While prolonged use of smartphones and other digital devices has long been linked to nearsightedness, a rare eye ailment is becoming more common in today's digital age, with those impacted, particularly young people, having an eye turn inward, making them appear cross-eyed.
The condition known as acquired esotropia — a form of "smartphone strabismus" in which one eye directs toward the nose while the other eye remains in a natural position — is being seen more and more frequently among young people in Japan.
Photo courtesy of Hamamatsu University School of Medicine, Kyodo News
Experts warn that excessive use of digital devices can contribute to the condition's onset, recommending that people promptly see an ophthalmologist if they notice abnormalities such as children's eyes that do not align properly, since it is treatable if caught early. Strabismus is a misalignment of the eyes, often causing double vision or difficulty in depth perception.
According to a study conducted by Kyoto University, approximately one in 50 people in Japan have strabismus, and the most common type among Japanese is "external strabismus," in which one eye deviates outward.
In recent years, however, as people use smartphones, tablets and gaming devices for longer periods at a time, it has been reported both in Japan and abroad that "internal strabismus" is on the rise.
In particular, there has been a sharp increase in the number of publications on acute esotropia, rather than congenital forms of the condition, since 2020 when the coronavirus pandemic forced people indoors and onto their addictive devices.
Back in 2020, at a public lecture entitled "Lights and Shadows of Smartphones" sponsored by the Science Council of Japan, experts introduced data showing that myopia in children is rapidly increasing worldwide, and has tripled in Japan in the last three decades. In addition, there is also an increased risk of strabismus, caused by lying down and looking at screens and having the focus shift from side to side, or having the screen too close to the eyes.
Kyoko Ono, a professor of Tokyo Medical and Dental University Hospital's department of ophthalmology, cautioned that staring at small screens up close on a smartphone is "a strong stimulus that the human eye had never experienced before."
"Some data show that people who use smartphones frequently underestimate the amount of time they spend using them," she said. "In children, we hope that parents will manage the time of use properly and ensure that they have time to play outside."
According to a survey conducted by the Cabinet Office on the average daily internet usage time, elementary school students spent 118 minutes, junior high school students 164 minutes and high school students 217 minutes with their devices in fiscal 2018. In fiscal 2022, they spent 214 minutes, 277 minutes, and 345 minutes, respectively — an increase of approximately 100 to 130 minutes in each group.
The Japanese Association for Strabismus and Amblyopia and the Japanese Association of Pediatric Ophthalmology called on ophthalmologists to track the use of digital devices and the course of the condition nationwide.
As a result, 194 patients with acute acquired strabismus developed within a year were registered. Those whose condition was brought on by accidents or brain abnormalities were excluded from the study.
Those surveyed ranged in age from 5 to 35, with the highest number of sufferers being 16 years of age. Those experiencing a higher frequency of the condition were middle and high school students, followed by elementary school students.
Only people who used smartphones or other devices for 60 minutes or more per day for elementary school students and younger, and 120 minutes or more for middle and high school students and older were defined as the excessive use groups.
Excluding those who did not use devices, there were 156 in the overuse group and 25 in the non-overuse group.
The overuse groups were instructed to limit their use of devices to under the excessive times. They were also required to keep at least 30 centimeters between their eyes and the devices and to take 5-minute breaks every 30 minutes of viewing time. Changes were examined after three months.
The results showed that 68, or 44 percent, of the patients in the overuse group improved their strabismus symptoms, but only 10 of such patients were completely cured. The majority, 88, or 56 percent, had either no change in symptoms or saw their conditions worsen.
Many of those who were cured had less severe strabismus at the onset of their diagnosis and were able to reduce their viewing time by more than half of the original time. Conversely, those whose strabismus was quite advanced at the time of their diagnosis and those who did not reduce their viewing time got worse.
The degree of strabismus is diagnosed by measuring the angle of the deviation and the ability for a patient to perceive depth and three-dimensional space.
"Symptoms are easily improved by seeing a doctor while they are mild, said Miho Sato, a visiting professor of ophthalmology at Hamamatsu University School of Medicine who compiled the survey.
Provided by Kyodo News
"It's also clear that the symptoms can be improved by changing the way people use their digital devices, such as by reducing the amount of time spent on them or by looking at the devices at a distance."
"But once the disease develops, it can be cured only in very mild cases, even if the method of use is improved, so it is advisable to prevent it by using devices properly," she added. According to Sato, strabismus can occur regardless of excessive use of digital devices. When improvement cannot be expected from changes in device usage, injections into the eye muscles to make them less likely to lean in, or surgery to shift the position of the eye muscles, are other options.