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C-52154

Putting myopia control into practice

There is strong scientific interest in understanding factors leading to myopia development and progression, and options for myopia control. In this article, scientific evidence will be combined with clinical experience to outline best practice myopia management.

Introduction

If you are cognisant of the rise in myopia, and the risks this entails for the lifelong eye health of each paediatric myope in your practice, then you’ll be wondering how to put the vast scientific data on myopia control into practice. Myopia control research spans epidemiology, genetics, environment, binocular vision, spectacle and contact lens optics and pharmacology, and as yet there are no internationally accepted clinical guidelines for managing progressive myopia. Over a decade ago, increased understanding of how central corneal thickness affected intraocular pressure measurement and how this related to risk of glaucoma progression revolutionised clinical management of this condition1 – the Scoring Tool for Assessing Risk (STAR II) calculator was developed and as practitioners we benefited from better guidelines around how to manage this multifactorial condition, leading to better patient outcomes.2 More recently, improved understanding of the mechanisms of dry eye led to robust scientific discussion through the Tear Film and Ocular Surface Dry Eye Workshop (TFOS DEWS) Report, offering evidence based strategies for clinical management of these patients.3 The next key clinical evolution for our profession may be myopia control – there is much understood about its development, progression and management, but we are yet to see this consistently translated into practice for best patient benefit. 

While most practitioners consider themselves active managers of progressive myopia, most are also prescribing single vision spectacle or contact lens corrections to these patients,4 which is not evidence based.5,6 A recent survey of almost 1000 practitioners from a dozen countries showed that 80% of practitioners in Asia, 70% of practitioners in Australasia and Europe and 40-50% of North and South American colleagues consider themselves clinically active in myopia control.4 On a 10-point scale, there was a similar level of concern (7/10) across the globe about the increasing frequency of paediatric myopia. Overall, orthokeratology (OK) was graded with highest efficacy for myopia control but only prescribed to an average of 14% of progressing myopes. Single vision soft contact lens (SCL) wear was considered suitable for commencement in younger children (6.5 ± 3.4 years) well before OK (8.8 ± 3.1 years) or multifocal SCLs (8.9 ± 3.1 years).

There are currently no government licensed or FDA approved products for myopia control, which affects practitioner confidence and engagement in this area of clinical practice. The ideal myopia-controlling device has yet to be designed – it would include beneficial alteration of relative peripheral optics, spherical aberration and binocular vision, and would likely be best suited to a contact lens modality. It may also include real time monitoring and feedback of the visual environment, and incorporate delivery of low dose atropine or other suitable pharmacological treatments.7 This perfect device may remain theoretical as there is much evidence indicating that myopia development and progression is multifactorial and highly individual. However, there is a wealth of scientific evidence for engaging products and management processes today, in your practice, to slow down the race of your paediatric patients towards ever increasing myopia, and the associated escalating risks of ocular pathology.8

When to start myopia control

Firstly, when should you start a myopia management programme? A previous article by this author (Optometry Today, June 2016) described the pre-myope – the child with a cluster of risk factors for future development of myopia. He has one or two myopic parents, is less hyperopic than expected for his age, and may also exhibit esophoria and accommodative lag at near.9–11 A key research finding in large-scale studies is that the fastest change in refraction occurs in the year just prior to myopia onset,10 so it is crucial to watch these at-risk future myopes closely for shifts in their risk profile and especially in their manifest hyperopia. Currently, evidence based practice for these children includes regular monitoring – at least every six months is prudent – along with managing esophoria and accommodative lag, and providing advice on visual environment.

For the manifest myope, the earlier you start a myopia management programme, the better their outcome is likely to be. Children who exhibit myopia by age six to seven years are over six times more likely to progress to high myopia (over 5D) compared to older age of onset of 11–12 years of age, independent of ethnicity and gender.12 Younger children progress by at least 1D per year, slowing to around 0.50D per year by 12 years of age.6 While the perfect myopia controlling strategy is yet to be determined, various spectacle, contact lens and pharmacological strategies can be employed with success rates of 30-60%.13-18 A summary of the scientific data on myopia control strategies is provided in Table 1 (a summary of myopia control intervention). It can be difficult to understand how a percentage reduction in axial elongation relates to the individual patient in your chair – there is no way to know how much this particular child may progress, and hence how effective a myopia control strategy will be. Modelling has shown that application of a 33% effective myopia control strategy would result in a 73% reduction in the frequency of myopia over 5D, and a 50% efficacy would result in 90% less high myopia, and the consequent reduction in ocular pathology risk across the population.19

