Could it be something similar to those optical illusions that when you stop looking at it the image perisists for a bit? I think it's completely a mental thing, it's not like any part of the physical visual system got deformed, it's something in the way that the brain interprets visual data and produces visions. Maybe it can be simplified as the weights in the neural networks responsible for vision needing time to come back to their base values.
With dmt, since the visions are not coming from a physical visual input, it's maybe not the networks related to interpretation of visual data but only production of visions.
Does the wispy spider webby tangles somehow correspond to the dmt visions? Like edges in a geometric visual?
"Is this the end of our adventure? Nothing has an end. We came in search of the secret of immortality, to be like gods, and here we are... mortals, more human than ever. If we have not obtained immortality, at least we have obtained reality. We began in a fairytale and we came to life! But is this life reality? We are images, dreams, photographs. We must not stay here! Prisoners! We shall break the illusion. This is Maya. Goodbye to the holy mountain. Real life awaits us." ~ Alejandro Jodorowsky