Depth perception distortions from Memantine

Depth perception distortions are defined as alterations in how a person perceives the distance and spatial relationships between objects within their visual field. During this state, the various layers of scenery can become exaggerated, skewed, compressed, expanded, or completely rearranged in ways that fundamentally alter the apparent three-dimensionality of the environment. Objects may seem much closer or further away than they actually are, and the spatial hierarchy of foreground, middle ground, and background can become jumbled or inverted.

One common manifestation is the swapping of layers in a given environment, in which objects that are physically in the background begin to appear as though they are in the foreground and vice versa. A distant mountain might suddenly seem to loom directly overhead, while a nearby table appears to recede into the far distance. In other instances, the same distortion is applied uniformly across the entire visual field, such that everything appears miniaturized and far away (as if looking through the wrong end of binoculars) or magnified and oppressively close (as if the walls and ceiling are pressing inward).

Another significant manifestation is the complete loss of depth perception, in which the different sections of a scene appear to unify into a flat, two-dimensional image regardless of their actual distance from each other and the observer. The world may look like a painting, a photograph, or a flat projection on a screen, with all sense of spatial depth and volume collapsed into a single plane. This can be accompanied by a surreal, dreamlike quality as the brain struggles to reconcile the flattened visual input with its knowledge of three-dimensional space.

Depth perception distortions can also produce the opposite effect, with depth becoming dramatically exaggerated. Rooms may appear to stretch into vast caverns, hallways may seem to extend infinitely, and the gaps between objects may appear enormous. This hyper-dimensionality can create a sense of awe or vertigo, particularly when looking at landscapes, architectural spaces, or even relatively mundane environments that are suddenly imbued with a sense of immense spatial grandeur.

This effect is most commonly induced under the influence of moderate dosages of psychedelic compounds such as LSD, psilocybin, mescaline, and DMT, where it frequently co-occurs with other visual distortions. Dissociatives like ketamine, PCP, and DXM can also produce significant depth perception distortions, often manifesting as a characteristic feeling that the world has become flat or tunnel-like. Cannabis at higher doses may occasionally produce mild versions of this effect, particularly in less experienced users.

Depth perception distortions are often accompanied by other coinciding effects such as perspective distortions, drifting, size distortions, and visual acuity changes. While the effect is generally considered benign and self-limiting, significant distortions of depth perception can impair the ability to navigate physical environments safely, making activities like driving, climbing stairs, or crossing streets potentially hazardous during the experience.