Myopia

is the medical term for near-sightedness.  Those with myopia see nearby objects clearly, but objects in the distance are blurry.  This occurs because either the depth of the eyeball is too great or the cornea is too curved.  Nearsightedness is a very common vision condition that affects nearly a third of the American population.  This can be easily identified in children because they often squint and have trouble seeing things that are across the room.  This condition is typically corrected with the use of prescription eye glasses or contact lenses, which work by refracting light in a way that will reverse what the eye naturally does.

Hyperopia

is the medical term for far-sightedness.  Those with hyperopia see distant objects somewhat clearly, but near objects are difficult to focus on for periods of time.  Hyperopia occurs when either the length of the eyeball is too short, or the curvature of the cornea is too flat.  Many people have some degree of farsightedness and tend to notice this defect more later in life.  The condition is only a problem if it significantly affects a person’s ability to see.  Expert opinions suggest that over half the people who wear glasses do so because of a focusing problem induced by farsightedness or Presbyopia, a natural decrease in focusing ability at near distances.  Common symptoms of farsightedness include difficulty in concentrating and maintaining a clear focus on near objects, blurred vision, eye strain and fatigue, and/or headaches after close work.  If you are farsighted, you involuntarily exert extra effort to maintain clear distance vision and even greater effort to see clearly at close range.  

Astigmatism

is a condition in which the cornea of the eye has an abnormal curve, causing out of focus vision.  While the direct cause of astigmatism is unknown, it is a very common diagnosis and is usually present at birth, often occurring along with nearsighted or farsightedness.  Although small amounts of astigmatism may not need correction, patients who have this defect will notice eye strain and fatigue more in the later part of day due to the extra effort your eye exerts to properly focus light.  Children who need a slight astigmatism correction can often train their eyes to reverse this disorder with proper use of prescription eye glasses or vision therapy.

Presbyopia

is a condition in which the lens of the eye loses its ability to focus. The condition is associated with aging and is suspect to progressively get worse. People who have presbyopia have difficulty seeing objects close-up. The focusing power of the eye depends on the elasticity of the lens. This elasticity is gradually lost as people age, resulting in a slow decrease in the ability of the eye to focus on nearby objects.  People usually notice the condition around age 45. Presbyopia is a natural part of the aging process and affects everyone.  This condition is easily corrected with the addition of some type of bifocal to the current prescription.