Topical review: Twenty-five years of silicone hydrogel soft contact lenses

Abstract

The impact of silicone hydrogel (SiHy) contact lens materials on clinical contact lens practice and patient care over the past 25 years is reviewed, along with identifying areas for future innovation in material science and clinical practice to further improve outcomes for contact lens wearers.A quarter of a century since the launch of SiHy contact lens materials, with many current eye care professionals having never practiced without them as an option, this literature review reflects how this significant change in soft lens material technology has impacted routine clinical contact lens practice and patient care. SiHy lenses now account for approximately 75% of all new daily wear soft lenses fitted and they are available in a wide variety of modalities, replacement frequencies, and designs, including daily disposable, torics, and multifocals. From the physical properties of SiHy materials and their adoption to their use in helping meet patient needs, conclusions can be made where historical clinical issues have been solved, and where innovation in material science and evolution in clinical practice are still required to deliver the best outcome for contact lens wearers. SiHy materials have largely eliminated hypoxia as a complication seen in contact lens clinical practice, and when used for daily wear, in particular as daily disposable lenses, they provide an exceptional option for vision correction that is minimally invasive, comfortable, and effective. This review helps with the understanding of how the eye care profession has adopted the use of these lenses over the last 25 years, and questions what comes next for these widely used family of materials and the opportunities that exist for them to continue contributing to patient satisfaction and to growing the contact lens market.

FIGURE 1.

Graph of water content (WC) versus oxygen permeability (Dk) for a number of SiHy (solid symbols) and hydrogel lens (open symbols) materials. A clear trend of reducing Dk with increasing WC can be seen for the SiHy materials. SiHys Pearson correlation r = −0.65; p=0.01; hydrogels Pearson correlation r = 0.97, p<0.01. All hydrogel Dk figures are calculated from manufacturer’s stated water content using the formula outlined by Morgan and Efron and SiHy Dk values are gathered from various public sources.

FIGURE 2.

Graph of water content (WC) versus modulus for a number of SiHy (solid symbols) and hydrogel lens (open symbols) materials. A clear trend of reducing modulus with increasing WC can be seen for all materials. Pearson correlation was r = −0.73; p<0.01. Note that no one standard measurement for determining modulus exists and values vary depending on methodology. Modulus values are from manufacturer’s websites where available; where not available, values have been used from Bhamra and Tighe and Sulley et al. SiHy = silicone hydrogel.

FIGURE 3.

Prescribing of SiHy lenses, presented as a proportion of all soft lens fits from 2000 to 2024. Data are courtesy of the International Contact Lens Prescribing Survey Consortium and for markets reporting at least 15 years of data and for years with at least 100 reported fits per country. See Efron et al. for details of methodology of data capture. SiHy = silicone hydrogel.

FIGURE 4.

Twenty-five SiHy contact lens materials launched since 1999 (with a few no longer commercially available). Note how there is no clear increase in Dk values over time, with all SiHy materials offering Dk values between 55 and 150 units. SiHy = silicone hydrogel.

FIGURE 5.

The proportion of SiHy lenses used when lenses are prescribed for monthly replacement or daily disposable. Data are courtesy of the International Contact Lens Prescribing Survey Consortium and for markets reporting at least 15 years of data and for years with at least 100 reported fits per country. See Morgan and Efron for details of methodology of data capture. SiHy = silicone hydrogel.

FIGURE 6.

SiHy replacement frequency for different markets. Data are courtesy of the International Contact Lens Prescribing Survey Consortium and for markets reporting at least 15 years of data and for years with at least 100 reported fits per country. See Morgan and Efron for details of methodology of data capture. Abbreviations are for Italy, Taiwan, United Kingdom, Australia, Japan, Canada, Israel, Denmark, Lithuania, Norway, Hungary, Spain, New Zealand, Sweden, United States, Greece, Czechia, Portugal, and Bulgaria, respectively. SiHy = silicone hydrogel.