The prevalence of refractive error worldwide varies from country to country, but currently it is estimated that 26.5%, 30.9%, and 40.4% of adults have myopia, hyperopia, and astigmatism, respectively.¹ These proportions outnumber not only the count of regular contact lens wearers but even the number of spectacle wearers worldwide as well. The Centers for Disease Control and Prevention estimates that one out of six Americans wears contact lenses, translating into approximately 45 million people in the United States.² Worldwide estimates of contact lens wear are more difficult to source, but it is estimated to be in excess of 140 million wearers.^3,4 While this is a significant number of wearers, it does lag behind the number of patients who have refractive error and could potentially be wearing contact lenses. Additionally, the total number of contact lens wearers has not appreciably grown in recent history, reflecting no net gain between the number of new wearers and those who drop out of wearing lenses completely. Lack of growth in contact lens wear is a concern not only for the manufacturers but also for the clinicians tasked with prescribing and supplying them. In this article, I will outline six factors that may be preventing a significant increase in new contact lens wearers and causing patients to drop out of lens wear. I also will identify three areas to which the contact lens industry may realistically look for growth.

LIMITATIONS OF GROWTH AND CONTRIBUTORS TO DROPOUT

Factor 1: Comfort, Discomfort, and Patient Expectations The largest factor contributing to the loss of contact lens wearers is contact lens discomfort, which prevents long-term sustained growth as previously successful wearers are lost. Between 12% and 51% of patients will discontinue contact lens wear, with a lack of comfort being the most often cited reason for discontinuation.³ One-half of patients experience discomfort issues with their contact lenses at a somewhat regular frequency.³ Whether this is discomfort upon application, in the middle of the day, or at the end of the day, or whether the lens is being worn for the first or 30th time, lens awareness and discomfort are major factors in preventing seamless contact lens wear for patients.

The inability of patients to consistently wear contact lenses comfortably presents a major barrier for contact lens wear growth within the population. The difficulty for the industry has been the lack of reliably designed clinical trials to identify specific predictors of successful or unsuccessful lens wear or even the ability to predict which lenses would be more or less likely to be successful in a given patient.³

What ultimately leads patients to be uncomfortable with contact lenses is likely an interaction between the contact lens and its care system with the tear film, cornea, conjunctiva, ocular adnexa, and nervous system as well as patients’ expectations and tolerances.³ Basically, until some or most of the key factors that contribute to contact lens discomfort are identified and compensated for, patients will continue to drop out of contact lens wear due to discomfort and, therefore, reduce the contact lens-wearing population.

Factor 2: Who gets eye care and what type of eye care do they get? Safe and effective contact lens wear requires not only an appropriately trained eyecare practitioner for fitting and safety but also an established infrastructure to reliably supply lenses. We need only to examine the burden of uncorrected refractive error to see the difficulties in providing even the most basic forms of refractive correction to people worldwide. In 2010, it was estimated that upward of 101 million people worldwide suffered from moderate-to-severe visual impairment; of that, 6.8 million were blind due to uncorrected refractive error.⁵ Uncorrected refractive error is the second leading cause of blindness and is the most common cause of visual impairment worldwide.⁵ Social determinants of health, including poor economic stability, health literacy, and access to care, all contribute to people living with uncorrected refractive error.⁶ For these people, access to reliable, trained, and affordable eyecare practitioners is already elusive and, thus, so is the opportunity to wear contact lenses safely.

Factor 3: A Ready-Made Soft Contact Lens for Every (Average) Person Historically, one of the greatest factors that has contributed to increasing the number of contact lens wearers was a readily available, in-office supply of soft contact lenses in an assortment of prescription powers, materials, and replacement schedules from a variety of manufacturers. Being able to provide patients with a trial lens to take home and wear in their own environment on the same day that they are assessed and fit is an enormous factor in patients eventually choosing to wear contact lenses. However, even with the growing array of off-the-shelf, non-custom materials, some part of the population is still invariably left out, which may be preventing those patients from ever wearing lenses.

