Paper title: Association between digital smart device use and myopia: a systematic review and meta-analysis
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, VIC, Australia; Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia; Plano, Singapore.
- Plano, Singapore.
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.
- Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, VIC, Australia; Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia; State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
- Vision and Eye Research Institute, School of Medicine, Anglia Ruskin University, Cambridge, United Kingdom.
- Plano, Singapore; Singapore Eye Research Institute, Singapore National Eye Centre, Singapore; Duke-NUS Medical School, National University of Singapore, Singapore.
Date: December 2021
Reference: Lancet Digital Health 2021 Dec;(3):e806-818.
A review and meta-analysis of digital screen time and myopia, published in January 2020, concluded that there was no overall increased incidence, prevalence or progression of myopia linked to use of digital devices. Of the 15 studies included in that meta-analysis, seven found a link between myopia and digital device use and the rest did not. Five studies qualified for inclusion in the meta-analysis, finding an overall odds ratio of 1.02 with a 95% confidence interval range of 0.96 to 1.08. An odds ratio indicates the increased risk compared to a reference, so an increased risk of only 2% with the confidence interval (CI) crossing into less than 1 indicates a lack of correlation relationship. This study has been taken as evidence since that digital devices are not linked to myopia.
In this new systematic review and meta-analysis, published in December 2021, studies were sought which quantified 'smart device' (smartphones and tablets) use in three categories: studies investigating smart device use independently; studies measuring smart device use in combination with computer use; and finally smart device use in combination with other non-screen based near-vision tasks.
Thirty-three articles were included in this systematic review and 11 in the final meta-analysis. Results were again mixed, with just over half of articles finding a link and the rest not finding a link between screen time and myopia.
- Sample sizes ranged from 155 to almost 20,000 participants, with age ranges of 3 years to early adulthood (which will affect rates of myopia)
- Smart device use alone had an odds ratio of 1.26 (95% CI 1.00-1.60), meaning the risk increased 25%
- Smart device use in combination with computer use increased the odds ratio to 1.77 (95% CI 1.28 to 2.45)
- All 33 studies were cited by the authors as "not including reliable measures of screen time", relying on subjective questionnaire data for screen time while only one study included a form of objective measure (smartphone data consumption).
What does this mean for my practice?
When parents ask if screen time could contribute to their child's risk of myopia onset or progression, our previous evidence-based answer was 'maybe not' but this study indicates the answer should instead be 'likely yes'. This then leads to helpful discussion about managing childhood screen time - read more in Screen Time Guidelines For Children – Resources For Eye Care Practitioners.
What do we still need to learn?
As cited by the authors, we need objective measures of digital device time to better understand the link between screen time and myopia, and the impact of specific types of screen-based media - from those held in the hands to desktop or laptop computers. The authors mention that people tend to underestimate their own digital screen time by as much as 40%. We would also benefit from studies which examine children at the time of fastest myopia progression, around ages 7-9 years, to evaluate impacts separately to children of younger and older ages.
Title: Association between digital smart device use and myopia: a systematic review and meta-analysis
Background:Excessive use of digital smart devices, including smartphones and tablet computers, could be a risk factor for myopia. We aimed to review the literature on the association between digital smart device use and myopia.
Methods: In this systematic review and meta-analysis we searched MEDLINE and Embase, and manually searched reference lists for primary research articles investigating smart device (ie, smartphones and tablets) exposure and myopia in children and young adults (aged 3 months to 33 years) from database inception to June 2 (MEDLINE) and June 3 (Embase), 2020. We included studies that investigated myopia-related outcomes of prevalent or incident myopia, myopia progression rate, axial length, or spherical equivalent. Studies were excluded if they were reviews or case reports, did not investigate myopia-related outcomes, or did not investigate risk factors for myopia. Bias was assessed with the Joanna Briggs Institute Critical Appraisal Checklists for analytical cross-sectional and cohort studies. We categorised studies as follows: category one studies investigated smart device use independently; category two studies investigated smart device use in combination with computer use; and category three studies investigated smart device use with other near-vision tasks that were not screen-based. We extracted unadjusted and adjusted odds ratios (ORs), β coefficients, prevalence ratios, Spearman's correlation coefficients, and p values for associations between screen time and incident or prevalent myopia. We did a meta-analysis of the association between screen time and prevalent or incident myopia for category one articles alone and for category one and two articles combined. Random-effects models were used when study heterogeneity was high (I2>50%) and fixed-effects models were used when heterogeneity was low (I2≤50%).
Findings: 3325 articles were identified, of which 33 were included in the systematic review and 11 were included in the meta-analysis. Four (40%) of ten category one articles, eight (80%) of ten category two articles, and all 13 category three articles used objective measures to identify myopia (refraction), whereas the remaining studies used questionnaires to identify myopia. Screen exposure was measured by use of questionnaires in all studies, with one also measuring device-recorded network data consumption. Associations between screen exposure and prevalent or incident myopia, an increased myopic spherical equivalent, and longer axial length were reported in five (50%) category one and six (60%) category two articles. Smart device screen time alone (OR 1·26 [95% CI 1·00-1·60]; I2=77%) or in combination with computer use (1·77 [1·28-2·45]; I2=87%) was significantly associated with myopia. The most common sources of risk of bias were that all 33 studies did not include reliable measures of screen time, seven (21%) did not objectively measure myopia, and nine (27%) did not identify or adjust for confounders in the analysis. The high heterogeneity between studies included in the meta-analysis resulted from variability in sample size (range 155-19 934 participants), the mean age of participants (3-16 years), the standard error of the estimated odds of prevalent or incident myopia (0·02-2·21), and the use of continuous (six [55%] of 11) versus categorical (five [46%]) screen time variables INTERPRETATION: Smart device exposure might be associated with an increased risk of myopia. Research with objective measures of screen time and myopia-related outcomes that investigates smart device exposure as an independent risk factor is required.
Interpretation: Smart device exposure might be associated with an increased risk of myopia. Research with objective measures of screen time and myopia-related outcomes that investigates smart device exposure as an independent risk factor is required.