Another Insight Into COVID-19–Associated Nearsightedness

In a May 2020 Letter to the Editor, Pelligrini et al¹ noted the possibility that prolonged home confinement due to the COVID-19 pandemic could result in more myopia development and worsening of preexisting myopia among children. The authors termed this quarantine myopia and observed that this would represent a serious public health concern owing to myopia-associated visual disability that would particularly affect children in low- and middle-income countries and the known sight-threatening complications in later life associated with high myopia. In an article from July 2020, Wong et al² reviewed studies that evaluated the association of myopia onset and progression with digital device use, near work, and outdoor time and concluded that these direct associations could result in increased myopia development and progression not only during the COVID-19 pandemic, but also beyond if behaviors such as increased use of digital devices continued after COVID-19. Recommendations were made to mitigate these factors for parents, schools, eye care professionals, and government agencies, which were promoted in a September 2020 article by Wong.³

We now have supportive evidence from several studies documenting what was considered a possibility has indeed happened. Wang et al⁴ evaluated noncycloplegic refractive error values from annually performed screenings of 123 535 children aged 6 to 13 years from 10 elementary schools in Shandong, China. During the 5 years preceding the COVID-19 pandemic, mean spherical equivalent refraction (SER) values were relatively stable within all age groups, whereas in the June 2020 screenings that took place when schools reopened after 5 months of home confinement, the mean SER reflected a myopic shift of about −0.3 diopters (D) and the prevalence of myopia (defined as a SER of −0.50 D or less) was substantially higher, especially among younger children. A second report relied on information from the 2019 and the June 2020 National Student Physique and Health Survey data. Students from primary grades through high school from Chongqing, China, were randomly selected from the 2019 and 2020 surveys (n = 1728 and 1733, respectively), which included refractive data recorded by an optometry unit. The overall percentage with myopia (defined as a mean uncorrected visual acuity <5.0 with a mean SER <−0.50 D) in 2019 was 44.62% and increased to 55.02% in 2020 (P < .001), with significant differences in the same direction found in the primary, junior, and high school student groups.⁵

In the current study, Hu et al⁶ had access to cycloplegic refraction values collected on second- and third-grade students in Guangzhou, China. A nonexposure group (n = 1060) included students who were examined in late 2018 (grade 2) and then in late 2019 (grade 3), and an independent exposure group (n = 1054) included students examined in late 2019 (grade 2) and again in late 2020 (grade 3). Compared with the unexposed group, the exposed group experienced a 0.36-D greater myopic shift in SER, an increased axial length of 0.08 mm, and a 7.9% higher incidence of myopia (defined as a SER <−0.5 D). The 95% CIs of all 3 measures excluded 0. This study adds substance to the prior reports because it relied on cycloplegic (rather than noncycloplegic) refractive data, it included axial length data, and its longitudinal data allowed for comparing changes in refraction of 2 independent groups of students in the second and third grades. The cross-sectional nature of the 2 prior studies did not provide information on each child’s change over time.

The 3 studies varied somewhat in their definition of myopia, and information is lacking on factors consistently associated with myopia risk, such as the amount of daily time children spent outdoors, their screen time, or their near-work time, which would allow for associating these exposure variables with the myopia outcome. However, they do show consistent increases in measures of myopia from the pre–COVID-19 to the COVID-19 period wherein these risk factors were affected negatively. Of note is the consistency, temporality, strength, and plausibility of the findings, which are among the important criteria that Hill⁷ posed for establishing a causal relationship. The fact that these studies’ findings are all based on large groups of school children being monitored for vision in China may raise questions regarding external validity, but this should not detract from the message they convey that the dramatic changes in children’s lives caused by the pandemic consistently, across numerous independent studies, have been associated with a greater myopic shift in second and third graders. These findings should prompt parents, schools, and governmental agencies to recognize the potential value of providing children with outdoor activity time and monitoring how much time is spent on near work. Attention to this could be one positive outcome within the many devastating outcomes of the COVID-19 pandemic.

Corresponding Author: David C. Musch, PhD, MPH, Kellogg Eye Center, 1000 Wall St, Ann Arbor, MI 48109 (dmusch@med.umich.edu).

Published Online: September 16, 2021. doi:10.1001/jamaophthalmol.2021.3564

Conflict of Interest Disclosures: None reported.