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Contact Lens Spectrum

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HALF A CENTURY OF SOFT CONTACT LENSES

Where are we headed? A reflection on the difficult early years of soft lenses, a review of soft lens prescribing so far this century, and predictions for prescribing trends.

By: NATHAN EFRON, AC, DSC, PHD, PHILIP B. MORGAN, PHD, MCOPTOM
Contact Lens Spectrum May 1, 2023 Vol 38, Issue May 2023 Page(s): 36-38, 40-43

WHEN SOFT CONTACT lenses entered the market in 1971, their comfort compared to rigid lenses was the main driver for the initial enthusiastic response by contact lens prescribers. This excitement was quickly dampened after it became apparent that the thick, 38% water hydroxyethyl methacrylate (HEMA) material from which the original soft lenses were made resulted in a suboptimal physiological response. Thus began an effort over the next half century—52 years, to be precise—to develop safe, physiologically biocompatible, comfortable, convenient, and affordable soft lenses and wearing modalities…and this effort is still ongoing today.

In this article, we will briefly review the difficult early history of soft contact lenses (1971-1999), consider prescribing trends in this century so far (2000-2022), and predict what might occur in the next 28 years (2023-2050) with regard to five key soft-lens categories.

INSUFFICIENT OXYGEN

Perhaps the biggest problem in the early days of soft lenses was the low oxygen permeability of the materials from which they were fabricated. It was soon realized that the corneal hypoxia induced by these lenses caused high levels of corneal swelling.1

Other adverse ocular reactions that were becoming apparent (Figure 1) were attributed to a combination of lens-induced hypoxia and hypercapnia, mechanical effects, and immunological reactions to lens deposits. These included corneal staining (Figure 1A); increased conjunctival redness (Figure 1B); papillary conjunctivitis of the tarsus of the upper lid (Figure 1C); and corneal epithelial microcysts (Figure 1D), stromal neovascularization (Figure 1E), and endothelial polymegethism (Figure 1F).2

FIGURE 1. Complications encountered with early-generation hydrogel lenses. (A) corneal staining; (B) conjunctival redness; (C) papillary conjunctivitis; (D) epithelial microcysts; (E) stromal neovascularization; and (F) endothelial polymegethism.
FIGURE 1. Complications encountered with early-generation hydrogel lenses. (A) corneal staining; (B) conjunctival redness; (C) papillary conjunctivitis; (D) epithelial microcysts; (E) stromal neovascularization; and (F) endothelial polymegethism.

UNCERTAINTIES ABOUT LENS MAINTENANCE

A parallel problem during the 1970s and 1980s was uncertainty about the best way of caring for HEMA lenses; these were the days prior to regular lens replacement or daily disposable lenses. In fact, many patients used the same pair of soft lenses for many years and ended up developing visible gross lens spoilation (Figure 2), such as jelly bumps (mucus-protein aggregations) (Figure 2A), rust spots (oxidized iron deposits) (Figure 2B), and calcium deposits (Figure 2C).3

FIGURE 2. Long-term visible deposit formation on early-generation hydrogel lenses. (A) jelly bumps; (B) rust spots; and (C) calcium deposits.
FIGURE 2. Long-term visible deposit formation on early-generation hydrogel lenses. (A) jelly bumps; (B) rust spots; and (C) calcium deposits.

Options for lens maintenance at the time included heat disinfection (Figure 3), whereby lens wearers placed their lens cases (containing the lenses) into a special heating unit. The theory was that the heat would destroy potential noxious microorganisms.4 This worked to some extent, but unfortunately the repeated heat treatment accelerated lens degradation, causing the lenses to become discolored, misshapen, and slightly brittle, with denatured protein “baked” onto the lens surface.4

FIGURE 3. Heating unit used to disinfect early-generation hydrogel lenses.Courtesy of Bausch & Lomb Slide Library.
FIGURE 3. Heating unit used to disinfect early-generation hydrogel lenses.Courtesy of Bausch & Lomb Slide Library.

