Emmetropia focuses light on the retina
The eye is like a camera that has two lenses. One of these lenses is the crystalline lens inside the eye. The other lens is the cornea, which is positioned in the eye like a watch crystal but actually provides 2/3 of the eye's focusing power. When the light rays that enter the eye are perfectly focused on the retina, then the eye is neither nearsighted nor farsighted. This condition is called “emmetropia.”