Mathematics. 1  Also called relative maximum, local maximum. the value of a function at a certain point in its domain, which is greater than or equal to the values at all other points in the immediate vicinity of the point. 2  the point in the domain at which a maximum occurs.
For other uses, see Blindness (disambiguation). Visual impairment, also known as vision impairment or vision loss, is a decreased ability to see to a degree that causes problems not fixable by usual means, such as glasses. Some also include those who have a decreased ability to see because they do not have access to glasses or contact lenses.
The study defines visual impairment as visual acuity of 20/50 or worse in the better-seeing eye. Visual acuity refers to the sharpness of vision at 20 feet from an object. A person with 20/50 vision can clearly see something 20 feet away that a person with normal vision can see clearly from a distance of 50 feet.