A Policy Statement
Dr. Mohamed Moussa MBBCh, MSc, OD, FAAO,
Dr. Ronald Gall OD, MSc, FAAO, FCOVD, Diplomate BVPPO,
Dr. Shirley Ha HBSc, OD, FCOVD,
Dr. Brij Patel BMSc, OD,
Mr. Drew Herder BSc
*All authors are affiliated with the Vision Therapy Canada (VTC) Science Committee. This policy statement was commissioned by VTC and authors worked together in its production.
Digital Eye Strain
Digital Eye Strain (DES), also called Computer Vision Syndrome    is an extension of previously described visual and ocular symptoms (asthenopia) with demanding near tasks prior to the “digital age”. Most people have clear and comfortable vision while reading, doing computer work, or using a smart phone. However, about 10 to 20% experience visual and ocular symptoms with demanding near tasks with a challenging cognitive load . Additionally, over 50% experience Digital Eye Strain mainly due to the increased amount of time spent using a digital screen 1 2 3 .
The “digital age”, over the last 15 years or more, has created much easier communication of written words and videos; this ease of communication has increased the time in front of a digital screen. More time is spent in front of a digital screen due to the desire for entertainment and human-engagement and the demands of school and work. The prevalence of Digital Eye Strain is higher if using two or more digital devices at one time  or wearing contact lenses .
Self-report questionnaires are available to quantify the level of Digital Eye Strain, including the Rasch-based Computer-Vision Symptom Scale (CVSS17) , Computer Vision Syndrome Questionnaire (CVS-Q) , and existing vision-quality of life tools like the Vision Quality Scale (VQS)  and COVD-QOL .
Digital Eye Strain includes visual and ocular symptoms or asthenopia with demanding near tasks. It may be categorized as internal (visual) or external (ocular) symptoms.
External (ocular) symptoms of eye dryness, burning, irritation and protective tearing are made worse with:
- Dry Eye Disease 
- Reduced blink rate (from 20 to 10 times per minute) caused by increased concentration (cognitive load), smaller font size, reduced letter contrast and increased squinting due to glare and blurred vision . There was, however no difference in reduced blink rate when comparing digital screen versus printed hard copy reading .
- Incomplete blink (upper lid does not cover the entire front surface of the eye) – increases from 5 to 15% of blinks with digital screen use 
- Glare from surrounding light-environment and/or digital screen  
- Duration 
Internal (visual) symptoms of eye strain, tired eyes, blurred vision, frontal headaches, and loss of concentration with binocular use of the two eyes are made worse with:
- Gaze angle from normal reading position 1
- Smaller size of text 
- Closeness of digital screen 1
- Lack of best optical correction 1 3
- Eye teaming dysfunction (challenging to attain and maintain eye alignment on digital screen also called vergence dysfunctions) 1 3 4
- Eye focusing dysfunction (challenging to attain and maintain accurate focus on digital screen also called accommodative dysfunctions) 1 3 4
- Eye tracking/movement dysfunction (challenging to follow a moving target, jump to a new target or produce detailed reading eye movements also called oculomotor dysfunctions of saccades, pursuits and fixations) 4
Visual Symptoms are similar to printed material use, yet magnified due the increased time spent on digital screens 13
Visual symptoms are related to time spent on near tasks and cognitive load 18. Most individuals do not have visual symptoms with digital screens. Visual symptom level is the same with printed material or digital communications 13. However, more time is spent now on digital communication due to the “digital-age”, leading to higher levels of visual symptoms. There is a direct (positive) correlation of visual symptoms with time spent on demanding near visual tasks. That is, the more time spent on a near task, the worse visual symptoms. There is reported increased prevalence and severity of visual symptoms since the spring of 2020 with COVID-19 safety measures including stay-at home measures.
Light (blue light) from digital communication compared to printed:
Effects of blue light:
- Reduces melatonin production 21 – a benefit during the day, yet not before bed when melatonin helps you sleep.
- May cause visual symptoms yet there is little research to support this idea  . It is rare for patients to have this type of visual symptom and even more rare for blue-blocker filters to help.
