Normal vision occurs when light is focused directly on the retina rather than in front or behind it.
Review Date 2/28/2019
Updated by: Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.