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What The Fli*ckering?

If you find LED lights oddly annoying, you’re not alone. They can cause headaches and - wait for it - general malaise. Before we begin, it’s important to understand what a saccade is. This is the abrupt movement your eyes make when they change direction. In some cases, saccades can be as fast as a high-speed train. When your eye is stationary, flashing images typically blur into one continuous stream. But if your eye moves at the same speed as the flashing image, you'll be able to see it. Scientists originally thought we could see about 90 flashes of light per second, but during a super fast saccade, they now think we can see about 2,000 flashes per second. So, back to those pesky LED lights...


Most bulbs use an alternating current (AC), as that's what most - if not all - homes are run on. Power is generated by oscillating a current between positive and negative poles a certain number of times per second (60 cycles per second in the U.S. and 50 cycles in the U.K.) Traditional bulbs work by heating a central filament, which glows. When the current alternates, the glow isn't interrupted as it doesn’t have enough time to cool down between oscillations. LED lights, on the other hand, don't have a heated filament, which means every time the current alternates it effectively turns it off and on again - creating a super fast flicker. You can’t see it directly, but as soon as you whip your eye around the room, you may pick up on the flashes. And you move your eyes more often than you probably realize. Whether glancing from your laptop to the clock, to your phone and back to your laptop, your eyes are constantly moving. 


Studies have shown that people are more likely to get headaches when surrounded by flickering LED lights. In 2018, the Scientific Committee on Health, Environmental and Emerging Risks (SHEER) released this statement: “LED lighting can produce a stroboscopic effect, depending on the degree of modulation. The use of modulated LED lighting in domestic and other non-industrial environments where awareness is likely to be low is of a concern. Although no published case studies were identified, there are claims that a small number of people are very sensitive to temporal light modulation at about 100 Hz, triggering symptoms such as headaches, migraine and general malaise."


What's the solution? Some LED lights come equipped with technology that reduces the flicker. You can also use a DC (direct current) power supply, as the current stays constant. Or, you can keep your flickers slow and moody by using a candle.


Learn more:

The scientific reason you don't like LED bulbs

Types of eye movements and their functions

Lighting ergonomics - Light flicker

Image by Daniel Reche

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