Chemical disinfection was the primary alternative care regimen. Lens wearers were required to purchase a “chemistry set” of solutions, such as a separate cleaning solution, disinfecting solution, saline solution for lens rinsing, in-eye lubricant, and protein-removal tablets. One problem that quickly emerged was that patients often developed adverse reactions to the preservatives used in many of these solutions—such as chlorhexidine and thimerosal—resulting in a temporary or permanent cessation of lens wear.4

Other lens maintenance systems that have been attempted over the years, with varied levels of success, include ultraviolet radiation, ultrasound, chlorine solutions, and one-step or two-step hydrogen peroxide systems.4 Most of the above problems were subsequently solved by the introduction of multipurpose solutions incorporating preservatives that are compatible with the ocular surface.4

THE SOFT CONTACT LENS REVOLUTION

A major turning point in the evolution of soft lenses came in 1985 with the publication of a scientific paper—popularly known as the Gothenburg Study—by Holden and co-workers.5 This study examined the impact of extended lens wear on ocular structures, that were being used in a forward-thinking contact lens practice in Gothenburg, Sweden, which was at the time experimenting with regular lens replacement.

The major findings of the Gothenburg Study formed the blueprint for the development of contact lenses over the next 35 years by demonstrating that the long-term adverse effects of contact lens wear on the ocular surface could be minimized by fitting lenses that were more frequently replaced and manufactured from materials that had higher oxygen permeability.5

These revelations from the Gothenburg Study led to the “soft contact lens revolution” of the 1990s, including arguably the two greatest developments in the field of soft contact lenses since their invention: the introduction of daily disposable contact lenses and highly oxygen permeable silicone hydrogel lenses in 1994 and 1999, respectively.6,7 This same decade also saw the beginning of dramatic improvements in the designs of toric and multifocal lenses.

TRACKING SOFT LENS PRESCRIBING

Assisted by an international consortium of colleagues in the contact lens field, we have been tracking contact lens prescribing trends on an annual basis since 1996.8 The timing of this work is fortuitous, as the commencement of these surveys coincided approximately with the start of the soft contact lens revolution, allowing us to track the clinical uptake of these improved daily disposable, silicone hydrogel, toric, and multifocal lenses in real time.

We also tracked other aspects of soft lens wear, such as tinted lenses, myopia control lenses, and utilization of extended wear. Prescribing trends relating to the latter will also be considered in this paper.

Our survey work, which is reported in the January issue of Contact Lens Spectrum every year and is still ongoing, involves asking contact lens practitioners to provide 11 items of information from 10 consecutive contact lens fits between January and March each year.9 Over the 27 years of this survey, data relating to over 422,160 contact lens fits have been collected from 71 countries, generating around 4.5 million data points.

Below we shall briefly review trends in contact lens prescribing, in five key soft lens categories, between 2000 and 2022. Data are presented in graphical form relating to 17 featured countries that have returned largely continuous prescribing data over this period (other countries have dropped in and out of the survey over time). The mean trend line for these data is shown in these graphs by the red dots. Based on an analysis of these established trends, we shall perform a little “crystal ball gazing” to predict likely contact lens prescribing patterns until 2050 (shown by green dots on each graph).

SILICONE HYDROGEL LENSES

Soft contact lenses today are manufactured from either silicone hydrogel or hydrogel materials. The proportion of silicone hydrogel lenses fitted between 2000 and 2022 is shown in Figure 4 (the balance being hydrogel lens fits). Clearly, there has been a dramatic increase in silicone hydrogel lens fitting throughout the survey period, and this change has been remarkably similar in most of the countries studied in our survey work.

  

FIGURE 4. Trends in the proportion of all soft lens fits that are silicone hydrogel lens fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.
FIGURE 4. Trends in the proportion of all soft lens fits that are silicone hydrogel lens fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.

