Eyes always feel foggy, usually due to the following reasons: First, due to refractive error, when the eyes have myopia, hyperopia, astigmatism and other refractive error diseases, will lead to light refraction through the eyes, the focal point can not be accurately convergence in the retina, cause to see things foggy, blurred. Second, due to cataracts, when the lens is cloudy, that is, cataracts occur, it will prevent light from penetrating into the eye and cause vision loss and blurred vision. Third, due to corneal edema, such as glaucoma, corneal degeneration, etc. may cause corneal edema, reduce the transparency of the cornea and cause foggy symptoms. Fourth, due to fundus lesions, such as macular precursor membrane, macular degeneration, etc., the ability of the retina to feel visual stimuli decreases, causing blurred vision.