The effective term for visual problems is called refractive disorders. Refraction refers to the bending or deflection of the light rays.

Refractive visual disorders are related to how your eye focuses light. The curvature of your cornea and the power of your lens, the length of your eye all influence how the eye refracts or bends rays of light.

Nearsightedness: Technically, it is called myopia. If you are nearsighted it means you have trouble seeing far. When the eye is too long in relation to the curvature of the cornea, images focus in front of the retina instead of on it and objects at distances appear blurred. Patients with myopia are able to see near objects.

Astigmatism: Many patients with myopia have some degree of astigmatism. This means that your eye is slightly oval and your cornea is shaped like a football rather than a sphere. People with astigmatism experience distortion or tilting of images due to unequal bending of the rays of light entering your eyes. High degrees of astigmatism will cause blurred vision for distance and near objects.

Farsightedness: Technically is called hyperopia, farsightedness means you have trouble with close up vision. It occurs when the eye is functionally too short. The rays of light are focused behind the retina producing a blurred image. Some people who are farsighted are able to use their focusing muscle (accommodation) to bring the image forward allowing them to see clearly. This ability worsens with age and reading glasses or bifocals may be needed. Farsighted people see distance objects more clearly than near objects.

Aging eyes:Presbyopia is a normal aging process. As we get older, the lens loses its ability to flex and focus at near. The onset of presbyopia typically is between 40 and 50. When this occurs people who already wear glasses may need bifocals and those who have never worn glasses may require reading glasses. Presbyopia is an important concept to understand if you are considering laser correction. One advantage of mild nearsightedness (myopia) is the ability to remove your glasses after presbyopia sets in and still be able to read

If you have Laser Vision Correction for nearsightedness, you will lose this ability. That's because your vision typically becomes normal, and normal for the aging eye usually will require reading glasses for small print. The excimer laser has no effect on your focusing muscles and therefore cannot treat presbyopia.