At the completion of this article, the reader should be able to align their clinical protocols more closely to a best-practice approach to myopia intervention, including:
- Understand why measurement of axial length is integral to the emerging standard of care in myopia management
- Be aware of the demographic and cultural confounders in myopia research
- Develop a more methodological approach to the use of atropine doses in myopia management
- Determine patient conditions that encourage a more tailored-approach to myopia management
In the rush to establish effective myopia control strategies, many eyecare professionals may be too reliant on rigid treatment protocols that fail to observe specific patient needs. DR LOREN ROSE says an effective plan addresses the patient’s unique physiology, culture and sociodemographic profile.
Dr Loreto (Loren) Rose
BSc (HONS) MBBS (HONS) FRANZCO PhD
Paediatric and General Ophthalmic Surgeon
Clinical Senior Lecturer, Macquarie Medical School
Founding member of Myopia Australia (www.myopiaaustralia.com.au)
Although there has been a considerable amount of progress in childhood myopia research in recent years – understanding how myopia occurs in children, its progression and useful intervention strategies – there still remains a considerable amount of confusion regarding the best protocol for management.
Admittedly, the number of articles published monthly on myopia causes and interventions can be overwhelming. This expansion of information has led to confusion about the best treatment for myopia progression in children.
One of the common issues is how to measure myopia progression in children. Traditionally, optometrists use the diopter progression to measure how much the eye has progressive myopia with the increase in dioptres. Most studies and publications measure the fast progression of myopia in children as half a dioptre per year.1-3 This is a measurement of the actual change power of the lens needed to improve vision to the macular of the eye. The accuracy of this method required cycloplegia given a child’s ability to accommodate significantly.
However, the more objective, accurate and reproducible measure of progression is axial length (AL) growth, best measured with interferometry.4,5 Interferometry gives us a very accurate non-contact method of measuring how the actual length of the eye changes, hence myopia progression in childhood.
The AL is the underlying cause relating high myopia to pathological myopia in adulthood. It has become the standard in research studies and is quickly becoming the standard of care in clinical practice. Historical data suggested an average childhood AL growth of 0.1 mm per six months.6,7 An analysis of average axial change in Europe is variable with age, with greater progression in under nine years.8 There is also an ethnic difference with greater progression noted in the Asian population (average of 0.30 mm/year).9-11 The common conversion is -0.5 dioptre per year equates to 0.2 mm elongation per year.4
Atropine dosage: side effects vs efficacy
Alongside the controversy on measuring progression is the question of what atropine dosage to start with when treatment is initiated – and how to progress in a treatment algorithm. In fact, there is a surprising variability of the initial doses of atropine drops used by clinicians when they commence their myopia management treatments in children.
It is not uncommon to hear and see patients starting their first dose of low-dose atropine at 0.05%, while some clinicians will start on 0.025% and others on 0.01%. The source of this confusion is the recent studies showing the efficacy of atropine to be dose-related. The stronger the dose, the more the powerful the effect on retarding axial elongation, which is the aim of myopia intervention.
There is no debate that the stronger the dose of the atropine, the more the effect. However, equal attention needs to be made to the fact that the stronger the dose of the atropine, the more likely the patient will be affected by the side effects. These side effects include blur, glare, and rebound when we stop the drops too early.
‘Confounding’ patient demographics
Taking a step back, the basis of these doses follows the three-year Low-Concentration Atropine for Myopia Progression (LAMP) studies conducted by researchers from the Chinese University of Hong Kong.9,12,13 Collectively, the LAMP Studies directly compared low concentrations of atropine (0.05%, 0.025% and 0.01%) and ultimately concluded that atropine 0.05% appears to work best over three years to control axial elongation.
However, the study left a vital question unanswered: How do these concentrations perform in other patient demographics?
Simply put, the LAMP Studies are based on an Asian population and may have ethnic and lifestyle confounders. The study was based on four to 12-year-olds in Hong Kong. We know that the Asian population generally experiences myopic progression faster than those in Western populations.
In a population study in Australia, myopia in the Asian cohort progressed faster than myopia in the Caucasian cohort. However, the Asian cohort did not progress as fast as the Asian counterparts in Asian studies.14 These observations suggest that besides ethnicity, there are other contributors to myopia progression in these Asian studies. These may be different cultural environments, such as time spent outside and doing near work, which are known as ‘confounders’.15-17
Geography and lifestyle
Additionally, there are concerns that lighter irises (more common in Australia) are more likely to experience the side effect profile of higher doses of atropine, and may not tolerate the higher doses due to blur and glare, especially in Australian children who have better light-exposure compared to some Asian countries.18 Higher atropine concentrations have greater side effects of dilation and cycloplegia, which are tolerated best by dark irises.
