Is the 20-20 rule effective advice in myopia management?

Using digital devices for extended periods of time has been associated with asthenopia, which includes symptoms of eyestrain, dry eye, binocular dysfunction and glare sensitivity. Symptoms can increase with longer time spent on device use.

Computer, tablet and smartphone use is commonplace for many adults and children, but usage was especially increased during COVID-19 lockdown periods. Schoolchildren were particularly susceptible to lifestyle and visual changes when their learning was only available online. Wang et al found an unanticipated increase in myopia occurred for children aged 6-8yrs over the lockdown in China and suggested the lifestyle change of home confinement and subsequent increased online learning had been responsible.¹ Another study found the prevalence of digital eyestrain symptoms in children rose to 50-60% during this time where outdoor activities were restricted.²

Alongside asthenopia symptoms in children, there is also concern among eyecare practitioners and parents that prolonged near work can be a risk factor for increased myopia in children. The visual system needs to consistently focus on near objects such as tablets and smartphones, which are usually held much closer.³

A systematic review and meta-analysis by Huang et al in 2015⁴ examined the effect of near work on myopia in children and found the effects may be cumulative: near work was associated with higher odds of myopia and these odds increased by 2% for each 'dioptre-hour' more of near work each week.

Near work-related behaviours of Shanghai primary schoolchildren were examined in a study that found an association between myopic shifts in refractive error and inappropriate working distance, inadequate lighting and continuous near work without an eye break.⁵

Suggestions of how to address increasing digital screen time in have involved using easy to remember advice such as:

• the 'elbow rule' of keeping an elbow-to-hand distance away from near work to avoid holding too close to the eyes,
• a 2-hour rule to limit screen time (other than for schoolwork) for schoolchildren
• and the '20-20-20' rule of looking away every 20 minutes at an object at least 20-foot away for at least 20 seconds.

Most eyecare practitioners are familiar with these advice snippets and probably suggest them to patients and parents already - but how much evidence is there to suggest these are effective measures?

We feature two studies here which provide conflicting results:

Talens-Estarelles et al tested the benefits of using the 20-20-20 rule for adults using laptop computers. Digital eye strain (DES), dry eye symptoms and binocular visual function symptoms were assessed before and after two weeks of using computer software to provide reminders to take breaks and a laptop webcam to monitor eye gaze and blinking patterns.

• No differences were found for binocular functions. However, dry eye and DES symptoms improved with the reminders but returned a week after the reminders stopped.
• Despite the 20-20-20 rule appearing to be effective in managing dry eye and eyestrain symptoms, a fortnight may not be long enough to provide a long-standing improvement of symptoms.

Johnson and Rosenfield aimed to establish if taking regular breaks from computer work were able to offset adverse effects from using digital devices. Reading speed, task accuracy and ocular and visual symptoms were compared before and after a 40min reading task with series of 20 second breaks.

• There was an increase seen for post-task symptoms, but the schedules break had no effect on the symptoms, reading speed or task accuracy.
• Although the results did not find 20-second breaks relieved digital eyestrain symptoms, the authors conceded that this does not mean having longer breaks, or a different frequency of breaks, wouldn't be effective.

There may be a lack of consensus of the ability of the 20-20-20 rule to meaningfully reduce eyestrain symptoms

• However, it is an easy concept to explain to patients and parents and emphasises the need for regular breaks from concentrating at near distances, especially for children.
• Some kind of break from excessive close work may be better than no break at all

Parents and practitioners need to be aware that there may be a risk of myopia onset or progression from excessive digital device use.

• Regularly checking children's visual and ocular health is necessary to assess signs of digital eyestrain symptoms or binocular dysfunction which may indicate visual stress or myopic changes.

Until research confirms an association between device use and myopia, being aware of digital eyestrain symptoms in children and encouraging good visual hygiene habits, such as the 20-20-20 rule, will make sure children can enjoy using digital devices without potentially risking myopia progression.

These studies were similar in that neither were of a longitudinal design, both investigated the effects of screen use in adults only and consequently, neither investigated the role of the 20-20-20 rule on myopia management.

However, they have also highlighted potential impact of digital eyestrain and myopia progression and measured the impact of clinical advice we give to children on potential myopia risks and digital eyestrain.

