Hallucinating seeing light in a pitch-black room is a common phenomenon known as the "visual snow" or "phosphene" effect. There are several reasons why this might occur:
Neural noise: The human visual system is sensitive to even the tiniest amounts of light. In complete darkness, the neurons in your visual cortex may still generate random electrical signals, known as neural noise. This neural noise can sometimes be interpreted by your brain as faint points or flickers of light, creating the illusion of seeing light in the dark.
Retinal afterimages: If you were exposed to bright light before entering the dark room, you might experience retinal afterimages. These afterimages occur due to photoreceptor cells in your retina becoming overstimulated. When you move to a dark environment, you may still "see" these afterimages as faint light patterns for a short period until your visual system adapts to the darkness.
Phosphene phenomenon: Mechanical or physical pressure on the eyes can also lead to the perception of light in the dark. For example, rubbing your eyes or applying gentle pressure on your closed eyelids can stimulate the photoreceptor cells, resulting in phosphene-like light patterns.
Neural adaptation and visual processing: The brain continually processes sensory information and attempts to make sense of the signals it receives. In the absence of external visual stimuli, the brain may attempt to fill in the gaps and create its own visual experiences, which could include perceiving light patterns that aren't actually present.
Sensory deprivation effects: Being in a pitch-black room can be an example of sensory deprivation, which may lead to the brain generating its own stimuli to compensate for the lack of external input. This can manifest as visual hallucinations, including the perception of light.
It's important to note that these visual experiences are typically harmless and not indicative of any underlying health issues. They are a normal part of how the brain processes sensory information under certain conditions. However, if you experience persistent or concerning visual hallucinations in any setting, it's essential to consult a healthcare professional to rule out any potential medical conditions.