Tolerating outdoor time is important as part of the strategy to reduce the risk of myopia progression,19 especially in the Australian sun. Finally, an American study showed that in doses of more than atropine 0.02%, children were more likely to experience the side effects profile of atropine.20
Therefore, atropine 0.025% dose has limited benefit on axial growth but a similar side effect profile (as 0.05%), especially in lighter eyes. Given the dose consideration in the Australian context, a more methodological approach to atropine doses should be considered.
Best practice approach to myopia intervention in Australia
In keeping with this theory, we need to understand our children’s needs. There should be a best-practice approach to myopia intervention, including atropine drops, that accommodates the specific conditions found in this specific population.
It is important that myopic children are diagnosed early and monitored for fast growth. Interferometry provides high accuracy and ease of use in children to monitor the progression of axial growth. As myopia prevalence and incidence are predicted to increase, such tools will be invaluable in optometry practices. The use of interferometry helps to monitor change precisely, so if a patient is a fast progressor (>0.1 mm/6 months), then atropine can be initiated and interferometry can be used to monitor the response in the next six months.
In some children, axial elongation progresses very slowly and they may not benefit from an intervention such as atropine. In such cases, the favoured approach would entail a discussion about lifestyle with less near-work, increased time in natural light and monitor for change.
On the other hand, the sequential approach is the best and safest for children who are considered to be fast progressors. As with any medication, the lowest clinically significant dose should be the first prescribed as part of the treatment algorithm. Ultimately, a sequential approach to treatment, including dose concentration, allows for monitoring of treatment effects and side effects.
Atropine 0.01%
The lowest dose of atropine known to be effective should be the first dose in treating myopia progression. Apart from the ATOM and LAMP studies, the effect and benefit of atropine 0.01% have been widely established.2,4,21,22
This research includes an Australian-based study which resulted in a mean 50% reduction of axial progression in fast progressors based on the previous six months of axial growth, and this effect was sustained during the two years follow-up.4
Recently, the 0.01% dose of atropine has been TGA-approved and is available in sterile, preservative-free, single-dose formulation (EIKANCE 0.01%). The approval is for myopic children ages four to 14 years with progression greater than one dioptre/year. It is useful to consider measuring the axial length greater than 0.1 mm/6 months or 0.2 mm in one year.
My clinical atropine protocol
My practice is to titrate the dose if the low dose is tolerated but does not have enough of the desired effect to control myopia growth. The next dose is usually atropine 0.05%, given that the side effect profile is similar to 0.025%, but the greater efficacy of 0.05%. I schedule regular review intervals at six months to reassess the axial growth with each intervention.
I feel it is also important to ensure that the patient and their family can report and intervene earlier if they feel that glare and/or blur are significantly a problem. I also feel it’s important to educate patients and their families that stopping a higher dose without follow-up can lead to a higher chance of a rebound, and explain how the rebound may undo some of the good work that atropine is done for them.
Contraindications
The best practice and management of myopia will continue to evolve as more research helps us find new ways of intervening in the axial length growth of the eye. However, it is important to remember that these new therapies are done safely and monitored.
One of the safety measures is the correlation between axial length and dioptre change. If the dioptre change does not match axial growth, other causes of perceived myopia progression may exist. These conditions include keratoconus and spherophakia, which may contraindicate the use of atropine. Additionally, some syndromic causes of high myopia, including connective tissue diseases, also contraindicate the use of atropine.
The bigger picture
Patient education is vital to understand that atropine therapy has side effects and, importantly, rebound. Therefore, treatment and cessation must be monitored for at least six months to a year.
Alongside lifestyle, suggestions must be made to ensure the best treatment response. Near-work of all forms, including reading and screen time, has an undesired effect of increasing myopia progression and natural light has the desired effect of retarding progression.
Talking about ‘screen and green’ time as an adjuvant to any intervention for myopia management is important. As in any medical treatment/intervention, the use of lifestyle to achieve the maximum effect is universal. Patient and parent education needs to include the bigger picture of myopia, where increasing myopia means not just thicker glasses but the bigger issue of progression to high myopia and potentially pathological myopia that can cause significant sight-threatening eye diseases in adult life.
References
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2. Sacchi M, Serafino M, Villani E, et al. Efficacy of atropine 0.01% for the treatment of childhood myopia in European patients. Acta Ophthalmol. 2019;97(8):e1136-e1140.
