Home confinement during the coronavirus disease 2019 pandemic was associated with a significant myopic shift among Chinese children aged 6 to 8, according to new research published in JAMA Ophthalmology.
Home confinement during the coronavirus disease 2019 (COVID-19) pandemic was associated with a significant myopic shift among Chinese children aged 6 to 8, according to new research published in JAMA Ophthalmology.1 However, because young children are in a critical period for the development of myopia (nearsightedness), this population’s refractive status may be more sensitive to environmental changes compared with older individuals.
By 2050, the World Health Organization (WHO) estimates half of the world’s population may have myopia, while in recent years, research has shown insufficient time spent doing outdoor activities is a major risk factor for myopia development, the authors wrote.
During the COVID-19 lockdown in 2020, it is estimated that over 220 million school-aged children and adolescents in China were confined to their homes. As a result, “concerns have been raised about whether the period of lockdown may have worsened the burden of myopia due to significantly decreased time spent outdoors and increased screen time at home.”
To investigate the association of home confinement with myopia development in this population during the lockdown, the researchers assessed annual photoscreenings performed on children attending 10 elementary schools in China.
The screenings took place each September from 2015 through 2019. In 2020, because schools were closed from January through May, photoscreenings took place in June. All students who routinely wore contact lenses were asked not to wear them on the day of the screening while whose who wore glasses took them off for the refraction test. In addition, “students with current corneal refractive therapy (ortho-K) were also asked not to wear the ortho-K lenses the night before the screen date and wear eyeglasses instead on the screen date.”
The researchers defined myopia as a spherical equivalent refraction (SER) of −0.50 diopters (D) or less. Age of children reported in the study refers to the age at time of screening.
A total of 194,904 test results from 389,808 eyes were included in the analyses, with 123,535 children undergoing screening. Ages ranged from 6 to 13 years, and the number of observations for reach child ranged from 1 to 6 (as some were screened in consecutive years).
Most of the increased cases of myopia were considered mild. But based on the findings, the authors argued that if home confinement is necessary, “parents should control the children’s screen time as much as possible and increase the allowable outdoor activity while maintaining safe social distancing.”
Despite the fact that older children (grades 3-6) completed more intense daily online learning courses (2.5 hours) compared with younger students (grades 1-2, 1 hour daily), those aged 6 through 8 exhibited higher rates of myopia than the older cohort. This finding led researchers to hypothesize that younger children are more sensitive to environmental changes than older children. Specifically, between ages 6 to 8, “the plasticity of myopia is high and myopia control may be easier. Beyond this age window, the plasticity of myopia is low and myopia is harder to control during environmental changes.”
To determine whether the myopic shift is temporary or permanent and if it is reversible, the researchers plan to follow-up with the same population in the future.
A lack of data on preschool-aged children, and information on the ocular biometry, including axial length and cornea curvature, mark limitations to this study. In addition, the researchers did not include the number of children who participated in the screenings each year.
In an accompanying commentary,2 experts highlighted the clinical relevance of the age shift, as it is well recognized that age of myopia onset corresponds to final refractive error at adult ages.
“The higher the refractive error, the more likely the occurrence of sight-threatening complications, such as myopic retinal degeneration, glaucoma, and retinal detachment,” they wrote. “Given that 1 in 3 people with high myopia becomes severely visually impaired, mostly at working age, it is clear that China is facing a serious public health problem. Much of the rest of the world may be likely to follow.”
1. Wang J, Li Y, Musch DC, et al. Progression of myopia in school-aged children after COVID-19 home confinement. JAMA Ophthalmol. Published online January 14, 2021. doi:10.1001/jamaophthalmol.2020.6239
2. Klaver CCW, Polling JR, and Enthoven CA. 2020 as the year of quarantine myopia. JAMA Ophthalmol. Published online January 14, 2021. doi:10.1001/jamaophthalmol.2020.6231