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Myopia Control: Treatment Strategies

2 in Australia | 1CD in New Zealand | 8 December 2018




EXCLUSIVE TO LUXOTTICA

While working at the coal face of the myopia boom in clinical practice, I’ve shared my communication tools and management processes for progressive myopia across the world. In doing so, I have seen a burgeoning interest in this area from eye care professionals, while also a hesitancy to put research into practice without having the ‘perfect’ product to prescribe or system to follow.

Learning Outcomes
• Understand the increasing prevalence of myopia
• Be aware of the scientific evidence behind options for myopia control
• Have an understanding of strategies for treating and managing myopia
• Be aware of the factors influencing myopia development and progression
• Be equipped to determine an evidence based management plan for paediatric myopia in practice
• Be familiar with strategies for communication about myopia with patients and their parents.

A 2015 survey of more than 1,000 practitioners, from a dozen countries, showed that while most considered themselves active in myopia management, they prescribed single vision distance spectacle and contact lens corrections more than 50 per cent of the time to their progressing myope patients1 – a management choice which, in most cases, is simply not evidence based. A growing number of myopia management tools are available to the practitioner, and while the hard fact is that there is not, and likely will never be the ideal system to guarantee a halt to excessive axial elongation, we are remiss to not provide advice and options to each of our young progressing myopic patients.

The core message is to just do something – something more than prescribing a single vision correction.  Depending on mode of practice, the individual practitioner may have access to few or all corrections, which have been scientifically investigated for reducing the speed of axial elongation in progressive myopia.
Outside of Australia, NZ and the USA, very few countries allow optometry prescribing of atropine in any concentration. The basis of myopia management starts with prescribing the best vision correction, which also provides efficacy for myopia control – necessitating a longsighted view of the future risks of pathology, while holding in check the short sighted concerns of treatment risk, such as with pharmacological or contact lens options.2 The following aims to collate a vast amount of research into clear messages and imperatives for clinical practice.

THE ‘WHY’ OF MYOPIA CONTROL

It is commonly understood that myopia prevalence is growing globally. By 2050, it is predicted that half of the world’s population – five billion people – will be myopic, with nearly one billion at risk of myopia related ocular pathology.3 The late Brien Holden was a champion of ensuring myopia is placed on the world health agenda – high myopia is strongly linked to higher risk of cataract, retinal detachment and myopic maculopathy,4 and increasing rates of vision impairment and blindness due to the latter are already evident in Asian countries.5,6 The World Health Organization now recognises the public health issue of myopia, releasing a joint report with the Brien Holden Vision Institute in 2016.7

The myopia control imperative is understanding that even -1.00D of myopia carries an additional lifelong risk of posterior subcapsular cataract (PSCC), retinal detachment (RD) and myopic maculopathy (MM). A  convincing case has been previously made by paediatric ophthalmologist Ian Flitcroft that the delineation of physiological and pathological myopia is not valid, as the term ‘physiological’ implies that there is a level of myopia which could be considered ‘safe’ in comparison to emmetropia. Using odds ratios, which describe the increased risk of a conditionover a reference of 1 (this being the risk of emmetropia), Table 1 summarises Flitcroft’s data,4 which shows that even 1D of myopia doubles the risk of MM and PSCC, and triples the risk of RD compared to the emmetrope. At 3D of myopia, the risk of PSCC triples, with the risk of RD and MM being nine times that of the emmetrope. Higher levels of myopia bring more eye-watering risks.

Table 1. Odds ratios of increased risk of ocular pathology with increasing levels of myopia, summarised from Flitcroft, 2012.4

While dioptres of myopia are easily measurable and a good surrogate, ultimately myopia control is about axial length control. Tideman and colleagues from the Netherlands evaluated the prevalence of lifelong visual impairment (6/12 or less) with increasing axial length, using data from over 10,000 Dutch people with an average age of 61 years – an axial length of 24–26mm was used as the referent. Axial length of 26–28mm doubled the risk of visual impairment by age 60, while 28–30mm increased the risk by 11 times and an axial length of 30mm or more by 25 times. The prevalence of visual impairment by age 75 for the longest eyeballs (over 30mm) was 90 per cent. Between 26–30mm axial length, the likelihood of being visually impaired by age 75 was around 25 per cent, with the difference between shorter (26–28mm) and longer (28–30mm) eyes being the age of onset – the person with longer eyeballs is likely to suffer visual impairment for a longer duration of their life.8 This is sobering data and provides the clear message to both patients and parents that controlling axial elongation also controls lifelong risk of visual impairment.

