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Closed-eye hallucinations and closed-eye visualizations (CEV) are hallucinations that 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's retina, or some other non-visual external cause stimulates the eye.
Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light." [1] It is a disorientation-, vertigo-, and nausea-inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves.
Peripheral (posterior) vitreous detachment occurs when the gel around the eye separates from the retina. This can naturally occur with age. However, if it occurs too rapidly, it can cause photopsia which manifests in flashes and floaters in the vision. Typically, the flashes and floaters go away in a few months.
A phosphene is the perception of light without light actually entering the eye, for instance caused by pressure applied to the closed eyes. A phenomenon that could be entoptical if the eyelashes are considered to be part of the eye is seeing light diffracted through the eyelashes.
Isolation tank – Pitch-black, light-proof, soundproof environment heated to the same temperature as the skin; Prisoner's cinema – Visual phenomenon involving seeing animated lights in the darkness; Scintillating scotoma – Visual aura associated with migraine; Photopsia – Presence of perceived flashes of light in one's field of vision
Cosmic ray visual phenomena, or light flashes (LF), also known as Astronaut's Eye, are spontaneous flashes of light visually perceived by some astronauts outside the magnetosphere of the Earth, such as during the Apollo program.
Illusory palinopsia is often worse with high stimulus intensity and contrast ratio in a dark adapted state.Multiple types of illusory palinopsia often co-exist in a patient and occur with other diffuse, persistent illusory symptoms such as halos around objects, dysmetropsia (micropsia, macropsia, pelopsia, or teleopsia), Alice in Wonderland Syndrome, visual snow, and oscillopsia.
While cones (which are responsible for color perception and detail) are activated in brighter light, the rods provide vision in low light, but with a loss of precision. Therefore, the graininess we perceive in the dark is a natural adaptation of our vision to photoreceptor limitations, not a sign of some abnormality.