Smartphone use in myopic vs non-myopic Irish students

Authors: Saoirse McCrann PhD BSc (1), James Loughman PhD BSc (1)(2), John S Butler PhD MSc BA (3) Nabin Paudel PhD BOptom (1) Daniel Ian Flitcroft DPhil MB BS MA FRCOphth (1)(4)

1. Centre for Eye Research Ireland, School of Physics, Clinical and Optometric Sciences, Technological University Dublin, Dublin, Ireland.
2. Department of Optometry, African Vision Research Institute, University of KwaZulu Natal, Durban, South Africa
3. School of Mathematical Sciences, Technological University Dublin, Dublin, Ireland.
4. Department of Ophthalmology, Children's University Hospital, Dublin, Ireland.

Date: May 2020

Reference: Clin Exp Optom 2020 May 25. doi: 10.1111/cxo.13092. Online ahead of print [Link]

Smartphones have been commonplace devices for several years and many of us own one, but young children are increasing likely to own their smartphone, too.  Anderson et al found that approximately 95% of children in America in 2018 either had access to a phone or owned one themselves¹ and 85% of UK children aged between 12 and 15yrs used a smartphone every day in 2017 (Ofcom)².

The working distance while using a smartphone is typically much closer than if using a computer or a laptop as the devices are small and hand-held.  While they offer entertainment and education, there is concern over both the time spent concentrating on smartphones and the viewing distance with the risk of developing or experiencing progression of myopia.

The authors of this study aimed to discover the association between refraction status, whether myopic or non-myopic, and smartphone use.  Children and young adults in school settings were provided with a questionnaire to establish self-reported daily use of smartphones and their beliefs on how technology impacts eye health. Average daily smartphone data usage was established from the usage statistics recorded by their smartphones operating system.

Average data used daily by all the participants was found to be 873 MB and the time they spent on smartphones every day was 4hrs 32mins.  Myopic children were using nearly double the phone data compared to non-myopes, although their reported daily time spent using their smartphones was similar.  There was a statistically significant relationship found between myopia and increased screen time, myopic parents and increasing age. When questioned on their perception of screen usage and their eye health 73% of the students felt smartphones adversely affected their eyes, however only 31% of myopes felt that there is a relationship between increased time looking at a screen and myopia.

Compared to the pre-smartphone era children and adolescents are now spending substantially more time on near tasks.

• The relationship between time spent on close work and myopia remains contentious, however the near doubling of close work time reported in this study compared to studies from two decades ago, and dramatic increase in prevalence of childhood myopia across this period, indicates the need for more detailed research on this potential environmental interaction.
  • Clinically this has little relevance, other than you being aware that increased uptake of smartphones appears to have resulted in schoolchildren and adolescents spending greater time outside of school hours concentrating on close objects.

In this study the disparity in self-reported daily use of smartphones between myopes and non-myopes was considerably lower than the disparity in data usage - more daily data was used by myopes but self-reported daily use of smartphones was similar between the refractive groups.

• The study design prevents accurate inference, however it seems unlikely that myopic children would use more data that non-myopes while reporting similar daily phone use, which suggests that the myopic students are under-estimating their phone use time.
  • Clinically this potential for under-reporting is something to be aware of if you asking myopic children about their smartphone usage

The authors report that study outcomes suggest that "... believing phone usage is deleterious to eye health does not limit use." and that "This belief was expressed more often among young myopes, in whom smartphone use was the greatest."

• These observations suggest that advising children and adolescents to reduce smartphone use is unlikely to change behavior.
• You may instead want to consider advising:
  • awareness of how close near work including smartphones is being held and extending this distance wherever possible.
  • setting a timer to take regular breaks from close work to relax focus to the far distance.

The case control limits prevents being able to make any causal inferences, but it does allow for a large study sample to give insights across an entire education level and age spectrum.

There is no prior validation of the questionnaire used in this study.

• This means that deductions from questionnaire responses should be considered with caution.
• Greater emphasis should be placed on the objective measure of data used as an indicator of daily phone use.

While there was a significant correlation between self-reported daily time using smartphones and data use, the model only revealed a 3% effect indicating considerable disparity between reported time spent and measured data used on smartphones.

• This suggests that myopes are under-reporting the amount of time they spend on smartphones.
• However, limitations of data capture in this study prevent more detailed evaluation to validate this observation.
• The authors reported that data collection was conducted before more recent smartphone operating system updates that allow more detailed reporting on time spent on specific apps - future studies conducted using similar methodology are therefore likely to provide more detailed insights into how children and adolescents use their smartphones.

Refraction was not measured or validated beyond categorizing students as being either myopic or non-myopic based on subjective observation of current optical correction by a qualified optometrist.

• This approach simplifies the study design but limits sensitivity of classification - i.e. it's possible that some of the students classified as non-myopic may have been early yet to be diagnosed myopes.
• The authors compared prevalence of myopia in this study to other published data to reveal similar values, leading them to report that underestimation of myopia classification was unlikely.

Time spent outdoors was not recorded. Increased time spent on close work would reduce the time available to spend outdoors meaning that if this were the case and the myopic children in this study did spend less time outdoors, then reduced outdoor time may instead be influencing their myopia development.

To investigate the relationship between myopia, the objective measure of smartphone data usage and self reported duration of smartphone use in school children and university students. A secondary purpose of this study was to establish whether study outcomes changed with age.

The authors conducted a case-control study in the Republic of Ireland between January and March 2018 comprising 402 school children and young adults aged between 10 and 33yrs classified into three groups: Kindergarten (6yrs); Secondary school (7-12yrs); Tertiary (university level). Participants completed  a questionnaire to establish self-reported estimated time spent using a smartphone each day. Smartphone data use over time was recorded from their smartphone and divided by the data measurement period to establish average daily data use.

