Black shadows in front of the eyes are mostly seen in mosquitoes, some people do not have any lesions in the fundus of the eye, the vitreous body is not degenerative, but always visible in front of the eyes with black shadows, these black shadows can be very long, months or even years without much change. The examination also found no obvious intraocular abnormalities and lesions, this situation is “mosquito flying”, because mosquito flying generally does not affect visual function, so there is no need for any treatment. Black shadows in front of the eye may also be the vitreous body out of the problem. The human eye has a cavity in front of the retina, filled with jelly-like material called vitreous, which is composed of uniformly transparent colloid, thus ensuring that external objects in the retina when imaging clear, undisturbed. However, the vitreous humor also degenerates as the body ages, becoming uneven and even forming less transparent membranes and streaks and lumps of material. In addition, inflammation, hemorrhage, and retinal fissures and detachments inside the eye can cause these opaque cellular materials to enter the vitreous, and when the human eye looks at external objects through these opaque materials, it will feel a dark shadow floating in front of the eyes, and move as the eye turns back and forth. Especially when looking at the sky or white background more obvious. This is vitreous opacification. It is especially worth emphasizing that if a flash occurs in a fixed part of the eye, accompanied by an increase in black shadows, followed by a curtain-like black curtain covering a certain direction in front of the eye, it should be given great attention and need to go to the hospital immediately to check whether there is a retinal fissure and detachment or other diseases, once it occurs, surgery should be performed as soon as possible, so as not to delay the treatment and cause irreparable damage.