It is a physiological phenomenon, not a pathology. Why does this happen? Because the normal vitreous body is a colorless and transparent colloid body that does not block light from entering the eye. There are residual embryonic cells or degenerated cells in the vitreous body, and when blood cells flow through the retinal blood vessels, the images of these cells are projected on the retina. At the visual cell layer, just like a few tea leaves floating in a glass of clear water, a dark shadow will appear in front of your eyes. This dark shadow is generally lighter in color, translucent, and smaller in number. It appears gradually and lasts for a long time. . After examination, the vision was good and the fundus was normal. So don't worry and don't pay too much attention to it.