Night blindness is when you have very poor or complete blindness in a dark environment or at night. Once we understand the physiological process of dark adaptation, it is not difficult to understand night blindness. The root cause of night blindness is a lack of raw materials for retinal rod cells to synthesize retinas or a lesion of the rod cells themselves. Night blindness is commonly known as “bird’s eye”, and is characterized by difficulty in seeing and moving at night or in dimly lit environments. Night blindness is classified as temporary night blindness, congenital night blindness, and acquired night blindness. It is not difficult to prevent night blindness by eating more vitamin A rich foods, such as: eggs, animal liver, etc. For patients with severe disease, they should lie quietly in bed at night. Supplement with vitamin A nutrients or carotene extract. beta-carotene can be converted to vitamin A without side effects. The causes of night blindness are as follows: 1. Temporary night blindness: Night blindness is caused by a lack of vitamin A in the diet or by certain digestive diseases that affect the absorption of vitamin A, resulting in the absence of raw materials for the synthesis of retinal rods. This kind of night blindness is temporary, as long as more pig liver, carrots, cod liver oil, etc., can supplement the vitamin A deficiency, and will soon be cured. 2, acquired night blindness: often caused by retinal rod cell malnutrition or its own lesions. It is common in diffuse chorioretinitis, extensive choroidal ischemic atrophy, etc. This kind of night blindness will gradually improve with effective treatment and healing of the disease. 3, congenital night blindness is congenital genetic eye disease: such as retinal pigment degeneration, rod cell dysplasia, lost the function of synthesizing retinal red matter, so night blindness occurs.