The increased use of digital devices such as smartphones and tablets among children has led to more near work time, promoting the onset and progression of myopia. Myopia is a condition in which parallel light rays from infinity focus in front of the retina when the eye is at rest.
The severity of myopia is classified as follows.
Myopia always has a focal point, so it does not cause amblyopia even in young children. However, progression to high myopia increases the risk of retinal degeneration, macular degeneration, retinal detachment, and glaucoma due to mechanical stretching of the choroid, retina, and sclera.
Eye problems related to digital device use are broadly divided into three categories: ① onset and progression of myopia, ② digital eye strain, and ③ acute acquired comitant esotropia (smartphone esotropia). The diagnostic criterion for myopia in children is a spherical equivalent of -0.5D or more under cycloplegic refraction. 2)
With the GIGA School Initiative in 2021, one ICT device per student was distributed, and the time spent using devices at school increased rapidly. Increased near work time is known as a risk factor for the onset and progression of myopia in children, and the impact since GIGA School is being monitored. Balancing ICT use at school with myopia prevention is a challenge.
The combination of close screen distance, prolonged near work, and reduced opportunities for outdoor activities may promote myopia progression. A management system combining regular school vision screenings and ophthalmology visits is important.
Smartphone use itself does not directly cause myopia. However, prolonged use at close distances is considered a risk factor for the onset and progression of myopia. The risk is even higher when accompanied by insufficient outdoor activity. 1) It is important to balance usage time, viewing distance, and breaks.
It is important to understand eye symptoms in children related to digital device use by distinguishing between symptoms due to myopia itself and those due to digital eye strain or acute esotropia.
Symptoms of Myopia
Decreased distance vision: Difficulty seeing the blackboard is the most characteristic complaint.
Squinting: Unconsciously performed to improve vision through the pinhole effect.
Near vision is relatively clear: In myopia, near objects are visible, so close-up tasks can be performed without problems.
Detection at school health checkups: This is often the opportunity for discovery.
Digital Eye Strain
Eye fatigue, dryness, pain: Temporary symptoms that occur after prolonged device use.
Decreased blink rate: Normally 15–20 blinks per minute, but decreases to 3–5 blinks per minute during device use.
Headache, neck and shoulder stiffness: Symptoms associated with poor posture or excessive accommodation.
20-20-20 rule: Can be alleviated by looking at a distance of about 6 meters for 20 seconds every 20 minutes.
Acute Smartphone Esotropia
Acute acquired comitant esotropia: Develops after prolonged near-distance use of smartphones.
Diplopia: Often the main complaint.
Exclusion of organic disease is essential: Differentiation from central nervous system diseases such as brain tumors is important.
Specialized treatment may be needed: May be subject to prism therapy or surgery.
Myopia and digital eye strain are different conditions. Digital eye strain is a temporary symptom that improves with rest, while myopia is a refractive error accompanied by axial elongation and is an irreversible change. Prolonged near work is also a risk factor for myopia progression.
They are different conditions. Digital eye strain is a temporary symptom (fatigue, dryness, blur) that improves with rest. Myopia is a refractive error accompanied by axial elongation and is an irreversible change. Prolonged near work is also a risk factor for myopia progression, so if eye strain persists, an eye examination is recommended.
The main mechanisms of myopia progression can be categorized into three types.
Near work: Prolonged use of digital devices leads to excessive accommodation, promoting axial elongation.
