From the time we are born to about 8 years of age, our eyeballs undergo remarkable changes. Normally, as the front of the eye grows, it flattens, which sends images deeper inside the eye. If the eye grows as it should, light will converge on the retina. But if the convergence is off by even a hair's breadth, vision will be blurred.

Most preschool and elementary school children are slightly farsighted. This lessens as children grow, usually stabilizing by adolescence.

During these years of growth, the eye senses where images are focusing and compensates accordingly. If light is converging in front of the retina, the eye will stop growing longer until images catch up to the retina. If the focus is behind the eye, it will grow longer at a remarkable rate, pushing the retina further from the source of light until images can be focused. The eyes are generally able to maintain clear focus throughout childhood even though the size of the eyeballs is continually changing.

The ability to see in three dimensions, stereoscopic vision, is usually fully developed by the age of 6 or 7.