Older people or young people with myopia often have the experience of small black shadows or dots floating in front of their eyes, which are often more pronounced when looking at white objects, blue skies, or when looking down at the level of a glass of water, and can sometimes be seen with closed eyes, floating with eye movements, which sometimes exist and sometimes disappear. This phenomenon sometimes exists and sometimes disappears. This kind of floating small black shadow in front of the eyes can be dotted, cotton wool, filaments or “mosquito-like” floaters, but the objective examination can not find any vitreous lesions, this phenomenon is called physiological flying mosquitoes. It is generally believed to be due to vitreous liquefaction and basement membrane thickening, vitreous cortex cells in the retina projection caused by myopic eyes, more in the 30 years of age after the emergence of; generally do not need special treatment. If the following conditions occur, you need to visit the hospital ophthalmology department in time to do the necessary examination to exclude pathological eye lesions. 1, a sudden increase in black spots or dark shadows in front of the eyes in a short period of time, should be considered pathological vitreous turbidity, but to exclude uveitis, intravitreal blood accumulation, etc., so need to make a comprehensive examination. If simple mosquito flying, clinical examination in addition to vitreous detachment, often can not find vitreous clouding point, this no serious consequences, also do not need special treatment. If the examination does have obvious vitreous turbidity to actively treat. 2, the black shadow does not float with the rotation of the eye, often suggesting macular degeneration, retinal detachment, cataract, etc., need to promptly seek medical attention and conduct a comprehensive examination. When these lesions appear, they are often combined with vision loss or blurred vision. 3. Flashing sensation, light flashes similar to lightning in front of the eyes, which is also felt when the eyes are closed or the flashing sensation is more pronounced. These symptoms are caused by the pulling and stimulation of the retina after vitreous degeneration or liquefaction, which may be the precursor manifestation of retinal detachment. Need to promptly seek medical advice except retinal fissure, early retinal detachment, etc. It can be said that mosquito flying is a frequent clinical subjective symptoms, most of them belong to the physiological. For the elderly and young people with myopia, once the flashing sensation in front of the eyes, vision loss, etc., need to promptly seek medical advice.