Closed-eye hallucination
Closed-eye hallucinations and closed-eye visualizations (CEV) are a distinct class of hallucination.  These types of hallucinations generally only occur when one's eyes are closed or when one is in a darkened room.  They should not be confused with phosphenes, perceived light and shapes when pressure is applied to the eye.
Certain users report closed-eye hallucinations under the influence of psychedelics. These are reportedly of a different nature than the "open-eye" hallucinations of the same compounds.

# Levels of CEV perception
There are several levels of CEV perception which can be achieved either through chemical stimuli or through meditative relaxation techniques.

## Level 1: Visual noise
The most basic form of CEV perception that can be immediately experienced in normal waking consciousness involves a seemingly random noise of pointillistic light/dark regions with no apparent shape or order.
This can be seen when you close your eyes, but try to actively look with your eyes at the back of your closed eyelids. In a bright room, a dark red can be seen, owing to a small amount of light penetrating the eyelids but taking on the color of the blood within them. In a dark room, blackness can be seen. But in either case it is not a flat unchanging redness/blackness. Instead, if actively observed for a few minutes, one becomes aware of an apparent disorganized motion, a random field of lightness/darkness that overlays the redness/blackness of your closed eyelids.
For a person who tries to actively observe this closed-eye perception on a regular basis, there comes a point where if you look at a flat-shaded object with your eyes wide open, and try to actively look for this visual noise, you will become aware of it and see the random pointillistic disorganized motion as if it were a translucent overlay on top of what is actually being seen by your open eyes.
When seen overlaid onto the physical world, this CEV noise does not obscure physical vision at all, and in fact is hard to notice if the visual field is highly patterned, complex, or in motion. When you stop trying to actively observe it, it is not obvious or noticeable, and seemingly disappears from normal physical perception.

## Level 2: Light/dark flashes
Some mental control can be exerted over these closed-eye visualizations, but it usually requires a bit of relaxation and concentration to achieve. When properly relaxed it is possible to cause regions of intense black, bright white or even yellow to appear in the noise. These regions can span the entire visual field, but seem to be fleeting in nature.

## Level 3: Patterns, motion, and color
This level is relatively easily accessible to people who use LSD, and appears to be what most people refer to as colorful visuals.
However, it is also accessible to people involved in deep concentration for long periods of time. When lying down at night and closing the eyes, right before sleep the complex motion of these patterns can become directly visible without any great effort.

## Level 4: Objects and things
This is a fairly deep state. At this level, what you are thinking becomes visually manifest as if it were a real object or environment. When this level is reached, the CEV noise seems to calm down and fade away, leaving behind an intense flat ordered blackness. The visual field becomes a sort of active space where what you think is what you get. A side component of this is the ability to feel motion if your eyes are closed. For example thinking of moving down may cause the interior of an elevator to manifest in the CEV field, along with the distinct perception of physically moving downward.  Sometimes it feels like you are in a room that is familiar to you.
Opening the eyes returns one to the normal physical world, but still with the CEV object field overlaid onto it and present. In this state it is possible to see things that appear to be physical objects in the open-eye physical world, but that aren't really there.

## Level 5: Overriding physical perception
This is the point where it appears to the outside world that a person is either unconscious or insane. The internal CEV perceptions and think-it/feel-it perceptions become stronger than physical perceptions, and completely override and replace open-eye physical perceptions. This can be a potentially dangerous state if a person is still mobile while literally off in their own little world, but by this time most people are motionless are not likely to do something hazardous to themselves or others.
This is the point where most hallucinogenic references say it is a good idea to have a "sitter" present to watch over the person using the chemicals, and keep them from accidentally harming themselves or others while deep into their own world.
The way you can achieve this manifestation easily is by placing a palm over your eyes and staring into your hand. What will soon follow is what appears to be fading in and out manifestations or strong visuals that seem very life-like. The color is not true however, as in a dull yellow almost a sepia tone may be visible only on certain hallucinogens such as DXM.

# What is not a CEV

## Image burn-in
Image burn-in occurs when very bright objects lie in one's field of vision, and should not be confused with closed-eye hallucinations. Visual burn-in from bright lights is visible for a few minutes after closing the eyes, or by blinking repeatedly, but the burn-in effect slowly fades away as the retina recovers, whereas the waking-consciousness CEV noise will not disappear if observed continuously over a period of time.

## Protein strings
Protein strings, which can be found floating in the liquid inside the eyeball, can be seen when looking at bright point-light sources with their glasses or contact lenses removed. They are, however, not exclusively associated with shortsightedness.
Protein strings tend to remain motionless if the eyes are still, rotating vertically if one looks up and down rapidly, and horizontally if one looks right to left rapidly. In either case these slow down and stop after a few seconds. The motion of waking-consciousness CEV noise cannot be controlled so actively.

## Corneal liquid
This perception does not involve the liquid and air bubbles on the surface of the cornea, which can also be seen by extremely nearsighted people when looking at bright point-light sources with glasses/contacts removed. Half-closing and reopening the eyelids creates a very definite wiper-ridge in the corneal liquid that is readily visible. Fully closing and reopening the eyelids also stirs up the corneal liquid which settles down after a brief moment. The motion of waking-consciousness CEV noise is not so directly and physically controllable and repeatable. This is not necessarily only associated with extreme nearsightedness.

## Blue-sky sprites
This perception does not seem to be related to the "sprites" (blue field entoptic phenomenon) that can be seen as dots darting around when staring up into a bright blue sky on a sunny day (not looking at the sun). These dots superimposed over a flat blue background are white blood cells moving through the blood vessels of your retina. The motion of waking-consciousness CEV noise is uniformly random compared to the waking-consciousness blue-sky sprite motion.

## Physical retinal stimulation
This perception is unrelated to the visual noise seen when the retina is physically stimulated.  The retina can be made to produce light patterns of visual noise simply by one rubbing their eyes somewhat forcefully in a manner that increases intraocular pressure.  Additionally retinal noise can be produced by touching near the rear of the eyeball (for example, if one closes their eyes, looks all the way left, and lightly touches the rightmost part of the eye socket, this produces visual noise in the shape of a circle that appears at the left side of the visual field - a practice that is neither painful nor dangerous). None of these are closed-eye hallucinations.