The vitreous humor is gel-like at birth, and signs of liquefaction begin to appear within the vitreous humor at the age of 4 years. Liquefaction refers to the gradual dehydration and shrinkage of the gel-like vitreous body and the separation of water from collagen. The incidence of posterior vitreous detachment is 58% in people over 50 years of age and 65-75% in people over 65 years of age. After the occurrence of posterior vitreous detachment will appear floating objects in front of the eyes, such as dots, fly-like, ring-shaped objects, etc., which is caused by changes in the vitreous body as we age, black shadow floating in front of the eyes. Flying mosquitoes: also known as flying mosquitoes phantom vision, is the development of the eye embryonic residual fine cells or fibers in the vitreous body, floating when the retina caused by projection. There will be strips, filaments, dots such as fly wings of translucent floating, eyes look at the sky or white background, more obvious, does not affect vision, floating objects will not significantly increase, fundoscopy, slit lamp, ultrasound examination of the vitreous and no clouding, is a physiological mosquito flying disease. Inflammatory vitreous clouding is caused by inflammation of the grape, retina and other tissues, inflammatory cells, exudates and necrotic tissue and other pathological products into the vitreous. For example, posterior uveitis, intermediate uveitis, white stuffing syndrome, Vogt-Koyanagi-Harada syndrome, sympathetic uveitis, nodular uveitis, and acute retinal necrosis. Hemorrhagic vitreous opacities are a common complication of ocular trauma or retinal vascular disease causing visual impairment. The vitreous itself is not vascular and does not bleed. Retinal hemorrhage in small amounts into the vitreous can occur as vitreous opacities, with black shadows floating in front of the eyes. Such as diabetic retinopathy, retinal vein obstruction, ocular trauma, retinal perivasculitis, hypertensive retinopathy, high myopia fundus hemorrhage or retinal detachment, etc. Degenerative vitreous opacities are most often seen in people with high myopia, and the higher the myopia, the earlier the age of onset, and can be secondary to inflammation and hemorrhage. As the eye axis is too long, the original normal gel structure of the vitreous body is damaged, the gel-like vitreous body gradually dehydrated, shrinkage occurs condensation degeneration and become soluble, the vitreous cavity appears in the cavity containing water, vitreous liquefaction, can also appear in front of the black shadow floating. In short, if there is no other symptom of sudden appearance of black shadow in front of the eyes, no obvious change in vision, no inflammation and hemorrhage in slit lamp and fundus examination, generally no treatment is needed; if the black shadow gradually increases, or sudden appearance of a large number of black shadows in front of the eyes, and vision loss, you should go to the hospital to check the cause of its development and timely treatment.