Myopia, or nearsightedness, is the most common vision problem, affecting approximately one in four people. People with myopia can clearly see objects up close but not those at a distance. Myopia occurs when the cornea is either curved too steeply, or the eye is too long, or the combination of both. In myopic eyes, light rays from distant objects are focused in front of the retina, so that the image projected on the retina is blurred.
Hyperopia, or farsightedness, is a focusing problem which occurs when the cornea is either not curved enough or the eye is too short, or the combination of both. The reduced length means the light rays focus behind the retina, producing a blurred image.
As we age, the natural lens in our eye becomes less flexible. This lack of flexibility compromises the eye’s ability to switch from one focal point (objects at a distance) to another focal point (objects that are close). The practical effect of this loss of flexibility in the natural lens of the eye is that we lose our ability to read or see close objects without reading glasses or bifocals. This is called presbyopia.
Astigmatism is an uneven curvature of the cornea resulting in blurry vision. With astigmatism the cornea is shaped like a football. Astigmatism can result in an inability to focus clearly at any distance, because light rays entering the eye are bent unequally by the cornea, preventing the formation of a sharp point of focus on the retina. Astigmatism often occurs in conjunction with myopia or hyperopia.