Visual perception in humans occurs through absorption of electromagnetic radiation from
400 to 780 nm by photoreceptors in the retina. A photon of visible light carries a sufficient
amount of energy to cause, when absorbed, a cis, trans-geometric isomerization of the 11-
cis-retinal chromophore, a vitamin A derivative bound to rhodopsin and cone opsins of
retinal photoreceptors. The unique biochemistry of these complexes allows us to reliably
and reproducibly collect continuous visual information about our environment. Moreover …