Fogging in the eyes of patients may be related to refractive error, or it may be caused by cataract or corneal opacity. 1. Refractive error: patients with refractive error may exhibit a foggy feeling in their eyes because light entering the eye is deflected and cannot be focused on the retina, resulting in blurred vision. 2. Cataract: this disease is usually caused by nutritional disorders, poisoning, trauma, metabolic abnormalities, etc., which can lead to the reduction of the optical quality of the patient’s lens and the reduction of the transparency of the lens, thus causing the patient’s blurring of vision, and may show the feeling of fogging up in the eyes, and it is difficult to see things. 3. Corneal opacity: corneal opacity is usually caused by eye trauma or ocular surface inflammation and other factors, resulting in corneal ulcer surface healing, the formation of local cloud-like scarring turbidity, which can affect the patient’s normal vision, the patient can appear blurred vision, often described as fog in the eyes. It is recommended that patients with blurred vision consult a doctor to evaluate their condition and follow the doctor’s instructions for treatment.