Short-sightedness or Myopia or Nearsightedness

A person suffering from this problem i.e myopia can see only near object lying beyond a certain limit. In other words, far point P for a myopic eye is much nearer than infinity. The parallel rays of light from a object at infinity are brought to focus at a point O ( i.e X in figure) in front of retina as shown in figure below. This defect in eye occurs, when either:

i]  the eye ball becomes longer than the normal size i.e the distance between crystalline lens and retina increases.

ii]  the focal length of the eye lens, when eye is fully relaxed, become short.  

Shortsightedness or Nearsightedness, or myopia, as it is medically termed, is a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Shortsightedness or Nearsightedness is when light entering the eye is focused incorrectly, making distant objects appear blurred. Nearsightedness is a type of refractive error of the eye. Young persons suffer from this defect.

If you are nearsighted, you have trouble seeing things that are far away.

Remedy:

The myopic eye will be cured from this defect, if it is able to see clearly the objects at infinity. In order to correct this defect, a concave lens of suitable focal length is placed close to the eye such that the parallel rays of light from the object at infinity after refraction through lens appear to come from the far point 'P' of the myopic eye as shown if figure below.

Causes, incidence, and risk factors

People are able to see because the front part of the eye bends (refracts) light and points it to the back surface of the eye, called the retina.

Nearsightedness occurs when the physical length of the eye is greater than the optical length.

This makes it more difficult for the eyes to focus light directly on the retina. If the light rays are not clearly focused on the retina, the images you see may be blurry.

Nearsightedness affects males and females equally. People who have a family history of nearsightedness are more likely to develop it. Most eyes with nearsightedness are healthy, but a small number of people with severe myopia develop a form of retinal degeneration.

Symptoms:

A nearsighted person sees close up objects clearly, but objects in the distance are blurred. Squinting will tend to make far away objects seem clearer.

Nearsightedness is often first noticed in school-aged children or teenagers. Children often cannot read the blackboard, but they can easily read a book.

Nearsightedness gets worse during the growth years. People who are nearsighted need to change glasses or contact lenses often. It usually stops progressing as a person stops growing in his or her early twenties.

Other symptoms may include:

• Eyestrain
• Headaches (uncommon)