| Normal Vision |
Good vision results
from a sharp image being produced on the retina at the back
of the eye.
The optical system (cornea, crystalline lens and vitreous body) of a normally sighted eye diverts light rays such that they land exactly in focus at the point of best vision on the retina. This diversion of light rays is called refraction.
The total power of refraction from all components of the optical system of the eye is expressed in diopters (D).
When the total refraction is zero diopters, then objects
viewed by an eye will be imaged in focus on the retina.
