Summary

Myopia, commonly called nearsightedness, is a refractive error of the eye in which distant objects appear blurred while close objects remain clear. Since the release of the 1989 National Academies of Sciences, Engineering, and Medicine’s report, Myopia: Prevalence and Progression, the prevalence of myopia has increased globally. At the same time, understanding of myopia has been enhanced by advances in genetics, ocular imaging, epidemiology, and physiology, by new investigations employing animal models, by research on the visual environment, and by clinical trials of intervention strategies. This includes a growing body of evidence suggesting that increased risk of myopia may be associated with deficient outdoor exposure. Spending time outdoors, particularly in natural sunlight, appears to stimulate specific retinal pathways that have a protective effect against myopia development. Other developments since the 1989 report was released include new approaches to measuring the prevalence, prevention, and treatment of myopia. It is clear there is potential for more progress with concomitant research.

The National Academies appointed the Committee on Focus on Myopia: Pathogenesis and Rising Incidence to identify and assess the current mechanistic understanding of myopia pathogenesis and the causes of myopia’s increased prevalence, to identify knowledge gaps and barriers to progress, and to develop a research agenda aimed at better understanding the biological and environmental factors that could explain its increasing incidence. Experts in vision science, visual neuroscience, ophthalmology, optometry, physical and physiological optics, experimental methodology, human factors, genetics, computer sciences, psychology, population studies, and healthcare delivery, organization, and financing were considered for committee membership to address the committee charge from a holistic perspective.

To carry out its charge, the committee reviewed the literature on six topics: global data on myopia prevalence, technologies to assess and diagnose myopia, environmental and genetic contributions to myopia onset and progression, the mechanistic causes of myopia pathogenesis, treatment optics for myopia, and barriers to vision care for children with myopia. The major conclusions and recommendations are summarized below.

UNDERSTANDING MYOPIA AND ITS PREVALENCE

Conclusions: The prevalence of myopia appears to be increasing worldwide, including in the United States. Most research comes from international studies, with limited evidence available in the United States due to a lack of standardized definitions of myopia, irregular and inconsistent screening practices locally to nationally, and the use of varied assessment techniques. (Conclusion 3-1)

Recommendations: The Centers for Disease Control and Prevention and state health departments should collect consistent, harmonized data on the prevalence of myopia in the

United States, prioritizing longitudinal surveillance on refractive error prevalence in children using standardized procedures (Recommendation 3-1). Furthermore, the Centers for Disease Control and Prevention should coordinate with the World Health Organization to create consistent, harmonized definitions and monitoring methods that would benefit the global community (Recommendation 3-2).

ASSESSMENT AND DIAGNOSTIC TECHNOLOGIES

Conclusions: There is no consensus as to the mandatory assessment and diagnostic components of a clinical examination of the myopia patient (Conclusion 4-1). Diagnostic technologies sensitive to newly understood biomarkers are under development that may improve diagnostics, management, and understanding of myopia (Conclusion 4-2).

Recommendations: To obtain a consistent retinoscopy/refractive reading, ophthalmologists and optometrists should use cycloplegic eye drops (which temporarily dilate the pupil and prevent the eye’s crystalline lens from changing focus) in children (Recommendation 4-1). Researchers and developers of assessment and diagnostic technologies should design assessments and tests to better understand the myopic eye, its development, and its environment (the visual diet). This could lead to better methods to identify myopic eyes and those at risk for myopia (Recommendation 4-2).

ONSET AND PROGRESSION OF MYOPIA

Conclusions: Environmental factors, particularly the protective effect of outdoor time during daylight, appear to play a significant role in myopia development, suggesting a larger influence than genetics (Conclusions 5-1, 5-2). Important gaps in knowledge exist as to the impact on myopic eye growth of “near work” (such as reading, with the eyes focused up close), both with and without electronic devices (Conclusions 5-3, 5-6). While evidence suggests other aspects of the visual diet (like spectra and contrast from different light sources) also affect eye growth, important details are lacking (Conclusions 5-4, 5-5).

Recommendations: The Centers for Disease Control should produce evidence-based guidelines, supported by Departments of Education and healthcare providers, promoting more time outdoors (at least one hour per day) for children (Recommendation 5-1). The National Institutes of Health and other funding agencies should solicit and fund research to investigate novel questions about the genetic and environmental mechanisms in myopia (Recommendation 5-2).

