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Research focuses on growing myopia epidemic
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In recent years, diabetes and age-related macular degeneration have been increasingly described as emerging epidemics that will affect millions of subjects throughout the world. Today, we have to address a condition that will dramatically influence society and health care systems.
Myopia is also reaching epidemic dimensions. In East Asia, its prevalence has moved from 10% to 20% during the middle of last century to 90% today among teenagers and young adults. South Korea probably holds the record with 96% prevalence. Europe and the United States have also doubled the prevalence of half a century ago with about half of young subjects today affected by myopia. By the end of this decade, 2.5 billion people, ie, one-third of the world’s population, may be shortsighted. Compared with 400 million people living with diabetes, this is a scary scenario. Myopia does not represent a refractive defect only, but a condition associated with retinal detachment, cataract, glaucoma and ultimately blindness. About one-fifth of the university population in East Asia has severe forms of myopia and will incur irreversible vision loss.
Despite the fact that sophisticated technologies and techniques for the refractive correction of myopia and the repair of retinal detachment secondary to this condition are available, the challenge is a better understanding of the pathogenesis of this disabling disease and finding adequate strategies for its prevention.
Animal models of myopia have been available since the 1970s, and this has supported the idea that behavior, environment and lifestyle may have a major role in this new epidemic despite the fact that for many years scientists believed that everything was caused by genes. This was due to the fact that myopia was more frequent in genetically identical twins than in non-identical ones. Also, more recent studies found a link between more than 110 regions of the genome and shortsightedness. However, lifestyle changes have been found to be significantly associated with an increased incidence of myopia. This is the case of adults of isolated populations who have a very low frequency of this defect whereas their children and grandchildren show myopia in half of the subjects.
New fascinating data are emerging in support of the fact that relatively inexpensive methods may effectively prevent the occurrence and worsening of myopia by modifying the lifestyles and environment of where our children grow and are educated.
For years, researchers believed that the increased incidence of myopia correlated with behavioral attitudes such as reading, studying and, more recently, working with computers, using smartphones and playing video games. All of those activities account for a significant amount of time during the day, especially in East Asian countries where teenagers spend an average of 14 hours per week on homework, compared with 5 hours in Europe. The tentative explanation was found in the growth and elongation of the eye secondary to continued close activities and efforts of focusing close-up images. Therefore, low-dose atropine eye drops have been proposed as a method to limit progression of myopia.
However, massive educational demand does not fully explain the epidemic.
More recently, time spent in outdoor activities has been reported as the most important protective factor related to myopia. More specifically, exposure to environmental light may protect against the development of abnormal eye elongation. This evidence was shown over a period of 3 years in Australian, Chinese and Taiwanese children who were at greater risk of developing myopia if they spent less time outside. This has also been shown in animal models that developed myopia under ocular occlusion conditions whereas were they protected from it when exposed to illumination similar to outside conditions. Biochemical data show that light exposure may interact with the dopamine cycle that in turn influences eye growth. This recent evidence has prompted health authorities from Asian countries to introduce more time spent outdoors for students and limit the time spent on homework.
As time passes, new notions on the multifactorial pathogenesis of myopia are becoming evident, giving hope to new modalities of prevention and early treatment based on behavior and lifestyle, which will hopefully reduce the need and resources for more invasive interventions for curing both the refractive error and the severe complications of this epidemic condition.
- References:
- Ashby R, et al. Invest Ophthalmol Vis Sci. 2009;doi:10.1167/iovs.09-3419.
- French AN, et al. Ophthalmology. 2013;doi:10.1016/j.ophtha.2013.02.035.
- Rose KA, et al. Ophthalmology. 2008;doi:10.1016/j.ophtha.2007.12.019.
- WU PC, et al. Ophthalmology. 2013;doi:10.1016/j.ophtha.2012.11.009.
- For more information:
- Paolo Lanzetta, MD, OSN Europe Edition Board Chairperson, can be reached at IEMO – Istituto Europeo di Microchirurgia Oculare, Via M.A. Fiducio, 8; 33100 Udine, Italy; email: paolo.lanzetta@iemo.eu.
Disclosure: Lanzetta reports no relevant financial disclosures.