Layers of the retina, Courtesy of SIGHT, Koenig Films

By Mark Mattison-Shupnick, ABOM

Blue light takes two different pathways in the eye for use in our bodies. One uses the Optic Tract, i.e., photons received by the rods and cones of the retina form electric pulses interpreted as objects in color by the brain as well as visual reflexes. The other is the Retinohypothalamic Tract, a portion of the brain producing essential substances for the body. Here, long wavelength blue light is received and used by the ganglion cells to affect acute factors like melatonin and cortisol secretion, body temperature, heart rate, alertness and psychomotor performance. Longer-term effects are circadian rhythm and light therapy.

I bet you are surprised that the eye is involved in all of these things that promote good feelings and good health. The longer blue wavelengths, about 459 nm to about 486 nm, are key influencers of the retinohypothalamic tract. This means that all that stuff about bad blue needs to also be balanced by good blue and any lenses that we place in front of the eye should correctly differentiate how they affect the two.

Discovered in 1998, this new retinal photoreceptor named melanopsin ganglion cell, is activated by blue wavelengths, as part of the synchronization of our circadian clock. Retinal ganglion cells transmit light signals to the hypothalamus, an area of your brain. In the absence of strong light, the hypothalamus tells the pineal gland, a small organ situated in the brain, to release melatonin. Melatonin is a biological clock synchronizer to get the body ready for sleep. It’s also a powerful antioxidant so critical for many other body functions, implicated in cancer prevention and treatment. During daylight hours, the opposite occurs, the pineal gland produces very little melatonin. And as a result, we are alert and ready to learn more from 20/20 Magazine.