Fog in front of the eyes may be caused by the following factors: first, dry eye disease, patients with too little water secretion or too much evaporation of tears, the lipid layer of the tear film is too thick will appear in front of the eyes fog symptoms; second, corneal epithelial damage, such as electrophthalmia, the corneal epithelium will appear diffuse punctate defects, affecting the refractive state; third, iritis, the acute stage will occur in the atrial water turbidity or crystal before the iris Pigmentation, which may also appear as a feeling of fog in front of the eyes; fourth, cataract, if the cataract patient has a uniform increase in density of the lens rather than a large patchy clouding that completely obscures it, there will be a feeling of a white film in front of the eyes; fifth, refractive error, especially if astigmatism is suddenly aggravated, may appear as a symptom of fog in front of the eyes and blurred vision.