An analogy can be drawn to the association between diabetes and sugar intake. While suspected and  observed historically, it was unclear whether multiple factors such as obesity, sedentary behaviour, consumption of other foods, ageing, urbanisation and income confounded the link between sugar intake and diabetes prevalence in overall populations. However recent data evaluating 175 countries, and controlling for each of these confounders, found a dose dependent relationship whereby every 150kcal per person per day increase in sugar availability was associated with an increased diabetes prevalence of 1.1 per cent.9 Similarly, every part-millimetre increase in axial length in the myope brings an increased risk of pathology. Just as the optometristwill discuss the link between good blood sugar level control and eye health, in the same way, myopia must be controlled to reduce risks to long term eye health.

MYOPIA RISK FACTORS

The younger a child becomes myopic, the faster they will progress, with children seven years of age progressing by at least 1D per year, and this halving by age 11 to 12.10 The institution of a myopia control strategy as early as possible is evidence based practice. However myopia control is not just applicable to the myope – exhibiting less than 0.50D of manifest hyperopia at age six to seven is the most significant risk factor for future myopia, independent of family history and visual environment.11 Moreover, the fastest rate of refractive change in myopic children occurs in the year prior to onset,12 so the child who is less hyperopic than age normal should be closely monitored, especially if concurrent risk factors of family history or binocular vision status are evident.

Risk factors for development and/or progression of paediatric myopia are summarised in Table 2. A child with one myopic parent has a three-fold risk of myopia development compared to their peers without this family history, and two myopia parents doubles this risk again.13 Risk factors for progression to high myopia, and hence higher risk of future ocular pathology, include having two myopic parents, and onset at age six to seven years which increases risk 6.6 times compared to older (11 years) age of onset. This is independent of ethnicity and gender.14 Children with two myopic parents have been shown to be the fastest progressors in single vision spectacle and atropine corrections, and children with one myopic parent progress less than the former but more than the child without such family history.15,16 On the positive side, a strong family history of myopia has resulted in stronger treatment effects in studies investigating efficacy of progressive and novel spectacle lens designs for myopia control.15,17 Asian ethnicity has been linked to faster myopia progression,10,18 but more recent data indicates that progression in Asian and Caucasian children may be similar.19

Table 2. Summary of risk factors for development and progression of myopia (references in text)

Time spent on near work activities has long been considered a risk for myopia development and progression, however when controlled for parental myopia and time spent outdoors, it does not hold as an independent risk factor.13,20 Increased outdoor activity, regardless of the type of activity, has been shown to be protective against development of myopia with low and moderate levels of near work, regardless of ethnicity, gender, parental myopia, employment and education – this relationship has been affirmed in Australian, American and Asian studies.13,20,21 Children with low outdoor (0-1.6 hours per day) and high out of school hours near work (>3 hours per day) at age 12 have a two to three fold higher odds for myopia than their peers with high outdoor (<2.8 hours per day) and low near work (0-2 hours per day) activity levels.20

Further risk factors include the presence of esophoria, accommodative lag and higher accommodative convergence (AC/A ratio) at near. Pre-myopes show a higher accommodative lag than their peers who do not become myopic, although the correlation is stronger after onset of myopia, indicating that this may be a feature rather than a cause of myopia.22 Children with higher response AC/A ratios have an increased risk of myopia development within one year of over 20 times.23 In myopia control studies of progressive addition spectacle lenses (PAL), children with esophoria in single vision spectacle control groups were found to progress more quickly,24 and children with a larger baseline accommodative lag in the PAL groups showed statistically greater treatment effect.25 Fitting bifocal soft contact lenses to myopic children with esophoria at near, where the add was chosen to neutralise the associated phoria, has resulted in a 70 per cent reduction in axial elongation over twelve months compared to single vision soft contact lens wearing controls.26 Children with lower baseline accommodative amplitude have shown a greater myopia control response to orthokeratology contact lens wear compared to normal accommodators.27

Myopia has long been associated with inaccurate and insufficient accommodative behaviour at near and increased accommodative convergence in comparison to emmetropes.23,28-31 Detecting these conditions in both the at-risk emmetrope and myopic child can reveal the picture of myopia progression risk.

