A black line inside the eye is usually a case of physiological vitreous opacity. This is a condition similar to flying mosquitoes, so it is also known as flying mosquitoes. Mainly due to the growth of myopia or age caused by vitreous degeneration, opaque phenomenon, this situation belongs to the normal physiological changes, so generally do not take the way to intervene and treatment. There is no good way to treat vitreous clouding, so the main focus is on observation and review. However, if there is a significant black shading, i.e., the black line is fixed and tends to increase, there may be pathological vitreous opacity or retinal detachment, which requires timely examination in the hospital. If there is retinal detachment or hemorrhage in the fundus, surgery may be required to resolve the problem.