Objectively monitoring light and activity levels for myopes

[Link to abstract]Paper title: Objective Measures of Near Viewing and Light Exposure in Schoolchildren during COVID-19

Authors: Bhandari, Khob R;¹ Shukla, Divya;¹ Mirhajianmoghadam, Hanieh,¹ Ostrin, Lisa A¹

1. University of Houston College of Optometry, Houston, Texas

Date: Mar 22

Reference: Bhandari KR, Shukla D, Mirhajianmoghadam H, Ostrin LA. Objective Measures of Near Viewing and Light Exposure in Schoolchildren during COVID-19. Optom Vis Sci. 2022 Mar 1;99(3):241-252.

The development and progression of myopia in children has been associated with environmental and behavioural factors such as the time spent on close work, using digital devices, being outdoors and even sleeping. This study assessed these behaviours in 14yr old myopic and non-myopic schoolchildren in the United States during the COVID-19 epidemic period.  

Forty children participated in the study who each wore two devices for a week to measure their near viewing times and light exposure (Clouclip) and their activity levels and sleep duration (Actiwatch).  

The close work distance, time spent per day (in periods of either less than a minute or 30 minutes or more) and how often near work was carried out in a day were all measured.   Exposure to light, time outdoors, electronic device use and sleep duration times were also assessed and parents answered a questionnaire on their child’s activity levels.  The mean near viewing time per day was 7hrs with similar short and long viewing times for myopes and non-myopes.  Sleep duration (approx. 8hrs per day) and electronic device times (approx. 12hrs per day) were also similar for both groups.

However, the myopic children spent more time viewing at near and intermediate distances than non-myopes, with higher dioptre-hours.  Myopes also showed less exposure to daylight and spent less time outdoors.

This study used wearable devices to objectively measure children’s visual environments and showed that myopic children had different behaviour patterns to non-myopes by spending less time outside and more time on near work.

• This mirrors results from previous studies which also found behaviour differences, albeit for younger children^1,2,3.
• All the studies highlighted a need for children to have a lifestyle balance between excessive digital device use or near work and spending time outside, particularly if their age means they are more vulnerable to environmental influences.

The participants in this study were 14yr olds rather than young children.

• The Generation R study⁴ found that teenagers in the Netherlands did not spend extra time outdoors during the COVID-19 home confinement period despite being able to and spent more time indoors on home learning.  However, there was little difference in behaviour between myopes and non-myopes.
• Eyecare practitioners should be aware that teenagers as well as younger children may be progressing after a long period indoors and lifestyle advice is appropriate for children of all age groups.

We have the abstract for now, but the full text would provide details on:

• the range for the refractive error groups and how myopia was confirmed for the participants
• if there were differences in behaviour between the refractive error groups and if the behaviour patterns for indoor and outdoor time were different on weekdays and weekends.
• if the children’s visual environments and activity levels were measured during or after an enforced COVID-19 home confinement period
• whether the parents had under or over-reported their child’s activity levels on the questionnaire answers compared to the device measurements
  • a previous study by Bhandari et al⁵ found that adults wearing the Clouclip and Actiwatch devices over-reported their near work and outdoor time.

 Further research would reveal:

• if measuring the impact of children’s visual environments for longer than a week would reveal a more realistic ‘average’ of time spent in and of outdoors and on near work
  • a change of myopic prevalence might also be seen over a longer study period
• if the behaviour pattern difference seen between myopes and non-myopes teenagers would still hold true for younger age groups for near work, device use and outdoor time 

Title: Objective Measures of Near Viewing and Light Exposure in Schoolchildren during COVID-19

Authors: Khob R Bhandari, Divya Shukla, Hanieh Mirhajianmoghadam, Lisa A Ostrin

Purpose: Wearable sensors provide the opportunity for continuous objective measurement of the visual environment with high resolution. Our findings show that absolute and temporal properties of near viewing and time outdoors vary between myopic and nonmyopic schoolchildren, which are important considerations when studying refractive error pathogenesis.

Numerous behavioral factors, including near work, time outdoors, electronic device use, and sleep, have been linked to myopia. The purpose of this study was to assess behaviors using subjective and objective methods in myopic and nonmyopic schoolchildren in the United States.

Methods: Forty children (aged 14.6 ± 0.4 years) simultaneously wore two sensors for 1 week, a Clouclip for objective measurement of near viewing and light exposure and an Actiwatch for objective measurement of activity and sleep. Parents completed an activity questionnaire for their child. Near-viewing distance, daily duration, short-duration (>1 minute) and long-duration (>30 minutes) near-viewing episodes, light exposure, time outdoors, electronic device use, and sleep duration were analyzed by refractive error group and day of the week.

Results: Objectively measured daily near-viewing duration was 6.9 ± 0.3 hours. Myopes spent more time in near + intermediate viewing than nonmyopes (P = .008) and had higher diopter hours (P = .03). Short- and long-duration near-viewing episodes were similar between groups (P < .05 for both). Daily light exposure and time outdoors were significantly lower for myopes (P < .05 for both). Electronic device use (12.0 ± 0.7 hours per day) and sleep duration (8.2 ± 0.2 hours per night) were similar between groups (P > .05 for both).

Conclusions: Objective and subjective measures confirm that myopic and nonmyopic schoolchildren exhibit different behaviors. Combining wearable sensors with questionnaires provides a comprehensive description of children's visual environment to better understand factors that contribute to myopia.

[Link to abstract]