I had slight hppd (some visual snow on walls and the sky and slight bending of things if I stared long enough, but It doesn't really bother me as it's quite subtle) since I used LSD twice in two weeks. That was 2 months ago.

I haven't done any psychedelics since because I wasn't really interested, but yesterday I did ketamine and kholed.

Just now I thought about how things looked somewhat clearer, and looking at the sky, I realized that I don't have any more snow or at least much much less. Anyone ever had an experience like this?

My theory is that LSD causes hppd by creating some connections (or by making some connections more active) in the brain. Those connections remain (and slowly fade obviously) and the ketamine, also being a promotor of neuroplasticity removed them, or put the focus on different connections as it also has a completely different mechanism of action. Though it's probably impossible to understand what's really going on in the fleshy computer we have in our heads

Edit: wording