How to manage myopia

Having determined a child’s best distance refraction, it is imperative to know how this influences their near point binocular vision function. Myopes tend to show more enhanced accommodative convergence (esophoria and elevated AC/A ratios), along with insufficient accommodative responses (accommodative lag) compared to their emmetropic counterparts.39,40 Since these are associated with increased myopia progression,26 management of this risk involves ensuring that pursuit of best distance acuity doesn’t come at the expense of comfortable near vision. When appropriately managed with multifocal spectacles or contact lenses, these children show more successful myopia control results than their binocular vision-normal myopic peers.15,17

Table 1

Clinical management of esophoria and accommodative lag with bifocal or multifocal spectacle lenses is well understood.41,42 However, its management with bifocal or multifocal contact lenses is less straight-forward. Both bifocal soft contact lenses (BFSCL) and orthokeratology (OK) have been shown to increase accommodative responses, hence decreasing accommodative lags, in young adult myopes.43,44 Aller et al describe individually selecting the add of BFSCLs to neutralise esophoria in progressing paediatric myopes, resulting in a myopia controlling effect exceeding 70% over 12 months.15 In selecting the appropriate add, one study has shown that BFSCLs reduce accommodative lag by an average of around half of the listed add power, with significant individual variation.43 Hence, if electing to fit BFSCLs or the more readily available multifocal soft contact lenses (MFSCLs) it would make clinical sense to consider the ideal add you would prescribe in spectacles and aim to double that as your first trial lenses. Commercially available MFSCLs in adds up to +4.00D are available, but it is worth noting that adds of +3.00 and above have been shown to result in a loss of best corrected acuity of around a line compared to OK, so may not be universally tolerated from a visual perspective.45 OK has the same propensity as a BFSCL or MFSCL to reduce accommodative lag, with the peripheral ‘add’ effect equivalent to the central power of treatment.46,47 It has been demonstrated that OK beneficially influences accommodative function in the myope,44 and that children with lower baseline amplitude of accommodation show a greater myopia control response to OK than those with normal accommodation.48 There is currently no published data on how the peripheral ‘add’ effect of OK may specifically relate to changes in on-axis optics of the eye, including binocular vision function.

Figure 1 (Flow chart for clinical myopia management, adapted from www.myopiaprofile.com) presents a decision-making flow chart for myopia management. After determining whether your progressing myopic patient demonstrates a high-risk binocular vision profile for progression (esophoria and accommodative lag), the next key decision involves whether the patient is suitable for contact lens wear. The aforementioned options for managing binocular vision include MFSCL and OK, with careful monitoring of resultant improvement in esophoria and accommodative lag. If these do not sufficiently improve, progressive or bifocal spectacles can be additionally prescribed to manage the associated progression risk. If your young myopic patient exhibits normal binocular vision function, but is still demonstrating progressive myopia, this would indicate that other mechanisms are at work such as relative peripheral hyperopia, on-axis aberrations or the influence of visual environment. A previous article by this author in this publication provides more detail on the scientific understanding of myopia development and progression. It is not evidence based to prescribe single vision distance spectacles or contact lenses to a progressing myope; these corrections are used as control groups in myopia progression studies,6 and single vision rigid and soft contact lenses have no demonstrated efficacy for myopia control.5,20 In this case, if the child is suitable for contact lens wear, MFSCL or OK offer the best evidence-based option. If the child is not suitable for contact lens wear, progressive or bifocal spectacles have shown minimal effects for myopia control in the binocular vision normal-child, however, these results still exceed those of single vision corrections.17,26 If you are confident that your patient has stable myopia, then prescribing a single vision correction is justifiable, however, if a contact lens wearer, it could be argued that applying some form of multifocal correction involves minimal change in chair time, cost or visual result for the patient and a more assured efficacy for myopia control.

Figure 1

Regardless of binocular vision status and your prescribed modality of vision correction, your young myopic patients and their parents should be provided with advice on visual environment. 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.9,49,50 Children with low outdoor (0–1.6 hours per day) and high out-of-school hours near work (>three 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 (zero to two hours per day) activity levels.49 The young myopic ‘bookworm’ should of course be encouraged to read, but to balance this by reducing other leisure activities involving near work, and ensure more time is spent outdoors.