- No harm or photochemical effect on the retina 20 21 22. It may happen after 1000 days of continuous viewing (over 2.5 years). It may happen after 50 days of continuous blue sky viewing. To understand the amount of blue light from a digital screen consider that 30 minutes spent outdoors on a sunny day is equal to about 10 hours on the digital screen. Fluorescent lights have a similar Relative Blue Content as digital screens and decades of fluorescent light have not caused concerns. “There are no safe wavelengths of light, only safe quantities”. The higher the Correlated Colour Temperature (CCT) or Colour Temperature (K) the higher the Relative Blue Dose 22. A Warm White colour temperature of 3000 degree K has 50% less blue light than a White Colour temperature of 5000 degree K 22.
The risk of the incremental increase in blue light from digital screens over the decades is not understood and remains to be studied. Outdoor workers over the decades have been safe from blue light yet needed protection from UV light. The luminance of a normal digital screen is about 100 cd/M2 compared to a blue sky on a sunny day is about 7000 cd/M2. Note: 1 cd/M2 equals 1 lumen/M2/steradian
Myopia risk with digital communication compared to printed
Myopia development channels through genetically programmed ocular growth and visually driven growth. It is unclear if environmental (visual) risk factors for myopia is different with digital screens compared to printed material. Overall, due to ease of communication with digital screens, there is more time is spent on demanding near tasks.
A study showed children ages 6 to 13 years are at more risk of increasing myopia with increased digital screen time – especially the younger children . In the previous 5 years, overall, for all children, the year-to-year increase in myopia is low and only about 0.05 D per year. During 2020 with increase digital screen time, younger children (6 to 8 years) increased their myopia by 0.25D and older children (9 to 13 years) increased their myopia by 0.08 D.
Myopia risk factors include genetic susceptibility, environmental and cultural risk factors (intensive education, near work time and limited outdoor time) , diet (lower protein and fat intake), less sleep/sleeping disorders, and increased anxiety. 
Impact of Technology Use and Social Media on Mental Well-Being
According to the World Health Organization (WHO), an estimated 10-20 percent of children and adolescents worldwide experience mental health disorders. Nearly 50 percent of all mental health illnesses begin by age 14 and 75 percent by mid 20s. With nearly half the world connected to the internet where digital interactions are fast becoming the norm and people are spending more time online, risk factors that have negative consequences on the mental and social/emotional well-being of an individual must include the use of technology and the influence of social media.
Social networking sites and social media apps can support collaborative informal and formal learning, opportunities for greater online interactions/socialization and provide entertainment. They can also help people create phoney personas, superficial relationships and virtual environments that make it harder for them to develop intimate, face-to-face connections and live in the real world; This type of communication may result in fewer personal friends, more detachment, more isolation and increased depression than the initial intent of staying connected with peers. Body image concerns, disordered eating as well as both positive and negative impact on cognitive areas have also been found to be linked to social media usage.
In a 2017 literature review, researchers found an increase in symptoms of depression and suicide risk factors/rates in teens from 2010 to 2015 when smartphones became more widespread and prevalent. The same study made a strong correlation to screen time use, citing those spending more than five hours are 71 percent more likely to have one risk factor for suicide, no matter what they were doing online. Other reviews and studies similarly linked high daily smart phone or social media use with increases in depression and anxiety   as well as ADHD, OCD symptoms and hostility/aggression.
The American Psychological Association’s Stress in America™ survey conducted by Harris Poll in 2017 of 3,511 American adults 18 years and older reported 86 percent of Americans reported they constantly check their texts, e-mails and social media account and 1 in 5 Americans indicate the use of technology as a source of their stress. More than 2 in 5 (42 percent) of the constant checkers worry about the negative effects of social media on their physical and mental health compared to 27 percent of people who do not check as frequently. Even though 65 percent report they moderately or strongly agree that unplugging is important, only 28 percent actually do so 39.
