Blindness facts The Concept of "Blindness" could be strictly defined as: "the state of being totally sightless in both eyes. A completely blind individual is unable to see at all. The word blindness , however, is commonly used as a relative term to signify visual impairment, or low vision , meaning that even with eyeglasses , contact lenses , medicine or surgery, a person does not see well. Vision impairment can range from mild to severe." Worldwide, between 300 million and 400 million people are visually impaired due to various causes. Of this group, approximately 50 million people are totally blind, unable to see light in either eye. Eighty percent of blindness occurs in people over 50 years old. Common causes of blindness include diabetes , macular degeneration , traumatic injuries, infections of the cornea or retina , glaucoma , and inability to obtain any glasses. Less common caus...