The black shadow floating in front of the eye is mostly seen in vitreous opacity caused by mosquitoes, divided into physiological mosquitoes and pathological mosquitoes. Physiological flying mosquitoes consciously have floating flying mosquitoes in front of the eyes, is relatively transparent, occasionally found about 2-3, does not affect vision, and will not gradually increase, objective examination is difficult to find, pathological flying mosquitoes consciously have more, countless flying mosquitoes in front of the eyes, size, shape, number, color, suddenly or gradually increase, slit lamp, fundoscopy, eye ultrasound examination, visible vitreous floating objects, with the eye The slit lamp, funduscopy, eye ultrasound, can be seen floating objects in the vitreous body, with the eye and fluttering, mostly in the middle-aged, elderly, myopic patients, uveitis, vitreous blood, eye trauma is the main eye disease causing pathological mosquitoes.