The phenomenon you're experiencing, seeing waves of light in pitch darkness or with your eyelids closed, is known as the "phosphene effect." Phosphenes are the perception of light in the absence of an external light source, and they can be caused by various factors. Here are a few possible explanations:
Pressure on the eyes: Applying pressure to the eyeballs, either by gently pressing on them or rubbing your eyes, can stimulate the cells in the retina, causing phosphenes. The pressure activates the cells, which in turn send signals to the brain, leading to the perception of light.
Mechanical stimulation: Mechanical stimulation of the visual system, such as when you move your eyes quickly or even during eye movements during sleep, can also generate phosphenes. These movements can create electrical signals in the retina, which are then interpreted by the brain as light sensations.
Neural activity: Even in complete darkness, there is still some level of spontaneous neural activity occurring in the visual system. This intrinsic activity can generate random signals that the brain interprets as light. These neural signals can give rise to the perception of waves or patterns of light.
Retinal afterimages: After being exposed to a bright light source, such as a camera flash or a strong light, the retina can retain an image of that light for a short period. These retinal afterimages can persist even when you close your eyes or are in a dark environment. The retained image can create the perception of waves or patterns of light.
It's important to note that phosphenes are subjective perceptions and can vary from person to person. They are generally harmless and temporary, lasting only for a few moments. However, if you consistently experience unusual visual phenomena or have concerns about your vision, it is advisable to consult an eye care professional for a thorough evaluation.