Monovision is a condition in which each eye is able to focus on objects of different distances. With monovision, each eye aids one another in seeing objects of different distances.
For younger people, eye accomodation allows each eye to see objects of different distances. However, as one ages, the ability to accommodate deterioriates, casuing a condition known as a presbyopia. With presbyopia, each eye has limited visual range.
With Near Vision correction, each eye is intentionally corrected to see objects of different distances and create monovision. Thus, Near Vision correction can be an alternative to treat presbyopia. In preparation for Near Vision correction, your ophthalmologist will have you try a contact lens which will induce a monovision condition.