Flying mosquitoes is a medical term for vitreous clouding caused by liquefaction of the vitreous body, which is a degenerative disease of the vitreous body. The vitreous body is normally colorless and transparent, but the symptoms of “floating black shadows in front of the eyes” due to various causes of vitreous clouding are called mosquito flying. The manifestation varies from person to person, and there are various forms, such as black dots, filaments, stripes, cobwebs, flocculence, etc. Vitreous clouding, there are physiological vitreous clouding (good prognosis) and pathological vitreous clouding (poor prognosis). Physiologic vitreous clouding occurs in two groups of people: those with refractive problems, mainly myopia and high myopia; and those over 50 years old. Physiologic vitreous clouding is usually not a serious problem, although the patient has symptoms of blurred vision, but does not have an impact on vision, poor vision table, vision can still be normal. In addition, the posterior detachment of the vitreous cortex can also cause the occurrence of mosquitoes. Pathological pathological vitreous clouding mainly has the eye itself, trauma and other systemic systemic diseases secondary cause. Commonly there are fundus vascular diseases, such as diabetic retinopathy, central retinal vein obstruction and other causes of vitreous clouding. Eye trauma can also cause the occurrence of flying mosquitoes. These conditions, which are genuine eye diseases, must be treated, including medication and surgery. In short, regardless of the type of flying mosquitoes, it is caused by a change in the nature of the vitreous body and a clouding, liquefaction or post-detachment.