The sudden increase in the rate of silicone hydrogel lens fitting around 2004 is thought to be largely due to the introduction of these lenses for daily wear at that time. Between 1999 and 2003, silicone hydrogel lenses were approved only for extended wear, and were not popular with clinicians for reasons explained in this feature (see “Extended Wear Lenses” on page 41).

Our prediction, from now until 2050, is shown by the green dots in Figure 4. We predict that silicone hydrogel lenses will plateau at around 90% of all soft lenses prescribed by 2050. A small percentage of hydrogel lenses will likely remain available, largely in Asian markets, due to the potential of such lenses to be manufactured at an extremely low cost. The reason for our prediction of silicone hydrogel dominance simply relates to their high oxygen transmissibility,10 resulting in the virtual elimination of hypoxia-induced adverse ocular reactions and whiter, healthier-looking eyes.11

DAILY DISPOSABLE LENSES

The proportion of daily disposable lenses fitted in the 17 featured countries each year between 2000 and 2022 is shown in Figure 5, with the balance being almost entirely every-two-week or monthly replacement lenses. Again, the mean trend is for increased prescribing of daily disposables, although there are substantial differences in the extent of fitting this lens type between countries. These differences are thought to be primarily due to differences in national affluence; the rate of prescribing daily disposable lenses is higher in more affluent nations, as indicated by a higher gross domestic product.12

FIGURE 5. Trends in the proportion of all soft lens fits that are daily disposable lens fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.
FIGURE 5. Trends in the proportion of all soft lens fits that are daily disposable lens fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.

Many brands of daily disposable lenses are available today13 due to significant advances in contact lens manufacturing, driving down the cost per lens and making daily disposability affordable for many.14 Daily replacement of contact lenses has the advantages of convenience,15 better compliance,16 improved cost efficiency for part-time wearers,14 minimal environmental impact,17 and superior ocular health.18

As for our prediction for the future (shown by the green dots in Figure 5), there is likely to be an ongoing increase in daily disposable prescribing as the cost per lens continues to decrease. Reusable lenses will probably always be less expensive for full-time wearers (those who wear lenses four or more days per week), however, even with the associated solution costs, reusable lenses will still be used by a small minority of full-time lens wearers, especially those living in less affluent regions.14,18

TORIC LENSES

The proportion of toric lenses fitted for standard fits (i.e., not including multifocal, monovision, myopia control, or cosmetically tinted lenses) in the 17 featured countries each year between 2000 and 2022 is shown in Figure 6 (the balance being spherical lenses). The percentage of fits with toric lenses increased throughout the survey period, although again, there were substantial differences in the extent of fitting this lens type. The prevalence of the population with astigmatism ≥ 0.75DC in at least one eye is 47.4%.19 This level of astigmatism can be considered a “target value” that would signify full correction of astigmatism among contact lens wearers, given that manufacturers typically provide toric lens correction for astigmatism in powers ≥ 0.75DC.13 This target value is shown as a black dotted line in Figure 6.

FIGURE 6. Trends in the proportion of all soft lens fits that are toric lens fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors. The black dotted line indicates the “target value” (47.4%) for full correction of astigmatism.
FIGURE 6. Trends in the proportion of all soft lens fits that are toric lens fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors. The black dotted line indicates the “target value” (47.4%) for full correction of astigmatism.

As can be observed in Figure 6, the mean level of toric lens prescribing is growing and has reached the target value referred to above in a number of markets. This success can be attributed to the growing skill set and confidence of practitioners in fitting this lens type.

Toric lenses have historically been considered difficult to fit; however, with improvements in lens design and optics and ongoing expansion of available toric lens powers and cylinder axes,13 practitioners have become better equipped and more comfortable fitting toric lenses in recent years. International differences in the rate of toric lens prescribing could be due to the extent of astigmatism in people of different ethnicities20 and differences in the training, attitudes, and collective confidence of the predominant practitioner groups—opticians, optometrists, and ophthalmologists—in relation to toric lens fitting.

