Tear Film Dysfunction and its Association with Smartphone Usage in Adolescents

INTRODUCTION

Smartphones have become an indispensable part of modern life, with their usage growing exponentially among youth worldwide [1,2]. The widespread adoption of smartphones among adolescents has led to a marked increase in screen time, compared to traditional mobile phones, as these devices offer diverse functionalities beyond mere communication [3]. Activities such as reading, watching videos, social networking, and attending virtual classes demand prolonged visual engagement, contributing to extended digital exposure. While the COVID-19 pandemic initially drove a surge in digital device use, this pattern has continued post-pandemic, with screen time among youth steadily increasing as digital devices remain integral to education, communication, and entertainment. These patterns are especially worrisome for adolescents (aged 10–19 years), as numerous studies suggest that behaviors established during this critical developmental stage tend to persist into later life [4]. Therefore, contemporary adolescents are anticipated to experience greater lifetime exposure to smartphones in the future, and there exists a deficiency in awareness concerning prudent smartphone usage among the youth.

Notably, a recent meta-analysis reported that 19.7% of children experienced asthenopic symptoms, reflecting a significant burden of visual fatigue in this age group [5,6]. Binocular functions, including near point of convergence, accommodative convergence /accommodation (AC/A) ratio, and binocular accommodative facility, are more likely to exhibit abnormalities with prolonged smartphone use, particularly when usage exceeds sixhours per day [6]. Prolonged smartphone engagement may lead to Acute Acquired Concomitant Esotropia, as sustained near work can disturb the balance between accommodation and vergence, particularly in younger individuals [7]. A study investigated the relationship between smartphone-based video gaming and strabismus in children aged 4 to 10 years. The study found that 40% of the participants used smartphones for video gaming more than 2 hours daily. Among these, 59.5% had exotropia, 27% had esotropia, and 13.5% exhibited combined deviations. Statistical analysis revealed a significant association between over 2 hours of daily smartphone gaming and the occurrence of exotropia in these children [8]. Prolonged screen exposure in children has also been significantly linked to reduced tear break-up time (TBUT) and decreased blink rate, which are key contributors to tear film dysfunction and the development of dry eye disease (DED) [9].

DED is a complex, multifactorial condition that occurs when the natural balance of tear film production, distribution, and drainage is disrupted. It is associated with various symptoms and clinical signs, including tear film instability, ocular surface inflammation, and neurosensory abnormalities [10]. While DED can occur across all age groups, it is considerably less common in children than in adults [11]. However, with the steady rise in screen time, this trend is shifting, and the younger population is increasingly being recognized as an at-risk group for developing DED [12]. Unlike conventional mobile phones, smartphones require sustained visual attention, leading to prolonged near-work and reduced blink rates. Excessive smartphone use has been shown to negatively impact tear film dynamics by decreasing blink rate, causing incomplete eye closure, and increasing ocular surface exposure [1,13]. Studies have linked excessive screen time to digital eye strain and DED, with growing evidence suggesting that children and adolescents who frequently use smartphones are at a heightened risk of developing tear film dysfunction [14].

Adolescents (aged 10–19 years) are particularly vulnerable to DED due to their increasing reliance on digital screens for education, communication, and recreation. This age group is in a critical phase of visual development, and sustained near work on screens, often without regular breaks, can significantly reduce blink rate and promote incomplete blinking, both accelerating tear film evaporation. The early onset of DED in this age group can have long-lasting implications. Studies have shown that visual disturbances caused by DED, such as blurred vision, light sensitivity, and difficulty in concentrating can severely affect school performance, self-esteem, and overall quality of life [15]. Given the formative nature of this developmental window, unaddressed dry eye symptoms could contribute to persistent ocular surface dysfunction and chronic visual strain well into adulthood.

The impact of digital device usage on dry eye symptoms is well-documented in adults. However, the specific effects on younger populations, particularly concerning tear film dynamics, remain inadequately explored [16]. Therefore, this hospital-based cross-sectional study explored the association between duration of smartphone usage and tear film function in adolescents aged 10–19 years. By assessing key tear film parameters, this study aims to provide insights into the ocular health implications of prolonged smartphone use in this age group and to highlight the need for preventive strategies and increased awareness to mitigate potential risks.

