Your vision depends on how light is focused in your eye. The eye has different parts, such as the cornea, lens, and iris. These parts work together to bend (refract) and focus light rays. With normal vision, light is focused on the back of the eye. This area is called the retina. But in some cases, the eye is not the right shape. This causes light to focus in the wrong place. It makes vision blurry. There are 3 common problems with focusing: farsightedness (hyperopia), nearsightedness (myopia), and astigmatism.
Normal vision happens when light focuses on the retina.
Farsightedness happens when light focuses behind the retina. Nearby objects look blurry.
Nearsightedness happens when light focuses in front of the retina. Distant objects look blurry.
Astigmatism happens when light focuses in more than one place. Both nearby and distant objects can look blurry.
With age, the lens becomes stiff. Stiffening of the lens makes it harder for the lens to change shape to focus light. This leads to trouble focusing on nearby objects (presbyopia).