In today's increasingly technological society, most people spend a considerable amount of time looking at digital devices. Studies suggest that 60% of people spend more than six hours in front of a digital device (TVs, computers, smart phones and tablets), on a daily basis. Over 40% of adults have jobs that require prolonged use of a computer or tablet while 74% of teenagers aged between 12 and 17 have access to the internet on their devices. Moreover, a large percentage of people use bulbs for lighting at night. The digital devices and light bulbs have one thing in common; blue light.

What is blue light and how does it affect eyesight?

Blue light is a colour in the visible light spectrum that can be seen by the human eye. Blue light has a wavelength of between approximately 380nm and 500nm; making it one of the shortest, highest-energy wavelengths.

According to a Harvard health publication from May 2012, blue wavelengths, when coming from the sun (the only natural source of blue light), are beneficial during daylight hours because they boost attention, reaction times and emotions. Blue light is also responsible for regulating the body’s sleep and wake cycles as well as memory and cognitive function.

However, the shortness of the energy wave lengths causes them to flicker more frequently than other forms of light and this flickering affects the eyes’ sharpness, clarity and contrast. The more obvious short-term effects include strain and fatigue.

According to Dr Matthew Alpert, the Chairman of Optometric Innovation, VSP Global, fatigue and strain come about because when we look at a screen. "Our blink rates drop significantly, and our eyes won’t put up with that for too long,” he explains. Signs of fatigue include; dry eyes and headache. In the long run, exposure to blue light can lead to retinal damage and age-related macular degeneration which can lead to significant vision loss.

If you’re keeping your children entertained with television or video games, it might be time to rethink the strategy.

Yellowing of the lens, which usually starts to occur at the age 20, is responsible for protecting the retina from damage. Therefore, children have little or no yellowing of the lens. As a result, if blue light enters the eye, it is unfiltered and this means that it will strike the retina at full length, exposing it, and the lens to damage.

However, video games, specifically those that are action-oriented are said to have some health benefits. In a study by Live Science, 10 male college students who were previously non-gamers were given 30 hours of training in video gaming. Results showed that after the training, there was a substantial increase in their ability to see objects clearly in cluttered spaces. The finding therefore suggests; "Playing first person action video games could be a useful rehabilitation therapy for people with certain vision problems such as amblyopia.” However, exposure should be regulated, ensuring breaks and access to natural light.

Other effects of blue light

Blue light can cause chronic insomnia for both adults and children. According to studies, exposure blue light at night has the tendency to throw off the body’s biological clock, thus affecting our ability to sleep. This is because it suppresses the secretion of melatonin, the hormone responsible for sleep. Lack of sleep has damaging health effects since sleep helps restore our mental and physical energy, and helps to rebuild our muscle tissue.

Short-term effects of insomnia include depression, loss of concentration, disruptive behaviour and low energy and performance while long-term effects include heart disease, high blood pressure, stroke, diabetes, among other things.

In women, suppressing the secretion of melatonin increases the risk of breast cancer. Several scientists found that women who work night shifts are more likely to develop breast cancer, than those who sleep at night. In an article by the Breast Cancer Fund, it is stated; "Genes that are associated with the regulation of the daily melatonin cycle also regulate other pathways that may be involved in the development of breast cancer.”

What you can do to keep healthy

While digital devices are important for work, social and recreational purposes, experts advise us to take regular breaks while using them and overall, use them in regulation. According to the May 2012 Harvard health publication, it is advisable to avoid looking at bright screens beginning two to three hours before bed. It is also advised that you expose yourself to bright light during the day because this will boost your ability to sleep at night, as well as your mood and alertness during daylight.

Dr Alpert advises people who are constantly exposed to blue light, to blink more. This, he says, keeps eyes lubricated. Additionally, he encourages the use of the "20-20-20” rule. "Every twenty minutes, stare at something else at least 20 feet away. This exercise engages your distant vision and helps the eye to rest,” he explains.

When you go to bed at night, experts advise that you sleep in total darkness. According to the National Sleep Foundation of the USA, one should keep one’s sleep environment dark. And if one wakes up in the middle of the night, one should avoid as much light as possible since unnatural light disrupts the sleeping cycle.