Smartphone gaming induces dry eye symptoms and reduces blinking in school-aged children

The study addresses how short-term smartphone use affects the ocular surface and blinking in school-aged children with healthy eyes. Contextually, smartphone ownership and use are widespread among children worldwide, with many exceeding recommended daily screen-time limits. Excessive screen viewing is linked to adverse general and mental health outcomes, and ocular risks such as myopia progression. Adult studies show that even brief smartphone tasks can induce ocular discomfort, dry eye symptoms, altered tear function, and reduced blinking. However, prospective evidence in children with healthy eyes is lacking; prior pediatric work has primarily involved children diagnosed with dry eye. Blinking is critical for tear film homeostasis and is known to slow during visually demanding digital tasks in adults, but measurement during smartphone use is challenging. Using a wearable eye-tracking headset that permits natural head movements, this study aims to determine the immediate effects of one hour of smartphone gaming on symptoms, blinking, and tear film function in healthy school-aged children.

- Device use: Smartphones are the most common digital devices among children, with ownership high in the UK, US, Australia, Europe, and SE Asia; many exceed WHO and national recommendations for screen time, exacerbated by COVID-19. - Ocular risks: Digital device use is associated with myopia progression; evidence suggests increased odds of eye fatigue and dry eye symptoms after more than 2 hours of smartphone use. Pediatric guidance commonly recommends the 20-20-20 rule. - Adults: Smartphone/tablet use can induce discomfort, dry eye symptoms, reduced blink rate, changes in blink patterns (including incomplete blinks), and sometimes altered tear stability, with effects reported after as little as 1 hour (and up to 4 hours). - Children: Prior studies largely involve children with dry eye, showing increased symptoms with higher smartphone use and symptom improvement after cessation for weeks. A report indicated reduced blink rate with more than 3 hours/day of smartphone use in school-aged children. No prior prospective study has examined short-term smartphone effects on blinking and ocular surface in healthy children. - Blinking: In adults, blink rate typically decreases with computer/smartphone tasks requiring higher cognitive demand; literature is mixed for interblink interval and incomplete blinks. Measurement constraints in earlier studies motivate the use of wearable eye-tracking to capture naturalistic blinking during smartphone use.

Design: Prospective interventional study conducted at children’s events of the Federation of Helsinki; approved by UNSW Human Research Ethics Committee (H1084201). Parental/guardian consent obtained. Participants: Children aged 6–15 years, English-speaking. Inclusion required minimum unaided or aided visual acuity of 0.20 logMAR at 6 m and 40 cm; age-appropriate binocular vision (accommodation, convergence). Exclusions: ocular disease (including allergies), contact lens wear within prior 24 h, systemic disease (e.g., Parkinson’s, diabetes), or medications affecting ocular surface/tears. A priori sample size target was 45 to detect a 3.6 blinks/min change in blink rate (alpha 0.05, accounting for 20% attrition) and to detect clinically relevant changes in symptoms, NIBUT, and TMH. Intervention/task: Participants played two smartphone games (Despicable Me: Minion Rush; Racing Penguin) continuously for 1 hour on an iPhone 5S (4-inch display, 1136×640 px, 326 ppi, 60 Hz). Participants held the phone at their habitual distance. Real-time adherence monitoring used a scene camera and eye camera feed from the eye-tracking system. Outcomes and instruments: - Ocular symptoms: Self-administered questionnaires suitable for children and responsive to change, including SANDE, IOSS (Instant Ocular Symptoms Survey), and a Numerical Rating Scale (NRS; comfort, dryness, tiredness and average), administered per published protocols. - Tear film function (right eye): Lipid layer thickness (LLT) via LipiView (reported in interferometric color units, UCI); Tear meniscus height (TMH) and non-invasive tear breakup time (NIBUT) via Oculus Keratograph 5. TMH measured at three locations (under pupil center, nasal, temporal corneal edges) and averaged; first break recorded for NIBUT. - Blink parameters: Measured in situ with a child-sized monocular wearable eye-tracking headset (Pupil Labs GmbH, Berlin), worn over spectacles if needed. Baseline blink activity recorded during conversation for 10 min (first 3 min discarded to allow adaptation); then continuously recorded throughout the 1-hour gaming session. Blink events were detected using Pupil Labs Core/Pupil software (v2.0) leveraging pupil confidence (0–1) to identify blinks when the pupil is obscured; poor confidence unrelated to blinks (e.g., eyelashes) was considered in quality control. Data handling: Of 45 intended participants, data from 36 were analyzed (14 male, 22 female; mean age 10.3 ± 2.6 years, range 6–15). Nine participants were excluded (three for pupil detection confidence <0.6; six due to non-retrievable recordings). Excluded participants’ symptoms/signs were within the range of included participants. Statistical analysis: Normality assessed using Kolmogorov–Smirnov tests with descriptive statistics, histograms, and QQ-plots. Pre–post differences in symptoms and tear film were tested using paired t-tests. Blink rate and interblink interval changes during the first 10 min and across the 1-hour session (10-min blocks) relative to baseline conversation were analyzed with repeated-measures ANOVA and Bonferroni-corrected post hoc tests. Associations between changes in blink parameters, symptoms, and tear film were assessed using Pearson correlations. Two-tailed tests with significance at p < 0.05.