The International Contact Lens Prescribing Survey Consortium (ICLPSC) has conducted numerous international surveys of eyecare practitioners for almost 20 years, quantifying and describing the current and evolving landscape of contact lens fitting and prescribing patterns. While there are some regional differences, the reports themselves paint an interesting picture of the trends in contact lens prescribing on a global scale and highlight some of the challenges in fitting all people with these devices.

For example, as identified by the surveys, the change over time in the fitting of patients who have astigmatism in contact lenses is indicative of the evolution of the industry over time. It is estimated that approximately 47% of patients have, at minimum, 0.75D of astigmatism in one eye; this suggests that at least this proportion of patients could potentially be fit with toric contact lenses.⁷ Yet, when surveyed, practitioners report that only 22% of all soft contact lens fits are toric.⁸

This gap between the proportion of patients being prescribed toric soft contact lenses versus the demographics of clinically significant astigmatism has implications, both in terms of which patients are being encouraged by practitioners to wear lenses as well as what some patients are asked to endure to wear lenses. Some patients who have astigmatism are being fit with spherical lenses and are asked to cope with the compromise to their vision, and/or practitioners are knowingly or unknowingly avoiding fitting astigmatic patients with lenses, leading to this fit/demographic mismatch.

From the practitioners’ point of view, some factors preventing widespread toric lens prescribing include a perceived increase in chair time due to difficulty of the fit process, an assumption that some degree of astigmatism may be “masked” by spherical lenses (particularly those made from a higher-modulus material), and, finally, concern regarding patient acceptance of toric lenses due to lens rotation causing variability in vision. Cost is also proposed as a major factor, with estimates that the premium for a toric lens design ranges from 11% to 19% depending on the region.⁸ The off-the-shelf availability of parameters is also limited. To better manage the logistics of supply, manufacturers have chosen to limit the sphere, cylinder, and axis combinations offered, often resulting in only four cylindrical powers offered across a limited range of axes. This is a compromise due to chosen supply and manufacturing constraints, and, therefore, some part of the population will always be inadequately served. In many instances, those who are left out are the patients whose refractive needs are less common, whether it be a greater amount of astigmatism or a rare oblique axis. For example, 10% or more of the population is estimated to require astigmatism corrections of equal to or greater than −2.25D,⁹ and these patients have limited lens options available to them. The encouraging part at least is that, over the many years during which the survey has been performed, the proportion of toric fits has been increasing steadily, although it is still under the 45% that would match the levels of astigmatism in the population.⁸

Factor 4: Do we have a demographic problem? Patient demographics are another factor that limit contact lens wear. The areas in the world where the contact lens industry is most mature are the developed areas of the Western world and parts of Asia. These areas are also experiencing an overall aging of the population. Between 2002 and 2014 in the United States, the average age of new contact lens wearers and of refits of successful contact lens wearers rose, with the average age of new fits rising from 28 years to 32 years and refits from 34 years to 39 years.¹⁰

The aging of the population can have two counteracting impacts on fitting contact lenses. First is the influence of cosmesis. While the fits and refits are happening at older ages, as mentioned earlier, this may simply be reflective of the aging of the population as a whole, or it may also represent a desire by the older population to wear contact lenses for cosmetic reasons. Particularly, some may not want to wear reading glasses. There are also many regular contact lens wearers who are reaching presbyopic age, which is reflected in the increase in multifocal contact lens fits over time.¹¹

The second impact of the aging of the population on contact lens wear is the utility of presbyopic contact lens corrections. Widespread successful multifocal contact lens correction continues to be a challenge but does appear to be increasing in use over time, with a corresponding decrease in monovision.¹¹ There is, however, an absence of complete transition of all contact lens patients who have presbyopia to multifocal lenses. This may be due to limitations in practitioner fitting knowledge, the impact of the designs on compromises in vision necessitating a variable adaptation period, and again, limitations on available parameters, materials, and wear modalities. Presbyopic patients reportedly would prefer to wear contact lenses over spectacles as long as good comfort and vision can be achieved.¹²

Armed with this knowledge, practitioners should not automatically assume that presbyopic patients are averse to contact lenses as long as comfortable and effective presbyopic lenses are available.¹² Notably, toric multifocal soft contact lens designs continue to be limited, preventing many previously successful contact lens-wearing patients from being able to seamlessly transition to multifocal contact lens wear after years of single-vision wear. Finally, aging also has an impact on contact lens comfort, with changes to the tear film and ocular surface contributing to a decrease in comfortable contact lens wear times.³

What happens when patients cannot be readily corrected in-office with contact lenses? They may mentally discount the potential to wear contact lenses for the rest of their lives even if new developments occur that would allow them to wear lenses. They may also discontinue lens wear once parameters are no longer available due to changes in their refractive status, or they may opt for permanent refractive correction such as laser eye surgery, ultimately reducing the number of potential patients wearing contact lenses with each procedure.

