Common Eye Problems
In normal vision, light rays coming through the cornea and the lens focus perfectly on the retina at the back of the eye.
People who are nearsighted ( myopia ) see close objects more clearly than distant ones. Their eye may be longer than a normal eye or their cornea and natural lens may be too powerful, so that light rays focus before they reach the retina .
People who are farsighted (Hyperopia) see distant objects more clearly; however, all objects may be blurred. Their eye may be shorter than a normal eye or their cornea and natural lens may be less powerful, so light rays focus behind the retina .
Astigmatism is an optical imperfection of the eye in which the cornea is shaped more like a football, when in a non-astigmatic eye it would be shaped like a soccer ball. Most of us have this imperfection to some degree and due to this non-spherical curvature of the cornea , light rays focus at various points within the eye causing distorted vision. Astigmatism is often combined with nearsightedness and farsightedness.
This normal, age-related change occurs around our mid-forties. The lens of the eye becomes less elastic because older lens fibres are compressed into the center of the lens where they both harden and yellow. The lens becomes inflexible and we lose our ability to change focus, which necessitates the use of readers, progressive lenses or bifocals.