Low dose atropine is an emerging treatment for progressing myopia with a greatly reduced side effect profile compared to standard doses used clinically for mydriasis or pharmacological patching. Recent studies have shown that 0.01% atropine shows the strongest overall treatment results for myopia control over a two-year treatment period, one year cessation then additional two-year treatment.18 This methodology was employed as previous studies of 1% and 0.5% atropine had shown strong myopia control effects, but a concerning acceleration of axial growth after cessation, termed a rebound effect.23 While the authors describe low dose atropine as having minimal effect on accommodation and pupil size, it would be useful to understand more on this to inform clinical decision making – perhaps low dose atropine will be less suited to the myope with baseline lower accommodative function. With no commercially available 0.01% atropine preparation, prescribing of this myopia control strategy will depend on the regulatory and compounding pharmacy supply issues particular to their country of practice.

Clinical considerations

The safety of paediatric contact lens wear is of concern to the practitioner active in myopia control. Research indicates that after 10 years of wear there is no difference in risk of adverse events, duration of comfortable wearing time or long term eye health outcomes in contact lens wearers initially fitted as children (age 8–12) compared to those fitted in their teens (age 13–17).51 Moreover, children and teens may be more compliant than their adult contact lens wearing counterparts, especially when it comes to daily lens cleaning.52,53 Children and teens are highly capable of understanding contact lens care instructions. However, children may require more reinforcement at aftercare visits to ensure recall of compliance processes.54 Dry eye symptoms occur in only 4% of paediatric contact lens wearers compared to over 50% of adults.55 There is no doubt that contact lens wear increases risk of microbial keratitis (MK) – from 0.014% per year in the non-contact lens wearing population to 0.131% in contact lens wearers,56 and case study analysis of paediatric OK has shown a 0.3% risk per year of wear.57 By comparison to the risks of lifelong myopia-associated ocular pathology, though, the paediatric contact lens wearer is 32 times more likely to be diagnosed with glaucoma than to develop MK. If this myope progresses to 5D of myopia or more, they are 12 times more likely to suffer retinal detachment than contact lens related MK.58 There is a clear case for the risk-to-benefit ratio of paediatric contact lens wear when successfully prescribed for myopia control.

There is increased complexity in clinical management of several types of myopes including: the astigmatic myope who has reduced MFSCL and OK contact lens options; the severe esophore and profound under-accommodator who may not be normalised with spectacles or contact lenses; the very high myope who may only achieve partial correction with OK or reduced acuity with a high add MFSCL; and children who are unable to wear contact lenses for individual or anatomical reasons.58 There may be a clear evidence based imperative for these myopes but the practical application is difficult – combinations of spectacle and contact lens corrections may be necessary, in addition to possible use of low dose atropine. It is worth noting that partial correction with OK for high myopes has been investigated, with paediatric myopes greater than 6D corrected to 4D of myopia, with residual refractive error corrected with single vision spectacles, showing a 62% reduction in axial growth over two years compared to single vision fully corrected spectacle wearers.36 An individualised approach to myopia control is necessary, taking into account your patient’s refractive and binocular vision status, along with their ocular health and personal capabilities. In terms of clinical decision-making, key consideration of binocular vision function and suitability for contact lens wear helps to direct the evidence based best practice management. In future, the clinical realm can hope to see the academic and industry realms of our profession provide myopia management guidelines, increased prescribing options and perhaps one day, the myopia control panacea. Until this day, though, there is overwhelming evidence of the benefit we can provide to our patients through taking an active approach to myopia control, both in their short term visual experience and long term eye health outcomes.

About the author

Kate Gifford operates an independent practice in Brisbane, Australia, with specialty interests in contact lenses, binocular vision and myopia control. Graduating from Queensland University of Technology (QUT) in 2003 with First Class Honours and a University Medal, Kate is now undertaking a part-time PhD by clinical research. She is a fellow of the BCLA, IACLE, CCLSA (Australia) and AAO and is the current National President of Optometry Australia. Kate is an award-winning clinical supervisor and visiting lecturer at QUT, holds 28 peer reviewed and professional publications, and has presented over 60 lectures at conferences in Australia and internationally.

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