Geometry

Geometry is the perception of structured, repeating visual patterns — grids, lattices, fractals, and spirals — that appear across the visual field without an external source.

As a drug effect it is acute and dose-proportional, fading as the substance wears off, which distinguishes it from the persistent visual disturbances seen in certain neurological conditions. It ranges from faint patterned shimmer at the visual periphery to dense, self-similar formations that fill the entire field at high doses.

Geometry is among the most widely reported perceptual effects across psychoactive classes. It is most commonly induced at moderate to high doses under psychedelics such as LSD, psilocybin mushrooms, and DMT, and under cannabinoids such as JWH-018 and 5F-PB-22; it also appears under depressants such as GBL and zolpidem, and at high doses under stimulants such as amphetamine.

Geometry is felt as an overlay of structured pattern on ordinary vision: repeating forms — hexagons, triangles, branching lattices, and spirals — tile surfaces and fill the space behind closed eyes. It commonly comes with intensified color saturation and a sense of the patterns slowly shifting or rotating in place.

Attending closely to one region tends to draw it inward, sharpening detail and pulling more of the visual field into pattern. At high doses, particularly under psychedelics, the forms become fractal and layered, absorbing ordinary visual content entirely.

Geometry arises through different pathways depending on the drug class:

• Psychedelics — act on 5-HT2A receptors in visual cortex, disrupting thalamocortical gating and surfacing spontaneous patterned activity.
• Cannabinoids — act on CB1 receptors across the visual system, altering cortical feedback in ways that produce comparable geometric activity.
• Depressants — GBL and zolpidem suppress inhibitory circuits in visual cortex at sedative doses, releasing geometric patterning.
• Stimulants — produce geometry less reliably; high-dose arousal of visual cortex through noradrenergic and dopaminergic pathways appears to be the route.

How much each pathway contributes in a given case is not fully understood.

Who experiences it, and how strongly, varies widely. Dose is the primary driver — geometry scales reliably from faint peripheral shimmer at low doses to field-filling pattern at high ones.

Set and setting shape its character — lighting and whether eyes are open or closed alter the forms considerably, especially under psychedelics and cannabinoids. Prior experience with patterned visual states tends to make the forms feel familiar rather than disorienting. Fatigue can lower the threshold at which it appears.