Light plays a crucial role in regulating our circadian rhythm, the body’s internal clock that regulates our sleep-wake cycle. Specifically, melanopic light, a band of light that stimulates OPN4, melanopsin cells in our eyes, has a significant impact on our circadian rhythm.
What is Melanopic Light?
Melanopic light is a band of light detected by a specific group of cells in our eyes called melanopsin cells or OPN4, one of many non-visual photoreceptors all over the body. These specific "opsin" cells are primarily located in the retina and are responsible for regulating our circadian rhythm. When melanopsin cells are stimulated by melanopic light, they send a signal to the suprachiasmatic nucleus (SCN) - the body’s master clock. The SCN then sends signals to other parts of the body, regulating everything from hormone levels to body temperature.
Melanopic light can be talked about in terms of melanopic lux, which takes into account the sensitivity of the melanopsin cells to different wavelengths of light. The amount of melanopic light that we are exposed to during the morning and daytime can have a significant impact on our circadian rhythm and overall health. Melanopic sensitivity peaks at ~480nm sky blue (cyan) at over 6x sensitivity compared to the visual lux of that same wavelength. This means that while this cyan light may appear less bright to the eye, the biological action to OPN4 is far greater than with red for example, where there is zero activation. Below in grey is the melanopic action curve. The red portion shows the light that is able to pass though our Carbonshade melanopic light blocking glasses, these lenses block 99.8% of all melanopic light, and are intended to be used for the last hour or two before bed, creating a sort of artificial darkness for the OPN4 cells, sensitive the grey band of light.
The Impact of Melanopic Light on Circadian Rhythm
Melanopic light is most effective at regulating our circadian rhythm when it is present in the morning and daytime, and most disruptive in the evenings. Exposure to melanopic light in the daytime can help to reset the body’s internal clock, leading to better sleep quality and overall health. Exposure to melanopic light at night can have the opposite effect, disrupting our circadian rhythm and leading to sleep disorders and other health problems. We cover both sides of this light/dark cycle.
Sources of Melanopic Light & Cellular Darkness
Melanopic light can be found in a variety of sources. Sunlight is the most potent source of melanopic light, with natural daylight containing up to 100,000+ melanopic lux. Indoor lighting can also provide melanopic light, but typical indoor lighting is roughly 100x dimmer than the outdoors. We designed the Sky Portal device to offer a personal source of melanopic light during the day, and designed our Carbonshade glasses with red lenses to block this light in the evenings when on the flip side, it's nearly 100x brighter inside than it is naturally outside.
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