Are computers bad for your eyes? And if so, what can be done about it? These are questions that thousands of Australians ask every week. The past ten years has seen enormous changes in the use of computer screens.
Once a desktop screen used only at work, the computer screen has been promoted to a mobile device that is with us 24/7. The latest generation of teens and young adults stare at their smart phones, iPads and games consoles all day. Coupled with this increased exposure is the increased intensity of light emitted from these screens. Is this harming our eyes?
This series of posts looks at the 3 biggest dangers of digital screen exposure. This article examines the role of blue light in harming our eyes.
LCD versus LED screens – which is better?
This is one of those questions that anyone buying a new TV asks but most people are unaware that it’s a misleading question. Technology manufacturers like to draw an artificial distinction between their LED and LCD monitors. This cons us into believing that the LCD has been superseded by the LED, when in actual fact all that’s changed is the way the LCD monitor is backlit.
LCD (liquid crystal display) technology – to the uninitiated – involves sandwiching a liquid layer between two layers of glass and backlighting it. Older technologies backlit the screen using fluorescent light – called CCFL (or cold cathode fluorescent light). This produced light across all parts of the spectrum, with the peak in the green light part of the spectrum (see image, left).
More modern computers still use LCD screens but the backlighting used is more often LED (light emitting diode) technology. This has many advantages over the older fluorescent light technology. It provides a thinner, lighter and more energy efficient display – generating less heat and consuming less power. However, the LED light spectrum is very different to the older fluorescent technology and emits a lot more light from the blue-violet end of the spectrum (see image, right).
Are there good and bad kinds of blue light?
UV light is invisible, but its very short wavelengths allow it to penetrate the delicate superficial tissues of our eyes and skin and cause oxidative damage. This is what leads to skin cancers as well as contributing to many eyes diseases particularly of the cornea and lens – i.e. cataract, pinguecula and pterygium.
Blue-violet light is visible light, but is on the part of the spectrum right next to ultra-violet. Blue-violet light has been shown to be toxic to the delicate structures of our eyes. It can penetrate deeper into the eye – as far as the retina – and it is emerging in clinical data that is has a negative effect on the health of our eyes, particularly for age-related macular degeneration. The mechanism by which blue-violet light damages the retina is still being studied but it is thought to disrupt cellular metabolism at the back of the eye. Blue blockers are glasses which filter out blue-violet light. The filter can be worn with or without a glasses prescription.
Not all blue light is bad! At the greener end of the spectrum is blue-turquoise light. Unlike blue-violet light this kind of blue light is beneficial to us. This is the light that helps regulate our bio-rhythms, telling our bodies when to wake up in the morning and slow down before sleep. Blue light suppresses melatonin production in our bodies, so it is not healthy to be exposed to artificial blue light late at night as it prevents us our natural winding down mechanism from kicking in. This is a good reason why digital screen use should be avoided in the hours preceding sleep, regardless of whether blue-blockers are worn.
What about children and blue light from computers?
The negative effects of blue light on the eye are especially true for children. We previously wrote about kids’ eyes and computers here. (Link to clock-lock-block article). The image below shows the relative intensity of light at various wavelengths for a typical L ED screen. It doesn’t matter what the device, if it’s modern, it’s typically emitting most light at the blue end of the spectrum. This is bad news for our kids, who often spend hours per day on digital devices such as tablets and smartphones.
Take home message? Exposure to blue-violet light should be limited as much as possible. Companies like BenQ now make all their screens with blue light filtering technology. Children’s use of digital screens should be limited, to protect their particularly delicate eyes. For the rest of us, blue blockers can provide protection from harmful blue-violet light but to get a good night’s sleep you should also limit screen exposure before bedtime. And yes, that means TV too!