Factor 5: Do we have enough materials? The ICLPSC surveys have also been quite clear regarding the continued decrease in rigid contact lenses as a material, with the most recent publications reporting that rigid contact lens prescribing has declined and settled at approximately 10% of all lenses fit.¹³ Rigid lens wear is unlikely to be eliminated completely, but it likely will be increasingly relegated for speciality uses such as the management of pathology.

The one notable area in which there has been an increase in rigid contact lens use has been in orthokeratology (ortho-k), in which rigid lenses are used to reshape the cornea while they are worn overnight.¹⁴ The success of ortho-k and the increase in its use likely reflect the newfound evidence and support of this type of contact lens wear on affecting the progression of myopia, particularly in children.

The double application of ortho-k to both correct refractive error while also having an effect on slowing axial length growth will likely allow this type of wear modality to increase in prevalence over the course of time as myopia management becomes more of a mainstream part of practice and as further research supports its application in this manner.¹⁴ While increasing, it should still be noted that ortho-k represents only a very small proportion (~1%) of all contact lens fits. However, this varies widely among different countries, reflecting different levels of enthusiasm and expertise in this form of contact lens fitting worldwide.¹⁴

The introduction of silicone hydrogel lenses in the late 1990s and early 2000s was intended to herald a new age in contact lens fitting and practice. No longer would patients be bound by the limitations of water to transmit oxygen to the cornea, opening the door for different wear modalities and applications that could not be safely accomplished before. These lenses would be able to reduce hypoxia-related complications, such as neovascularization, and potentially contact lens complications overall due to a healthier ocular surface.

True to their design mandate in delivering an increased amount of oxygen to the ocular surface, silicone hydrogel lenses have effectively eliminated hypoxia-related complications in the vast majority of patients.¹⁵ Classic acute and chronic corneal signs of hypoxic stress with lens wear—including redness, microcysts, neovascularization, and refractive error changes—are all reduced with silicone hydrogel lens wear to levels similar to non-lens wearers.¹⁵ The oxygen benefits have led silicone hydrogels to be the most prescribed material for new contact lens fits and have also induced a significant number of refits of current contact lens wearers into this material upon introduction.^10,16,17

Unfortunately, the oxygen benefits conferred by these lenses have not had an appreciable impact on the rate of sight-threatening infections, with overnight lens wear still increasing the risk of microbial keratitis significantly.¹⁸ The inherent increase in risk of infection and complications with contact lens wear, whether it be extended wear or daily wear, likely causes some proportion of the population to resist choosing to wear contact lenses.

Factor 6: What has been the impact of wear modality? Silicone hydrogels were also intended to herald a potential endgame lens wear modality in the form of extended wear, in which the lenses could safely be worn continuously for 30 days and nights without the need for removal, cleaning, and storage, significantly improving the convenience of lens wear. Unfortunately for this wear modality, extended wear only slowly increased to a peak of 12% of all fits in 2006 before falling back to 8% by 2010.¹⁹ It is speculated that further increases in risks of corneal infections to levels higher than observed with daily wear likely render both patients and practitioners wary of this type of wear modality in general, opting for its use in only a subset of the clinical population who have high motivation or lifestyle factors for which the benefits of convenience allow for acceptance of this increased risk. At a rate of less than 10% of lens wearers, it is unlikely that extended wear will have the momentum to become a more mainstream wear modality.¹⁹

Increases in the efficiency and cost effectiveness of soft contact lens manufacture have also allowed daily disposable contact lens wear to become a greater reality for a larger proportion of patients. More lens parameters, including toric, hyperopic, and multifocal contact lenses, are available than ever before in a daily disposable wear modality in a plethora of lens materials, including some exclusively used only for daily disposables. The convenience of daily disposables is appealing from a prescriber and patient perspective because it is often touted as a safer option due to the absence of a reusable case and solutions; although, the rate of serious infections with daily disposable wear modalities remains approximately the same as with other daily wear lenses.