3. Wu PC, Yang YH, Fang PC. The long-term results of using low-concentration atropine eye drops for controlling myopia progression in schoolchildren. J Ocul Pharmacol Ther. 2011;27(5):461-466.
4. Rose LVT, Schulz AM, Graham SL. Use baseline axial length measurements in myopic patients to predict the control of myopia with and without atropine 0.01. PloS one. 2021;16(7):e0254061.
5. Wolffsohn JS, Kollbaum PS, Berntsen DA, et al. IMI – Clinical Myopia Control Trials and Instrumentation Report. Invest Ophthalmol Vis Sci. 2019;60(3):M132-M160.
6. Chua WH, Balakrishnan V, Chan YH, et al. Atropine for the treatment of childhood myopia. Ophthalmology. 2006;113(12):2285-2291.
7. Hou W, Norton TT, Hyman L, Gwiazda J, Group C. Axial Elongation in Myopic Children and its Association With Myopia Progression in the Correction of Myopia Evaluation Trial. Eye Contact Lens. 2018;44(4):248-259.
8. Tideman JWL, Polling JR, Vingerling JR, et al. Axial length growth and the risk of developing myopia in European children. Acta Ophthalmol. 2018;96(3):301-309.
9. Yam JC, Li FF, Zhang X, et al. Two-Year Clinical Trial of the Low-Concentration Atropine for Myopia Progression (LAMP) Study: Phase 2 Report. Ophthalmology. 2019.
10. Wei SF, Li SM, Liu L, et al. Sleep Duration, Bedtime, and Myopia Progression in a 4-Year Follow-up of Chinese Children: The Anyang Childhood Eye Study. Invest Ophthalmol Vis Sci. 2020;61(3):37.
11. Yi S, Huang Y, Yu SZ, Chen XJ, Yi H, Zeng XL. Therapeutic effect of atropine 1% in children with low myopia. J AAPOS. 2015;19(5):426-429.
12. Yam JC, Zhang XJ, Zhang Y, et al. Three-Year Clinical Trial of Low-Concentration Atropine for Myopia Progression (LAMP) Study: Continued Versus Washout: Phase 3 Report. Ophthalmology. 2022;129(3):308-321.
13. Yam JC, Jiang Y, Tang SM, et al. Low-Concentration Atropine for Myopia Progression (LAMP) Study: A Randomized, Double-Blinded, Placebo-Controlled Trial of 0.05%, 0.025%, and 0.01% Atropine Eye Drops in Myopia Control. Ophthalmology. 2019;126(1):113-124.
14. Ip JM, Huynh SC, Robaei D, et al. Ethnic differences in the impact of parental myopia: findings from a population-based study of 12-year-old Australian children. Invest Ophthalmol Vis Sci. 2007;48(6):2520-2528.
15. French AN, Morgan IG, Burlutsky G, Mitchell P, Rose KA. Prevalence and 5- to 6-year incidence and progression of myopia and hyperopia in Australian schoolchildren. Ophthalmology. 2013;120(7):1482-1491.
16. Morgan IG, French AN, Ashby RS, et al. The epidemics of myopia: Aetiology and prevention. Prog Retin Eye Res. 2018;62:134-149.
17. Morgan IG, Wu PC, Ostrin LA, et al. IMI Risk Factors for Myopia. Invest Ophthalmol Vis Sci. 2021;62(5):3.
18. Rose KA, Morgan IG, Ip J, et al. Outdoor activity reduces the prevalence of myopia in children. Ophthalmology. 2008;115(8):1279-1285.
19. Lingham G, Yazar S, Lucas RM, et al. Time spent outdoors in childhood is associated with reduced risk of myopia as an adult. Sci Rep. 2021;11(1):6337.
20. Cooper J, Eisenberg N, Schulman E, Wang FM. Maximum atropine dose without clinical signs or symptoms. Optom Vis Sci. 2013;90(12):1467-1472.
21. Tsai HR, Chen TL, Wang JH, Huang HK, Chiu CJ. Is 0.01% Atropine an Effective and Safe Treatment for Myopic Children? A Systemic Review and Meta-Analysis. J Clin Med. 2021;10(17).
22. Zhao Y, Feng K, Liu RB, et al. Atropine 0.01% eye drops slow myopia progression: a systematic review and Meta-analysis. Int J Ophthalmol. 2019;12(8):1337-1343.
More reading
Aussie myopia study reveals who benefits the most from low-dose atropine
Atropine for myopia control: science and practice
Axial length matters in myopia management
