Control de la miopía: ahora es el momento ophtalmic & physiological optics 34 (2014)

Ophthalmic & Physiological Optics ISSN 0275-5408 Myopia control: the time is now For over a century parents have asked clinicians if anything Refractive development is regulated by visual feedback and can be done to slow the progression of myopia in their chil- the process can be manipulated by optical interventions.9,10 dren. Most practitioners shrug their shoulders, add another Because of the prominence of central vision in primates, it 0.50 DS to the child's prescription and see him or her in has generally been assumed that signals from the fovea a year. The tide has now turned. A number of treatments determine the effects of vision on refractive development,11 have been shown to cut progression rates in half and a however, experiments in laboratory animals demonstrate motivated clinician could expand his or her practice to that ocular growth and emmetropisation are mediated by incorporate myopia control.
local retinal mechanisms12,13 and that foveal vision is notessential for many vision-dependent aspects of refractivedevelopment.14,15 The peripheral retina, in isolation, can Optical methods of myopia control effectively regulate emmetropisation and mediate many of Progressive addition spectacle lenses (PALs) produce a sta- the effects of vision on the eye's refractive status.14 More- tistically significant but clinically irrelevant 11–13% slowing over, when there are conflicting visual signals between the of myopia progression based on 2 and 3 year randomized fovea and the periphery, peripheral vision can dominate clinical trials.1,2 Other clinical trials of PALs and flat-top refractive development.16 Collectively, these results suggest bifocals in hypothetically high-risk groups have found simi- that optical treatment strategies for myopia that manipulate larly modest treatment effects.3–5 Larger treatment effects peripheral vision offer promise.
from spectacle lenses have been reported recently usingexecutive bifocals.6,7 Myopic Chinese Canadian children Myopia control using peripheral retinal hyperopic were randomly assigned to one of three treatments: single- vision lenses, executive bifocals, or executive bifocals withbase-in prism in the near segment of each lens. After Sankaridurg et al.17 reported the impact of novel spectacle 3 years the treatment effect was 39% and 51% for bifocals lens designs intended to reduce peripheral hyperopic de- without and with prism, respectively, although the axial focus. Myopic Chinese children were randomised to wear- elongation was similar for each of the two bifocal treatment ing either one of three novel spectacle lens designs or groups. The aforementioned studies of multifocal spectacle conventional, single-vision spectacle lenses for 1 year. For lenses have been predicated on the hypothesis that myopia the entire group, no statistically significant reduction in progression may be slowed by the reduction in accommo- myopia progression was observed with the novel designs dative lag by a reading addition. Based on this hypothesis, although, in children under 12 years with a parental history one might expect that all multifocal modalities would pro- of myopia, progression was 30% lower than with control duce similar effect sizes, but PALs have the smallest effect spectacles. With spectacles the eye moves behind the lens and executive bifocals the largest, with flat-top D-segments and this may diminish the effectiveness of the treatment. If falling in between. In other words, the larger the near por- the peripheral hyperopic defocus is manipulated with an tion, the greater the treatment effect. Taken together, these optical device whose position remains essentially fixed rela- studies support an alternative mechanism, that a reduction tive to the visual axis, greater benefits may be accrued.
in peripheral retinal hyperopic defocus slows myopia pro- Modern overnight corneal reshaping or orthokeratology gression and that interventions that reduce peripheral (Ortho-K) is effective for temporary myopic reduction18 hyperopic defocus should be developed. Indeed, a number and there was anecdotal evidence that these lenses may slow of treatments based on this hypothesis have already been myopia progression in children. Cho et al.19 and Walline evaluated. These are discussed below, but first the compel- et al.20 both conducted 2-year case series with historical ling evidence from animal models of myopia is reviewed.
controls (soft lenses and spectacles, respectively) and foundthat wearing overnight corneal reshaping contact lenses sig-nificantly slowed axial elongation by 46% and 56%, respec- Evidence for optical methods from animal studies tively. These preliminary findings were validated by Cho In his 2010 Prentice Award Lecture at the Annual Meeting and Cheung21 who reported a 43% treatment effect in a of the American Academy of Optometry, Earl Smith 2 year randomised clinical trial. Overnight corneal reshap- reviewed over a decade of careful research demonstrating ing contact lenses produce a flattening of the central cor- the viability of optical methods of myopia control.8 nea, leaving the peripheral cornea largely unchanged. One 2014 The Author Ophthalmic & Physiological Optics 2014 The College of Optometrists Ophthalmic & Physiological Optics 34 (2014) 263–266 effect of this is a change in corneal spherical aberration myopia.34,36 Time spent outdoors in childhood is not asso- resulting in foveal vision being corrected to near emmetr- ciated with rates of myopia progression,37,38 nor does it opia while the peripheral retina is relatively myopic.22–24 appear to be related to myopia stabilisation.39 A prelimin- Thus the retardation of myopia progression produced by ary clinical trial in China has suggested that the incidence overnight corneal reshaping contact lenses provides seren- of myopia can be lowered by a program of outdoor activ- dipitous support for the peripheral hyperopic defocus ity,37 although, even with incentives, children may be reluc- tant to persist with such a program.40 Regardless, Sankaridurg et al.25 reported intriguing results with a practitioners should encourage parents to have their young novel contact lens designed specifically to reduce relative children spend more time outdoors. This can be part of a peripheral hyperopia. Progression was 34% less than for broader public health message in the light of increasing single-vision spectacles. Walline et al.26 recently reported rates of childhood obesity.
