By Raman P. Sah, B.Optom
Review of Optometry, January 2019
The rapid increase in myopia prevalence over the last 50 years has occurred simultaneously during a period of rapid technological advances, resulting in the dominant use of electronic devices for displaying everything from text, pictures, movies, games and more. As technology advanced, the spatial resolution of these displays improved from Video Home System (VHS) in the 1970s with resolutions of roughly 333 pixels by 480 pixels to current Macintosh retinal displays with native resolution up to 2,880 pixels by 1,800 pixels in 2018.1,2 However, as screen resolution improved, display sizes have reduced, and we now have high resolution (up to 2,436 pixels by 1,125 pixels) displays that are handheld (14cm by 7cm) that can be viewed at close distances without visual detection of individual pixels.
Also, as might be expected with these great advances, the prevalence of handheld electronic devices that children and teenagers use has grown exponentially. A 2017 report by the Common Sense Media, a nonprofit organization, suggests that 98% of households with kids under eight have a mobile device.3 It is also reported that 42% of children of age eight and younger now have their own mobile devices, with the average usage being two hours and 19 minutes.
A similar report cites that a majority of teenagers spend more than four hours per day with screen media.4 Therefore, children and teenagers are exposed to these short viewing distances and electronic displays for a significant amount of time. Could an unintended consequence of the improved display resolution in modern electronic displays be a worldwide myopia epidemic?
In a lab study, we examined the accommodative behavior of young children (ages seven to 16) when binocularly viewing different targets presented on electronic displays (as they do in real life), and monocularly. We quantified the accommodative lag in diopters of hyperopic defocus. Our results revealed that both emmetropic and myopic children experience typical lags of accommodation (mean +0.54D and +0.32D, respectively) at the routinely experienced viewing distances of these devices between 33cm and 20cm.5
Research with infant monkeys has shown that exposing young primates to artificially induced chronic hyperopic defocus will trigger compensating axial myopic eye growth.6,7 In our study, however, we did not find larger accommodative lags in children viewing the electronic displays than those shown in reports published previously for children viewing printed text materials.
Therefore, if the electronic displays are a contributing factor in myopia development, it is likely that they do so by increasing the amount of time children are exposed to hyperopic defocus and not the magnitude of the hyperopic defocus. In particular, recent studies on myopia control suggest that spending time outdoors might be a preventive factor for myopia.8 These electronic devices could indirectly be contributing to myopia development by influencing children to spend more time inside and less outside.
In general, myopia is considered to have a multifactorial etiology (combining genetic, environmental and hereditary influences), and studies show that early onset is often linked to increased myopia in adulthood. Thus, it is sensible to adopt preventive measures early in life with regular comprehensive eye examinations. Further research is needed to know what part, if any, controlling digital device use may ultimately play as a clinically recommended preventative measure in possibly minimizing myopia progression.
Dr. Sah is currently a Vision Science PhD student at Indiana University Bloomington and presented the study, “Accommodative Behavior and Behavior Defocus in Children Viewing Electronic Devices” at the 2018 AAO Meeting in San Antonio.
- Media Formats. ABS Techonologies. www.abstechnologies.net/abs/pdf/Media-Formats.pdf. Accessed January 2, 2019.
- MacBook Pro Technical Specifications. Apple. www.apple.com/macbook-pro/specs/. Accessed January 2, 2019.
- Common Sense Media. 2017 the Common Sense census: media use by kids age zero to eight. 2017;47:1–36.
- Mcclain-Delaney A. The Common Sense census: media use by teens and tweens. www.commonsensemedia.org/sites/default/files/uploads/research/census_researchreport.pdf. 2015. Accessed January 2, 2019.
- Yeo ACH, Atchison DA, Schmid KL. Children’s accommodation during reading of Chinese and English texts. Optom. Vis. Sci. 2013;90(2):156-63.
- Smith III EL, Hung L-F. The role of optical defocus in regulating refractive development in infant monkeys. Vision Res. Pergamon; 1999;39:1415–35.
- Smith EL, Bradley D V, Fernandes A, Boothe RG. Form deprivation myopia in adolescent monkeys. Optom. Vis. Sci. 1999;76:428–32.
- Xiong S, Sankaridurg P, Naduvilath T, Zang J, Zou H, Zhu J, et al. Time spent in outdoor activities in relation to myopia prevention and control: a meta-analysis and systematic review. Acta Ophthalmol.Wiley-Blackwell; 2017;95:551–66.