Here is how I make sense of unusual visual experiences, be it through psychedelics or meditation
Someone else's unusual visual experiences
It was as if some sort of round energy ‘portal’ opened up or appeared on the wall behind me. It was about eight feet across and high, filling the wall. For a minute or so I looked into it, into the doorway to heaven, as that is how it felt. I felt an extreme, almost bristling, blistering coldness (not unlike that of my dream where I was forced to the ground and then hung upside down), with an eternal fullness and incredible potential. As I looked into it, the question I was psychically or intuitively being asked was whether I would like to be One with it.I didn’t need to get up from the chair. I only needed to say yes internally and I would be ‘One’. It was as if the doorway was genuinely open...
Explanation from the point of view of the Bayesian brain hypothesis
This is the kind of "seeing" through psychedelics, especially ayahuasca.
Science (predictive processing theory or Bayesian brain theory) tells us that we don't really "see" in a bottom-up way (e.g. photons hitting the retina, with all the subsequent processing into higher and higher abstractions). Instead, most of our processing is top-down. This can be traced by the following information flows in the brain between different nodes/modules.
The brain creates a model of what it expects to see next , it is projected into awareness, and it compares it with sensory feedback. The feedback is the corrective difference between the model and the prediction. So we never actually see reality, we only see what we project - it's literally like a screen that is constantly refreshed with every tiny eye movement, very Buddhist indeed, and very energy intensive (that's why the visual cortex is so big).
Now with psychedelics, and sometimes spontaneously, the brain/mind can change the way it generates the visual model, e.g. it can change the weight it gives to the bottom-up flow and the top-down "priors" that shape the model. This means that the way the model is built can override our normal expectations.
For example, we usually have a 'prior' or 'guiding modelling assumption' that walls are stable and immobile objects. However, the first thing you may literally experience with a psychedelic is that "walls can breathe" (or "flowers can dance" in their vase, etc).
I couldn't believe it when I experienced it for the first time at the age of 62. I walked closer and closer to the flowers to inspect them, and they still swayed, quite seductively, in their vase. Or I literally 'saw' geometric patterns running across my partner's face, from left to right, gold, blue... beautiful. Her face had also changed, extremely symmetrical, round eyes, goddess-like. The patterns appeared like the typical 'visions' described in Dzogchen Thogal practice. Diamonds, nets, threads, "like a waterfall" etc.
Years later, on a Mahamudra/Dzogchen meditation retreat (my first and only experience of a retreat I ever had), something similar happened to my vision, specifically the appearance of a stripe of colour changing to a deep blue described in Dzogchen texts, and then a visualisation of "awareness showing itself to awareness".
What I am saying is that I absolutely believe that you "really" saw this. Your mind, through whatever Barry Long had triggered, gave you a psychedelic/Dzogchen moment where it loosened its normal constraints on how to construct your world model and allowed something deeply symbolic and meaningful to be represented through the visual system. In your case, a vortex, something that also had an energetic component that drew you in. Vortexes are also typically psychedelic shapes.
It is also typically "psychedelic" that what you see has a higher degree of significance and meaning than what you normally see. It represents a kind of "message". In brain-speak, that's the salience network going into overdrive. The world is suddenly filled with deep meaning, which can extend to the smallest thing - like Aldous Huxley admiring the folds of his trousers (in "The Doors of Perception") when he first experimented with mescaline.
You may be interested listen to Shamil Chandaria (here in a podcast with Michael Taft) on Youtube, who comes from Google AI, is neuroscientist, meditator and apparently has experienced psychedelics.
Also of interest is Andrew Gallimore (here in a podcast), who investigates the effect of various classes of psychedelics, down to the individual neuron.
Resources
Chandaria, S. (2022, October 30). The Bayesian Brain and Meditation: A predictive processing account of radical changes in the character of phenomenal experiences [Video]. YouTube. https://www.youtube.com/watch?v=Eg3cQXf4zSE
Gallimore, A. (2022). Reality Switch Technologies: Psychedelics as Tools for the Discovery and Exploration of New Worlds: Gallimore, Andrew R: 9781739110109: Amazon.com: Books. https://www.amazon.com/Reality-Switch-Technologies-Psychedelics-Exploration/dp/1739110102
Jesso, J., & Gallimore, A. (2023, May 18). Adventures Through The Mind - Using Psychedelic Molecules to Explore Alternate Worlds | Andrew Gallimore, PhD ~ ATTMind 176. Retrieved May 18, 2023, from https://podcasts.google.com/feed/aHR0cDovL2phbWVzd2plc3NvLmxpYnN5bi5jb20vcnNz/episode/NTJiYzMyYzktNjBmOS00MmRjLTgzMzMtMzdlZTFjYWM2OWVh?sa=X&ved=0CAgQuIEEahcKEwjIlPTt7v7-AhUAAAAAHQAAAAAQLA
Taft, M., & Chandaria, S. (2022, December). Meditation and the Bayesian Brain with Shamil Chandaria. Retrieved December 19, 2022, from https://deconstructingyourself.com/meditation-and-the-bayesian-brain-with-shamil-chandaria.html