The sensation of flying insects fluttering in front of the eyes is a phenomenon called flying mosquitoes. Clinically, it is mostly a vitreous clouding. There are many causes of vitreous clouding, the majority of patients are caused by vitreous degeneration. It may be related to age, eye trauma or high myopia. However, some pathological vitreous clouding may be caused by eye diseases, such as uveitis, fundus hemorrhage, retinal fissure, retinal detachment, etc. Therefore, if the eyes suddenly appear mosquito-like symptoms need to go to the ophthalmology clinic for routine examination, need to dilate the pupil to check the fundus and eye ultrasound examination. If the result is only simple vitreous turbidity, temporary observation, but regular re-examination. If the flying mosquitoes in front of the eyes increase significantly or with a sense of flash, you need to go to the ophthalmology clinic to check the fundus, especially the peripheral part of the retina, there is a possibility that the formation of retinal fissure or detachment.