The Rapid Increase of "Smartphone-Induced Acute Internal Strabismus" — Protecting Children Worldwide

Table of Contents

1. Introduction: What is Happening Now

2. Trends in Cases and International Comparison

3. What is Smartphone-Induced Acute Convergent Strabismus: Medical Mechanisms

4. Risk Factors: Usage Time, Distance, Age, and More

5. Impact of the Pandemic

6. Preventive Measures: 30-30-20 Rule and Lifestyle

7. Latest Insights on Diagnosis and Treatment

8. Actions for Families, Schools, and Government

9. Recommendations for the Industry: Tech Solutions

10. Conclusion: Protecting "Vision Power"

1. Introduction: What is Happening Now

On July 8, 2025, TBS NEWS DIG reported a sharp increase in cases of "smartphone-induced acute convergent strabismus" among elementary, junior high, and high school students in Kumamoto Prefecture. While the peak is during adolescence, cases among lower-grade elementary students are also becoming noticeable.newsdig.tbs.co.jp

A nationwide multi-facility survey released by the National Center for Child Health and Development around the same time found that of the 656 cases diagnosed with AACE between 2019 and 2024, 83% regularly engaged in prolonged close-range smartphone viewing.ncchd.go.jp

2. Trends in Cases and International Comparison

Similar surges have been reported in Asia, including South Korea, Taiwan, and China. According to the Taiwan Ophthalmological Society's national registry, the number of new AACE cases in 2024 was 2.8 times higher than in 2015.pmc.ncbi.nlm.nih.gov

In Europe and the United States, regions with high digital device usage rates have seen an increase in pediatric strabismus consultations. The Royal College of Ophthalmologists in the UK has issued a statement saying, "Prolonged near work during school years, regardless of whether for gaming or learning, is the greatest risk."

3. What is Smartphone-Induced Acute Convergent Strabismus: Medical Mechanisms

AACE is characterized by rapidly occurring concomitant esotropia without brain tumors or trauma, and it does not involve extraocular muscle paralysis. It is believed that strong accommodative demand and excessive convergence from close work sustain the tension in the medial rectus muscle via the trigeminal reflex, leading to a breakdown in binocular vision. bmjophth.bmj.compmc.ncbi.nlm.nih.gov

MRI findings show few abnormalities in the extraocular muscles themselves, suggesting that the main cause is the breakdown of neurological adaptation due to excessive near work. A review from Taiwan points out that latent strabismus can easily manifest in a short period when the "plasticity limit of accommodative tension" is exceeded.pmc.ncbi.nlm.nih.gov

4. Risk Factors: Usage Time, Distance, Age, and More

A prospective study in BMJ Ophthalmology identified independent risk factors for onset as viewing distance less than 30 cm, continuous viewing over 30 minutes, and total daily screen time over 4 hours. Meeting all three criteria resulted in an odds ratio of 7.6.bmjophth.bmj.com

The median age of onset in the Child Health and Development Center survey was 16 years, with a male ratio of 54%. The average viewing distance was 25 cm, and the incidence rate was 2.1 times higher in the ultra-close distance group of less than 16 cm.ncchd.go.jp

5. Impact of the Pandemic

During the lockdowns in various countries from 2020 to 2022, online classes and gaming time surged. The British Pediatric Ophthalmology Society reported that AACE cases increased by 248% compared to 2019. In Japan, the number of cases exceeded 100 for the first time in the 2021 fiscal year.newsdig.tbs.co.jp

The reduction in outdoor activity time indirectly increases the risk of AACE, similar to the progression of myopia. The WHO recommends 2 hours of sunlight exposure per day and maintaining an "elbow rule" distance (at least the length of the forearm) indoors.who.int

6. Preventive Measures: 30-30-20 Rule and Lifestyle

The American Academy of Pediatrics (AAP) revised its 2016 recommendations, urging families to create an "age-appropriate media plan." The guideline suggests zero screen time for children under 2 years, up to 1 hour per day for ages 2–5, and a maximum of 2 hours per day for school-aged children, excluding educational purposes.aap.orgaap.org

Ophthalmology experts advocate the "30-30-20 rule"—maintain a distance of over 30 cm, and every 30 minutes, look at something 20 ft (about 6 m) away for 20 seconds. Research reviews indicate this habit reduces the risk of digital eye strain and AACE by about 30%.healthline.comaoa.org

Outdoor activities should be at least 60 minutes in the morning, as strong sunlight may promote dopamine secretion and alleviate accommodative tension. While blue light-blocking glasses and night mode are effective in the short term, the fundamental measures are maintaining viewing distance and taking breaks.

7. Latest Insights on Diagnosis and Treatment

Diagnosis involves confirming concomitant esotropia without binocular movement restriction using the cover test, and MRI is recommended to rule out neurological disorders.

The treatment hierarchy includes

1. Digital Device Restriction: Reduce usage time by more than 50% and observe for 2 weeks

2. Prism Glasses: Applied for residual esotropia of 8 prism diopters or more

3. Botulinum Toxin A Injection (BTX-A): Optimal within 6 months of onset and for angles of 30 prism diopters or less

4. Strabismus Surgery: Performed in cases where BTX is ineffective or for severe angles
   
   
   

In a multi-center trial by the Indian Ophthalmological Society, 85.7% maintained orthophoria or within 2 prism diopters one year after BTX-A alone, with quality of life indicators comparable to the surgery group.journals.lww.compubmed.ncbi.nlm.nih.gov
In a Chinese age-group cohort, the 2-year efficacy rate of BTX-A was reported to be 67–92%, and it is increasingly becoming the first choice as a minimally invasive treatment.pubmed.ncbi.nlm.nih.gov

8. Actions for Families, Schools, and Government

Families: Designate the dining and living rooms as "digital-free zones" and prohibit screens one hour before bedtime. Parents demonstrating exemplary media use themselves increases children's compliance rates.

Schools: When using ICT devices in class, incorporate exercise breaks every 45 minutes, and adjust desk and chair heights to ensure a viewing distance of over 30 cm.

Government: Add binocular vision function tests to regular health check-ups and distribute symptom checklists to families. WHO VESIH offers free remote training programs for school doctors.who.int

9. Recommendations for the Industry: Tech Solutions

• Distance Sensors: Automatically dim the screen when the viewing distance is less than 20 cm

• Screen Time Management Apps: Preset age-specific limits

• Low Blue Light & PWM-Free: Promote the use of such displays

• Educational companies should adopt a "paper + digital" hybrid design to distribute near work tasks
  
  

According to estimates by MyKidsVision, device-side interventions alone can reduce near-screen time during school years by an average of 38%.mykidsvision.org

10. Conclusion: Protecting "Vision Power"

Smartphone-induced acute convergent strabismus is a "new public health challenge" brought about by the rapid