Many people may have this experience: often see like a mosquito-like black shadow floating around in front of the eyes, especially when looking at bright places, white walls and blue sky more obvious. What’s going on here? The original is the eye in the vitreous body problems. The vitreous humor is a gelatinous, transparent substance in the eye that allows light to pass through our cornea and crystalline lens, and then through the vitreous humor to the retina. However, once the vitreous body for some reason and “cloudy”, when looking at the bright background, this “cloudy” shadow will be projected on the retina, so we see a variety of forms in front of the “floaters ” fluttering, some like bugs, some like thread, some thick, some fine, medically known as “flying mosquitoes”. A small amount and long-term unchanged black shadow wavering is generally physiological, can be divided into the following three kinds: congenital mosquito flying, age-related vitreous degeneration, myopic vitreous degeneration. This physiological flying mosquitoes without treatment; if the black shadow suddenly increased, should be alert to the possibility of pathological flying mosquitoes, such as retinal fissures, retinal detachment, vitreous hemorrhage, uveitis, etc., should be promptly to the hospital for medical consultation. The appearance of black shadows floating in front of the eyes, must go to the hospital for examination, and to dilate the pupil examination, so as not to miss the peripheral retinal lesions. When a retinal fissure is found, retinal laser photocoagulation should be performed in time to close the fissure and prevent it from developing further into retinal detachment. However, one thing we should know is that laser photocoagulation of the fundus only closes the fissure, while the black shadow in front of the eyes is caused by vitreous opacity, the laser cannot solve the vitreous opacity, so the floating black shadow will not disappear, but the vitreous opacity can be mechanized and concentrated, so the black shadow may become smaller and lighter.