MYOPIA PATHOGENESIS: FROM RETINAL IMAGE TO SCLERAL GROWTH

Conclusions: Retinal images regulate eye growth, with the entire retina (not just fovea) playing a critical role (Conclusion 6-1). The retinal network, which encodes light intensity, provides a mechanistic link between reduced time outdoors and increased incidence of myopia that is supported by multiple lines of evidence (Conclusion 6-2). The specific retinal image properties and mechanisms encoding the retino-scleral signaling cascade for homeostasis of eye growth are currently unknown (Conclusion 6-3). Animal models have provided important insights into

potentially conserved processes controlling postnatal eye growth, such as visually driven signaling events in the retina, retinal pigment epithelium, and choroid that regulate the rapid remodeling of the scleral extracellular matrix, thereby changing eye size and refraction (Conclusions 6-4, 6-5).

Recommendations: Funding agencies, including the National Institutes of Health, the National Science Foundation, the Department of Defense, and private foundations, as well as industry, should seek to fund proposals across disciplines for both human and animal studies to investigate the mechanisms of emmetropization and myopia, including candidates for retino-scleral signaling, retinal neurons that detect the sign of defocus, the role of the choroid in regulating eye growth, the changes in the sclera that lead to axial elongation, gene–environment interactions, and the development of in-vitro experimental models (Recommendation 6-1). Furthermore, these funding agencies should target audacious proposals to foster the innovative, multi-disciplinary research that is needed to fully harmonize our understanding of the visual information processing by the retina that leads to changes in scleral remodeling (Recommendation 6-2). The field of myopia research should adopt an approach that considers the whole retina rather than the fovea alone (Recommendation 6-3).

CURRENT AND EMERGING TREATMENT OPTIONS FOR MYOPIA

Conclusions: Treatment options for myopia progression have increased in the last 20 years and include multifocal optical corrections and the sole pharmacological treatment: atropine eye drops (Conclusions 7-1, 7-2). Time outdoors during daylight is an emerging treatment strategy, especially in the younger years (Conclusion 7-3). Further research is needed to understand the mechanism of action of the current treatments that have limited effects and can cause rapid eye growth after cessation of treatment (Conclusions 7-4, 7-5). Safety of myopia treatments is paramount due to the probable need for daily applications (e.g. of atropine) for a decade or more of life (Conclusion 7-8). The current state of knowledge of treatment options reflects our limited understanding of both the fundamental mechanisms of eye length regulation and how treatments act to alter the progression—and perhaps even the onset—of the disease (Conclusion 7-9).

Recommendations: Funding agencies, including the National Institutes of Health, Research to Prevent Blindness, and others, should support research to develop new treatment strategies for myopia as well as to determine the mechanisms underlying current treatments. Progress in this area needs intentionally integrated, multidisciplinary research in basic and clinical vision science to understand the mechanisms by which therapies can control eye growth (Recommendation 7-1). Scientists should develop treatment strategies to minimize short- and long-term side effects and maximize safety (Recommendation 7-2). Funding for multi-center randomized clinical trials should be directed toward longer-term human studies, starting at earlier ages, to determine long-term benefits with respect to ultimate refractive error and ocular health (Recommendation 7-3).

IDENTIFYING CHILDREN WITH MYOPIA AND THE LINKS TO TREATMENT: METHODS AND BARRIERS

Conclusions: Multiple socioeconomic barriers to vision care for children exist, with the most significant being an uneven awareness of the importance of checking children’s ocular health, parents’ difficulties in gaining access to an eye care professional, and barriers to compliance with prescribed treatments (Conclusion 8-1). Vision screening and referrals are important for identifying children with vision impairment and facilitating access to treatment (Conclusion 8-2).

Recommendations: The U.S. Department of Health and Human Services, in collaboration with departments of education at the state level, should take measures to ensure that children receive a vision screening before first grade and a comprehensive eye exam when needed. (Recommendation 8-1). An integrated, national data surveillance system is needed for collecting state-level data on vision screening, referrals to eye care providers, sociodemographics (age, race/ethnicity, sex, and geographic location) and outcomes of referrals. This data system would not only enhance care integration and communication but also enable monitoring to ensure that follow-up care is received, especially in high-risk populations (Recommendation 8-2).

Myopia is a disease with increasing worldwide prevalence and severity--recognition of the impact of its downstream complications needs to be taken seriously. Importantly, the committee recommends that the Centers for Medicare & Medicaid Services classify myopia as a disease and therefore a medical diagnosis (Recommendation 8-5). This reclassification is to ensure efforts are undertaken not only to treat blurry vision resulting from uncorrected or undercorrected refractive error but also to ensure that stakeholders such as federal and state agencies, professional associations, patients, and caregivers are investing in the prevention and management of myopia. Funding agencies should support innovative, multidisciplinary research to identify mechanisms and novel treatments for myopia. Collaborative efforts involving healthcare providers, policymakers, researchers, and funding agencies are essential to tackle this disease effectively.