Have you ever wondered what triggers us to get tired every night and what wakes us up in the morning (Besides that pesky alarm clock)? It’s our circadian rhythm and it is regulated, in large part, by our eyes. Certain retinal cells, called intrinsically regulated ganglion photoreceptor cells, become inactivated when they absorb blue light. When these cells are inactivated, they send a signal to the pineal gland to start producing melatonin. Melatonin makes us feel sleepy. So we start to feel tired when it gets dark outside because our retinal cells stop absorbing blue light which triggers a release of melatonin from the pineal gland.
Blue light can be divided into two types, blue-violet and blue-turquoise. Blue turquoise light is between 460-500 nanometers, while blue violet light is at the far end of the visible light spectrum at 380-455 nanometers. This means that blue-violet light is very close to the non visible and hazardous ultraviolet light at 10-380 nm.
Blue light, especially blue-turquoise light, during the day is good for us, because the absence of melatonin helps us feel alert and energized. When we are exposed to too much blue light, especially blue-violet light as opposed to blue-turquoise light, it can cause problems with our circadian rhythm and our ocular health. Exposure to blue-violet light for as little as 30 minutes has been shown to disrupt our melatonin production, which affects our sleep cycle. Experts, therefore, say that people should avoid exposure to blue light for at least 1 hour before bedtime to help trigger our melatonin production and get our full 8 hours. Some new studies have even shown that shorter wavelengths of blue light, or blue-violet light, can have harmful effects on our ocular health. Blue-violet light has been shown to cause retinal cell death, cataracts, and acceleration of macular degeneration. The shorter blue wavelengths are also more easily scattered in our eye, which can decrease contrast sensitivity and make our eyes feel strained or fatigued.
Exposure to blue light is becoming more of a concern because we are now more exposed to blue light than we have ever been. Artificial sources of blue light include smartphones, tablets, TVs, computers, fluorescent light bulbs, and LED lights. These are becoming more and more prevalent and so our exposure to blue light is drastically increasing.
Luckily, lens technology is keeping up with gadget technology and there are innovative new lenses that will shield eyes from the flood of blue-violet light. These lenses selectively filter only blue-violet light, while still letting in blue-turquoise light. This allows the wearer to maintain normal color vision and circadian rhythm while protecting the wearer from the blue-violet rays that can contribute to cataracts and macular degeneration. Another way to help decrease your exposure to blue-violet light is to keep devices further from your eyes – less light will enter the eye when the device is held further away.