contact lens materials

What Contact Lens Materials are Patients Wearing?

BY KATHY DUMBLETON, MSC, MCOPTOM, FAAO, & LYNDON JONES, PHD, FCOPTOM, FAAO

Silicone hydrogel (SiHy) and daily disposable (DD) lenses now comprise at least 60 percent of the lenses currently prescribed in the United States (Nichols, 2009; Morgan et al, 2009). The Centre for Contact Lens Research recently conducted a study to assess the compliance of eyecare practitioners (ECPs) and patients with recommendations for replacement frequency of DD and SiHy lenses in the United States (Dumbleton et al, 2009)

As part of this study, ECPs were asked to record which lens types were being worn by the patients completing the study survey. One-hundred-fifty-eight ECPs and 1,654 patients took part in the study. Lens types were recorded by the ECPs on envelopes in which the patients had sealed their completed surveys. A table showing the lens types worn by the patients, as reported by the ECPs, is available at the bottom of this Web page.

DD lenses were worn by 16 percent of the study patients, and 55 percent of these DD lenses were nelfilcon A (Focus Dailies, CIBA Vision). Two-weekly replacement lenses were the most popular SiHy lenses (worn by 45 percent of the patients), and 64 percent of these were senofilcon A (Acuvue Oasys, Vistakon). Monthly replacement SiHy lenses were worn by 39 percent of the patients, and just under one-third of these were lotrafilcon B (O₂Optix, CIBA) with a similar proportion being lotrafilcon A (Night & Day, CIBA). Balafilcon A (PureVision, Bausch & Lomb) lenses were worn by 27 percent and comfilcon A (Biofinity, CooperVision) lenses were worn by 10 percent of the patients who had been prescribed monthly replacement SiHy lenses.

Lens Wear Patterns

Ninety-two percent of lenses were prescribed for myopia, with a median and mean spherical power of −3.00D. The majority of the lenses were spherical, with toric lenses worn by 16 percent and multifocal lenses worn by only 3 percent of the patients. It is likely that the number of toric and multifocal SiHy lenses will increase in the near future because of the recent introduction of several new designs in SiHy materials.

SiHy lenses were worn for more days per week (6.2 ±1.4 days) compared with DD lenses (5.7 ±1.9 days). The mean wearing time of lenses worn for daily wear was 12.8 ±3.2 hours each day, with no significant differences between the SiHy lenses and the DD lenses. Twelve percent of patients wore their lenses on an extended wear (EW) basis; lotrafilcon A was the most frequently worn material for this modality, with 42 percent of these lenses being worn on an EW basis. Somewhat surprisingly, with DD lenses 14 percent of patients reported wearing their lenses to sleep overnight "occasionally," 3 percent "frequently," and 2 percent almost every night.

Comfort Still an Issue

ECPs are fortunate to have such a wide range of material options available for their patients today, but improvements could still be made to increase comfort with these lens types. In this recent study, 47 percent of patients reported that their lenses became less comfortable later in the day, but they continued to wear their lenses for another two-and-a-half hours despite the reduced comfort. Clearly, further modifications to DD and SiHy materials are still required for our patients to achieve all-day comfort. CLS

For references, please visit www.clspectrum.com/references.asp and click on document #165.

Dr. Dumbleton is a senior clinical scientist at the Centre for Contact Lens Research in Ontario, Canada. Dr. Jones is the associate director of the Centre for Contact Lens Research and a professor at the School of Optometry at the University of Waterloo, Ontario, Canada. He has received research funding from Alcon, AMO, B&L, CIBA Vision, CooperVision, Johnson & Johnson, and Menicon.