other contact lenses have the ability to block or absorb UV, but not to this extent.)

A word about presentation

Moving patients into silicone hydrogel lenses requires different strategies for existing patients than for new patients. With new patients, it's easier. They seek our guidance. We simply present and prescribe silicone hydrogel lenses as the latest technology, and we highlight a few patient benefits, such as comfort and long-term health. Patients who are new to contact lenses don't know what kind of lenses they want. However, they likely have heard about different products and benefits, and we want to be sure to let them know we offer the newest options.

For existing contact lens patients, we explain the benefits relative to the lens materials they now wear and present them with the healthiest technology available today. A discussion of pricing comes after they try a demonstration pair of lenses. We believe that ancillary staff, not the doctor, should initiate and engage in discussions of cost.

We find that giving veteran contact lens patients a demonstration pair of silicone hydrogel lenses is an effective way to spark their interest (people are prone to stick with what they know). After a week's wear, about seven in 10 tell us they found the lenses more comfortable. The remainder tell us they're about as comfortable in their old lenses, and because silicone hydrogel lenses are more expensive, they'll stay with what they've been wearing.

Solution Savvy

In our practice, we make certain to prescribe the lens care solutions we want our patients to use with their silicone hydrogel lenses. When patients return for follow-up, we ask them to confirm that they're using what we recommended. That way, we uncover the patient who switched to an inexpensive solution that was on sale at a discounter, which often increases the chances of ocular irritation.

Fortunately, silicone hydrogel lenses are fully compatible with the leading no-rub solutions that render lens care a snap. We do, however, recommend rubbing lenses when you clean them; it's simply more effective than just soaking lenses in a no-rub multipurpose solution. Silicone hydrogel lenses have often been called "lipid lovers" due to silicone's tendency to attract deposits. However, with proper care and frequent replacement schedules, lipid deposits have not been a significant problem in our practice.

Understand the benefits

One of the key benefits to silicone hydrogel lenses is increased patient satisfaction, which means patient retention — a key practice benefit. It is remarkable that each year approximately three million people come in to contact lens wear, but as many as 2.7 million contact lens patients drop out. That's an incredible loss of practice revenue.

At the same time, many practitioners lack a good understanding of how prevalent dropouts are — or how damaging this loss can be to practice income. Often a doctor doesn't know about a drop out. We frequently see patients who come over from another practice because they are interested in a more comfortable lens, but their current doctor didn't suggest any other options.

From an economic standpoint, silicone hydrogel lenses bear a higher profit margin than conventional hydrogel lenses. That's clearly a practice benefit. We also are able to price ourselves competitively and to offer direct-delivery. Patients can pick up their replacement lenses from our office, but it's beneficial to our practice not to warehouse lenses. It's also more convenient for patients to have replacement lenses shipped directly to their homes or offices.

Silicone hydrogel lenses also ease our patient load. With fewer problems of red, irritated eyes brought on by oxygen deficiency, we have fewer unscheduled office visits.

In the end, silicone hydrogel lenses provide more oxygen and a balance of properties that add up to better health benefits and patient satisfaction — and better benefits for the eyecare practice, too!

Dr. Smick serves as chief of primary care services at the Clayton Eye Center in Morrow, Ga.

Optometric Management, Issue: February 2006