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Contact Lens Selection in the Time of Coronavirus… and beyond

Published on Aug 3, 2021
15 Minutes Read

Cristina Schnider, OD, MBA, FAAO, Quan Wei Ng, OD, MSc

Introduction

The year 2020 brought the world fires, floods, hurricanes, locusts, murder hornets, famine, civil unrest and the COVID-19 pandemic. It will surely go down in the history books as changing almost everything about how lives are lived worldwide (Figure 1).1,2

The most pressing question around the prescribing of contact lenses in the time of COVID-19 revolves around finding a lens system that is safe, quick and easy to implement and associated with assurance of uninterrupted levels of outstanding on-eye performance. The key considerations here are lens wearing and replacement schedule, lens material, lens design and parameter availability. Some decisions are easier to make than others based on evidence at hand.

Figure 1: The way forward in the time of the COVID-19 pandemic: potentially more telemedicine to manage appointments and non-urgent cases and instituting changes to office spaces and hygiene practices to prevent inadvertent transmission of the SARS-CoV-2 coronavirus

Figure 1: The way forward in the time of the COVID-19 pandemic: potentially more telemedicine to manage appointments and non-urgent cases and instituting changes to office spaces and hygiene practices to prevent inadvertent transmission of the SARS-CoV-2 coronavirus.

Lens wear and replacement options

The least contentious decision revolves around the question of daily wear versus extended wear. Research over several decades has confirmed the increased risk microbial keratitis (MK) with the use of overnight wear, with a loosely dose-dependent relationship – occasional overnight wear is worse than daily wear only, and extended wear worse than occasional overnight wear.3 So, if you are looking to minimize serious complications...no sleeping in lenses – even occasionally.

If we next consider replacement schedules—daily wear with reusable lenses versus daily disposable/single use wear—the concern about microbial keratitis revolves primarily around hygiene and compliance factors – hand washing4, rubbing and rinsing prior to lens storage,5 solution type,5,6 topping off solution,7,8 exposure to water8 and perhaps the most important, the contact lens storage case. A model set forth by Stapleton that looks at population attributable risk predicts that disease load in daily wear reusable lenses could be reduced by almost two-thirds by attending to just TWO factors: storage case hygiene and storage case replacement.5

Daily disposable lenses do not eliminate risk entirely… careful and consistent attention to good instruction and ongoing surveillance of care and hygiene practices are still critical. But they do minimize the opportunity to transfer microbes to the eye, and have been shown to reduce the severity of severe disease if it does occur.5 So, our next step on the road to contact lens success in the time of COVID-19 is…prescribe more daily disposable contact lenses.

Next, practitioners must make decisions about material and design within the daily disposable space. Again, with a focus on achieving and sustaining high levels of performance and looking to the literature, we find several interesting studies regarding material properties that can guide us.

Material Selection

Lens comfort factors

Given the inability to differentiate by the purely health and safety measures and knowing that comfort is a key driver of patient satisfaction, looking at inputs to comfort is a logical next step. Surveys of existing contact lens wearers, both daily disposable and reusable, find that performance declines throughout the day for nearly 6 in 10 wearers (Figure 2).9 The most common symptoms experienced are tired eyes and feelings of dryness.9 When patients are uncomfortable, they tend to touch their eyes and lenses or use eye drops – all of which are things we’d like to avoid these days.10 This reported change in comfort shouldn’t be surprising in some respects… a soft contact lens placed on the eye effectively splits the tear film, and interrupts the natural communication of the membrane mucins originating in the cornea from communing with their free-floating counterparts in the tear film. The quest to recreate a more natural environment is one that occupies scientists and researchers around the world.

Figure 2: Pattern of decline in performance (aggregate of vision, satisfaction and comfort responses) from real time digital surveys of current contact lens wearers, and the symptoms reported by those experiencing declining performance (59% of 243 wearers surveyed)

Figure 2 graphic. Pattern of decline in performance (aggregate of vision, satisfaction and comfort responses) from real time digital surveys of current contact lens wearers.