Instigating a myopia management strategy for paediatric patients should ideally commence before they become myopic, in view of risk factors described above. The at risk emmetrope may exhibit any or all of the following: one or two myopic parents, lower than age-normal hyperopia, accommodative lag and esophoria at near. For the child who is already myopic, having two myopic parents is predictive of both high myopia and potential positive response to a myopia controlling strategy. Depending on the child’s characteristics and capability, myopic refractive error can be corrected and actively managed using spectacles, contact lenses, pharmacological treatments and visual environment modifications.

THE MYOPIA MANAGEMENT MESSAGE

The at risk emmetrope has presumably no refractive error to correct, but in view of risk factors as described, can be managed with advice on visual environment and amelioration of esophoria and accommodative lag at near. The simplest treatment for the latter involves prescribing of a near add for use during school hours and for near work tasks at home, usually in the form of bifocal or progressive addition spectacle lenses to neutralise the fixation disparity and bring accommodative lag at near back within the normal range of +0.50 to +0.75.32,33 At least 90 minutes spent outdoors per day, along with limitation of homework and leisure near work activities to less than three hours after school, will reduce myopia risk. This is the limit of evidence based practice at present.

Treatment options for the progressing myope include PAL, bifocal and novel peripheral defocus spectacle lenses; soft bifocal or multifocal contact lenses; orthokeratology and atropine. Once the imperative to manage myopia is understood, there are three key messages on treatment which are essential for the practitioner to recognise and explain to both the patient and parent – expectations, efficacy and safety.

Expectations

It’s important for practitioners, and by turn parents and patients, to understand that some myopia progression is to be expected. The paediatric eye is expected to grow until age 12 to 13 through the process of emmetropisation, hence some axial elongation over this period can be attributed to normal growth and not myopia progression. Don Mutti and colleagues analysed refractive and biometric data in the CLEERE (Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error) study and described that, on average, the paediatric eye will elongate by around 0.1mm per year before additional elongation contributes to myopia progression.34 Once accelerated growth has been triggered through myopia development, progression occurs at a faster rate for younger children – around -1.00D per year for a Caucasian seven year old and -1.25D for an Asian seven year old – than for older children, who reduce to around -0.50 progression per year, on average, if corrected with single vision distance (SVD) spectacles.10 The Brien Holden Vision Institute has recently released a myopia calculator whereby inputting the age and current refraction will output the predicted level of myopia by age 18. The user can then apply different treatments, which demonstrate the reduction in end-point myopia by their individual efficacy. The calculator can be freely downloaded from www.brienholdenvision.org/translational-research/myopia/myopia-calculator.html.

These predictions rely on averages, which is the best evidence based method with the current data available. There is potential for complication, though, in predicting a future-forward level of myopia when significant individual variation occurs. The aforementioned CLEERE study, which followed more than 2000 children over a decade, showed that the younger you become myopic the faster you will progress, and the more myopic you will become. However, their data also showed that for children who became myopic (<-0.50) at age six, some may only progress to -1.00 while others progress to -6.00.11 This pattern is also evident across older age groups – later onset generally leads to a lower final level of myopia, but myopia progression can be unpredictable, so an alternative approach is to compare progression, after it has occurred, to expected rates in ‘untreated’ children, where this refers to single SVD correction.10

If an eight-year-old Caucasian child has progressed -0.50 across one year of myopia management, their parents may be disappointed in the outcome, where in fact this represents a 50 per cent myopia control effect compared to their average SVD spectacle wearing counterpart. This much progression in an 11 year old however, indicates inadequate myopia management. Figure 1 provides a reference for the expected progression per year by age for Caucasian and Asian children (in red),10 with figures in yellow indicating the amount of progression per year, indicating 33 per cent myopia control efficacy (as achieved by progressive/bifocal25,35 or novel spectacle lens designs17 in certain conditions), and green figures indicating 50 per cent efficacy (typically achieved by multifocal soft contact lenses, orthoK and low dose atropine).36-39

 

Figure 1. Typical rates of myopia progression per year, by age, in Caucasian and Asian children wearing single vision distance spectacle lenses, derived from meta-analysis of control groups in myopia control studies are marked in red. Yellow numbers indicate the comparative amount of progression per year when achieving 33 per cent myopia control (possible with progressive / novel spectacle lens designs) and green numbers indicate 50 per cent myopia control (average result from meta-analyses of OrthoK, multifocal soft contact lens and low dose atropine studies). References in text. Courtesy of Paul Gifford.