Our future prediction is that the extent of toric lens prescribing (shown by the green dots in Figure 6) will continue to increase at the current rate and then reach an asymptote at the level corresponding to full correction of astigmatism (47.4% of soft lens wearers on average)19 within the next decade.

MULTIFOCAL LENSES

The proportion of multifocal lenses fitted to presbyopes (i.e., all those ≥ 45 years of age) in the 17 featured countries each year between 2000 and 2022 is shown in Figure 7 (the balance being non-multifocal lenses).

FIGURE 7. Trends in the proportion of all soft lens fits that are multifocal lens fits to presbyopes (those ≥ 45 years old) between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.
FIGURE 7. Trends in the proportion of all soft lens fits that are multifocal lens fits to presbyopes (those ≥ 45 years old) between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.

The percentage of fits with multifocal lenses increased for all countries throughout the survey period. The increasing use of multifocal soft lenses is likely due to increasing availability of multifocal lens types,13 expanding parameter ranges,13 and advances in optical designs that offer more acceptable vision with multifocal contact lenses than with previously available lenses.21

It should be noted that Figure 7 underestimates the full extent of soft lens correction of presbyopia, as patients are still receiving monovision lenses (i.e., correcting one eye for distance and one eye for near using single vision lenses). Despite the modest increase in multifocal contact lens prescribing and ongoing low-level monovision prescribing, it is evident from Figure 7 that currently around one-half of presbyopic contact lens wearers are being fitted with a distance correction only, and are presumably relying upon intermittent use of supplementary reading spectacles for close work.

The primary reason for the “under-prescribing” of multifocal contact lenses is likely a combination of a lack of confidence and fitting skills, a view held by some practitioners that the perceptual compromises of multifocal lenses are too great,22 and/or an absence of availability of a “perfect” multifocal contact lens.23

Looking to the future, we feel there will be a gradual increase in multifocal lens prescribing (shown by the green dots in Figure 7) as a result of accelerated professional education in presbyopic contact lens fitting, delivered by academic and professional institutions and the contact lens industry; continued research and development into optimized multifocal optical designs; and the potential for future radical, new-generation products.24 The trend line might flatten out at around 80% because there likely remains a minority of lens wearers who prefer to use plus-powered spectacles over their contact lenses for near work.

EXTENDED WEAR LENSES

The proportion of extended wear lenses fitted in the 17 featured countries each year between 2000 and 2022 is shown in Figure 8 (the balance being daily wear lenses). Many argued throughout the 1980s and 1990s that extended wear was the “holy grail,” and that most lenses in the future would be worn on an extended wear basis.25 This promise was never realized, and in fact, it can be observed that the percentage of fits with extended wear lenses decreased for most countries throughout the survey period.

FIGURE 8. Trends in the proportion of all soft lens fits that are extended wear fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.
FIGURE 8. Trends in the proportion of all soft lens fits that are extended wear fits between 2000 and 2022 for the 17 featured countries. The red dots show the mean data for all 17 countries and the green dots from 2023 to 2050 show the trend predicted by the authors.

Despite the obvious convenience of extended wear, silicone hydrogel lenses offer enhanced oxygen performance10 and consequent superior ocular health,11 causing practitioners to be more reluctant to prescribe lenses for extended wear. This probably relates to the known higher risk of developing severe keratitis when sleeping in all types of lenses, compared with daytime-only lens wear.26-28

Until a suitable material/design can be developed for extended wear that will result in the risk of developing severe microbial keratitis being no different to that with daily disposable lenses, we feel that the prescribing of soft lenses for extended wear will continue to wane. We predict that extended wear prescribing will drop to very low levels in the future (shown by the green dots in Figure 8), with a small number of wearers using such lenses for special vocational and avocational needs.