MATERIAL AND METHODS

The study followed the Guidelines of the Indian Council of Medical Research for ethical biomedical research on human subjects. This hospital-based cross-sectional study was conducted between May 2021 and November 2022, using a cross-sectional approach, in a tertiary care hospital of North India. The target population comprised adolescents (aged 10–19 years), attending the ophthalmic outpatient department, and having a history of smartphone use (for more than 6 months, but less than 2 years). Eligibility criteria included adolescents aged 10–19 years with a history of regular smartphone use, with best-corrected visual acuity (BCVA) of 6/6 or better, and near vision of N6 or better. Adolescents with a history of exposure to other digital screens (such as computers, tablets, and laptops), clinical evidence of strabismus, previous ocular surgery, amblyopia therapy, history of contact lens use, using tear substitutes, refractive error beyond the range of ±6 D or any other ocular co-morbidity that could independently affect tear film stability were excluded from the study. The study adhered to the tenets of the Declaration of Helsinki and approval from the Institutional Ethics Committee was obtained (letter number AIIMS/IEC/21/ 247 dated 15/05/2021). Written informed consent was obtained from participants aged 18 years and older. Assent was obtained from those below 18 years of age, along with consent from their parents/guardians.

All patients underwent basic ophthalmic work-up, including visual acuity assessment with best refractive correction and anterior and posterior segment examination. A detailed history was obtained from all the participants, including the type of smartphone use, duration of smartphone use, and average number of hours spent on the smartphone. Based on self-reported screen time over the past six months, participants were categorized into four groups: < 2 hours/day, 2–4 hours/day, 4–6 hours/day, and > 6 hours/day.

Tear Film Meniscus Height (TMH) was measured, using a slit-lamp biomicroscope with an illuminated horizontal slit beam aligned with the lower lid margin. The beam width was adjusted to match the height of the tear prism. A TMH value of < 0.25 mm was considered abnormal.

Tear Film Breakup Time (TBUT) was performed, using fluorescein strip paper moistened with one drop of balanced salt solution and applied to the lower conjunctival sac, using the cobalt blue filter of a slit-lamp biomicroscope. The time interval between the last blink and the appearance of the first dry spot on the cornea was recorded. The measurement was repeated three times for eye testing, and the mean value of the three measurements was taken as the final. A value of less than 10 seconds was considered abnormal.

In our study, 93.5% of participants used smartphones for more than 2 hours per day, with the majority (61.0%) using smartphones for over 6 hours daily. This finding is consistent with the increasing trend of prolonged smartphone use seen in studies by J. Kim et al., Golebiowski et al., Moon et al., Long et al., where digital device usage has been associated with various ocular problems, including DED [1,12,17,18]. Furthermore, Moon et al. reported that the prevalence of DED was higher in older children from the urban region, and that the symptoms and signs of DED improved after cessation of smartphone use for 4 weeks [12].

Similarly, we found a significant association between longer smartphone use and worsening of all three tear film parameters, including TMH, Schirmer’s I, and TBUT. Specifically, participants using smartphones for more than 6 hours per day had significantly lower values of TMH (< 0.25 mm), Schirmer’s I (< 10 mm), and TBUT (< 10 seconds), compared to those using smartphones for shorter durations. These findings align with previous studies, such as those by Jung Han Choi et al., Moon et al., and S. Khezrzade et al., which reported a decrease in TBUT as the duration of smartphone and screen time use increased [12,13,19]. However, these results contrast with a study by Golebiowski et al., that found no significant change in TBUT after 60 minutes of smartphone reading [17]. The discrepancy may be attributed to differences in study design, device type, or shorter duration of smartphone usage (60 minutes).

Cardona et al. found a statistically significant reduction in spontaneous blink rate, TMH and TBUT after just 20 minutes of computer use, suggesting that even relatively short durations of screen exposure can impact tear film function [20]. They assumed that the combined effect of a reduced blink rate and an increase in the incomplete blink rate may result in excessive evaporation of tears from the ocular surface and a reduced expression of tear film components, thus negatively affecting both the quality and volume of the tear film. Furthermore, the study suggested that the dynamic visual tasks on a visual display terminal may have a more pronounced effect on tear quality (as measured with BUT and NIBUT tests) than tear volume.

Similarly, we observed that among all three tear film parameters, there was a more pronounced reduction of TBUT than the other two parameters, TMH and Schirmer’s I. This finding contradicts the results of Golebiowski et al. and Choi et al., where no significant TMH changes were reported [14,17].