• Using adults in the studies who were taking regular breaks may mean there was a limit to the extent of changes that could have been measured. Binocular dysfunction may be more apparent in children, especially if the screen time was longer
• If the role of the 20-20-20 rule is to relieve the accommodative effort of near work, then 20 seconds may not be long enough before near work is resumed. A study exploring accommodative adaptation found 90 seconds or longer may be needed to return to baseline values.⁶

Both studies may have reached different conclusions due to their methodology:

• Johnson and Rosenfield found little evidence of impaired ability to concentrate on reading tasks without exploring accommodative effort, and only investigated eyestrain symptoms using self-reporting questionnaires.
• Talens-Estarelles et al measured binocular vision and found an improvement in binocular accommodative facility after following the 20-20-20 rule than before, even though no differences were found for accommodative or vergence parameters.

Repeating these longitudinal studies with children could yield different results and provide valuable information on myopia progression and digital device use, especially if accommodation and binocular function was assessed.

In the short term, exploring the impact of prolonged near work on the binocular vision and ocular health in children would add to the picture.

Title: The effects of breaks on digital eye strain, dry eye and binocular vision: Testing the 20-20-20 rule

Authors: Cristian Talens-Estarelles, Alejandro Cerviño, Santiago García-Lázaro, Andrej Fogelton, Amy Sheppard, James S Wolffsohn.

Purpose: To evaluate the benefits on the eyes of taking breaks based on the 20-20-20 rule.

Methods: Bespoke computer software using the laptop webcam to assess user breaks, eye gaze and blinking, and emitting personalized reminders of breaks based on the 20-20-20 rule, was downloaded onto the laptops of 29 symptomatic computer users. Digital eye strain (DES), binocular vision and dry eye were assessed before and after two weeks of using the reminders and one week after the discontinuation of the strategy. Binocular measurements included visual acuity, accommodative posture, stereopsis, fixation disparity, ocular alignment, accommodative facility, positive/negative vergences and near point of convergence. Symptoms were evaluated using the computer vision syndrome questionnaire, ocular surface disease index (OSDI), and symptom assessment in dry eye questionnaire (SANDE) versions one and two. Dry eye signs were assessed by measuring tear meniscus height, conjunctival redness, blink rate and incomplete blinking, lipid layer thickness, non-invasive keratograph break-up time, corneal and conjunctival staining and lid wiper epitheliopathy.

Results: A decrease in the duration of computer work and the duration of breaks, along with an increase in the number of breaks taken per day was observed as a result of the 20-20-20 rule reminders (p ≤ 0.015). No changes on any binocular parameter were observed after the management period (p ≥ 0.051), except for an increase in accommodative facility (p = 0.010). Dry eye symptoms and DES decreased with the rule reminders (p ≤ 0.045), although this improvement was not maintained one week after discontinuation (p > 0.05). No changes on any ocular surface and tear film parameter were observed with the rule reminders (p ≥ 0.089).

Conclusions: The 20-20-20 rule is an effective strategy for reducing DES and dry eye symptoms, although 2 weeks was not enough to considerably improve binocular vision or dry eye signs.

[Link to open access paper]

Title: 20-20-20 Rule: Are These Numbers Justified?

Authors: Sophia Johnson, Mark Rosenfield

Significance: The use of digital devices has increased substantially in recent years across all age groups for both vocational and avocational purposes. There are a wide range of proposed therapeutic and management options for this condition, including optical, medical, and ergonomic interventions.

Purpose: Regular breaks are frequently recommended by clinicians to minimize digital eye strain. The so-called 20-20-20 rule, whereby individuals are advised to fixate on an object at least 20 feet (6 m) away for at least 20 seconds every 20 minutes is widely cited. Unfortunately, there is relatively little peer-reviewed evidence to support this rule. The aim of this investigation was to determine whether scheduled breaks are effective in reducing the adverse effects of digital device usage.

Methods: The study was carried out on 30 young subjects who performed a 40-minute, cognitively demanding reading task from a tablet computer. The task required them to read random words and to identify which ones began with a specific letter chosen by the experimenter. The task was undertaken on four separate occasions, with 20-second breaks being allowed every 5, 10, 20, or 40 minutes (i.e., no break), respectively. Both before and after each trial, subjects completed a questionnaire regarding ocular and visual symptoms experienced during the session. In addition, both reading speed and task accuracy were quantified during each trial.

Results: A significant increase in post-task symptoms (with respective to the pre-task value) was observed for all four trials ( P < .001). However, there was no significant effect of scheduled breaks on reported symptoms ( P = .70), reading speed ( P = .93), or task accuracy ( P = .55).

Conclusions: Although widely cited as a treatment option, these results do not support the proposal of using 20-second scheduled breaks as a therapeutic intervention for digital eye strain.

[Link to paper abstract]