that daily wear distance-centre multifocal soft contactlenses slowed myopia progression by 50% in a 2 year The future is now study, although this was with respect to a historicalcontrol group and the reduction in axial elongation was Readers should anticipate additional evidence on clinical only 29%. Thus two contact lens modalities, that pro- myopia control to be forthcoming. Optical therapies will be duce similar peripheral optical profiles,22 offer promise refined, particularly for contact lenses, and additional clini- for myopia control, although practitioners will want to cal trials will enhance our understanding of the underlying make their own assessment of the low but finite risks mechanisms. Given the effectiveness of atropine, commer- associated with wear.27 cial development of designer myopia drugs has likelystalled, although a sustained release device would be anattractive alternative to daily drug installation.41 Finally, the mechanism underlying the benefits of outdoor activity Atropine is probably the most effective treatment to slow remain unclear42 with Vitamin D,43 light levels and spectral myopia progression with a mechanism of action that is reti- composition44 all potentially playing a role. The latter nal or scleral and not accommodative.28 It is used exten- could prompt changes in classroom lighting—perhaps rep- sively in Asian countries, but there has been general resenting the ocular equivalent of fluoride for teeth. In the resistance to its widespread adoption in the West given its meantime, now is the time for clinicians to offer treatment side effects of cycloplegia and photophobia. A recent clini- options to their young patients. Depending on your scope cal trial has demonstrated that the lower concentrations of of practice, overnight corneal reshaping contact lenses, 0.1% and 0.01% can slow progression by 68% and 59%, multifocal soft lenses, executive bifocals, or atropine are all respectively.29 At a concentration of 0.01% accommodation worthy of consideration. The children deserve something is relatively unaffected and symptoms absent30 making this other than an additional an attractive option that is gaining traction in the US. Theeffect size of low dose atropine is equal or larger than thatreported for selective muscarinic antagonists31 which, com- bined with the expense associated with drug development, Portions of this editorial were included in the author's will likely inhibit the commercialisation of new anti-myo- George Giles Lecture at the College of Optometrists' Optometry Tomorrow 2013 conference in Nottingham,UK.
Behavioural approaches Slowing myopia by changing a child's behaviour has a dubious history including the SeeClearly Method (http:// In the past 2 years the author has been a consultant for the en.wikipedia.org/wiki/See_Clearly_Method) and the Bates following companies who may have an interest in the tech- Method32 and recent attempts to control myopia by vision nology discussed: Alcon, Bausch & Lomb, Brien Holden training have failed.33 Furthermore, in spite of widely held Vision, and Paragon Vision Sciences.
beliefs that near work causes myopia, several well-designedlarge-scale studies have failed to find a compelling associa- Mark A. Bullimore tion between the amount of near work undertaken by a College of Optometry, University of Houston, child and the incidence or progression of myopia.34,35 In contrast, recent studies have found a strong evidence that E-mail address: [email protected] more time spent outdoors lowers the risk of developing 2014 The Author Ophthalmic & Physiological Optics 2014 The College of Optometrists Ophthalmic & Physiological Optics 34 (2014) 263–266 15. Smith EL 3rd, Ramamirtham R, Qiao-Grider Y et al. Effects of foveal ablation on emmetropization and form-depriva- 1. Gwiazda J, Hyman L, Hussein M et al. A randomized clini- tion myopia. Invest Ophthalmol Vis Sci 2007; 48: 3914–3922.
cal trial of progressive addition lenses versus 16. Smith EL 3rd, Hung LF & Huang J. Relative peripheral single vision lenses on the progression of myopia in chil- hyperopic defocus alters central refractive development in dren. Invest Ophthalmol Vis Sci 2003; 44: infant monkeys. Vision Res 2009; 49: 2386–2392.
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2014 The Author Ophthalmic & Physiological Optics 2014 The College of Optometrists Ophthalmic & Physiological Optics 34 (2014) 263–266

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Mark A. Bullimore Mark A. Bullimore is an independent regulatory consultant based in Boulder, Colorado. He received his Optometry degreeand PhD in Vision Science from Aston University in Birmingham, England. He was a Professor at The Ohio State UniversityCollege of Optometry for 15 years and taught a number of courses, including geometric optics and ophthalmic optics. Previ-ously, he spent 8 years at the University of California at Berkeley and is currently Adjunct Professor at the University ofHouston College of Optometry. His research interests include myopia, low vision, presbyopia, and refractive surgery. Hereceived grants from the National Institutes of Health to study adult myopia progression.
Mark is an Associate Editor of Ophthalmic and Physiological Optics and the former Editor-in-Chief of Optometry and VisionScience. He is former President and Development Director of the American Optometric Foundation, a philanthropic organi-sation devoted to the advancement of optometric education and research. He served a 4-year term on the U.S. Food andDrug Administration's Ophthalmic Devices Panel and is a consultant for a number of ophthalmic, surgical, and pharmaceu-tical companies.
2014 The Author Ophthalmic & Physiological Optics 2014 The College of Optometrists Ophthalmic & Physiological Optics 34 (2014) 263–266

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