Childhood myopia rate hits record high in Hong Kong

Myopia prevalence in school-age children has reached record high in Hong Kong and may remain high over the next few years, a cross-sectional study by researchers from the Chinese University of Hong Kong (CUHK) has found.

“Hong Kong tops the world ranking for myopia prevalence, with the condition affecting 40 percent of children aged 8.5 years,” said Professor Clement Tham of the Department of Ophthalmology and Visual Sciences, CUHK. The situation worsened with previous COVID-19 restrictions, which led to reduced time outdoors and increased use of digital devices for online learning among children. [JAMA Netw Open 2023;6:e234080]

The researchers conducted a population-based, repeated cross-sectional study to determine the prevalence of childhood myopia before (2015–2019), during (2020) and after (2021) COVID-19 lockdowns. Children aged 6–8 years (n= 20,527; mean age, 7.33 years; male, 52.8 percent) from the Hong Kong Children Eye Study were recruited.

“The COVID-19 pandemic has triggered a ‘myopia boom’ in school-age children,” noted Tham. Myopia prevalence was stable in 2015–2019 (23.5–24.9 percent; p=0.9), but markedly increased to 28.8 percent (p<0.001) during the COVID-19 pandemic. The prevalence soared to a record high of 36.2 percent (p<0.001) after COVID-19 lockdowns.

Notably, the prevalence doubled (from 12.7 percent in 2015 to 25.0 percent in 2021) in children aged 6 years after COVID-19 lockdowns. “Myopia is irreversible once it has developed. The earlier its onset, the higher the risk of developing high myopia later in life, which in turn increases risks of glaucoma, macular degeneration, cataracts, retinal detachment and blindness,” highlighted Professor Calvin Pang of the Department of Ophthalmology and Visual Sciences, CUHK.

“Our data showed that children’s lifestyles did not return to pre–COVID-19 levels after resumption of face-to-face lessons,” said Dr Xiu-Juan Zhang of the Department of Ophthalmology and Visual Sciences, CUHK. Mean time spent outdoors before the COVID-19 pandemic was 1.40–1.46 hours/day between 2015 and 2019, which decreased significantly to 0.85 hours/day in 2020 and 1.26 hours/day in 2021 (both p<0.001). An increasing trend was observed for near work and screen time.

“Parental myopia is one of the strongest factors associated with childhood myopia. In the study, however, children with both parents without myopia also developed myopia to a larger extent than before the pandemic,” added Zhang.

Risk factors of developing childhood myopia during the pandemic included younger age (odds ratio [OR], 1.84; 95 percent confidence interval [CI], 1.76–1.93; p<0.001) and low family income (ie, below HKD 25,000/month; OR, 1.05; 95 percent CI, 1.00–1.09; p=0.04). Children from low-income families had more near work (mean, 5.16 hours/day vs 4.83 hours/day) and longer screen time (mean, 3.44 hours/day vs 2.90 hours/day) vs children from higher-income families.

“Given the lifestyle changes, prevalence of childhood myopia may remain high over the next few years,” anticipated Zhang. In the context of the myopia boom, the researchers are recruiting children aged 4–12 years with myopic refraction of -1.0 D to -10 D and astigmatism of <2.5 D into the LAMP3 trial, which investigates the efficacy and safety of low-concentration atropine eye drops plus red-light therapy. Interested parties may contact the research team through WhatsApp (9137 1925) or email (childreneye@cuhk.edu.hk).