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.
When the vision in the better eye with best possible glasses correction is: 1  20/30 to 20/60 is considered mild vision loss, or near-normal vision. 2  20/70 to 20/160 is considered moderate visual impairment, or moderate low vision. 3  20/200 to 20/400 is considered severe visual impairment, or severe low vision.