Buildings, Lighting, and the Myopia Epidemic

Myopia, also known as nearsightedness, is an eye disease that most often begins in early childhood and progresses through late adolescence. It was once relatively rare, but within a few generations it has grown in prevalence (Morgan et al. 2018; Williams et al. 2015), and is now a global epidemic of astonishing proportions (WHO 2016). Holden et al. (2016) predict that 50% of the world’s population will be afflicted by 2050, up from 34% today and 23% in 2000. A severe form of myopia (high myopia) is associated with increased risk of vision loss through glaucoma and retinal detachment (Williams and Hammond 2019). Current myopia interventions emphasize clinical treatments rather than prevention and focus on medications and refractive correction (Cooper and Tkatchenko 2018). Uncorrected refractive error has been estimated to cost more than $200 billion annually in global GDP (Naidoo et al. 2019).

Many factors have been considered in myopia causation. Studies of genetic predisposition showed that the effect of any individual gene is small (Morgan and Rose 2019) and could not explain accelerating prevalence of the disease. This has refocused the myopia field on the question of whether changes in the human living environment are causing myopia. This thought progression is logical, not only because genetics are an inadequate explanation, but also because eye growth and focal length optimization are light-dependent.

In the category of environmental influences, it has been proposed that excessive focus on nearfield visual tasks (Morgan et al. 2021; Wildsoet et al. 2019), circadian rhythm disruption (Chakraborty et al. 2018; Stone et al. 2013), and geographical and seasonal factors that influence light exposure (Cui et al. 2013) might be causative. However, in addition, and germane to this discussion, epidemiological studies have repeatedly shown that time spent outdoors is associated with myopia reduction (Sherwin et al. 2012; Xiong et al. 2017), while time spent indoors is a risk factor (Morgan et al. 2021). What is it about the outside lighting environment that can protect against myopia? Recent basic science discoveries have helped to crystalize a hypothesis.

The light sensing proteins of animals are called opsins (Shichida and Matsuyama 2009). The human eye contains at least six opsins, four of which are involved in our visual function through rod and cone photoreceptors. The remaining two are the so-called nonvisual opsins, melanopsin (OPN4) and neuropsin (OPN5). Preclinical studies have implicated all six opsins in the regulation of eye growth and optimization of focal length (Brown et al. 2022). Melanopsin has a peak light sensitivity around 480 nm, a sky-blue color. This opsin has a role in systemic circadian function, but also regulates eye growth and focal length through its retinal expression (Chakraborty et al. 2022). Neuropsin is of special interest for this discussion because it has a peak sensitivity at 380 nm, a violet wavelength that is at the edge of visual perception for most adults. As with melanopsin, preclinical studies of the violet light-OPN5 response have shown that it regulates eye growth and focal length (Jiang et al. 2021). More specifically, when OPN5 is stimulated by violet light, myopic elongation of the eye is suppressed (Jiang et al. 2021). These basic science findings are complemented by studies performed in humans: Torii et al. (2017a) found that myopic children with corrective lenses that transmitted violet light had less myopic progression than those with lenses that blocked violet light. Likewise, in myopic adults, Torii et al. (2017b) found that wearing lenses with more violet light transmittance was associated with less myopic progression. When combined, these studies have led to the hypothesis that the myopia boom (Dolgin 2015) may be caused by a modern lifestyle that results in insufficient exposure to the violet light that stimulates OPN5 (Jiang et al. 2021).

How then, does this relate to buildings? Is there something about spending time inside of buildings that increases the risk of myopia? What is it about the modern built environment that may be exacerbating myopia risk? Might it be possible to design and engineer indoor environments to lessen the risk of myopia onset and progression, especially for the children and adolescents who are most at risk? The rapid increase in myopia prevalence makes clear that population-scale factors are at play, likely related to culture and environment. Population scale interventions may therefore be the most effective prevention strategies—and building design is one place where population scale changes can be most persistent. This may also be an opportunity to design a myopia prevention strategy, and prevention is always better than treatment.

There are many trends in building design that limit exposure to the shorter light wavelengths that are abundant in unfiltered daylight outdoors. These trends include rapid urbanization and increasing urban densities; proliferation of deep plate, high rise, and underground buildings that reduce or eliminate daylight exposure; energy policies that reduce allowable window areas and promote the use of “high-performance” glazing assemblies that specifically reduce transmission of short wavelength light; and increasing reliance on electric lighting that does not produce violet wavelengths.

In consideration of the above, we believe it is appropriate to acknowledge that buildings have likely been playing a role in the myopia epidemic. Hobday (2016), for example, has raised concerns about how school design and policies may be affecting the prevalence of myopia. Indeed, school schedules that include more time outdoors have been shown to reduce myopia onset and progression (Wu et al. 2013) and come with a host of other benefits (Jucker and von Au 2022). Realistically, however, moving more of the school day outdoors requires changes to educational infrastructure, public support, and political will, and is impractical as a universal panacea (Heschong 2021). Against this backdrop, what can building professionals do?

Though we do not yet have a comprehensive answer to that question, two areas of concern are particularly relevant to the lighting community. The first is the use of glazing materials that substantially change the spectral distribution of daylight. These include low-e coatings that greatly narrow the spectrum of transmitted light, reflective coatings and tints that vary greatly in their spectral transmission properties based on color and chemistry, and dynamic glazing systems, such as electrochromic glazing that can simultaneously change the spectral properties, timing, and relative intensity of daylight illumination. The second area of concern is electric lighting, which has traditionally been deficient in the shortest visible wavelengths of interest from 350 nm to 480 nm. Should the spectral power distributions of common LED products be modified? Might we consider yet another metric of lighting performance, beyond visual and circadian stimulation? And while human health must always surface as a top priority, there are pros and cons to short-wavelength light that need to be considered and balanced. We reiterate that children are the most vulnerable—lighting design for myopia prevention may therefore be most crucial in school and home environments, but less important for buildings only occupied by adults.

In addition, eye health is not currently on the building science community’s research roadmaps. There is little awareness among glazing manufacturers and the energy policy establishment of how the selective filtering of violet radiation may be inadvertently contributing to myopia onset and progression. Yet, buildings designed and built today will influence the health of building occupants for generations. To what degree and in what ways can daylighting design and electric lighting support ocular development and eye health?

Given the strong evidence that eye health is influenced by the characteristics of light in buildings, and the seriousness of the consequences, we believe that it is urgent to include eye health in energy and climate policies that are now being formulated. We invite the lighting community to work toward deeper understanding of how daylighting and electric lighting design may impact eye development and health. If buildings are to play a role in reversing myopia trends, it is building professionals who will need to step up, prioritize myopia risk, and exhibit the collective will to design and engineer buildings that support eye health. We encourage you to join this cause.