People with myopia can see objects closer to them, but have difficulty focusing on distant objects. The condition is caused by a cornea that has more curvature than normal, or an eyeball that is too long. In either case, light is focused at a point in front of the retina, causing a blurred image. About one in four American adults are myopic. The condition usually begins in childhood, and stabilizes in the late teen years.
Hyperopia is farsightedness, the opposite of myopia.
For people with hyperopia, objects at a distance are clear, while objects up close are blurry with uncorrected vision. Astigmatism , or oval ness of the cornea, is another refractive problem. With this condition, there is a distortion that tilts or bends the image due to an unequal bending of light as it attempt to focus. Nearsighted and farsighted people may also have some degree of astigmatism. Finally, presbyopia is a very common condition that is simply part of the normal aging process.