”Flying mosquitoes” generally occurs in the vitreous body of the eye, the vitreous body is the eye’s normal tissue, when young for jelly-like, as age increases suddenly liquefied. ”Flying mosquitoes” common causes are: physiological: high myopia, vitreous degeneration in the elderly; pathological: retinal, choroidal disease bleeding into the vitreous, congenital residual in the vitreous embryonic cells or tissue, eye trauma, intraocular foreign body, parasites and tumors. It is recommended to go to a specialized hospital for examination when the following conditions occur: 1) sudden increase of floaters in front of the eyes, which affect the vision; 2) darker or red color of floaters; 3) systemic bleeding-prone diseases such as hypertension and diabetes; 4) local fixed visual obscuration; 5) other accompanying symptoms. Specialized examination is best performed under dilated pupils, examining glasses or slit lamp anterior microscopy. If the clouding is severe and the fundus is not visible or there is no red reflection, ultrasound examination is required to assist in the diagnosis. Treatment: No treatment is needed for physiologic cases, while pathologic cases should be treated for the cause.