Participants were asked to provide a copy of their latest spectacle or contact lens correction. a qualified optometrist visual examined any worn spectacles to establish whether the prescription indicated myopia (minifying) or hyperopia (magnifying) and compared this against their prescription if provided to confirm prescription validity. Association between refractive status, self-reported daily time using a smartphone and objective daily smartphone data use was investigated. The relationship between self-reported time using a smartphone and average data use each day was also evaluated.

Out of the initial 418 participants who agreed to take part in the study, 99% owned a smartphone and 402 completed and returned their questionnaires. The mean age was 16.77 +/- 4.4yrs old and 34% were classified as myopic.

Smartphone use
Data use reported from participants' smartphones averaged 873 ± 1,038mb per day with students reporting average smartphone use of 272 ± 169mins per day with the longest period of use within a week at 208 ± 188mins.

• Data use was 84% higher in myopes, however self reported daily time spent on phones was not significantly different between myopes and non-myopes.  When sub categorised by education level:
  • There was only a significant difference in daily data usage between myopes and non-myopes in university students.
  • There was a significant difference in self-reported daily time spent on smartphones between myopes and non-myopes in kindergarten students.
• Overall, data use and self-reported daily time spent on phones increased with age.
  • However, smartphone usage was greatest in young myopes.
• 84% of students reported using smartphones in bed with younger students spending more time on a smartphone in bed compared to older students.
• 72% of smartphone time was spent using social media apps across all age groups and refraction error profiles.
• Self-reported smartphone daily use in this study is almost double that observed for all near work activities outside of school reported at the turn of the century (≈20 yrs ago):
  • Current study (Ireland) - 4hrs 32mins.
  • Singapore (2002)³ - 2hrs 42mins 
  • USA (2002)⁴ - 2hrs 18mins

Gender and parental myopia status

• Gender distribution was equal amongst the myopes.
• Participants with parental myopia were prescribed glasses at an earlier age compared to those with no parental myopia.

Participant beliefs regarding digital technology and eye health
Could digital technology adversely affect the eyes?:

• 73% of participants agreed.
• Greater representation of this belief in myopes (84%).

Inverse correlation with age - younger children more likely to hold this belief.

Does screen usage cause various eye symptoms?:

• Eye strain - 29%
• Dry eyes - 67%
• Headaches - 5%
• Difficulty with reading - 2%

Is there a link between myopia and increased time spent looking at a screen?:

• Myopes - 31%
• Non-myopes - 25% (no significant difference to myopes)

Associations with myopia
Myopic refractive status was significantly associated with increasing daily smartphone data usage, self-reported daily time spent using a smartphone, age, and number of myopic parents.

The authors suggested excessive accommodation or close work demands from using smartphones as well as higher accommodative convergence/accommodation ratios and peripheral defocus as potential mechanisms for myopia development which may explain the reported indication of greater smartphone use in myopes. A further potentially influential interaction suggested by the authors is that increased smartphone use in bed, as reported in this study, may disturb and delay onset of sleep. It needs to be kept in mind however, that this was a case control study meaning that causation between higher smartphone use and myopia can only be inferred - further studies are needed to investigate these potential interactions.

This study reveals that children are now spending more time on near tasks that were reported prior to the smartphone era, which posts an additional environmental risk factor for myopia. The case control nature of this study limits the reliability of the conclusions that can be drawn, however the measured greater daily smartphone data usage by myopic students indicating increased daily use of smartphones compared to non-myopes, warrants further and more detailed investigation.

Title: Smartphone use as a possible risk factor for myopia

Authors: McCrann S, Loughman J, Butler JS, Paudel N, Flitcroft DI

Clinical relevance: This study demonstrates an association between myopia and smartphone data usage. Youths now spend more time participating in near tasks as a result of smartphone usage. This poses an additional risk factor for myopia development/progression and is an important research question in relation to potential myopia management strategies.

Background: Children are now exposed to another possible environmental risk factor for myopia - smartphones. This study investigates the amount of time students spend on their smartphones and their patterns of smartphone usage from a myopia perspective.

Methods: Primary, secondary and tertiary level students completed a questionnaire exploring patterns of smartphone usage and assessing their attitudes toward potential myopia risk factors. Device‐recorded data usage over an extended period was quantified as the primary and objective indicator of phone use. Average daily time spent using a smartphone was also quantified by self‐reported estimates. Refractive status was verified by an optometrist.

Results: Smartphone ownership among the 418 students invited to participate was over 99 per cent. Average daily smartphone data and time usage was 800.37 ± 1,299.88 MB and 265.16 ± 168.02 minutes respectively. Myopic students used almost double the amount of smartphone data at 1,130.71 ± 1,748.14 MB per day compared to non‐myopes at 613.63 ± 902.15 MB (p = 0.001). Smartphone time usage was not significantly different (p = 0.09, 12 per cent higher among myopes). Multinomial logistic regression revealed that myopic refractive error was statistically significantly associated with increasing daily smartphone data usage (odds ratio 1.08, 95% CI 1.03-1.14) as well as increasing age (odds ratio 1.09, 95% CI 1.02-1.17) and number of myopic parents (odds ratio 1.55, 95% CI 1.06-2.3). Seventy‐three per cent of students believed that digital technology may adversely affect their eyes.

Conclusion: This study demonstrates an association between myopia and smartphone data usage. Given the serious nature of the ocular health risks associated with myopia, our findings indicate that this relationship merits more detailed investigation.

Abstract link is here