The Changing Face of Contact Lens Wearers Over 25 Years
25th Anniversary Perspective
The Changing Face of Contact Lens Wearers Over 25 Years
By Jeffrey J. Walline, OD, PHD, FAAO, & Nathan Efron, BSCOPTOM, PHD, DSC, FBCLA, FCCLSA, FIACLE, FACO, FAAO (DIPCCLRT)
A combination of factors has dictated patterns of prescribing to contact lens wearers in different age groups over time, such as the evolution of manufacturing technology in bringing better lens designs and replacement frequency options; the aging population demographic; and the knowledge and attitudes of practitioners. Here we explore evolving lens fitting practices at the opposite poles of the age spectrum—children and presbyopes.
Traditionally, contact lenses have not been prescribed for children until their teen years. Infants and toddlers only occasionally wear medically necessary lenses, primarily for unilateral aphakia. The invention of a silicone elastomer contact lens, Silsoft (Bausch + Lomb), significantly altered the traditional fitting of young aphakic patients.
The advent of 1-Day Acuvue from Vistakon and other daily disposable lenses has altered the landscape for fitting myopic children almost as significantly as the Silsoft lens affected the fitting of aphakic children. Now children can wear contact lenses without the responsibility of lens care—the lenses are simply discarded each night. The intrinsic compliance of daily disposable lenses provided the impetus for fitting children at younger ages.
Several studies have shown that pre-teen children are capable of wearing all contact lens modalities, including GP (Katz and Levy, 2003; Walline et al, 2004) corneal reshaping (Cho et al, 2005; Walline et al, 2009), and soft contact lenses (Horner et al, 1999; Walline et al, 2009).
Children between the ages of 8 and 12 years can benefit as much from contact lens wear as 13- to 17-year-old teenagers Walline et al, 2007a). They have similar short-term ocular health risk profiles as teens, and they require only about 10 minutes extra for all of the fitting and follow-up visits during the first three months of lens wear (Walline et al, 2007b). A serious imbalance in any of these factors may limit lens fitting to children 13 and older, but the risk-to-benefit ratio for pre-teens is similar to the ratio for teens, so children are being routinely fitted at younger ages.
Contact lenses provide benefits beyond just vision correction for children. Nearsighted children who switch from glasses to contact lenses feel better about their own appearance, athleticism, and peer interactions compared to children who continue to wear glasses. The contact lens wearers also feel better about their academic abilities compared to spectacle wearers if they initially don' t like to wear glasses (Walline et al, 2009). Likewise, children who wear contact lenses report better quality of life compared to children who wear glasses, especially in reference to their appearance and their participation in activities such as sports.
Another benefit of contact lens wear beyond vision correction for children may be slowed growth of the eyes. While GP (Katz and Levy, 2003; Walline et al, 2004) and soft contact lenses (Horner et al, 1999; Walline et al, 2008) do not alter eye growth, corneal reshaping (Cho et al, 2005; Walline et al, 2009) and soft bifocal (Aller, 2009; 2008) contact lenses may. Currently, several investigations are underway around the world to determine whether or not these lenses affect myopia progression, but the initial indications are that they slow the growth of the eye by about 50 percent.
If one or more contact lens modalities are found to slow eye growth, then the pediatric contact lens landscape will change dramatically. This relatively untapped population of contact lens wearers may drive the market for smaller-diameter, higher-modulus contact lenses that may ease lens application for children. Contact lenses that slow myopia progression will also provide more information about controlling eye growth, potentially leading to therapeutic contact lens wear prior to the onset of myopia.
Pediatric lens wearers may drive the future of contact lenses, but many past innovations are related to presbyopic lens wear.
Since 1950, the proportion of older persons (over 60 years) has been rising steadily, passing from 8 percent in 1950 to 11 percent at the present time; it is expected to reach 22 percent by 2050 (United Nations Department of Economic and Social Affairs/Population Division, 2009). This shift in age structure has important implications for the contact lens field: that is, the proportion of the world population that is presbyopic is increasing. This highlights the importance of providing a satisfactory means of correcting presbyopia with contact lenses. However, optically clear distance and near corrections with contact lenses has been a major challenge.
Rigid contact lenses can be designed in either translating or simultaneous vision forms. A translating bifocal design relies upon purposeful lid-lens interactions to position the appropriate optical portion of the lens over the pupil for clear distance or near vision. Various simultaneous vision rigid lens options are available in concentric, diffractive and aspheric designs. It can be difficult for presbyopes to adapt to the discomfort of rigid contact lenses, let alone to translating rigid bifocal lenses that require constant lid interactions with the lens edge (Meyler, 2010). However, those presbyopes who are able to adapt to rigid contact lenses often obtain acceptable visual performance with such lenses (Rajagopalan et al, 2006).
Translating bifocal soft contact lenses have appeared in the market from time to time (Ezekiel, 2002) but have met with limited success. The two main soft lens options for presbyopia are monovision and simultaneous distance/near vision bifocal corrections. Monovision involves fitting one eye for distance (typically the dominant eye) and one eye for near. This form of correction has the advantages of simplicity, flexibility, and reduced cost, and the disadvantage of visual compromise in the form of interocular rivalry (Evans, 2007; Chapman et al, 2010). Simultaneous bifocal corrections require perceptual adaptation to a form of intraocular rivalry, whereby mixed visual inputs of distance and near images (one of which is out of focus) are superimposed on the retina of each eye (Meyler, 2010).
There has been a dramatic shift over the past 20 years in the proportion of monovision versus bifocal soft lenses prescribed. In Australia, where good longitudinal prescribing data exist, monovision and multifocal corrections constituted 27 percent and 9 percent of soft lenses prescribed to presbyopes in the 1980s (Sweeney et al, 1991) versus 13 percent and 28 percent today (Morgan et al, 2011). This reflects a change in attitude and practice across the field. The contact lens industry is acutely aware of the aging demographic and has accelerated efforts over the past decade in bringing a range of new soft multifocal designs to market. For example, in Australia, only six soft multifocal lens designs were available in 2000 (2000-2001 Contact Lenses, 2000) versus 21 in 2009 (2009 Contact Lenses, 2009).
Despite the encouraging recent shift from monovision to bifocal lens designs, the rate of presbyopic contact lens prescribing to patients older than age 45 remains disappointingly low at 37 percent (Morgan et al, 2011). This suggests that most presbyopic contact lens wearers are being fitted with a distance prescription only and are relying upon intermittent use of reading spectacles for close work. The low rate of monovision or multifocal contact lens prescribing is likely due to a combination of: 1. a lack of fitting skills, technical knowledge, product awareness, or clinical confidence among practitioners; 2. a belief that the perceptual compromises of currently available alternatives (either multifocal contact lenses or monovision) are too great (Evans, 2007; Chapman et al, 2010); and/or 3. an absence of a “perfect” multifocal contact lens that provides good comfort and uncompromised simultaneous optical imagery for all distances.
Such barriers can only be overcome by accelerated professional education in presbyopic contact lens fitting delivered by academic and professional institutions and the contact lens industry, as well as continued research and development into optimized multifocal contact lens designs. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #183.
Dr. Walline is an assistant professor at The Ohio State University College of Optometry where he conducts studies of pediatric contact lens wear. He is a consultant or advisor for and has received research funds from Paragon Vision Sciences and Vistakon. Professor Efron is a research professor at the School of Optometry, and Institute of Health and Biomedical Innovation, at the Queensland University of Technology in Brisbane, Australia.
Contact Lens Spectrum, Issue: February 2011