Practitioner Attitudes to Extended and Continuous Wear of Silicone Hydrogels

Nicole Carnt - B. Optom (UNSW) 1989

Research Optometrist
Vision Cooperative Research Centre (Vision CRC)

While the initial uptake of silicone hydrogels was relatively slow, the market share has increased quite remarkably and is looking very healthy in many countries. So, what were the barriers? Patient enthusiasm has been high from the start, with one survey conducted in late 2000 finding that 86% of current wearers wished they could see upon waking ⁽¹⁾. However at the same time, research in the UK ⁽²⁾ and Australia ⁽³⁾ has shown that, at least in these countries, patients rely to a large extent on practitioner recommendations.

To determine practitioner attitudes to the new modality and whether there were differences between countries, we surveyed practitioners at four continuing education meetings across the world: BCLA, UK, May 2000; COE, Australia, October 2000; CLC Sweden, March 2001, AAO, US, December 2001.At the time of these surveys the lenses had been marketed with the CW option for approximately 1 year in the UK, 18 months in Australia and Sweden, and 1 month in the US.


Experience with Silicone Hydrogels

The practitioners surveyed had little experience at the time it seems, despite the lenses having been on the market for a reasonable length of time. In Australia, nearly 50% of the practitioners had not fitted any silicone hydrogel lenses. Yet, Australia is now one of the leading countries in silicone hydrogel sales, as are the UK and Sweden. .

How many patient have you fitted with the new silicone hydrogels?

Not more than 10% of the practitioners surveyed in Australia, the UK or Sweden had prescribed more than 50 patients with silicone hydrogels at the time of the surveys.
In Sweden, while initial interest in the product was high, growth was slow in the first 2 years, with many practitioners reluctant to fit lenses ⁽⁴⁾. The tendency in Sweden and perhaps in other countries, was an initial uptake by a small band of experienced practitioners which then filtered through to the wider contact lens fitting community ⁽⁴⁾.
This may have been particularly applicable to Sweden, however, where nearly 40% of practitioners report that word of mouth from colleagues most influences the way they practice. Most practitioners were influenced primarily by peer reviewed journals in the US, conference speakers in Australia and were divided between these two information sources in the UK.

Which of the following impacts the way you practice the MOST?

Prescribing Habits

What was their first lens of choice for the uncomplicated 3D myope to this point? In the UK, daily disposables were most popular as the first lens of choice, which corresponds to the high prescribing rate of daily disposables (33% of all fits, compared to 6% in Australia) ⁽⁵⁾. Most other practitioners opted at the time of the surveys for 2 week to 1 month disposable daily wear.

What is your lens of first choice for the uncomplicated -3.00D myope?

When asked if they had prescribed EW in the past, only 14% of practitioners surveyed in Sweden said that they had never prescribed EW compared to at least 40% in all other countries. Sweden was one of the leading countries to embrace disposable EW when it first became available so these results are not surprising.

In the US, 43% of the practitioners had never prescribed EW. Although it is indisputable that the US has maintained the highest level of hydrogel EW (10% of fits in 2000) ⁽⁶⁾, figures have consistently been dropping from 38% of market share in 1989 ⁽⁶⁾. It is no coincidence that results of studies published that year indicated a 5 times greater risk of developing ulcerative keratitis by sleeping in conventional soft lenses ⁽⁷⁾. With CL manufacturers in the US spending $65.8 million on consumer advertising ⁽⁶⁾, it shows strong resolve that only 14% of practitioners prescribed EW if wanted.

Have you prescribed extended wear in the past?

The Barriers

By far the most important concern with high Dk silicone hydrogels at the time of these surveys in all countries was safety, especially in Australia (87%) and the US (81%). While the concern was still high in Sweden and the UK (58% and 48% respectively reporting safety of most concern) there was a higher percentage than in other countries reporting adverse events as the highest concern. A recent survey in the UK found that 49% of practitioners who were not fitting the lenses said they needed to see more clinical information before recommending silicone hydrogel EW ⁽⁸⁾. Though adverse responses do occur with silicone hydrogels, they are manageable. This highlights that education and support are necessary for the practitioner to feel comfortable when initially fitting the lenses.

Cost was also more of a factor in Sweden which may reflect negative attitudes to proactive practitioner recommendations, perceiving them as pressured selling and unprofessional. The Contacta practices report that they regularly convert monthly disposable daily wearers to satisfied silicone hydrogel wearers at roughly twice the cost, so the patient does not appear to be the stumbling block here. ⁽⁴⁾

Please rate the order of importance of the following concerns with current high Dk SCLs from 1-6 where 1=most important

In Sweden and the UK, substantial proportions of practitioners (23% and 15% respectively) reported having seen microbial keratitis (MK) with daily disposable lens wear, which is not reflective of the accepted statistics of 1 in 5000 risk of MK with daily wear soft lenses ⁽⁷⁾.

What is the worst event you have seen with daily disposable wear?

As there are many similarities between Microbial Keratitis and Contact Lens induced Peripheral Ulcer as shown in the table below, (CLPU), it is understandable that the conditions can be misdiagnosed. CLPU is not a "serious" or sight threatening event and the symptoms are milder and self-limiting but in the early stages can mimic MK.

CLPU vs MK
CLPU: On removal of lenses there is rapid, uncomplicated resolution resulting in a small “bullseye” scar	MK: Worsens without aggressive treatment, stromal tissue destruction and scarring

How valid are these results?It may be argued that practitioners surveyed at continuing education meetings may not be reflective of all practitioners so these results may be skewed. However, their inexperience with silicone hydrogels at the time, which reflected the slow initial market response to the lenses and overall prescribing habits that concur with other studies would seem to indicate that these practitioners are reasonably representative of the majority in each of the countries ⁽⁵⁾. The PresentIt was estimated that during 2000, 16% of all fits in Australia were silicone hydrogel ⁽⁹⁾; the UK where 12% of refits were EW (96% of which were silicone hydrogels) in 2001, up from 3.6% in 2000 ⁽¹⁰⁾; and Sweden where growth rate is estimated at 200%+ on last year ⁽⁴⁾; the major barrier of practitioner fear certainly seems to have been overcome.

A study to determine the safety of silicone hydrogel EW is imperative and planning is underway. Microbial keratitis is inevitable with SH EW, as it is with DW of contact lenses. It is a matter of accurately determining the risk rate and balancing it with the long-term reduction in hypoxia and high patient satisfaction.

The FutureOf course, the lenses are not yet perfect. Patients still complain of dryness in the mornings and adverse events still occur. The dryness can be managed with saline rinses in the mornings. Motivated practitioners with the necessary understanding of the causes of adverse events and their appropriate treatment are key to successful CW. However, these problems can be troublesome or lead to drop outs in a small number of patients. As researchers we eagerly await the next generation of lenses, but it seems most of our patients are quite satisfied as they are, with over 80% of patients on a CW schedule at the Vision Cooperative Research Centre (VisionCRC) rating overall satisfaction as 85 or above out of 100 ⁽¹¹⁾. The attitude and support our patients get from their practitioners will be a major factor in the utilization of CW lenses in the future.