The dark side of blue light – By Jenny Livanos, Holistic Optometrist and Nutritionist
In the retinal layer at the back of our eyes exist both cone and rod photoreceptor cells that are responsible for light sensitivity. Recent and ongoing research has shown that there is a third type of retinal photoreceptor, and it is sensitive to blue light. These sparsely-situated blue-light receptors help differentiate between day and night, regulating our ‘sleep/wake’ cycles – known as circadian rhythms – and our pupil responses.
Let the sun shine in
Scientific research has shown that sunlight has a biological effect on our body. It helps visual acuity, contrasts colour perception and assists in various non-visual functions in the body, including vitamin D production, release of the ‘happy hormone’ serotonin, our moods, hormonal balance and general and visual health. Exposure to bright sunlight during the day regulates how we feel, our reaction time, alertness, cognitive function and energy levels.
The sun was our major source of light in the distant past, with people spending their evenings in relative darkness. Over the last 100 years, however, due to the invention and prolific use of the light bulb, and much more recently the introduction of digital devices, we are exposed to significantly more light at night. Prolonged exposure to light in the evening delays our body clock, leading us to delay our bedtime. Light is the most important factor that can affect our sleep.
Blue light exposed
Research is currently investigating the beneficial and adverse effects of blue light exposure during the day and at night. Blue light received through sunshine during the day through the eyes is necessary for optimal health. As diurnal beings, we are programmed to be outdoors while the sun is shining and asleep at night when it’s dark.
Nowadays it is common to come home after a long day at work or school and relax by surfing the Internet on our laptops, reading on an e-reader, playing games on our tablets, catching up with Facebook on our smart phones and/or watching television on our large screens – or a combination of these at the same time!
The light from these digital devices and to a lesser extent from light bulbs, LED lights and fluorescent tubes has a higher concentration of blue light than natural light. Scientists have warned against using light-emitting devices before going to sleep, as this intense blue-light exposure is disturbing our body’s rhythm and sleep patterns.
Blue light affects levels of the sleep-inducing hormone, melatonin, more than any other wavelength. Melatonin is created by the pineal gland in the brain during darkness and its production ceases during daylight. It is profoundly affected by light and darkness. Melatonin helps regulate other hormones while controlling the body’s circadian rhythm; it’s an internal 24-hour ‘clock’ that plays a significant role in when we fall asleep and when we wake up.
Shifting the body’s natural clock with blue light exposure at night can have a negative impact on health and has been implicated in depression, diabetes, immune problems, obesity, cancer and heart disease. Visual comfort and eye health are also affected, with an increased risk for retinal cell damage leading to macular degeneration.
Protect your eyes
The human eye is sensitive to visible light, a portion of the electromagnetic spectrum. This is seen by the eyes as the colours red, orange, yellow, green, blue, indigo and violet. Blue light has a very short wavelength, thus producing a higher amount of energy, creating flickering, glare and visual ‘noise’. Chronic exposure to blue light can have serious consequences for eye health and visual comfort.
Studies show that more than 60% of us spend more than six hours per day on digital devices. 70% of people who regularly use these devices report symptoms like loss of clarity and contrast, tired eyes, headaches, fatigue, blurry vision, light sensitivity, watery/dry/itchy eyes and neck and back pain.
Our eyes’ natural filters may not provide enough protection against the sun’s blue light rays, let alone the extra blue light from digital devices and artificial light sources. Prolonged exposure to blue light causes retinal cell damage by penetrating through to the back of the eye, and this may contribute to serious macular degeneration.
Who is more at risk?
We all need protection from blue light exposure at night, but some people are more vulnerable to its negative effects:
- Office workers in front of computers all day, with high exposure to fluorescent tubes and LED lights and minimal sunlight exposure;
- Teenagers and children who use digital devices late at night for study and personal use – they may have trouble getting to sleep, waking up easily and issues with mood;
- Shift workers – studies have linked working night shifts, and subsequent exposure to light and blue light, to several types of cancer (breast, prostate), diabetes, heart disease and obesity;
- People already more at risk for macular degeneration, including having a family history, smoking or having cardiovascular issues, diabetes or poor diet;
- Those with intra-ocular lenses who have had cataracts removed – exposed to more blue light penetration through to the retina.
Tips for better sleep and health
- Seek bright sunshine in the morning to set your body clock, improve your mood and increase alertness (get up early!).
- Expose yourself to bright natural light during the day – take your lunch breaks outdoors, go for a walk!
- Sunglasses may limit your eyes’ access to full sunlight. Go shades-free in the daylight, even for 15 – 20 minutes a day.
- Have lots of breaks away from your digital screens. Try the 20-20-20 rule: look up every few minutes to 20 feet away (6 metres) for 20 seconds and take a physical break every 20 minutes. Turn your screen brightness down and position screens and smart phones further away from your eyes.
- Lens companies now offer blue-light-blocking technology on spectacle lenses. These specialised coatings on lenses reduce blue light and are being recommended for all-day use.
- Avoid using digital devices for two to three hours before bed.
- Install an app that reduces blue light at night on your laptop and smartphone; for example, f.lux and Twilight. I-Phone users now have a blue-light reduction feature called ‘Night Shift’.
- Use 100% blue-blocking fit-over glasses in the evening, especially if using digital devices. Wear these glasses continuously for 2 – 3 hours before your ideal bedtime – with all TV viewing, computer, tablet, e-reader and smartphone usage. Remove these only after all lights have been switched off and you’re in bed! We have been using these fit-overs for the last year in the practice and have had great feedback about improvements in getting to sleep and quality of sleep!
- Dim general lighting in the evening.
- When you feel sleepy, go to bed – listen to your body!
- Sleep in complete darkness (avoid smart phones, night lights and alarm clocks in the bedroom).
Blue light has both beneficial and damaging effects. If you’re interested in optimal health, consider and manage your exposure to sunlight, artificial light and blue light, in addition to maintaining a healthy diet and lifestyle.
Jenny Livanos is an Optometrist/Nutritionist practising at Concord Eye Care, phone 02 8765 9600.