While the jury is out on why an increasing number of young children are being diagnosed with shortsightedness, a condition that makes distant objects appear blurry, ophthalmologists are focusing on promoting simple mantras that help protect vision.
With more than two dozen genes being linked to an increased risk of shortsightedness, or myopia, genetics does play a role, say medical experts. A study of more than 45,000 people from Europe and Asia, for instance, identified 24 new genes and confirmed the role of two in triggering shortsightedness, reported British researchers in the journal Nature Genetics last year. People who inherit some of these genes have a tenfold raised risk of being shortsighted.
In India, myopia affects about one in three people and 80% to 90% of people in East Asia, according to the study, which also found as many as 90% of children in the region to be short-sighted compared with less than 20% of them a few decades ago.
"An interaction between genes and the environment is believed to trigger myopia," says Dr Sri Ganesh, chairperson and medical director of Nethradhama Super Speciality Eye Hospital, Bangalore. "Ambient light levels in childhood are thought to affect the growth of the eyeball, with poorly-lit environments and prolonged indoor activity aggravating the problem."
Myopia is caused when the eyeball grows long, causing light to get focused just short of the light-sensitive retina at the back of the eye.
Shortsightedness has shot up in Indian children, with one in eight 12-year-olds needing glasses to read the blackboard, reported researchers from the All India Institute of Medical Sciences (AIIMS) in the peer-reviewed scientific journal PLOS ONE.
Shortsighted and aware of myopia's genetic link, Gurgaon resident Nishi Gandotra, 43, takes her daughter Nayesha, 13, for regular eye check-ups, and rations her screen time. (Sanjeev Verma/HT)
Published in February, the study screened close to 10,000 students in private and government schools in Delhi and found that 13.1% children at a mean age of 11.6 years were near-sighted, with myopia being more common in kids studying in private schools, those with shortsighted parents or siblings, and those with higher family incomes.
It was highest in kids who read for more than five hours a day, and watched television, or used computer, video and mobile games, for more than two hours. The AIIMS study also showed that only 5% shortsighted children were active for more than two hours outdoors, compared with 47.4% of children with normal vision, and less than one in four (24.7%) children wore appropriate spectacles.
OUT OF SIGHT
"Prolonged close work, looking at a book or screen at a distance of less than 30 cm for more than two hours a day, causes eyestrain and reduces blinking rate, signs of which include blurred vision and watery eyes," says ophthalmologist Dr Ritika Sachdev, director, medical services, Centre for Sight. "Add to this, reading in poorly-lit rooms, and you have children rapidly losing the eye's focusing ability."
Experts also stress that shortsightedness is not just an urban problem. Myopia's prevalence in 10- to 12-years-olds in rural Kerala was 51.47%, of which 43.1% were undiagnosed, reported K Rajendran in the journal Pediatrics, in November 2014.
Dr Ganesh says that close to 9,000 children with myopia visited Nethradhama in 2014-15, up from almost 7,500 children in 2012-13, and 7,762 in 2013-14. "As you can see, the numbers are steadily increasing every year, but not exponentially," he says.
However, kids who develop shortsightedness at a young age are more prone to suffer vision-related problems in mid-life. Refractive power usually shoots up in adolescence years when the eyes are growing, and it usually stabilises by age 20.
Three in four cases of impaired vision in India are caused by refractive errors, reported the National Blindness Survey 2002. Of the 1.1% of India's population with some degree of blindness, 19.7% lose vision because of refractive errors.
"Other than surgery, the options to reduce progression of myopia are very limited," says Dr Sachdev. " A drug called atropine reduces progression but I don't prescribe it, as it dilates the pupil and causes issues with light sensitivity and difficulty in reading."