piece of writing, written material, writing - the work of a writer; anything expressed in letters of the alphabet (especially when considered from the point of view of style and effect); the writing in her novels is excellent; that editorial was a fine piece of writing.
The Senses. Researchers have studied vision more thoroughly than the other senses. Because people need sight to perform most daily activities, the sense of sight has evolved to be highly sophisticated. Vision, however, would not exist without the presence of light. Light is electromagnetic radiation that travels in the form of waves. Light is emitted from the sun, stars, fire, and lightbulbs. Most other objects just reflect light. People experience light as having three features: color, brightness, and saturation.
What you are describing could be a visual hallucination or a delusion (a mistaken belief). In either case there are many possible causes. Sometimes sensory loss, in the form of vision and hearing loss, causes people to hear and see things that are not there. There are also medications that can cause hallucinations or delusions or medications that are not being prescribed or taken properly.