The National Eye Institute (NEI) was established in 1968 and is located in Bethesda, Maryland. The NEI is one of 27 institutes and centers of the US National Institutes of Health (NIH), an agency of the US Department of Health and Human Services. The mission of NEI is to prolong and protect the vision of the American people. The NEI conducts and performs research into treating and preventing diseases affecting the eye or vision.