"The visual pathway is not a one-way street."

Higher areas of the brain can also send visual input back to neurons in lower areas of the visual cortex. As humans, we have the ability to see with the mind's eye – to have a perceptual experience in the absence of visual input. For example, PET scans have shown that when subjects, seated in a room, imagine they are at their front door starting to walk either to the left or right, activation begins in the visual association cortex, the parietal cortex, and the prefrontal cortex - all higher cognitive processing centers of the brain.

The rudiments of a biological basis for the mind's eye is found in the deeper portions of the brain below the neocortex, or where the center of perception exists. The thalamus has been found to be discrete to other components in that it processes all forms of perceptional data relayed from both lower and higher components of the brain.

Damage to this component can produce permanent perceptual damage, however when damage is inflicted upon the cerebral cortex, the brain adapts to neuroplasticity to rapidly begin mending any occlusions for perception. It can be thought that the neocortex is a sophisticated memory storage warehouse in which data received as an input from sensory systems are compartmentalized via the cerebral cortex.

This would essentially allow for shapes to be identified, although given the lack of filtering input produced internally, one may as a consequence, hallucinate - essentially seeing something that isn't received as an input externally but rather internal (i.e. an error in the filtering of segmented sensory data from the cerebral cortex may result in one seeing, feeling, hearing or experiencing something that is inconsistent with reality). Perceived from within the confines of  the "gate" or "bridge" to the inner realms and spaces of spiritual higher consciousness.

Perhaps lamentably so, not all people have the same internal perceptual ability. For many, when their eyes are closed, the perception of darkness remains. Perhaps this is why, when I have on numerous occasions witnessed this heavenly realm or state as "clusters of energy of varying light intensity" and of variable dimensions . Some people are able to perceive colorful, dynamic imagery. Some shaman's and mystics, for want of a better collective noun, use hallucinogenic drugs to increase their subject's ability to consciously access a higher psychic state.

This is however, not a line of thought I have ever had to pursue or resort to as my point of departure is, and always will be, that the dream giver, God, knows full well, what every individual needs from his or her conception without any human or man-made inducement or intervention of any kind.
"The one claiming to abide in Him ought also walk just as in the same way that He walked."

John 15:4
Jesus said:"Remain in Me, and I will remain in you. Just as no branch can bear fruit by itself unless it remains in the vine, neither can you bear fruit unless you remain in Me."John 15:4