During the COVID-19 pandemic, youngsters’ screen time increased exponentially as they had to attend online classes frequently. In addition to that, video calls have also become the only possible way to get in touch with families and friends outside the Hong Kong Special Administrative Region. As a result, myopia (more commonly known as shortsightedness or nearsightedness) has deteriorated among youngsters.
In fact, even before the pandemic, the prevalence of myopia in certain age groups in Hong Kong had reached as high as 90 percent, one of the highest in the world, and compared with the prevalence of 5 to 10 percent in developing countries.
The reported overall prevalence of myopia in primary school students in Hong Kong was 36.71 percent in 1998-2000, 47.5 percent in 2005-2010, and 37.7 percent (54.7 percent in grade-six students) in a recent study done by this author in 2019. This is significantly higher than that reported in Beijing and Shanghai. The prevalence of myopia in Shanghai in 2016 was 3.4 percent, 6.0 percent and 12.7 percent in children aged 6, 7 and 8 years old respectively. In Beijing, myopia in children aged 7 to 11 years was 11.7 percent, 14.6 percent, 31 percent, 37 percent, and 46.7 percent respectively (data published in 2014). It’s believed the prevalence has further increased over the past two years because of wider use of online learning.
Myopia progresses at the fastest rate at 6 and 7 years old and tends to slow down after 11 and 12 years of age. Hence the population most at risk are primary-school children. In addition to the inconvenience of wearing corrective lenses, those with high myopia also have higher risk of various sight-threatening eye conditions, including glaucoma, retinal detachment and maculopathy. The earlier the onset of myopia, the faster the progression. If more than half of the students already had myopia by the completion of primary school education, a high proportion of them will develop high myopia (greater than 600 degrees). Almost 4 percent of myopic primary school children already have high myopia. It’s predicted that they will have a high chance of developing sight-threatening complications later in life.
According to our study, risk factors for myopia progression include young onset age, higher myopia at baseline, and having two myopic parents. Lifestyle factors include low outdoor activity and more time spent on near work.
The younger the onset age, the higher the degree of myopia is. Hence, preventive measures should start as young as possible. It’s believed that myopia is caused by a combination of genetic and environmental factors. Our researchers identified a higher proportion of moderate or high myopia in children with parental myopia, suggesting children with parental myopia are more likely to develop moderate or high myopia. Therefore, parents should be vigilant and bring their children for regular checkups at a young age.
The use of electronic devices is common among primary school students. The effect of near work on myopia development has been extensively studied for years. Our researchers noticed that it triggered a rapid progression of myopia. Just recently, I came across a 4-year-old child with 400 degrees of myopia, and another one with the progression of more than 200 degrees in a year, which would have been considered very rare in pre-COVID-19 times. These children usually will not notice any difficulty in looking at the screen at a short distance (during online classes), and hence they would not alert their parents for an early checkup.
Most recent studies demonstrate that outdoor activity time helps prevent myopia onset. Parents and educators should now rethink if we are doing the best for our children.
WHO estimates that 12.8 million children aged 5 to 15 are visually impaired from uncorrected or inadequately corrected refractive errors worldwide. In Hong Kong, a significant proportion of the children who ought to be wearing spectacles are not doing so. The main factors for the noncorrection of refractive errors include lack of awareness, unavailability and/or unaffordability of ocular examinations, non-affordability of corrective lenses, as well as cultural issues.
In Hong Kong, optometrists and opticians are readily available and the prices of corrective lenses are affordable. Therefore, a lack of awareness of the need for refractive correction may be the major contributing factor. Researchers of our study found that among children with myopia, less than 20 percent of the parents knew their children had refractive errors, and only 18 percent of the children wore glasses. There is also a misconception by parents that, once the children start wearing glasses, the degree of myopia will progress more rapidly. Therefore, even if they are told their children need glasses, many of the parents are reluctant to let their children wear glasses. This is especially a problem with children below the age of 8 years, because of the chance of lazy eye if they are not provided with proper glasses. Moreover, undercorrection of myopia might affect the students’ academic performances, since they may not be able to see the blackboard or screen clearly. They may not be able to focus and tend to be distracted from learning. Parents should be educated on the importance of optimal correction of their children’s vision, especially before the age when amblyopia may develop. In addition, the children, especially those in lower grades, might not be able to inform the parents of their visual problems. Parents need to have their children get regular eye checks to screen for any problems and correct them in time.
The good news is that there are ways to prevent myopia from getting worse. Orthokeratology (OK lenses) and atropine are effective in slowing the progression of myopia. Nowadays, preservative-free 0.01 percent atropine has gained much popularity because it is free from the potential sight-threatening complications of OK lenses, infective keratitis in particular. Early intervention of myopia control in high-risk children should be promoted, particularly among those with myopia onset at a very young age and/or those with (highly) myopic parents.
The author is an ophthalmologist and clinical associate professor at the University of Hong Kong.
The views do not necessarily reflect those of China Daily.