The two sides of blue light

By Rohan Paul

The present COVID-19 pandemic has made the workplace at home a reality for millions of employees almost overnight. Video conferencing with colleagues, homeschooling with the kids or online lectures – almost everyone spends a lot of time in front of screens and digital devices these days. The increasing use of such digital devices impacts work-life balance, but also health and vision. That’s why there is also an ongoing scientific discussion about whether and how blue light damages the eyes.

What is blue light?

“Visible light” is the part of the light spectrum that is visible to the human eye. Technically it’s described as electromagnetic radiation with a wavelength range from 380-780 nm. Blue light is the high energy part of this visible light spectrum ranging from about 380 nm in the blue-violet range up to 500nm. Basically, two types of blue light can be classified: the natural blue light of the sun and the artificial blue light emitted by LED lamps, energy-saving lamps, and smartphone and computer displays.

Beneficial aspects of blue light

Blue light is of paramount importance for a normal and rich color vision and high contrast vision. In fact, the human retina consists of three color receptors for the colors blue, red and green, and only the full functionality of all three cone-type receptors ensures normal color vision. Another kind of photoreceptors in the eye are allowing for vision at low light conditions in dark environments. These rod-type receptors are dominantly sensitive also in the blue and blue-green spectrum. Since the rod-type receptors are also dominant in the retinal periphery they therefore allow for peripheral vision and motion perception.

Additionally, blue light increases alertness and regulates the circadian rhythm – the body’s natural wake and sleep cycle. Exposure to blue light during the day thus contributes to a healthy circadian rhythm.

Hazardous effects of blue light

The relatively high levels of energy inherent in the comparatively short wavelengths of blue light have been shown to impact metabolic processes in retinal cells. It is entirely plausible that excessive exposure to blue light can cause damage to the retina. However, scientists are currently unable to say what dose and what light sources have significant damage-causing potential. So far available scientific results only imply that artificial blue light from typical architectural LED lighting, or displays is far below any known thresholds to create health damages in human ocular system.

However, exposure to artificial blue light, especially late in the day, can have a disruptive effect on the circadian rhythm and consequently on the sleep cycle and general well-being. Some parts of the blue light spectrum also affect the perception of glare. This unfocused “visual noise” can contribute to visual discomfort and symptoms associated with digital eye strain.

In conclusion, blue light is not only good or bad, as it has both beneficial and hazardous effects on the eyes. This is what we call the “dualism of blue light”.

For wearers of eyeglasses, protecting yourself against blue light is an easy choice. The blue-filtering properties of clear all-day lenses can be ordered as a lens upgrade with the purchase of new glasses.

(The author is Business Head- Commercial at ZEISS Vision Care India. Views expressed are personal.)