Efficacy

Understanding and communicating percentage rates of myopia control can be complex, as the study design and control group parameters affect the final outcome in a single study – for example, an older control group will generally show lower progression and hence a lower percentage efficacy – so meta-analyses provide the best indication. A recent meta-analysis of eight multifocal and novel myopia control soft contact lenses found a mean efficacy of 30–50 per cent,38 and similar meta analyses undertaken on orthoK studies showed a 45–50 per cent mean efficacy.37,40 The key paper published on low dose atropine in 2016 compared 0.5 per cent, 0.1 per cent and 0.01 per cent concentrations, and in the first two years of the study found a greater efficacy with the higher dosage.41

For the next year all treatment was ceased, and the higher dosage groups showed a greater percentage of rebound, defined as progression of 0.50D or more in that year. The third phase of this study saw all participants treated with 0.01 per cent atropine for a further two years, with the final outcomes showing that those children who had been treated with 0.01 per cent atropine throughout had the lowest mean rate of progression over the total five years.39 This group did discontinue treatment for one year in the middle of the study, and there was no control group throughout the five years (interestingly, the 0.01 per cent was employed as the control with evident plot twist result!) so a precise percentage efficacy is not calculable but is around 50 per cent, similar to the contact lens options.

Sixteen different interventions for myopia control were compared by Huang and colleagues36 who instead of using percentages, grouped the interventions by ineffective, weak, moderate and strong efficacy for both refractive and axial length outcomes. Strong efficacy (mean reduction of progression by >0.50D/year) was achieved by 0.1 per cent to 1 per cent atropine (not including rebound effects) while moderate efficacy (0.25 to 0.50D/year) was used to describe orthoK, multifocal and novel soft contact lens (SCL) designs and 0.01 per cent atropine. These findings allow the practitioner to simplify the myopia management efficacy message to parents – generally, we can expect around 50 per cent efficacy from each of these three options. In this way, the practitioner can consider firstly offering a contact lens correction to the progressing myope, and know that a similar myopia management result is likely to be achieved independent of the practitioner’s access to or experience with each of the treatments. Wide availability of distance centred multifocal SCL (Coopervision Biofinity or Proclear D lens) means that any practitioner has ready access to a myopia control tool, which also corrects ametropia, to offer to progressing myopic patients. Increasing uptake of paediatric orthoK42 and availability of daily disposable myopia control SCL designs such as CooperVision’s Misight (in Australia and the UK) and Visioneering Technologies’ NaturalVue (in the USA) will see more tools added to the armament for many practitioners in the near future.

For the child not yet willing or suitable for contact lens wear, atropine could be initially considered. Parents can suffer misconceptions that atropine will also correct ametropia, so optometrists should firstly aim to correct the ametropia in such a way that will also help to manage myopia (orthoK, multifocal or myopia control SCLs or even progressive spectacle lenses) and then add atropine if sufficient myopia control is not achieved, or if there is evidence or risk of faster progression. There is early research evidence that atropine and optical corrections may have an additive effect for myopia control, by mechanism of choroidal thinning and thickening.43 While studies are underway, this is yet to be confirmed in clinically applicable studies and when using the clinically typical 0.01 per cent concentration.

If a child is not yet willing or suitable for contact lens wear, and exhibits the specific binocular vision disorders discussed above – esophoria and accommodative lag – then progressive addition or bifocal spectacles do show clinically useful effects of around 33 per cent efficacy on average.36,44 Side effects of atropine treatment should also be considered whereby a near add or photochromatic spectacle lenses may be required. If the child is suitable for contact lens wear, there is little evidence to support prescribing a single vision correction (except for very occasional wear, for example for sport). OrthoK or multifocal/myopia control soft contact lenses should be offered, with knowledge that a selection can be made on what is best for the patient, and all will likely have a similar efficacy for myopia control.

Safety

There is no doubt that the best first choice for myopia control is a contact lens option as described above, which both corrects ametropia and shows reliable myopia control efficacy. One of the key barriers to paediatric contact lens wear is concern about safety, and this leads to the final key message for parents. Mark Bullimore45 recently published a meta analysis of paediatric SCL studies, which indicated that children (aged eight to12) and teens (aged 13–17) are no more risky contact lens wearers than adults, with no higher rates of microbial keratitis (MK) or inflammatory complications. Importantly, evidence indicated a lower rate of infection in children than teens and adults, which he attributed to better compliance and closer parental supervision. This key paper should give both practitioners and parents confidence in considering childhood SCL wear – if the practitioner and parent is comfortable with fitting a teenager with SCLs, there is no safety reason to not consider the same for a younger child. When adding this finding to the functional and psychological benefits of childhood contact lens wear,46 the myopia managing practitioner should discuss contact lens correction from the outset and plant the seed for future uptake, even if the child and parent
aren’t ready in the short term.