CONCLUSIONS

Prior to 1990, soft contact lens practice was fraught with difficulties, but major changes occurred just before the turn of the century that radically changed the contact lens landscape for the better. Resultant trends in soft contact lens prescribing that we have tracked this century can be summarized as follows: increasing dominance of silicone hydrogel lens materials and daily disposable lenses; increased prescribing of toric lenses; increased prescribing of multifocal lenses; a substantial proportion of contact lens wearers ≥ 45 years of age not being prescribed a presbyopic contact lens correction; and ongoing low levels of extended lens wear.

It is notoriously difficult to predict what the future will hold. A good example of this is the proclamation by noted British contact lens clinician and researcher Norman Bier. In his book on rigid contact lens fitting titled “Contact Lens Routine and Clinical Practice” in 1957 (prior to the advent of soft lenses), he wrote, “It would be safe to say that the days of basic discoveries ... [in the field of contact lenses] ... have passed. New or revolutionary theories will probably not be forthcoming.”29

Keeping Bier’s words in mind, we predict that the contact lens field is headed in the following directions over the next 25 years or so: silicone hydrogel and daily disposable lens prescribing increasing to 80% to 90% of all lenses prescribed; increased prescribing of toric lenses for the correction of astigmatism to the theoretical maximum of 47.4% of all soft lenses fitted in the near future;20 ongoing increase in the prescribing of multifocal lenses; and even lower levels of extended lens wear prescribing.

Perhaps in 2050 someone will unearth this paper from the deep archives of the ophthalmic literature and judge the accuracy of our year 2023 predictions of future trends in contact lens prescribing. Maybe another contact lens revolution will occur, resulting in our predictions being derided in the same way we have derided those of Norman Bier! CLS

