CW WORLDWIDE: An update on silicone hydrogel use

Silicone hydrogel lenses represent a major step forward in the development of vision correction, offering our patients convenience, comfort and good vision.

Are patients happy with silicone hydrogels? Patients enjoy the freedom of 30 days and nights of continuous wear together with the advantages of soft lenses, and rapidly increasing sales figures indicate that the lenses are being warmly welcomed in the marketplace.

Are practitioners happy with silicone hydrogels? Practitioners are seeing high levels of patient satisfaction and good corneal health with the lenses. Many practitioners are now seeing high Dk silicone hydrogel lenses as the first choice lens for their patients, irrespective of wear schedule, because these lenses offer superior metabolic health for the patient.

Practitioners have a major influence on the products used by their patients. In a landmark study published in 1991, Tony Hanks showed the difference between a proactive and reactive approach to prescribing contact lenses [or introducing contact lenses to patients]. With 50 patients, contact lenses were offered only if a patient initiated interest. With another 50 patients, the practitioner raised the topic. Hanks found that lenses were discussed with only 4% of patients in the first group, resulting in one fitting In contrast, contact lenses were discussed with 100% of patients in the second group, and 22% of patients were fitted with lenses.

The impact of practitioner attitudes on silicone hydrogels was obvious. Despite patient enthusiasm about the well-publicised convenience of CW, silicone hydrogel CW had a somewhat slow beginning because of practitioner wariness about the safety of the modality.

Since then, worldwide studies looking at the performance of silicone hydrogels have clearly demonstrated that the lenses have indeed solved the problem of hypoxia with extended wear. The results of these studies and the positive experiences of colleagues are now convincing practitioners that the lenses are a valuable option for all contact lens patients.

Figure 1 - click to enlarge

As Figure 1 illustrates, Australia and the UK are currently leading the world in practitioner confidence. The early launch of silicone hydrogels in these countries has undoubtedly contributed to these figures, as practitioners rapidly gain experience and trust in the new materials once they see their successful performance in practice. It is expected that the US and Canada will reach similar levels of confidence in the near future.

With the change in practitioner attitude we are seeing a significant increase in worldwide silicone hydrogel use. Silicone hydrogels are the fastest growing segment of the CL market, with many existing and new lens wearers attracted to their convenience and health benefits.

Silicone hydrogel use has doubled in the past year, and it is estimated that there are now one million high Dk wearers around the world ( Figure 2 ). In Australia, there was a 46% growth in value in the silicone hydrogel market in 2001-2002, and silicone hydrogels now comprise 16% of the total worldwide CL market.

Figure 2 - click to enlarge

The convenience of extended wear has certainly been one of the key drivers behind the growth in silicone hydrogel wear, and myopes have made up a large proportion of the market. The most recent market growth may be more due to market expansion, however, as practitioners recognise the value of the lenses for a wider range of patients.

Silicone hydrogels are increasingly being used for both continuous and daily wear. The flexibility of wear time makes them an attractive option for all patients. The lenses also often provide better comfort than conventional daily lenses, and can be of use for dry eye patients. The wider choice of powers is also opening up options for more patients.

Silicone hydrogels have great potential to be used for presbyopic patients using monovision (see Jacqueline Tan's editorial 'Contact Lens Options for Presbyopia' from December). Monovision is the most successful form of contact lens wear for presbyopes, and silicone hydrogels offer ocular health and the option of continuous wear. Silicone hydrogel monovision also offers existing satisfied lens wearers the chance to continue wear as their vision correction needs change with presbyopia.

Silicone hydrogels are also finding a place as a therapeutic lens for a range of conditions. Again, the ocular health benefits of high oxygen permeability combine with the comfort of a soft lens to make silicone hydrogels an excellent choice as a bandage lens.

New vs existing

Anecdotal reports indicate that spectacle wearers are attracted by the convenience of CW; however, there are no specific data yet available on this aspect of the market. In practitioner surveys Morgan and Efron have found that silicone hydrogels are more often used for refits than for new lens fittings ( Figure 3 ).

Figure 3 - click to enlarge

Australian practitioners similarly seem to be more prepared to prescribe silicone hydrogels for existing CL wearers to silicone hydrogels than to prescribe new wearers with CW ( Figure 4 ).

Figure 4 - click to enlarge

These fitting trends may reflect practitioner caution, wishing to provide patients with experience in conventional soft lenses before transferring them to CW. This strategy may provide a valid test of patient compliance, to ensure that patients do not become complacent with the additional convenience of CW. It is to be hoped, however, that patients fitted with conventional lenses do not become part of the contact lens 'drop out' statistics before reaching CW.

In 2003, a Vision Cooperative Research Centre (VisionCRC) research team led by Fiona Stapleton undertook a household survey to determine lens prescribing and usage trends in Australia. 7,865 households (18,192 individuals) were contacted. The results ( Figure 5 ) show:

• 4.6% penetration of CL wear
• 64% of CL wearers are female

• The figure below illustrates the distribution of practitioners prescribing trends in Australia where the majority of lenses that are prescribed are disposable weekly or monthly use for daily wear. However, silicone hydrogel lenses already constitute an impressive 5.3%.

Figure 5 - click to enlarge

The future

Silicone hydrogels have revolutionised the vision correction market, and we will continue to see their exciting impact on patients and practitioners. CL and CW usage figures are rapidly changing as practitioners gain experience and confidence, as practitioners recognise their use for a wider patient range, as more patients express interest in the new lenses, and as additional designs expand the market. We look forward to seeing how practitioner confidence and CL use continues to develop throughout the world over the coming year.