Figure 2 graph of the symptoms reported by those experiencing declining performance (59% of 243 wearers surveyed).

Lubricity

One of the areas with numerous scientific publications in evidence is the concept of friction or lubricity. Brennan first reported on the inverse relationship between lubricity and comfort in 2009,11 and he and other authors continued to add data to corroborate the original data (Figure 3).12–14

While there is no current standard for lubricity measurement on contact lenses, several researchers have produced insights of note.15 Because friction is dependent on the interaction between two surfaces and any lubricants between them, and not just the surfaces themselves, measurement conditions can have a significant impact on the data. It is important to create an environment that closely mimics that of the ocular environment, but that allows a fair comparison between different materials. Sterner and colleagues have concluded that the commonly reported coefficient of friction (CoF) is not always applicable to soft materials such as hydrogels due to the frequently observed nonlinearity between lateral and normal forces. They therefore advocate the concept of average work to help understand the relationship between clinical comfort of soft contact lenses and material properties.16

Figure 3: Plot of median end-of-day comfort from Brennan14 and Coles15 (visual analog scale) versus coefficient of friction reported by Ross18 (open circles, dashed line, top scale) and Roba19 (closed circles, solid line, lower scale).

Figure 3: Plot of median endo-of-day comfort from Brennan14 and Coles15 (visual analog scale) versus coefficient of friction reported by Ross18 (open circles, dashed line, top scale) and Roba19 (closed circles, solid line, lower scale).

To that end and to return to the goal of recreating a system as close to the natural eye as possible, using the natural cornea as a standard to assess lubricity seems prudent. In 2005 researchers in the UK reported that senofilcon A, a silicone hydrogel incorporating long chain high molecular weight polyvinylpyrrolidone (PVP) had a coefficient of friction approaching that of the cornea.17 And as the eye blinks an estimated 12,000-14,000 times per day the ability to sustain low levels of friction is undoubtedly also important. When friction was measured at multiple times over the course of a simulated day using contact lenses with a long chain PVP molecule incorporated evenly throughout the lens matrix, frictional energy was low and quite consistent, versus an increasing level of both variability and amount of friction with the water gradient technology (Figure 4).18

The thinking is that less friction may result in higher and/or more sustained levels of comfort, particular during sustained digital device use where blink rate drops dramatically.19 The long chain PVP embedded in the lens may help re-establish a proxy for the normal tear film environment before it was interrupted by the placement of a contact lens by functioning somewhat like the membrane bound mucins in the cornea which interact naturally with the free- floating mucins in the tear film. PVP has many properties that are similar to mucins: it is amphiphilic or having both hydrophilic and lipophilic structures and biologically relevant properties that promote spreading and stability of all layers of the tear film. And as demonstrated by Sterner, long chain/high molecular weight PVP is better able to lower friction.20 So, when it comes to evaluating a material, select a material with a robust and lubricious wetting technology.

Figure 4: Friction over 18 hours of simulated wear of two daily disposable silicone hydrogel contact lenses incorporating differing wetting technologies with the cornea as a reference.

Figure 4: Friction over 18 hours of simulated wear of two daily disposable silicone hydrogel contact lenses incorporating differing wetting technologies with the cornea as a reference.

Design Considerations

Lens modulus and thickness profile

Other material and design factors have less obvious impacts on sustained lens wearing comfort and can be considered “necessary but not sufficient”, but practitioners should be aware of potential impact. Modulus and lens design work together to impact comfort. Modulus is a property that is intrinsic to the material, and is not influenced by lens geometry.21 Stiffness, however, is a structural property influenced by the geometry of the lens as well as the material of which it is comprised – a thin lens will be more flexible than a thick one. This relationship was well illustrated in work looking at the impact on edge shape and thickness on conjunctival staining. Maissa found that a thinner “knife” edge design was more comfortable than thicker “chisel” or rounded edge shapes, and when edge shape was controlled, the lower modulus design trended more comfortable.22 Modulus also plays a role in toric lens design, where a differentially thick zone such as in a prism ballast design will make the lens more difficult to flex and may impact lens removal. Additionally, the thick inferior portion will induce vertical prism and in cases of monocular astigmatism the impact on binocular vision should be considered*23,24.