References

  1. Holden BA, Mertz GW, McNally JJ. Corneal swelling response to contact lenses worn under extended wear conditions. Invest Ophthalmol Vis Sci. 1983 Feb;24:218-226.
  2. Efron N. Contact Lens Complications. 4th edition. Philadelphia: Elsevier; 2019.
  3. Hosaka S, Ozawa H, Tanzawa H, et al. Analysis of deposits on high water content contact lenses. J Biomed Mater Res. 1983 Mar;17:261-274.
  4. Morgan PB. Soft lens care systems. In: Contact Lens Complications. 3rd edition. Efron N, ed. Edinburgh: Elsevier; 2018.
  5. Holden BA, Sweeney DF, Vannas A, Nilsson KT, Efron N. Effects of long-term extended contact lens wear on the human cornea. Invest Ophthalmol Vis Sci. 1985 Nov;26:1489-1501.
  6. Efron N, Morgan S, Morgan PB. Clinical performance of a daily-wear, daily-disposable soft contact lens. Optician. 1995;210:18-22.
  7. Morgan PB, Efron N. Comparative clinical performance of two silicone hydrogel contact lenses for continuous wear. Clin Exp Optom. 2002;85:183-192.
  8. Morgan PB, Efron N. Global contact lens prescribing 2000-2020. Clin Exp Optom. 2022 Apr;105:298-312.
  9. Morgan PB, Woods CA, Tranoudis IG, et al. International contact lens prescribing in 2022. Contact Lens Spectrum. 2023 Jan;38:28-35.
  10. Efron N, Morgan PB, Cameron ID, Brennan NA, Goodwin M. Oxygen permeability and water content of silicone hydrogel contact lens materials. Optom Vis Sci. 2007 Apr;84:328-337.
  11. Covey M, Sweeney DF, Terry R, Sankaridurg PR, Holden BA. Hypoxic effects on the anterior eye of high-Dk soft contact lens wearers are negligible. Optom Vis Sci. 2001 Feb;78:95-99.
  12. Efron N, Morgan PB. Affluence and contact lens prescribing. Eye Contact Lens. 2022 Nov;48:455-459.
  13. Gulmiri A, Liao J, McNaughton J. 2022 Contact Lenses and Solutions Summary. Contact Lens Spectrum supplement. 2022. Available at clspectrum.com/resources/class-pdfs/0922-class_final_hyperlinks . Accessed Apr. 3, 2023.
  14. Efron N, Efron SE, Morgan PB, Morgan SL. A “cost-per-wear” model based on contact lens replacement frequency. Clin Exp Optom. 2010 Jul;93:253-260.
  15. Sulley A, Dumbleton K. Silicone hydrogel daily disposable benefits: The evidence. Cont Lens Anterior Eye. 2020 Jun;43:298-307.
  16. Morgan PB, Efron N, Toshida H, Nichols JJ. An international analysis of contact lens compliance. Cont Lens Anterior Eye. 2011 Oct;34:223-228.
  17. Smith SL, Orsborn GN, Sulley A, Chatterjee N, Morgan PB. An investigation into disposal and recycling options for daily disposable and monthly replacement soft contact lens modalities. Cont Lens Anterior Eye. 2022 Apr;45:1-6.
  18. Cho P, Boost MV. Daily disposable lenses: the better alternative. Cont Lens Anterior Eye. 2013 Feb;36:4-12.
  19. Young G, Sulley A, Hunt C. Prevalence of astigmatism in relation to soft contact lens fitting. Eye Contact Lens. 2011 Jan;37:20-25.
  20. Kleinstein RN, Jones LA, Hullett S, et al. Refractive error and ethnicity in children. Arch Ophthalmol. 2003 Aug;12:1141-1147.
  21. Remón L, Pérez-Merino P, Macedo-de-Araújo RJ, Amorim-de-Sousa AI, González-Méijome JM. Bifocal and multifocal contact lenses for presbyopia and myopia control. J Ophthalmol. 2020 Mar;2020:1-18.
  22. Evans BJ. Monovision: a review. Ophthalmic Physiol Opt. 2007 Sep;27:417-439.
  23. Pérez-Prados R, Piñero DP, Pérez-Cambrodí RJ, Madrid-Costa D. Soft multifocal simultaneous image contact lenses: a review. Clin Exp Optom. 2017 Mar;100:107-127.
  24. Bailey J, Clamp J, Farmer S, et al. Infrared triggered smart contact lens for the treatment of presbyopia. J Phys D Appl Phys. 2022 Feb;55:210001.
  25. Morgan PB, Efron N, Helland M, Itoi M, Jones D, Nichols JJ, van der Worp E, Woods CA. Global trends in prescribing contact lenses for extended wear. Cont Lens Anterior Eye. 2011 Feb;34:32-35.
  26. Poggio EC, Glynn RJ, Schein OD, et al. The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med. 1989 Sep;321:779-783.
  27. Morgan PB, Efron N, Hill EA, Raynor MK, Whiting MA, Tullo AB. Incidence of keratitis of varying severity among contact lens wearers. Br J Ophthalmol. 2005 Apr;89:430-436.
  28. Stapleton F, Keay L, Edwards K, et al. The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology. 2008 Oct;115:1655-1662.
  29. Bier N. Contact Lens Routine and Practice. 2nd edition. London: Butterworths; 1957.

Dr. Efron is an emeritus professor from the School of Optometry and Vision Science at Queensland University of Technology in Brisbane, Australia. He has proprietary interest in Elsevier, Quantel Medical, Espansione Group, and Bausch + Lomb; has received remuneration from Optometry Australia and Procter & Gamble; and has an educational grant or contract with Qatar Foundation and CooperVision.

Dr. Morgan is director of Eurolens Research at the University of Manchester, United Kingdom. He has received remuneration from CooperVision and PentaVision Powered by BroadcastMed, and has a research grant or contract with Alcon, CooperVision, Johnson & Johnson Vision, Menicon, and Visco Vision.

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