Poor night vision refers to a decrease in vision at night compared to day vision, or a condition in which dark vision has a decrease in bright vision. It can be caused by a variety of reasons, ranging from natural environmental causes to eye diseases or refractive problems. There are many different causes of poor night vision, including: Night blindness The underlying cause of night blindness is a lack of raw material for synthesizing retinal rods or a lesion of the rod cells themselves. (1) Temporary night blindness is caused by a lack of vitamin A in the diet or by some digestive diseases that affect the absorption of vitamin A. This causes the retinal rod cells to lack the raw material for synthesizing retinas and causes night blindness. This kind of night blindness is temporary, as long as you eat more pig liver, carrots, cod liver oil, etc., you can supplement the vitamin A deficiency, and will soon be cured. (2) Acquired night blindness Often caused by malnutrition of retinal rod cells or lesions of the retina itself. It is common in diffuse choroiditis, extensive choroidal ischemic atrophy, etc. This night blindness gradually improves with effective treatment and healing of the disease. (3) Congenital night blindness It is caused by congenital hereditary eye diseases, such as retinitis pigmentosa, in which the rod cells are dysplastic and lose the function of synthesizing retinal red matter, so night blindness occurs. Refractive error More severe symptoms of myopia, hyperopia and astigmatism. Especially astigmatism night pupils become larger, the ability to focus light is especially poor, compared to the daytime blurred vision and double vision will worsen. After laser surgery Night vision problems include glare (formation of a halo around the spot), starburst-like spots, or increased sensitivity to light at night – especially when driving. These problems usually appear only a few weeks after surgery. Some people may have night vision problems for more than 6 months after surgery. Inadequate blood supply to the brain Inadequate blood supply to the brain can just as easily lead to inadequate blood supply to the eye and its periphery, and because it is more prevalent at night, it can lead to poor night vision.