Photosensitive Ganglion Cells — the cells in your eye that set the circadian rhythm.
Interestingly, the light sensitive cells in your eyes that set your circadian rhythm (and that also suppress melatonin release) are
not the
rod and cone light sensitive cells of normal human vision, but a completely different type of light sensitive cell, called
photosensitive ganglion cells.
Both the rod and cone cells in your eye and the photosensitive ganglion cells are located in the retina, but the latter do not contribute to human vision at all. Photosensitive ganglion cells are blind to shape or form, but they do sense the level of ambient light.
These photosensitive ganglion cells, which were only relatively recently discovered (in 1991), are also the ones involved in seasonal affective disorder (winter depression).
Photosensitive ganglion cells employ a pigment called melanopsin to detect light. The turquoise curve in the graph below shows the sensitivity of melanopsin, and thus the photosensitive ganglion cells, to various color wavelengths. You can see from this graph that the photosensitive ganglion cells are most sensitive to blue light (the peak sensitivity occurs at the blue wavelength of 464 nm), but also have some sensitivity to green and violet light.
The turquoise blue curve in the graph shows the sensitivity of the photosensitive ganglion cells to various colors. These cells are most sensitive to blue light (of wavelength 464 nm), but as the graph indicates, they are also sensitive to green and violet. Source: here.
So it is likely that blue blocker lenses will not do a complete job of blocking out the light colors that affect the circadian rhythm, since these lenses do not block the green light that can also activate the photosensitive ganglion cells that control circadian rhythm. Though these blue blocker lenses will block the bulk of the colors that affect the circadian rhythm.
This means that even if you are using blue blocker lenses, it may still be a good idea to use computer software such as
Nocturne (for Mac), which you can set to block all blue and green colors on your computer monitor. And it may also be a good idea to dim the room lights, or use an orange or red light bulb.