As pointed out in the TFOS report, all the characteristics discussed probably impact comfort in some way,25 but the various lenses of a given manufacturer tend to share many properties, and it is conceivable that the gestalt of the properties is more influential. And in fact, these “clusters” of properties by manufacturer can aid you in moving between materials and modalities. Consistency in design and material characteristics across a manufacturer’s products combined with a wide parameter range and choice of replacement frequencies can make lens choices and changes much easier. Have a look at the summary graphic in Figure 5 for some recommendations to help you select your “pandemic and beyond” lens family of choice. And stay safe out there!

Figure 5: A judicious selection of material, design, parameters and replacement frequency can lead to fitting success in a time when “low-touch” eye care is a health concern.

Trash icon

Minimize Contamination
Daily Disposable Option

Flexibility icon

Maximize Flexibility in Fitting
Wide range of parameters

Contact lens icon

Minimize Mechanical Insult
Thin & uniform designs

Moisture drop icon

Maximize All Day Comfort
Robust & lubricious wetting technology 

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*Vertical heterophoria possibly caused by prism dissociation due to the prescne of induced optical prism is a relevant factor for practitioners to consider when fitting toric contact lenses for monocular astigmats or those requiring a mix of toric soft contact lens designs.26,27 Clinical studies have not been done to fully characterize the clinical effects of differences in base down prism among different contact lenses.

1.     Zeri F, Naroo SA. Contact lens practice in the time of COVID-19. Contact Lens Anterior Eye 2020;43:193–5.

2.     Jones L, Walsh K, Willcox M, Morgan P, Nichols J. The COVID-19 pandemic: Important considerations for contact lens practitioners. Contact Lens Anterior Eye April 2020.

3.     Stapleton F, Keay L, Edwards K, Naduvilath T, Dart JKG, Brian G, Holden BA. The Incidence of Contact Lens–Related Microbial Keratitis in Australia. Ophthalmology 2008;115:1655–62.

4.     Stapleton F, Naduvilath T, Keay L, Radford C, Dart J, Edwards K, Carnt N, Minassian D, Holden B. Risk factors and causative organisms in microbial keratitis in daily disposable contact lens wear. PLoS ONE 2017;12.

5.     Stapleton F, Edwards K, Keay L, Naduvilath T, Dart JKG, Brian G, Holden B. Risk Factors for Moderate and Severe Microbial Keratitis in Daily Wear Contact Lens Users. Ophthalmology 2012;119:1516–21.

6.     Lim CHL, Carnt NA, Farook M, Lam J, Tan DT, Mehta JS, Stapleton F. Risk factors for contact lens-related microbial keratitis in Singapore. Eye 2016;30:447–55.

7.     Levy B, Heiler D, Norton S. Report on Testing From an Investigation of Fusarium Keratitis in Contact Lens Wearers. Eye Contact Lens 2006;32:256–61.

8.     Carnt N, Stapleton F. Strategies for the prevention of contact lens-related Acanthamoeba keratitis: a review. Ophthalmic Physiol Opt 2016;36:77–92.

9.   Mathews K, Daigle B, Alford J, Jedraszczak AM. Performance: Exploring variability in soft contact lens performance. Optician 2019;2016:32–4.

10.   Schnider CM, Wales M. Monthly wearers – surviving or thriving? Opt Sel 2017;2017:153587–1.

11.   Brennan NA. Contact lens-based correlates of soft lens wearing comfort. Optom Vis Sci 2009;86:E-abstract 90957.

12.   Coles C, Brennan NA. Coefficient of friction and soft contact lens comfort. Optom Vis Sci 2012;88:e-abstract 125603.

13.   Brennan NA, Coles C. Supportive data linking coefficient of friction and comfort. Contact Lens Anterior Eye 2013;36:e10.

