| Nearsightedness - Myopia
Nearsightedness or Myopia is very common; 25% of adults woldwide live with this vision defect. For these people close objects are clear, but distant object are blurred and difficult to distinguish. Nearsightedness happens when light has to focus in front of the retina, as opposed to on the retina, because of the eye's unusually long shape. Passed on genetically, the condition is often detected between the ages of 8 and 12 years old. Nearsightedness worsens during adolescence, and stabilizes in early adulthood. Although most often benign, nearsightedness when very severe implies a higher risk of detached retina.
Farsightedness - Hyperopia
Farsightedness or Hyperopia occures when light has to focus behind the retina, as opposed to on the retina, because of the eye's unusually short shape. Farsighted people have blurred vision at all distances, and often suffer from headaches and eye fatigue, as they make a constant effort to focus. The condition is usually passed on genetically, and young children often are slightly farsighted if only temporarily. In most cases, the condition corrects itself as their eyes naturally grow in length. However, some, who remain farsighted and have enough focusing flexibility to fight the blur, are unaware of their condition.
Presbyopia
The eye lens starts out soft and flexible, and readily changes shape to focus. But as people get older, the lens gradually hardens, and has increasing difficulty to focus. Presbyopia is not to be confused with farsightedness. Unlike farsightedness, which causes blurred vision at all distances, presbyopia only affects close vision.
Astigmatism
Astigmatism affects the outer layer of the eye, called the cornea. It means that the curavature of the cornea is too severe, leading to a distorted vision of both near and far objects. Images are blurred because some of the light rays are focused and otheres are not. Astigmatism is a genetically inherited condition, and sometimes occurs in combination with nearsightedness or farsightedness.
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