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Orthokeratology for myopia control in Covid-19 era

Philip Morgan, Lyndon Jones and Kate Gifford evaluate considerations on using orthokeratology contact lenses for myopia control during the Covid-19 pandemic

The year 2020 was affectionately termed ‘the year of optometry’ but the new decade has brought numerous challenges to the profession as the ongoing Covid-19 pandemic has seen normal clinical practice greatly disrupted. As the lockdown begins to ease, many aspects of normal optometric and optical functions are being reconsidered.

Due to their application to the ocular surface, the use of contact lenses has faced particular scrutiny and some media reports have advocated the cessation of contact lens use despite the absence of clear evidence for an increased risk of Covid-19 infection or any increase of eye touching during lens wear. Indeed, a recent review of the literature found no relationship between lens use and Covid-19 infection1 and a separate report indicated that coronaviruses such as SARS-CoV-2 (the virus which causes Covid-19) are unlikely to bind to ocular surface cells to initiate infection.2 Related to this, although there are a number of reports of conjunctivitis occurring prior to symptoms of Covid-19,3,4 a United Kingdom report of over 20,000 hospital patients with the disease found that only 0.3% presented with conjunctivitis.5 Although more work is required to fully understand this area and new information is becoming available daily, it appears that the ocular surface is not a major point of ingress for the virus6 and overall, contact lens wear continues to be safe.

Professional bodies and regulatory agencies including the College of Optometrists,7 the British Contact Lens Association8 and the United States Centers for Disease Control and Prevention9 concur that there is no association between contact lens use and Covid-19 infection. However, all these groups stress the need for hygienic contact lens use at this time, a recommendation which in part may relate to the need to minimise the requirement for contact lens wearers to seek clinical advice at a time where optometric services may not be fully operational and other healthcare facilities are also offering a reduced service. Furthermore, contact lens wearers should ideally refrain from attending emergency departments where they may be exposed to the virus.

Orthokeratology for myopia control

While general contact lens wear can continue at this time, it is timely to consider the implications of the current pandemic for speciality forms of lens use, including the use of overnight orthokeratology contact lenses for myopia control. This approach to myopia management has been shown to be effective in multiple clinical trials10–12 and CE approval was granted in 2019 to a contact lens in this category for the first time, Menicon Bloom.13 The use of such lenses has increased in recent years and a 2018 report of contact lens prescribing in 31 countries found that around 20% of rigid lens fits to children were described as being for myopia control.14

Lens wear of this type differs from more mainstream use because patients are typically children (often with parental oversight) and the lenses are worn overnight and not during the day. It is pertinent to consider how these factors might impact the risks of lens wear and also if lifestyle changes during the Covid-19 pandemic have relevance.

To address this, it is key to evaluate the age of children using orthokeratology lenses for myopia control. Wolffsohn and colleagues15 reported that most contact lens practitioners would consider fitting this modality from the age of nine or 10 years and this is supported by extra analysis of the dataset of Efron and co-workers,14 which found that around two thirds of new fits of orthokeratology myopia control lens fits to children were to those aged 12 years and younger. At least at fitting therefore, the patient group under consideration is in the pre-teen category. Overall, the use of contact lenses in this age group has been found to be effective and safe16 and it is also noteworthy for this review that the hospitalisation of people of this age with Covid-19 is rare, although the reason why children are relatively protected from this disease is not clear.5

Safety and compliance of children using contact lenses

The most complete information about the safety and success of children in contact lenses derives from the Contact Lens Assessment in Youth (CLAY) study, which featured a retrospective analysis of the clinical records of over 3,000 contact lens patients attending for over 14,000 visits at six university-based contact lens clinics in North America.17 Patients were aged from eight to 34 years and various aspects of their contact lens wear were assessed and reported.

One part of the work was to consider contact lens compliance, including handwashing – an important part of any contact lens care routine18 but particularly relevant in the present pandemic, with the reported ability of soap to inactivate enveloped viruses similar to SARS-CoV-2.19 The CLAY study found the best clinical results in patients either below the age of 15 years or older than 25 years. With handwashing, for example, it was reported that 88% of those between 12 and 14 years washed their hands before removal ‘sometimes’, ‘fairly often’ or ‘always’, compared with 75-81% in patients between 15 and 25 years, 84% in those between 26 and 29 years and 92% in patients between 30 and 33 years. Similar results were found for the number of subjects reporting how often they rubbed their lenses with solution (Figure 1).20 In other words, for handwashing and lens cleaning across the different age groups, there was a U-shaped relationship, with the very youngest and very oldest patients in the participant pool performing best; analogous findings have been reported for attitudes to risk taking in many parts of the world in these age groups.21 This is particularly relevant for orthokeratology myopia control, where the patients are typically in the youngest of the age group studied in the CLAY work and these wearers are often supervised by their parents – a group perhaps sharing the same attitudes to hand hygiene as the oldest group in the CLAY project; that is, helpfully, the key people under consideration are those at each end of the U-shape.

