The Complex Nature of Myopia Control Research:

The prevalence of myopia is growing worldwide, with consequences that include decreased quality of life and economic costs to patients as well as an increased risk for developing serious eye pathologies. Efforts to control the progression of myopia date back to the mid-1800s, and since then have been constrained by complexity, uncertainty and debate, contributing to a lack of consensus as to which path is most effective.

Consider the following:

We still don’t know what causes myopia. There is no conclusive evidence that myopia is linked to

accommodation,1-3 although a number of interventions are based on this assumption. The role of environmental and genetic factors need further investigation.2,4-6

We don’t agree on what makes results clinically signficant. How many diopters’ shift in myopia constitutes a clinically significant difference, warranting a change in clinical practice?7

The benefits of research and interventions should be balanced with ethics and economic costs to patients as well as an increased risk for developing serious eye pathologies. Efforts to control the progression of myopia date back to the mid-1800s, and since then have been constrained by complexity, uncertainty and debate, contributing to a lack of consensus as to which path is most effective.

Consider the following:

We still don’t know what causes myopia. There is no conclusive evidence that myopia is linked to accommodation,1-3 although a number of interventions are based on this assumption. The role of environmental and genetic factors need further investigation.2,4-6

We don’t agree on what makes results clinically signficant. How many diopters’ shift in myopia constitutes a clinically significant difference, warranting a change in clinical practice?7

The benefits of research and interventions should be balanced with ethics and safety guidelines. At what point is it okay to expose myopic children to side effects such as pupil dilation and microbial keratitis?3,7

Clinical trials testing myopia control interventions have been inconsistent. Areas of contention includes the use of appropriate controls and sample size, effective masking and consistent randomization. There is also inherent bias in studies comparing discernable interventions such as spectacles and contact lenses.5, 7,8

We don’t know whether refractive error or axial growth is the best measure of myopic progression. This relatively recent question obscures comparisons between studies, complicating efforts to understand clinical relevance.8

Bifocal or progressive spectacles: Bifocal and progressive spectacles have been used with children as a means of reducing the need for accommodation. While there is some evidence of a positive effect on myopia, the research has for the most part failed to show a significant or clinically meaningful effect.1,3-4,8

Peripheral retinal defocus: In animal models, altering the peripheral power of a corrective lens affects axial length.3,10-11 Contact lenses designed to induce peripheral hyperopia in myopic children have shown promise in slowing the progession of myopia,12-13 but the magnitude and permanence of this effect remains unclear.4

Orthokeratology: Overnight wear of reverse geometry contact lenses can correct low levels of myopia via corneal flattening.14-15 Recent work has shown that the use of this technique can also slow the progression of myopia in children by slowing axial elongation,16 but the mechanism remains unclear at this time.

Undercorrection:

The rationale for undercorrecting myopia is unclear, and the method is not supported by research.3-4,8 This strategy is not recommended.

Pharmaceuticals:

Atropine has been reported to be themost clinically effective intervention,1,8,17 although the exact mechanism and optimum dosage both remain unclear.17 A low dosage may be most beneficial.18 Its use is linked to serious short- and long-term side effects1,8 and so should be limited to children at high risk for high myopia and associated complications.1

Time outdoors: There is some evidence that outdooractivity may prevent or slow the development of myopia, although the exact mechanism of this effect is unclear. It may be related to reduced accommodative response, or possibly light quality and subsequent light-related release of retinal dopamine, which may be critical to regulating ocular growth.5-6 A possible connection between Vitamin D and myopia requires further study.19

Visual training (with or without biofeedback):This approach suggests that myopia can be reduced by training patients to activate and relax their accommodation. Research suggests that the positive effects of this intervention are learned and not due to a reduction in myopia.3,20

The interventions

Arguably, clinically meaningful results have yet to be reported for myopia control research, particularly with respect to longer term effects.1,7-8 The following list outlines the major interventions explored to date.

Source: www.ContactLensUpdate.com

1. Leo S-W and Young TL. An evidence-based update on myopia and interventions to retard its progression. J AAPOS 2011;15(2)181-9.

2. Morgan IG, Ohno-Matsui K, Saw S-M. Myopia. Lancet 2012;379:1739-48.

3. Sivak J. The cause(s) of myopia and the efforts that have been made to prevent it. Clin Exp Optom 2012; 95(6):572- 82.

4. Sankaridurg PR, Holden BA. Practical applications to modify and control the development of ametropia. Eye 2014; 28(2):134-41.

5. Sherwin JC, Reacher MH, Keogh RH, et al. The association between time spent outdoors and myopia in children and

adolescents: A systematic review and meta-analysis. Ophthalmology 2012;119(10):2141-51.

6. French AN, Ashby RS, Morgan IG. Time outdoors and the prevention of myopia. Exp Eye Res 2013;114: 58-68.

7. Gwiazda J. Treatment options for myopia. Optom Vis Sci 2009;86(6):624 28.

8. Walline JJ, Lindsley K, Vedula SS, et al. Interventions to slow progression of myopia in children. Cochrane Database Syst Rev 2011(12).

9. Walline JJ. Myopia control with cornea reshaping contact lenses. Invest Ophthalmol Vis Sci 2012;53(11): 7086.

10. Smith EL 3rd, Kee CS, Ramamirtham R, et al. Peripheral vision can influence eye growth and refractive development in infant monkeys. Invest Opthalmol Vis Sci 2005;46:3965-72.

11. Woods J, Guthrie S, Keir N, et al. Inhibition of defocus-induced myopia in chickens. Invest Ophthalmol Vis Sci 2013; 54(4):2662-8.

12. Anstice NS, Phillips JR. Effect of dual-focus soft contact lens wear on axial myopia progression in children. Ophthalmology 2011;118(6):1152-61.

13. Sankaridurg PR, Holden B, Smith E. Decrease in rate of myopia progression with a contact lens designed to reduce relative peripheral hyperopia: One year results. Invest Ophthalmol Vis Sci 2011;52(13): 9362-7.

14. Swarbrick HA. Orthokeratology review and update. Clin Exp Optom 2006;89:124-43.

15. Sorbara L, Fonn D, Simpson T et al. Reduction of myopia from corneal refractive therapy. Optom Vis Sci 2005;

82(6):512-518.

16. Cho P and Cheung S-W. Retardation Of Myopia In Orthokeratology (ROMIO) Study: A 2-year randomized clinical trial. Invest Ophthalmol Vis Sci 2012;53(11): 7077-85.

17. Song YY, Wang H, Wang BS, et al. Atropine in ameliorating the progression of myopia in children with mild to moderate myopia: a meta-analysis of controlled clinical trials. J Ocul Pharmacol Ther 2011;27: 361-8.

18. Chia A, Chua WH, Wen L, et al. Atropine for the treatment of childhood myopia: changes after stopping atropine 0.01%, 0.1% and0.5%. Am J Ophthalmol 2014;157: 451-7.

19. Mutti DO, Marks AR. Blood levels of vitamin D in teens and young adults with myopia. Optom Vis Sci 2011;88(3): 377- 82.

20. Gilmartin B, Gray LS, Winn B. The amelioration of myopia using biofeedback of accommodation: a review. Ophthalmic Physiol Opt 1991;11(4): 304-13.


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