THREE CLINICAL PILLARS FOR MYOPIA MANAGEMENT

Once the myopia management message has been communicated to the parent and patient – information on expectations, efficacy and safety – and the correction has been selected, there are three key areas of clinical focus (Figure 2). Firstly, advice on visual environment is useful for both the child at risk of myopia development – those with a family history of myopia and less hyperopia than age-normal11 – as well as the myope. Secondly, contact lens options should be discussed and offered, as these show the best average efficacy for myopia management while also effectively correcting the ametropia. Where the child is not suitable for contact lens wear, spectacle lens options are available and the possible additive effect of atropine can also be employed. Finally, since binocular vision disorders such as esophoria and accommodative lag have been implicated in myopia progression,23,28-31 and also when present provide the greatest efficacy results for progressive spectacle lens myopia management,24,25 evaluation and management of these issues could provide added benefit to myopia control treatment. Binocular vision status is additionally relevant to visual comfort – ensuring children have functional skills for reading and schoolwork47,48 and acceptance of their correction. In time, these individual factors may help to predict those who will respond best to particular corrections – for example, orthoK appears to reduce both esophoria and accommodative lag,49-52 and a Chinese study has shown children with lower accommodative amplitude achieved a 56 per cent better myopia control effect with OK wear over two years.27

Figure 2: Three clinical pillars for myopia management (references in text).

SUMMARY

In summary, attempting to keep myopia below 3D and axial length below 26mm presents a significant opportunity to reduce lifelong risk of eye disease and visual impairment, in a similar way to reducing IOP in glaucoma. Intervention before age 12 will likely have the greatest impact on reducing progression, while ensuring that patients and parents have reasonable expectations of myopia progression and understand that the average efficacy achieved in scientific studies may be more or less successful for the individual for multifactorial reasons. Until mechanisms are better understood, it is reasonable to consider orthoK, multifocal and myopia control design SCLs and 0.01 per cent atropine as having similar efficacy for reducing axial elongation, by around 50 per cent. Children aged eight to12 are more likely to be safer contact lens wearers than teens, giving confidence to offering these options to young myopes at the time when intervention is likely to have the largest benefit. Finally, the clinical pillars of myopia management include discussion of visual environment factors, contact lens correction options wherever possible, and additionally, considering the impact of binocular vision.

Practitioners and researchers alike can look forward to reading the work of the newly established International Myopia Institute, composed of seven committees and involving over 80 noted myopia researchers from around the world, who aim to produce peer consensus scientific review papers in the model of the highly successful TFOS Dry Eye Workshop (DEWS) reports. All committees met for the first time at the IMC, and the reports are likely to be published at the end of 2018. Subscription to the website for updates is open to all at www.myopiainstitute.org.

References and tools available now for clinical practice include summaries of recent myopia control research at www.myopiacontrol.org and practitioner communication tools at www.myopiaprofile.com. A short survey and information resource to communicate the myopia message to parents is available at www.mykidsvision.org. Practitioners interested in peer discussion of cases and research with an international group of 3,500+ colleagues can join the closed Facebook group ‘Myopia Profile’, which is administered by this author. A wealth of scientific support and increasing prescribing options exist for myopia management – for the current and lifelong benefit of young myopic patients. We must ensure we are not myopic about myopia control.

Dr Kate Gifford, PhD, BAppSc(Optom)Hons, GCOT, FBCLA, FIACLE, FCCLSA, FAAO is a clinical optometrist, peer educator and researcher in contact lenses, binocular vision and myopia control. She holds four professional fellowships, 45 peer reviewed and professional publications, completed a PhD in 2018 on contact lens optics and myopia, and has presented over 100 conference lectures throughout the world. Dr Gifford is an optometrist with Gerry & Johnson Optometrists and Queensland University of Technology (QUT), Brisbane, Australia.






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' the myopia managing practitioner should discuss contact lens correction from the outset and plant the seed for future uptake, even if the child and parent aren’t ready in the short term '