Anatomy as Optics The body can be seen as a living optical system designed to distribute light intelligently. - The skin acts as a filter and diffuser. - The CSF serves as a light guide for the brain. - The blood vessels act as photon absorbers and transporters of NO-mediated signals. - The eye/sclera facilitate infrared light to the retina - The amniotic fluid ensures that the fetus is immersed in light. The optical properties of our tissues are not accidental. They are tuned by evolution to channel the wavelengths that sustain metabolism, regulate oxidative balance, and synchronize cellular rhythms with the external world. Nature has built optics into our biology. All you have to do is live a life in accordance with it.