Understanding and Treating Myopia: Yesterday, Today, and Tomorrow

This issue of Optometry and Vision Science presents highlights of the 15th International Myopia Conference (IMC 2015), which was also officially the 1st Chinese Myopia Conference. The local organizers and hosts—Profs. Dr. Jia Qu, Fan Lu, and Xiangtian Zhou—brought honor and respect to themselves, their university, their city, and their country by organizing and running a grand Conference. IMC 2015 provided wonderful opportunities for the growing body of Chinese scientists and clinicians working in this field to share knowledge and insights with their counterparts from around the world, and for the foreign visitors to see how myopia research has flourished in China in the past few years. It was a timely meeting of minds, given the recent surges of interest in the roles of outdoor activity/sunlight, special lens treatments, and low-dose atropine in combating the perceived “epidemic” or “boom” of myopia, especially in Asian cities. Two highlights of the Conference were lectures by honorary award recipients: the Sek Jin Chew Memorial Lecture for established researchers, by Frank Schaeffel, University of Tübingen; and the Josh Wallman Memorial Lecture for young investigators, by Scott Read, Queensland University of Technology. Written versions of their lectures are published here.1,2 The Conference closed with a mini-symposium that synthesized and critically assessed the current state of knowledge on the cause(s) and prevention of myopia. Major questions raised during the Conference were addressed by pairs of Presenter and Discussant, who were invited to submit written versions of these presentations. Accounts of most of those presentations are published in this Special Issue. Schaeffel’s article1 highlights the little-known work of 19th-century ophthalmologist Hermann Cohn, many of whose views predated modern thinking. “Taken together, many of Cohn’s ideas were partially correct, but his hypotheses did not survive him for very long because no data were generated at that time to prove or disprove them.”1 This serves as a welcome reminder to revisit now and then the neglected works of yesteryear. Read’s article,2 in contrast, transports us to the front lines of today’s thinking about myopia. It provides an overview of the author’s efforts to identify ocular and environmental factors that affect childhood eye growth, and it discusses the possible roles of ambient light exposure and responses of the choroid and their implications for myopia control. The title of the closing session—“Is ‘Light’ a Panacea for Myopia”—reflects the currently high level of interest in the ‘myopia boom [or epidemic]’ and the potentially protective role of light, in the popular press and optometric research and practice. By now, it is very clear that increased ‘outdoor activity’ is strongly correlated with reduced odds of becoming myopic.3,4 The recently completed ROAM (Role of Outdoor Activity in Myopia) study, discussed in Read’s lecture,2 confirmed objectively a significant association of daily light exposure with slowing of eye growth in human subjects. As reviewed by Norton5 and Ashby,6 this is consistent with findings in experimental animals under laboratory conditions and supports the protective role for outdoor light inferred from epidemiological studies.2 Norton5 points out that outdoor light levels are typically 60 to 260 times higher than indoor light levels, that low light levels themselves can induce myopia, and that light levels at the low end of the outdoor range are sufficient to reduce form-deprivation myopia in animals. Dopamine, acting via retinal targets (e.g. D2-like receptors in chicks), has been implicated in the light-driven inhibition of myopia induction.5,6 As noted by both authors, however, negative lens-induced myopia in animals—often regarded as the better model for human myopia—does not respond the same way to increased light intensity as does form-deprivation myopia, especially in a primate model, rhesus monkey. It remains unclear, furthermore, whether it is the amount or the spectrum of “outdoor light” that is responsible for its anti-myopia effect.6 In this, the 1st Chinese IMC, considerable time and emphasis were devoted to the effectiveness of lens treatments—not surprising, given widespread concern over the myopia ‘epidemic’ in China and the paucity of other treatment options. Although animal experiments have shown refractive compensation for imposed plus-, minus-, and astigmatic defocus, the relevance of these models to human refractive disorders remains unclear. Notably, the COMET trial of progressive addition lenses (PAL) provided little evidence for clinical effectiveness, and over-, under-, and true correction have also provided little benefit. IMC speakers devoted considerable attention to recent developments—including daytime wear of concentric multifocal lenses or lenses correcting for peripheral-retinal defocus, and nighttime wear of orthokeratology (cornea-reshaping) lenses. Atchison7 reviews evidence for and against the hypothesis that relative peripheral hyperopia leads to myopia. His conclusion, that evidence for this idea is weak, has important implications for design of lenses to retard human myopia development, and he offers alternative hypotheses. Troilo8 focuses attention on specific lens designs—in particular, multifocal lenses, which are known effective for myopia control—emphasizing that several proven treatments, both optical and pharmaceutical, are available now, and that they should be used, whether or not the underlying mechanisms are known, while further research and development continue. What do we need to do now? Sufficient data are available to support various private and public interventions for reducing the incidence and progression of myopia. Morgan9 reminds us that, although only in quite early stages, human studies largely confirm the results of animal studies showing that light of outdoor intensity is protective against myopia. He urges early intervention, by mandatory school-based programs and systematic monitoring of visual acuity and refraction, to forestall the projected explosion of pathological myopia in the near future. Verkicharla et al.10 further support this opinion, with particular focus on urban East Asia and the authors’ experience in Singapore. The authors recognize the importance of considering regional and ethnic differences in attitudes and behavior, when designing public policies to counter the “myopia epidemic.” What do we still need to know? Much, very much, about almost everything mentioned above. And how should we go about learning it? These questions are addressed by Sally McFadden in the closing paper of this series.11 There should be no dearth of interesting and useful things to be learned, and applied, in the next 5 to 10 years, and we may look back in amusement then, as we look back now on the early musings of Hermann Cohn, on the progressive but still imperfectly informed ideas that are prevalent today. Stay tuned! William K. Stell, PhD, MDCalgary, Alberta, Canadae-mail: [email protected]

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