The Physical and “Mental” Eye Emits Light

The eye itself, which is continually exposed to ambient powerful photons that pass through various ocular tissues, emit spontaneous and visible light-induced ultra-weak photon emissions.[3]  
It has even been hypothesized that visible light induces delayed bioluminescence within the exposed eye tissue, providing an explanation for the origin of the negative afterimage.[4]  These light emissions have also been correlated with cerebral energy metabolism and oxidative stress within the mammalian brain.[5] [6] And yet, biophoton emissions are not necessarily epiphenomenal. Bókkon’s hypothesis suggests that photons released from chemical processes within the brain produce biophysical pictures during visual imagery, and a recent study found that when subjects actively imagined light in a very dark environment their intention produced significant increases in ultra-weak photo emissions.[7] his is consistent with an emerging view that biophotons are not solely cellular metabolic by-products, but rather, because biophoton intensity can be considerably higher inside cells than outside, it is possible for the mind to access this energy gradient to create intrinsic biophysical pictures during visual perception and imagery.[8] (Source)