"Acute Internal Strabismus" Caused by Excessive Smartphone Use: Protecting Eye Health Worldwide with the 30 cm Rule and 30-Minute Breaks

Table of Contents

1. Introduction: Why "Smartphone-Induced Esotropia" is Increasing

2. What is Acute Esotropia? — Medical Definition and Mechanism

3. Global Incidence and Latest Research

4. Risk Factors: Distance, Time, Age, and Lighting

5. The 30-30-20 Rule and the Golden Rule of Prevention

6. Self-Check for Early Detection

7. Diagnosis and Examination Flow in Medical Institutions

8. Treatment Options: From Lifestyle Improvements to Surgery

9. Global Perspective: Measures by Countries and New WHO Standards

10. Action Plan to Protect Eyes in a Digital Society

11. Conclusion: Coexisting with Smartphones
    
    

1. Introduction: Why "Smartphone-Induced Esotropia" is Increasing

In Japan, the smartphone ownership rate among teenagers exceeds 95%, with an average daily usage time reaching approximately 4.3 hours. Similar prolonged usage is observed in the United States, South Korea, and China, with reports indicating a global average of over 7 hours. Staring at screens at a close distance for extended periods can cause excessive "convergence," where both eyes turn inward, increasing the risk of fixed eye position.apnews.comhealth.com

2. What is Acute Esotropia? — Medical Definition and Mechanism

Acute Acquired Comitant Esotropia (AACE) is a sudden inward deviation in healthy eyes without trauma or brain disease, often accompanied by double vision. According to a 2023 review, approximately 60% of cases were triggered by "excessive use of digital devices."pmc.ncbi.nlm.nih.gov

2-1. Convergence Excess Disorder

Viewing at less than 30 cm for extended periods causes tension in the medial rectus muscle, making it difficult for the lateral rectus muscle to function adequately when looking at a distance, resulting in difficulty returning the eye position. Kagawa Saiseikai Hospital reports that "viewing within 30 cm for more than 30 minutes" significantly increases the risk of onset.saiseikai.or.jp

3. Global Incidence and Latest Research

• South Korea: First reported the link between smartphone addiction and AACE in 2016.

• India: In a 2024 BMJ Ophthalmology study, 6% naturally recovered just by being advised on smartphone usage.dx.doi.org

• Western countries: Reports of cases doubling during remote classes under the pandemic.link.springer.com

4. Risk factors: Distance, Time, Age, Lighting

Outdoor activities after near work (2 hours/day) reduce the risk of both esotropia and myopia by about 50%.health.com

5. The 30-30-20 rule and the golden rule of prevention

1. Distance: Always keep the device more than 30 cm away.

2. Time: Limit continuous use to within 30 minutes.

3. Break: Every 30 minutes, look at something more than 6 meters away for 20 seconds (AOA recommends 20-20-20).apnews.com

4. Posture and Lighting: Keep the screen slightly below eye level, and room illumination at 300–500 lx.

5. Outdoor Activities: Aim to spend 2 hours a day under natural light.

6. Early Detection Self-Check

• Distant signs appear double

• Headache eases when one eye is covered

• The center of the pupils appears misaligned in the mirror
  If you notice any of the above, it is recommended to visit an ophthalmologist. A simple method to compare the position of the pupils is using a "selfie video" on your smartphone.saiseikai.or.jp

7. Diagnosis and Examination Flow in Medical Institutions

The degree of eye misalignment is measured using thePrism Alternating Cover Test, and an MRI may be performed to rule out brain diseases. WHO recommends the introduction of visual screening for school-aged children, and AI diagnosis using photographs is also being clinically applied from 2024.iris.who.intjamanetwork.com

8. Treatment Options: From Lifestyle Improvements to Surgery

Treatment costs vary by country, but in Japan, surgery costs around 100,000 yen per eye (with 30% insurance coverage).saiseikai.or.jp

9. Global Perspective: Measures by Country and New WHO Standards

In April 2025, WHO and ITU announced the **"Safe Viewing Environment Standards"**, urging device manufacturers to implement "distance warnings" and "automatic break reminders."In Taiwan and the EU, bills aimed at mandatory implementation are also under discussion. who.int

10. Action Plan to Protect Eyes in a Digital Society

1. Enable "blue light reduction" and "screen time limit" in device settings

2. If possible, use an external monitor at work to maintain distance

3. Look at distant scenery during commuting and breaks for "visual stretching"

4. Set a "Digital Detox Day" with family

5. Companies should specify VDT (Visual Display Terminal) guidelines in work regulations
   
   

Summary: Coexisting with Smartphones

Digital devices are indispensable tools, butthere's no need to sacrifice eye health. Simple habits like maintaining a distance of 30 cm and taking breaks every 30 minutes can directly prevent not only acute internal strabismus but also myopia and dry eyes. From children to adults, first incorporate "eye rest time" into your schedule and actively utilize the safety features of technology.

List of Reference Articles

• Saiseikai "Increasing Among Young Generations? Be Careful of 'Smartphone-Induced Acute Internal Strabismus'!"saiseikai.or.jp

• AP News Report on AOA Recommended 20-20-20 Rule 2025/02/03 apnews.com

• JAMA Network Open "Screen Time and Risk of Myopia: Meta-analysis" 2025/03/11 health.com

• WHO-ITU "Global Standard for Safe Viewing Devices and Systems" 2025/04/22 who.int

• BMJ Ophthalmology "Outcome of Acquired Comitant Esotropia with Digital Device Guidance" 2024/11/08 dx.doi.org

• Review "Acute Acquired Comitant Esotropia: Current Understanding" 2023/02/15 pmc.ncbi.nlm.nih.gov