Reduced outdoor activity: Lack of bright light (dopamine hypothesis) promotes axial elongation. Outdoor light intensity (10,000–100,000 lux) stimulates retinal dopamine secretion and suppresses axial elongation. 1)
Genetic factors: If both parents are myopic, the child’s risk of myopia increases. There is a genetic background for higher myopia prevalence in East Asians. Even among the same ethnic group (Chinese), myopia prevalence differs greatly between those living in Sydney (3.3%) and Singapore (29.1%), highlighting the importance of environmental factors. 1)
Increasing outdoor activity time by 76 minutes per day can reduce the onset of myopia by 50% (meta-analysis). Light intensity of 2,000 lux or more and continuous outdoor exposure for at least 15 minutes are considered effective. 1) During school closures in the COVID-19 pandemic, increased near work and decreased outdoor activity accelerated axial elongation in children. 1)
Peripheral hyperopic defocus (blur in the peripheral retina) also serves as a signal for axial elongation. There are two control systems for myopia control: ① dopamine-dependent light intensity and contrast detection, and ② dopamine-independent focus detection. 1) Myopia-control glasses and contact lenses suppress axial elongation by reducing this peripheral defocus. 3)
List of risk factors:
| Risk factor | Impact level | Notes |
|---|---|---|
| Insufficient outdoor activity | Strong | Less than 2 hours per day increases risk of onset |
| Increased near work time | Moderate | Screen time, reading, etc. |
| Shortened near viewing distance | Moderate | Increased risk when used at less than 30 cm |
| Parental myopia | Strong | Risk factor for early-onset myopia |
| Urban environment | Moderate | Children in cities have about twice the risk of those in rural areas |
| Early onset of myopia | Strong | Risk of future high myopia |
The proportion of individuals with uncorrected visual acuity less than 1.0 is increasing. In kindergartens and elementary schools, it is the second most common disease/abnormality after dental caries, and in junior high and high schools, it is the most common.
Statistics on uncorrected visual acuity (Ministry of Education, Culture, Sports, Science and Technology, FY2014):
| School type | Uncorrected visual acuity < 1.0 | Uncorrected visual acuity < 0.3 |
|---|---|---|
| Kindergarten | 26.53% | 0.97% |
| Elementary school | 30.16% | 8.14% |
| Junior high school | 53.04% | 24.97% |
| High school | 62.89% | 35.84% |
The increase in myopia and its severity in young children is a growing concern.
The global prevalence of myopia in children and adolescents increased from 24.3% in 1990 to 35.8% in 2023, and is projected to reach 39.8% by 2050. 1) In East and Southeast Asia, 49.7–62.0% of 12-year-olds have myopia, far exceeding other regions (6–20%). 1) By 2050, approximately half of the world’s population is expected to be myopic, with an estimated annual productivity loss of 250 billion USD. 3)
For each diopter of myopia reduction, the risk of myopic maculopathy is expected to decrease by 58%, open-angle glaucoma by 20%, posterior subcapsular cataract by 21%, and retinal detachment by 30%. 3) Early intervention to slow myopia progression is important for long-term risk reduction.
In young children, accommodation is strong and they lack concentration on distant objects, so instillation of cycloplegic eye drops is essential during refraction testing. This is why cycloplegic refraction is considered the gold standard.
First choice: Cyclogyl (cyclopentolate hydrochloride 1%)
Complete cycloplegia: Atropine 1%
Since accommodation persists after near work, care must be taken to avoid overestimation of myopia. In difficult cases, perform overrefraction using retinoscopy without cycloplegia. 2) To rule out amblyopia, confirm age-appropriate visual development. 2) Regular measurement of axial length is useful for accurate assessment of myopia progression. 2)
Normal refractive values by age (under cycloplegia):
| Age | Normal refractive value (under cycloplegia) | Refractive value requiring glasses prescription |
|---|---|---|
| 3 months | S+4D | S+6D or more |
| 1 year | S+2D | S+4D or more |
| 2 years | S+1D | S+3D or more |
| 3 years | S+1D | S+3D or more |
Vision tests during school health checkups are often the first opportunity for detection. Photoscreening and autorefractometers are useful screening tools but are insufficient for quantitative diagnosis. If reduced vision is noted during school checkups, cycloplegic refraction at an ophthalmology clinic is necessary.
Managing digital device use is fundamental for preventing and slowing the progression of myopia.
Mild myopia (up to -3D): Since myopia always has a world that is in focus, there is no risk of amblyopia even in young children. For up to moderate myopia, glasses prescription should not be rushed or forced. For children aged 3–6 years, the lower limit for prescribing glasses can be considered as S-3.00D or more.
Moderate or higher myopia (over -3D): Wearing glasses expands a child’s world; explain the benefits of glasses to parents.
High myopia (-6D or more): Full correction may not be desirable due to retinal image minification.
For follow-up after spectacle prescription, the first re-examination is performed 3–4 months later in myopic cases. Frame size updates are done every 6 months to 1 year.
