When a person’s visual field is dotted with bright white dots, it is referred to Blue field entoptic’ phenomenon, also known as Scheerer’s phenomenon. The dots, which are also sometimes in the form of irregular tiny worms, generally don’t last for long (one second in most cases), and move in random paths.
The phenomenon is more apparent when a person looks at a bright blue background, such as the sky.
The reason behind blue field entoptic’ phenomenon lies in the behaviour of red blood cells and white blood cells, that are present in our retina. The former has the tendency to absorb blue light, while the latter doesn’t.
This creates a gap in the blood column, which is observed in the form of bright dots.