- Participants: 36 analyzed; mean age 10.3 ± 2.6 years (6–15 y). - Symptoms: Worsened after 1 hour of smartphone gaming: SANDE +8.2 units (p = 0.01); JOSS/IOSS +1.3 units (p < 0.001); NRS-average +6.3 units (p = 0.03); NRS-comfort +7.6 units (p = 0.04); NRS-tiredness +10.1 units (p = 0.01). - Tear film: No significant changes after 1 hour: LLT 52.6 ± 16.3 to 56.7 ± 21.4 (p = 0.23; 32 participants for LLT due to upper UCI limits); TMH 0.26 ± 0.07 mm to 0.25 ± 0.06 mm (p = 0.25); NIBUT 10.4 ± 5.5 s to 11.7 ± 7.6 s (p = 0.36). - Blinking (first minute of gaming vs. baseline conversation): Blink rate decreased from 20.8 to 8.9 blinks/min (p < 0.001); interblink interval increased from 2.9 s to 8.7 s (p = 0.002). - Blinking over time: After the immediate change in the first minute, blink parameters remained at altered levels with no further significant change throughout the 1-hour session (p ≥ 0.1 across 10-min blocks). - Associations: No significant associations between changes in ocular symptoms and changes in blink rate or interblink interval from baseline to 1 hour.

The study demonstrates that one hour of smartphone gaming in healthy school-aged children promptly increases ocular discomfort, dryness, and tiredness while slowing blink rate and extending interblink interval. These alterations in blinking occur within the first minute of task engagement and persist for the full hour, indicating a rapid, sustained behavioral change likely driven by increased cognitive/attentional demand during gaming. Despite symptom worsening and blink changes, tear film metrics (LLT, TMH, NIBUT) measured pre- and post-task did not significantly change, aligning with some adult studies after 1 hour of smartphone use but differing from reports after longer exposures or with tablet use. The lack of correlation between symptom change and blink parameter changes is consistent with mixed literature that often finds weak coupling between subjective symptoms and objective signs during digital tasks. The wearable eye-tracking approach enabled naturalistic, continuous blink monitoring across varied head/gaze positions, overcoming constraints of previous methods. Increased interblink interval contrasts with some adult computer-use findings, suggesting task differences, age-related ocular surface responses, or reflex mechanisms. Collectively, the results highlight blinking behavior as a sensitive early indicator of ocular surface stress during smartphone use in children and support recommendations for regular breaks and blink awareness during screen activities.

This first prospective intervention in healthy school-aged children shows that one hour of smartphone gaming increases ocular discomfort and substantially slows blinking (to roughly one-third of baseline) with longer interblink intervals, effects that persist throughout the task without detectable short-term changes in tear film metrics. These findings underscore the rapid impact of smartphone viewing on ocular comfort and blink behavior in children and highlight blinking as a practical indicator for monitoring ocular surface stress during digital tasks. Future research should: (1) evaluate longer and repeated exposures to assess cumulative effects on symptoms, blink patterns (including amplitude and incomplete blinks), and tear film; (2) include control conditions and diverse tasks to isolate effects of cognitive demand and posture/viewing distance; (3) examine individual susceptibility (e.g., baseline tear stability, refractive status) and environmental factors; and (4) investigate interventions such as scheduled breaks, blink training, and ergonomic guidance to mitigate symptoms.

- No separate control condition (e.g., sitting without smartphone use) for the 1-hour period; baseline comparison relied on conversation prior to task. - Smaller analyzed sample (n = 36) than the a priori target (n = 45); nine datasets excluded for poor pupil detection confidence or technical data loss. - Short exposure duration (1 hour); may not capture delayed or cumulative effects on tear film or ocular surface. - Tear film assessed only pre- and post-task (right eye), not continuously; subtle transient changes during the task may have been missed. - Blink amplitude (complete vs. incomplete blinks) not measured, limiting interpretation of mechanisms linking blinking to symptoms. - Potential measurement artifacts in blink detection due to eyelash occlusion/pupil confidence variability. - Generalizability limited to healthy children 6–15 years; results may differ in younger children or those with ocular surface disease. - Smartphone model, screen size, and viewing distance/posture were not standardized beyond habitual use, potentially introducing variability. - Symptom measures rely on self-report in children, which may have variability in comprehension and reporting.