As the first domestically approved drug for myopia progression control, Rijusea® Mini Eye Drops 0.025% (Santen Pharmaceutical, approved December 2024) is now available. 2)
The myopia progression control effects of each intervention are shown below.
| Intervention | Refractive Control Effect | Axial Length Control Effect | Remarks |
|---|---|---|---|
| Low-concentration atropine 0.05% | Up to 67% | — | LAMP study1) |
| Orthokeratology | — | 32–59% | Infection risk management is important1) |
| DIMS spectacle lenses | 52% | 62% | 2-year data1) |
| HALT spectacle lenses | 67% | 60% | When worn full-time1) |
| MiSight 1 day CL | 59% | 52% | +2.00D add 3) |
As of April 2025, myopia progression control treatments other than low-concentration atropine eye drops are not approved in Japan. 2)
Orthokeratology is indicated for ages 20 and older according to the Orthokeratology Guidelines. Concerns include decreased night vision, increased higher-order corneal aberrations, risk of serious corneal infections such as Acanthamoeba keratitis, corneal oxygen deficiency due to overnight wear, and decreased corneal endothelial cells. Although axial length elongation suppression has been reported, long-term prognosis is currently unknown, and careful management is required.
Rijusea® Mini Eye Drops 0.025% have no age restriction, but accurate refractive evaluation is difficult in children under 5 years, so careful consideration is needed. 2) It is important to start treatment early after myopia onset, especially before the early teens when progression is rapid. 2) Before starting, confirm myopia with cycloplegic refraction.
Complete prohibition is not necessary. The key points are: ① Limit continuous use to 20–30 minutes per session, ② Maintain a distance of at least 30 cm from the screen, ③ Ensure at least 2 hours of outdoor activity per day. 1) Following these can reduce the risk of myopia onset and progression.
Multiple mechanisms are involved in the onset and progression of myopia.
Near work → Excessive accommodation → Axial elongation: Prolonged near work with digital devices increases accommodative load and promotes axial elongation.
Accommodative resting position (empty field myopia): In the absence of a fixation target, the accommodative position is located 0.5–1.7 D (60–150 cm in front of the eyes) on average from the far point. Prolonged time in dark places or staring at screens can cause the accommodative resting position to shift closer, leading to a myopic shift.
Dopamine hypothesis: Bright outdoor light (10,000–100,000 lux) promotes retinal dopamine release and suppresses axial elongation. A meta-analysis of red light (650 nm) has shown it to be most effective in suppressing axial elongation. 1)
Peripheral hyperopic defocus: Hyperopic blur in the peripheral retina serves as a signal for axial elongation. There are two control systems for myopia control: (1) dopamine-dependent light intensity and contrast detection, and (2) dopamine-independent focus detection. 1)
Mechanism of low-concentration atropine: It penetrates the eye and, via muscarinic receptors in the retina and sclera, participates in scleral remodeling and suppresses axial elongation. 2)
Mechanism of complications in high myopia: Severe progression of axial elongation causes mechanical stretching of the choroid, retina, and sclera, increasing the risk of posterior staphyloma, macular degeneration, retinal detachment, and glaucoma.
Myopia typically begins around the time of elementary school entry and progresses rapidly until junior high school graduation. It tends to stabilize in the late teens to early twenties, but early-onset and high myopia increase the risk of pathological myopia. Refractive changes due to axial elongation are irreversible.
Repeated low-level red light (RLRL) therapy: Irradiation with 650 nm red light increases choroidal thickness and suppresses axial elongation. It has been suggested to reduce the onset of myopia by about 50%, but long-term safety data are insufficient. 1)
Combination therapy considerations: Orthokeratology + 0.01% atropine has the most accumulated evidence. For rapidly progressing cases, orthokeratology + RLRL therapy and dual-focus CL + 0.05% atropine are also being considered. 1)
Novel spectacle lens technologies: Lenses with new optical designs such as PLARI, NLARI, and CARE are under development. 1)
Environmental and social approaches: Policy-based assurance of outdoor activity time at schools has proven effective in Taiwan, Singapore, and China. The reduction in ocular disease risk per diopter of myopia control (58% reduction in myopic maculopathy, 20% reduction in open-angle glaucoma, 21% reduction in posterior subcapsular cataract, 30% reduction in retinal detachment) has been demonstrated, 3) emphasizing the long-term significance of early intervention.
