Sometimes people see small spots or specks moving in their field of vision or experience flashes of light. These occurrences are called floaters and flashes. In some cases, these could be the symptoms of a more serious eye problem, such as retinal detachment.
Floaters
Floaters may be seen as dots, lines, cobwebs or spiders and are more noticed when reading, looking at a blank wall or a clear sky. Sometimes, they do not interfere with vision at all, but when a floater enters the line of vision, light is blocked and a shadow is cast on the retina.
Floaters are usually harmless, but in some cases may indicate a more serious condition, such as a retinal tear.
Flashes
Flashes may appear as flashing lights or lightning strikes in a person’s field of vision, although there is no light actually flashing. These are similar to the sensation of “seeing stars” when one is hit on the head. They are most often noticed at night or in a dark room.