Trends in the use of silicone hydrogel contact lenses for daily wear
Article Outline
Abstract
Although the first silicone hydrogel contact lenses introduced onto the world contact lens market in 1999 held approval for both daily wear and extended wear use, the latter modality was promoted much more heavily by the manufacturers. The first silicone hydrogel lenses specifically promoted for daily wear were introduced in 2003. Data that we have gathered from annual contact lens fitting surveys demonstrate an immediate increase in market share whereby this lens type now represents more than one-third of soft lens fits in the United Kingdom. The success of this lens category is attributed to the health and safety benefits of silicone hydrogel materials and the positive impact of lens manufacturers by way of the effective marketing and distribution of these products.
Keywords: Contact lens, Silicone hydrogels, Daily wear lenses, Prescribing, Fitting, Survey
1. Introduction
When silicone hydrogel contact lenses were first released onto the world market in 1999, the manufacturers of these products advocated that they be prescribed for extended wear. It was not until 2003 that silicone hydrogel lenses became available that were specifically promoted for daily wear. Because of their high oxygen performance [1], such lenses were expected to induce fewer hypoxic complications – the most obvious being reduced limbal redness, resulting in ‘whiter eyes’ [2]. In this brief communication, we examine patterns and trends in the prescribing of silicone hydrogel contact lenses for daily wear in the UK over the past few years.
2. Methods
Every year since 1996 a survey form was sent randomly to 700 optometrists and 300 dispensing opticians with a request that they provide a range of information about the next 10 patients fitted with contact lenses [3]. Over this period, replies were received from 1488 practitioners relating to 14,542 patients. This information was entered onto a Microsoft Excel® spreadsheet (Microsoft Corp., USA) and data were mined with the aid of the Excel® Pivot Table function. Statistical analysis was conducted using stepwise logistic regression models and linear regression models (JMP, SAS Institute Inc., USA).
3. Results
Four years after their introduction onto the market in 2003, daily wear silicone hydrogel lenses account for 38% of soft lens fits, a statistically significant increase in their use (p
<0.0001); Fig. 1 illustrates the dramatic rise in the prescribing of this lens type. The ratio of daily wear silicone hydrogel lenses prescribed for full-time and part-time wear is approximately 5:1 (p=0.002) (Fig. 1). The age of those fitted with silicone hydrogel lenses (34.0±13.6 years) is slightly higher than the age of those fitted with conventional hydrogel lenses (32.5±13.1 years) (p=0.02). This lens type is much more commonly prescribed to existing contact lens wearers (i.e. as a ‘refit’) than to new wearers (p<0.0001). For example, for 2006 and 2007, approximately 25% of daily wear soft lens new fits were with silicone hydrogel materials; this compares to about 40% of refits.
Fig. 1.
Percentage of daily wear silicone hydrogel lenses as new fits and refits over time, as a proportion of all soft contact new fits and refits.
The male:female gender balance of those fitted with non-daily disposable daily wear silicone hydrogel lenses (40:60) was not significantly different from that for those fitted with non-daily disposable daily wear conventional hydrogel lenses (36:64) (p=0.71).
Of all daily wear silicone hydrogel lenses prescribed, 72% were spherical design, 18% were toric design and 10% were designated as ‘other’ design. This design break-up was almost identical to that for conventional daily wear lenses (71%, 19% and 10%, respectively).
Fig. 2 displays the proportion of soft lenses fitted for daily wear in 2007 according to material (silicone hydrogel versus conventional hydrogel), replacement frequency (daily disposable versus non-daily disposable) and wearing frequency (full-time versus part-time). This figure illustrates the reason why silicone hydrogels represented the minority of daily wear soft lenses in 2007: that is, silicone hydrogels had not been released onto the market as a daily disposable lens (such lenses were introduced in mid-2008).
Fig. 2.
Proportion of soft lenses fitted for daily wear in 2007 according to material (silicone hydrogel [SH] versus conventional hydrogel [H]), replacement frequency (daily disposable [DD] versus non-daily disposable [Non-DD]) and wearing frequency (full-time [FT] versus part-time [PT]).
4. Discussion
The clear health benefits of silicone hydrogel materials [2] are likely to have been a major driving force in the instant market success of daily wear lenses made from these materials, which now represent more than one-third of all soft lenses prescribed in the UK. The rapid uptake of these lenses may have also been facilitated by the ease of communication of the benefits of increased corneal oxygenation from manufacturer to practitioner and then from practitioner to patient. A significant majority of these lenses are fitted on a full-time basis; this is also likely to be a reflection of the superior physiological responses to these lenses [2] and the consequent ‘trouble-free’, ease of wear.
The patterns of prescribing toric lenses for the correction for astigmatism are similar for hydrogel and silicone hydrogel lenses. This suggests that contact lens manufacturers have successfully transferred the principles of hydrogel toric lens design, accumulated over the past 30 years, into the silicone hydrogel domain. Details of the ‘other’ categories of silicone hydrogel lens design are not known, but may relate bandage lenses, monovision and ‘piggy-back’ lens approaches.
As is evident from the prescribing data for daily wear silicone hydrogel lenses presented here, the marketing and supply of contact lenses by the major contact lens manufacturers had a significant impact on prescribing trends. The development of these products is driven by a combination of practitioner/patient demand for better and healthier products, basic and applied research into the ocular response to lens wear [2], and epidemiological studies into lens safety [4]. Recent product launches suggest that the next major advance in the silicone hydrogel domain will be the use of daily disposable lenses; such products will combine the biocompatibility of silicone hydrogel materials with the added safety of a single use product, and will likely attract a major share of the UK soft contact lens market over the next few years.
References
- . Oxygen permeability and water content of silicone hydrogel contact lens materials. Optom Vis Sci. 2007;84:328–337
- . Short-term physiologic response in neophyte subjects fitted with hydrogel and silicone hydrogel contact lenses. Optom Vis Sci. 2004;81:911–921
- . A decade of contact lens prescribing trends in the United Kingdom (1996–2005). Contact Lens Ant Eye. 2006;29:59–68
- . Incidence of keratitis of varying severity among contact lens wearers. Br J Ophthalmol. 2005;89:430–436
PII: S1367-0484(08)00094-5
doi:10.1016/j.clae.2008.06.004
© 2008 British Contact Lens Association. Published by Elsevier Inc. All rights reserved.