Daily disposable lenses are reported to be the wearing modality most often recommended for new contact lens fits.²⁰ Daily disposable lens wear also has the potential to capture the part-time lens wearers, offering an opportunity to eyecare practitioners. The rate of daily disposable lens wear is increasing over time, and it likely will represent the majority of lens fits in the future if it does not already.^17,20

The downside to daily disposable lens wear likely pertains to concerns regarding costs, particularly for full-time wearers when compared to the cost of reusable lenses with solutions. There are also concerns regarding increased waste of both the lens materials and packaging, although there have been programs launched by manufacturers or contact lens dispensers to collect and return all materials associated with contact lens wear to be recycled.

HOW CAN THE NUMBER OF CONTACT LENS WEARERS GROW?

Children and Myopia Control The majority of contact lenses are fit to adults, with only 13% of contact lens fits to people younger than 18 years of age, the majority of whom are young adults and not children.²¹ With that in mind, perhaps consideration needs to be made as to when lenses can first be worn and recommended to patients. The recent developments and interest in myopia as a public health concern and the role of contact lenses of different types (e.g., multifocal, ortho-k) create an optimum environment for patients to start wearing contact lenses earlier in their lives.^22,23

Naïve young contact lens wearers between 8 and 16 years of age can be successfully taught how to handle, apply, remove, and maintain contact lenses, suggesting that with proper training, even young people can safely and effectively wear contact lenses.²⁴ The rate of contact lens-related complications is also reported to be similar if not lower in children wearing contact lenses compared to adults, suggesting that lens wear in children is not inherently more risky than in adults.²⁵ Long-term use of ortho-k in children also does not appear to cause any increase in complications compared to soft contact lens use.²⁶

The perceptions of parents and guardians on contact lens wear effectiveness and safety can have a huge influence on the tolerance for risk. In a telephone survey of Hong Kong parents who responded to advertisements for myopia control studies with contact lenses, the perception of the lenses being used for “treatment” significantly increased their openness to the use of contact lenses when compared to using lenses simply for correcting refractive error.²⁷ Regardless, children can be successfully fit with contact lenses, and thus practitioners have to consider whether they are willing and comfortable in fitting this demographic group. Additional indications for contact lenses in children in the form of myopia control can also lead to an increase in contact lens wear in this previously under-represented demographic group.

Emerging Markets Being able to tap into emerging markets that have less infrastructure can have an enormous effect on the raw number of people wearing contact lenses. This requires the development of distribution networks and infrastructure so that numerous companies and suppliers can provide options for both the patients and the practitioners prescribing the lenses. The nature, time, training, and ability of the prescribing practitioners is also crucial to ensure that there is a safe and effective means to access and use these lenses so that they will be accepted by the general population. The emergence of certain countries that have invested in the training of opticians, optometrists, and ophthalmologists in the fitting of contact lenses can have a significant impact on increasing the number of patient fits within different countries and will continue to develop over time.

Lifestyle and Sport, Occupational and Vocational Lenses Finally, with the increased availability of daily disposables in a variety of parameters, eyecare practitioners should be redoubling their efforts to inform patients of the potential of contact lenses for more part-time use. While not every patient may desire to wear contact lenses as a primary mode of correction, the flexibility afforded by daily disposables may be useful in lifestyle, sport, or vocational uses for which a ready supply of sterile, pre-packaged daily disposable lenses, which can be worn and discarded without the need for care, cleaning, and storage afterward, may prove to be an option that patients can incorporate into their refractive error solutions.

CONCLUSIONS

The contact lens industry continues to change and evolve over time, with the introduction of new materials, wear modalities, and product features to further promote successful contact lens wear. While there are challenges in contact lens wear, the impact of research, development, and feedback from both clinicians and patients will further the industry’s growth and development and will hopefully fuel the further growth of successful contact lens wearers worldwide. CLS

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