Blue Light: the Good and the Bad



The visible spectrum

The light that reaches and enters the human eye is divided into visible light, comprising wavelengths from about 380 to 780 nm, and the non-visible spectrum, which includes light in the ultraviolet range (UV light) and the infrared range (IR light).

Experts have been aware for some time that UV light can potentially cause damage to biological tissue such as our skin and eyes, and people typically use suitable means of sun protection to address this issue. However, blue-violet light also has the potential to cause damage, especially to our eyes. Blue-violet light may have less energy than ultraviolet light, but in contrast to UV light – most of which is absorbed by the front part of the eye – blue light reaches as far as the retina.

The component of light in the blue-violet band between 380 and 500 nm is known as high-energy visible (HEV) light. Wavelengths between 380 and 440 nm are seen as particularly critical and have been implicated as one of the possible causes of photoretinitis, which involves damage to the retina caused by high-energy incident light.


Beneficial aspects of blue light

Scientific studies have shown that light has a biological effect on our body, among other things helping to regulate our hormone balance. The hormone melatonin plays a significant role in regulating our sleep/wake cycle, and the light energy that we require for this process is largely absorbed through our eyes. Another key factor in this process is a light-absorbing pigment in the eye called melanopsin, which has been shown to be most active in the short-wavelength portion of the visible spectrum. That means that the blue light which reaches our retina also plays a part in ensuring our psychological well-being, which is why light therapy is successfully employed to treat winter depression and insomnia.

UV light is also involved in the production of vitamins, which means that light stimulation also has an important effect on our metabolism. In summary, our bodies need blue light.

To take one concrete example, many people are familiar with the concept of age-related insomnia, which refers to the fact that elderly people seem to require less sleep. The light that reaches the human eye seems to play an important role in this phenomenon. The cataracts that older people typically suffer from, prevent some of the blue light from reaching the retina – and the intraocular lenses used to treat patients with cataracts also have the effect of blocking blue light. This might causes perturbations in the day-night rhythm of these mostly elderly individuals and alters the amount of sleep they need.

But as in so many other cases, the rule that applies here is "everything in moderation."


Damaging effects of blue light





So far no studies have been carried out to answer questions such as whether using computer displays or staring at these new sources of light for long periods of time could damage the retina. But it is important to remember that spending one hour outside on a normal overcast day exposes our eyes to 30 times more blue light than spending one hour inside sitting in front of a screen.

Clear spectacle lenses with a blue light filter




DuraVision® BlueProtect is a lens coating for clear lenses which can be applied as an additional layer. It offers all the benefits of a traditional DuraVision® Premium coating by ZEISS, including optimized hardness in an easy-clean design. BlueProtect also includes a blue filter which attenuates blue light in the 380 to 440 nm band. That means improved visual comfort for anyone who wants protection against blue light during indoor activities without losing the beneficial effects of blue light in the 450 to 500 nm band! Spectacles with DuraVision® BlueProtect can be worn all day long, unless you choose to wear your sunglasses for outdoor activities or use PhotoFusion® lenses, which also offer 100% UV protection.

How digital devices are changing our vision


How digital devices are changing our vision



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