Night blindness, also known as nyctalopia, is a condition that makes it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases and may exist from birth or be caused by injury or malnutrition, such as vitamin A deficiency. Night blindness can also be caused by a deficiency of retinol, or vitamin A1, found in fish oils, liver, and dairy products. The inability to see in bright light is known as hemeralopia and is much rarer. Night blindness is not a disease in itself but rather a symptom of an underlying eye problem, usually a retina problem. Individuals with night blindness not only see poorly at night but also require extra time for their eyes to adjust from brightly lit areas to dim ones. Contrast vision may also be greatly reduced. The causes of night blindness fall into two categories: treatable and non-treatable. Treatable causes include cataracts, nearsightedness, use of certain drugs, and vitamin A deficiency (rare) . Nontreatable causes include inherited retinal or choroidal dystrophies. Treatment for night blindness depends on the cause and may be as simple as getting a new eyeglass prescription or switching glaucoma medications, or it may require surgery if the night blindness is caused by cataracts.