Figure 1: Proportion of patients reporting compliance to lens-care behaviours ‘sometimes’, ‘fairly often’ or ‘always’. From Wagner et al (2014)20

The youngest wearers in this work were also reported to have the lowest likelihood of corneal inflammatory events22 and clinically-related interruptions of their contact lens wear,23 again suggesting that the typical patients using orthokeratology myopia control contact lenses are not at any increased risk of hygiene issues or clinical problems; in fact, the opposite appears to be the case.

Orthokeratology care systems

In addition to handwashing and compliance with care systems, the performance of the care products used with orthokeratology myopia control contact lenses against the SARS-CoV-2 virus is worthy of consideration. Although direct evidence of product performance does not appear to be available at the current time, various components of contact lens solutions have been tested against similar viruses and this information provides helpful and reassuring insights.

Most patients using this lens type use a multipurpose solution (for example Boston Simplus multi-action solution with 0.03% chlorhexidine gluconate and 0.0005% polyaminopropyl biguanide) or a product containing sodium hypochlorite (for example Menicon Progent, 0.2% sodium hypochlorite for patient use and Menicon Menilab, 0.5% sodium hypochlorite for practitioner treatment), hydrogen peroxide (for example Alcon AOSept, 3% hydrogen peroxide)24 or povidone iodine (for example Ophtecs cleadew, 0.05% povidone iodine)25 for their lens care. At least one report suggests a move in recent years away from multi-purpose solutions to other types of products for orthokeratology use.24

At present, there is little direct evidence about the performance of the active ingredients found in multipurpose solutions against coronaviruses (although chlorhexidine gluconate 0.02% has been reported to have a limited effect after an exposure of 10 minutes26), but the vulnerability of lipid bilayer of viruses such as SARS-CoV-2 to soaps means that the presence of surfactants in multipurpose solutions is likely to provide improved efficacy.

Low concentrations of both sodium hypochlorite (0.1%) and hydrogen peroxide (0.5%) – much lower than those found in available contact lens solutions – have been shown to inactivate human coronaviruses within one minute, a much shorter exposure than that provided by commercial contact lens disinfection products.26

Povidone iodine also appears to be effective against this form of virus, although experiments with concentrations available in contact lens solutions do not appear to have been performed at this stage.26,27 However, one author suggests that a 0.025% solution (ie half that of a commercial contact lens solution) may be be used as a nostril disinfectant to kill SARS-CoV-2 prior to dental treatment.28

Overnight treatment and lifestyle changes

A further feature of orthokeratology that is different to other forms of contact lens wear is the requirement for patients to sleep in their lenses overnight and to be lens-free for the waking day. Whether eye touching during daily contact lens wear is a real issue in the current pandemic is yet to be fully explored and reported, but the use of lenses during sleep means that this is certainly not a consideration with orthokeratology lenses for myopia control. An indirect consequence of Covid-19 ‘lockdown’ is reduced formal schooling for children and perhaps less strict sleeping patterns, and there are anecdotal reports of corneal oedema with orthokeratology lenses due to longer sleeping durations for some patients.29 Practitioners should therefore consider the possibility of such observations in their orthokeratology patients.

Summary

Myopia control with orthokeratology is an effective form of contact lens wear offered to children. The high levels of compliance of the young patients typically fitted with this lens type (combined with similar compliance in people of the likely age of their parents), coupled with the performance of the associated care systems, suggests that confidence for this form of lens wear in the Covid-19 pandemic should be at least as good as more mainstream forms of contact lens use. Given the need for routine use of lenses for effective myopia control, practitioners prescribing this form of correction should be reassured that this review of the literature confirms that ongoing use can continue to be recommended, alongside the requirement for heightened compliance around solution use and other hygienic wearing behaviours.

Acknowledgements

This paper was supported by an educational grant from Menicon Co. Ltd.

References

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