Refractive Errors

A NEARSIGHTED person can see objects up close, while
distant objects are blurry. Nearsightedness occurs because the eyeball is too
long from back to front or the cornea is too curved. Since the eyeball is too
deep, the light rays from distant objects are focused before they hit the
retina.

A FARSIGHTED person can see objects far away, while
objects up close are blurry. Farsightedness occurs because the eyeball is too
short from back to front or the cornea is too flat. That shortness causes light
rays to focus behind the retina.

For someone with ASTIGMATISM, objects that are both near
and far seem blurry. Astigmatism usually occurs because the cornea has lost its
round shape. That means the light rays have more than a single point of focus
when they hit the retina, causing the image to become blurred.