Gamers with video game addiction or students who use the internet for non-academic activities intensively (more than 6 hours a day) have been found to feel more loneliness, have lower self-esteem and lower social competence, behavioural/emotional problems and hyperactivity. They have a greater risk of disengagement from school with a shorter attention span, poorer academic performance, lower life satisfaction, lower education expectations and a tendency to arrive late for school. Moreover, excessive screen time is interfering and impinging on everyday social and family interactions which researchers are calling technoference or evolutionary mismatch between smartphones and behaviours leading to disagreements, fights and arguments at home about when devices can be used and how much screen time is too much. Notwithstanding the suppression of melatonin production from the artificial blue lighting altering sleep patterns, a link between greater social media use with poorer sleep has been identified with a significant association found between lack of satisfactory sleep among teenagers and playing video games in the evenings. However, it remains unclear if the overall intense use of the digital technologies giving rise to the negative mental outcomes is the cause or a consequence of the reduced mental well-being. There are likely other variables affecting both 34.
For pre-school children, the Canadian Healthy Infant Longitudinal Development (CHILD) study showed parents were 5.9 times more likely to report inattention problems when screen time was more than 2 hours per day than when screen time was less than 30 minutes per day. Furthermore, there was an increased risk (7.7 times) of meeting the diagnostic DSM-5 criteria for ADHD as well. In addition to the psychological and behavioural effects, excessive screen time has also been found to affect the physical structure of the brain itself. A study published in the JAMA Pediatrics journal showed an association between increased screen time and decreased integrity of brain white matter tracts, associated with language and literacy skills, in preschool children .
Finally, increasing access to the mobile and online environments can increase exposure to the online risks of direct or anonymous cyber harassment, peer aggression and abuse, stalking, cyber-bullying and sexting beyond the traditional physical bullying which could negatively impact mental health. There is even evidence of a rise in cyberbullying in some countries with peak internet use.
- Sit about two feet away from a computer screen to reduce eyestrain. An easier way to visualize this distance is to use the distance from the end of your fingers to your elbow (Harmon’s distance).
- Make sure the center of the computer monitor is slightly lower than eye level — four to eight inches. This will allow for proper posture while using the computer. 49
- Using a larger font size can help to reduce strain on the eyes and make it easier to view. 49
- 20/20/20 rule – after 20 minutes of near work (such as working on a laptop), look at least 20 feet away for at least 20 seconds to allow the eyes to take a break and relax. 49
- Increase the amount of time spent outside! This will not only increase daily activity but will allow the eyes to relax and can be fun too!
- Contact your optometrist for an eye appointment to see if computer glasses could be beneficial. Blue light from computer screens can be quite offensive to the eyes, causing digital eye strain. Computer glasses with a blue light blocking coating can be effective in reducing the amount of blue light that passes on to the eyes, helping to reduce digital eye strain.
- Do your best to reduce or eliminate digital screen use starting two to three hours before going to sleep. The presence of light reduces the amount of melatonin produced in the brain, reducing our ability to fall asleep easily; blue light does this to a higher extent. Digital screens produce a significant amount of blue light, inhibiting the production of melatonin, causing a reduction in sleep length and quality.
- Sleep quality and duration is important to pay attention to. It has been seen that individuals who get less sleep show higher rates of depression.52
Recommended amount of screen time for children:
- 0-2 years old: No screen time with exception of live video chatting with parental supervision and support. Infants and toddlers have difficulty learning from 2D representation; therefore, 3D interaction such as face to face interaction with parents or caregivers is encouraged  .
- 2-5 years old: No more than one (1) hour per day. Age appropriate, educational content and supervision by parents is recommended. Quality educational screen time can foster early language and literacy development in children. Children tend to learn easier and efficiently via direct interaction with caregivers or parents.
- 5-18 years old: Ideally no more than 2 hours a day recreational screen time. Screen time for learning or school purposes is allowed but regular breaks, such as every 20 minutes, are recommended. Individual screen time plans for children between the ages of 5–18 years should be considered based on their development and needs 55 56.
Parents should ensure that screen time is not a routine part of child care for children younger than 5 years old. Regular “screen free” times are recommended especially during family meals, gatherings and play dates with other children. Parents are recommended to be present, whenever possible, when children are provided with screen time. Screen time content should be monitored by the parents, and educational, age appropriate and interactive programming should be prioritized.
Annual eye examinations are recommended for children to ensure that their visual skills can cope with the increased day to day visual demands. Appropriate treatment options such as glasses correction, contact lenses, vision therapy, myopia control, and dry eye treatments can be initiated to ensure ocular health and visual skills are maintained.
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