The COVID-19 lockdown last spring prompted many individuals across the globe to pause routine health care. Looking into how this impacted eye care, a new study found an acceleration of myopia progression in both Chinese children and teenagers during this time period; however, the trend was reversed after lockdown, suggesting that both accommodative spasm and structural change may have been contributing factors.
The investigation included 59,000 eyes of 30,000 participants enrolled in the Myopia Screening Survey of Children and Teenagers in Schools, a six-cohort study conducted in 46 primary and junior high institutions in Hangzhou, China. The first participants were examined in early 2019, with follow-ups performed at six-month intervals. The COVID-19 lockdown occurred during period two.
Presenting visual acuity (VA) was defined as either corrected VA in students with glasses or uncorrected VA. Refractive error was estimated through noncycloplegic autorefraction, and the spherical equivalent refraction (SER) was calculated as a sphere power of +0.5 cylinder power. Myopia of one eye was defined as SER of -0.5D or less, and high myopia was defined as SER of -6.0D or less. Myopic progression was defined as greater negative SER in the same eye.
The rates of myopia and high myopia at rounds one through four were 48%, 53.2%, 73.7% and 67.9% and 1.3%, 1.9%, 2.8% and 2.7%, respectively, which showed a general upward trend with a slight decrease at round four.
The mean rates of SER change during the first three periods were -0.030D, -0.074D and 0.016D per month, respectively, which reflected negative deviations in the first two and a positive shift in the last.
Considering age and gender, the differences in myopic proportion and SER were significant in rounds three and four, but not in round two. In round three, a greater risk of high myopia was noted; however, younger age and male gender were linked to a lower risk of myopia progression. Rounds one and two showed equal prevalence rates for myopia and SER, while round three curves were notably more myopic. The differences in the various rounds were more pronounced in younger students.
Additionally, the difference in SER change across the three survey periods was more remarkable in younger students, which indicated these individuals were more sensitive to myopic progression during the lockdown, the researchers said.
Also of note, the rate of myopic progression was greater during period two, followed by a hyperopic progression during period three. “We speculate that this may be explained by accommodative spasm during lockdown,” the researchers wrote in their paper. During the lockdown, restricted outdoor time, increased screen time and limited indoor space may have caused accommodative spasm in the students, which could have caused increased myopic progression, the researchers said.
At round four, which was about half a year after the lockdown was lifted, the accommodative spasm reversed, and the refractive state consequently became more hyperopic.
Caution should be exercised when interpreting evidence in other populations that live in different areas, the investigators suggested.
Chang P, Zhang B, Lin L, et al. Comparison of the myopic progression before, during and after COVID-19 lockdown. Ophthalmology. March 16, 2021 [Epub ahead of print].