This could be HPPD[1] or related. There seems to be uncertainty as to if hallucinogens cause some of these effects directly, or if they simply help train the mind to notice what was already there. For instance, is visual snow there already, and hallucinogens simply make one more aware of it and capable of focusing on it (similar to how tinnitus is worse if one focuses on it)?<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Hallucinogen_persisting_perception_disorder" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Hallucinogen_persisting_percep...</a>