From television to computers to tablets and smart phones—the last decades have seen an unprecedented rise in the use of screens to share information, be entertained and connect. Screens are seemingly ubiquitous with most households having several. The amount of time people spend watching a screen is mind-boggling: an international comparison found that on average, adults spent 5 to 9 hours per day watching their television, computer, smartphone or tablet in the 30 countries surveyed (1). On the one hand, screens have enabled us to learn better, communicate better and increase our productivity. On the other, large amounts of screen time encourage sedentary behavior and can cause eye problems that affect quality of life. Is there a way for us to stop our avid screen use from affecting our vision?
The different colors that make up the light we see are beautifully displayed when water droplets refract and disperse light into a rainbow. As the colors of visible light move from red through yellow and green to blue and violet, they increase in energy. Thus, blue-violet light has the greatest amount of energy in the visible spectrum.
Blue light is a normal component of all light, and sunlight is the main source. Indoors, digital devices expose our eyes to blue light. Although the amount of blue light from computer, smartphone and tablet screens is small compared to that from sunlight, the amount of time that we are exposed to blue light and our proximity to the source are a cause for concern. A further issue stems from knowledge that the lens and cornea are capable of blocking damaging UV-light, but not blue light (2).
The high energy content of blue light is likely responsible for its effects on the eye. Blue light increases oxidative stress within the eye when it interacts with vision sensors and pigments (5). Blue light exposure to the visual pigment responsible for vision in low light situations, rhodopsin, caused damage to the retina, whereas green light did not (6). It seems that blue light is more likely to cause discomfort to the eyes that other types of visible light (3), and this may increase eye strain due to squinting (4).
Computer vision syndrome
Overuse of screens has led to a rather common problem, particularly amongst office workers who use a computer for many hours per day: computer vision syndrome (7). Surveys find that between 25 and 40 percent of office workers are affected by a variety of symptoms (8-10). These range from mild to debilitating, and include tired or dry eyes, headache, blurred vision, eye and neck strain, and sensitivity to bright lights. In some cases, sufferers are sent to neurologists and stroke clinics to rule out more serious causes (7), which is concerning for all involved, and places an unnecessary burden on the health care system.
A range of strategies have been identified to help counteract the effects of computer vision syndrome (7):
- Receive counseling about good practices before prolonged use of screens
- Keep appropriate distances between the eyes and screens
- Take regular, short rest breaks for the eyes, such as the 20/20/20 rule: every 20 minutes, a 20 second break, looking 20 feet (7 meters) into the distance
- Take a longer break for 15 minutes every two hours
- Use screens in an ergonomic position
- Use computer glasses or filters on the screen
- Balance background lighting with screen illumination
- Treat other eye conditions that may contribute to computer vision syndrome such as dry eyes and astigmatism
Nutritional strategies for computer vision syndrome
Two eye-friendly carotenoids found in many yellow, orange and green leafy vegetables (11) may also help with computer vision syndrome. They are called lutein and zeaxanthin, and they are selectively placed at the back of the eye over the vision sensors responsible for central vision, called the macula (12). Their yellow color acts as a blue-light filter, potentially protecting the delicate photo-sensors from damaging blue light (13). They are also strong antioxidants, and this may be beneficial in highly metabolically active areas of the body such as the eye.
The effect of lutein and zeaxanthin supplementation on computer vision syndrome symptoms was recently tested in a randomized, placebo-controlled clinical trial (4). The study featured 48 college students who normally viewed screens for at least six hours per day at a distance of 3 feet or less, were assigned to a lutein and zeaxanthin supplement (24 mg lutein, zeaxanthin and mesa-zeaxanthin at a ratio of 83:10:7, suspended in oil) or a matching placebo control for six months. At baseline, three months and six months, participants underwent a series of visual tests, and completed questionnaires about their sleep quality and five indicators of excessive screen time. These were headache, blurry vision, neck strain, eye strain and eye fatigue (4).
At baseline, there was already a correlation found between higher levels of lutein and zeaxanthin in the eye (as determined by macular pigment optical density measurements) and less eye strain, eye fatigue and headache. After six months of supplementation, there was an increase in lutein and zeaxanthin in the eye. Headache, eye strain and eye fatigue decreased, and measures of visual performance improved. Interestingly, there was also an improvement in sleep as well (4).
The authors speculate that higher levels of lutein and zeaxanthin in the eye improve the ability of the light-sensitive pigments that are an essential part of vision to regenerate. Thus, the eyes maintain visual performance during long periods of exposure to the blue light from screens with the help of lutein and zeaxanthin. They also suggest that lutein and zeaxanthin screen out some blue light to reduce squinting, a cause of eye strain.
Two other studies that used bilberry extracts, which contain both anthocyanins and a range of carotenoids including lutein and zeaxanthin (14, 15), also showed an improvement in eye complaints due to using screens for an extended period of time (16, 17). The anthocyanins in blueberries could protect the layer of cells that supports the vision cells in the laboratory (18), and other clinical trials have shown that it can improve the ability of the eyes to recover after a flash of bright light (19).
Improved office ergonomics, appropriate lighting and treating other vision problems is one step to reducing computer vision syndrome. However, making small changes to the diet could also help, like increasing intakes of lutein, zeaxanthin and anthocyanin-rich foods may be a successful strategy to reduce vision complaints related to prolonged screen time.