14.   Kern J, Rappon J, Bauman E, Vaughn B. Assessment of the relationship between contact lens coefficient of friction and subject lens comfort. Invest Ophthalmol Vis Sci 2013;54:494–494.

15.   Hill GA, Roba M, Duncan EG, Tosatti SGP, Zürcher S. Comparative measurement of coefficient of friction of contact lenses: the need for an industry standard. Contact Lens Anterior Eye 2012;35:e10.

16.   Sterner O, Aeschlimann R, Zürcher S, Lorenz KO, Kakkassery J, Spencer ND, Tosatti SGP. Friction Measurements on Contact Lenses in a Physiologically Relevant Environment: Effect of Testing Conditions on Friction. Invest Ophthalmol Vis Sci 2016;57:5383–92.

17.   Wilson T, Aeschlimann R, Tosatti S, Toubouti Y, Kakkassery J, Osborn Lorenz K. Coefficient of Friction of Human Corneal Tissue. Cornea 2015;34:1179–85.

18.   McParland M, Pall B, Schnider C. New lens for demanding days - Optician. Opt Online 2016;2016:24–8.

19.   Cardona G, García C, Serés C, Vilaseca M, Gispets J. Blink Rate, Blink Amplitude, and Tear Film Integrity during Dynamic Visual Display Terminal Tasks. Curr Eye Res 2011;36:190–7.

20.   Sterner O, Karageorgaki C, Zürcher M, Zürcher S, Scales CW, Fadli Z, Spencer ND, Tosatti SGP. Reducing Friction in the Eye: A Comparative Study of Lubrication by Surface-Anchored Synthetic and Natural Ocular Mucin Analogues. ACS Appl Mater Interfaces 2017;9:20150–60.

21.   Stiffness. In: Wikipedia. Vol ; 2020.

22.   Maïssa C, Guillon M, Garofalo RJ. Contact Lens–Induced Circumlimbal Staining in Silicone Hydrogel Contact Lenses Worn on a Daily Wear Basis: Eye Contact Lens Sci Clin Pract 2012;38:16–26.

23.   Sulley A, Hawke R, Lorenz KO, Toubouti Y, Olivares G. Resultant vertical prism in toric soft contact lenses. Contact Lens Anterior Eye 2015;38:253–7.

24.   Nilsson M, Stevenson SB, Leach N, Bergmanson JP, Brautaset RL. Vertical imbalance induced by prism-ballasted soft toric contact lenses fitted unilaterally. Ophthalmic Physiol Opt 2008;28: 157–62.

25.   Jones L, Brennan NA, González-Méijome J, Lally J, Maldonado-Codina C, Schmidt TA, Subbaraman L, Young G, Nichols JJ. The TFOS International Workshop on Contact Lens Discomfort: Report of the Contact Lens Materials, Design, and Care Subcommittee. Invest Ophthalmol Vis Sci 2013;54:TFOS37–70.

26.   Jackson DN, Bedell HE. Vertical Heterophoria and Susceptibility to Visually Induced Motion Sickness. Strabismus 2012;20:17–23.

27.   Toit RD, Ramke J, Brian G. Tolerance to Prism Induced by Readymade Spectacles: Setting and Using a Standard. Optom Vis Sci 2007;84:1053–9.

Dr Cristina Schnider is the sole proprietor of C Schnider Insights, a company providing insights and content development services in the medical field; Quan-Wei Ng, MSc. Optom (UK), is Global Professional Education & Development Assoc Director at Johnson & Johnson Vision.

IMPORTANT SAFETY INFORMATION ACUVUE® Contact Lenses are indicated for vision correction. As with any contact lens, eye problems, including corneal ulcers, can develop. Some wearers may experience mild irritation, itching or discomfort. Lenses should not be prescribed if patients have any eye infection, or experience eye discomfort, excessive tearing, vision changes, redness or other eye problems. Consult the package insert for complete information. Complete information is also available from Johnson & Johnson Vision Care, Inc., by calling 1-800-843-2020, or by visiting jnjvisionpro.com

© Johnson & Johnson Vision Care, Inc., 2021

PP2020AO1D6223, January 2021