Several diseases affect the eye, either directly or as part of a system-wide problem. Often serious, these conditions require immediate professional care to preserve your vision.
NEARSIGHTEDNESS ( MYOPIA )
For a nearsighted person, close objects are clear, but distant objects-such as a school blackboard, a street sign, or a face across a room are blurred and difficult to distinguish. Over 25% of adults worldwide are nearsighted.
Technically known as myopia, nearsightedness occurs when the eye is unusually long, a shape that causes light rays to focus too far in front of the retina. An inherited condition, it is often discovered when children are 8 to 12 years old. During the teenage years, when the body is growing rapidly, nearsightedness gets worse. Then between ages 20 and 40 there is little change.
People who are nearsighted can have their vision corrected by several means, including:-
- Contact lens
- Laser surgery
Technically known as hyperopia, farsightedness occurs when the eye is shorter than normal. This shape causes images to be focused behind the retina rather than on it. The condition is usually inherited.
Contrary to what the name implies, people who are farsighted have blurred vision at all distances-unless they make a constant effort to focus, which can lead to strain, headaches, and eye fatigue. In fact, babies and children are usually slightly farsighted; as their eyes grow and lengthen, the condition corrects itself, generally by age seven or eight. However, some young people who remain farsighted are unaware of it, because they have enough flexibility in their focusing power to correct the condition without the aid of eye glasses or lenses.
People who are farsighted can have their vision corrected by glasses or contact lenses.
A normal cornea is round and smooth like a baseball. With astigmatism, the cornea curves more severely, like a football. Astigmatism is inherited, and can occur in combination with nearsightedness or farsightedness
For people with astigmatism, all objects-both near and far-are distorted. Images are blurred because some of the light rays are focused and others are not. This is similar to the distortion produced by a wavy pane of glass.
Astigmatism is corrected by bending the light rays onto a single plane. People who are astigmatic can have their vision corrected by several means, including
- Contact lens
- Laser surgery
- Astigmatic Keratotomy
In young people, the lens is soft and flexible, and readily changes shape to focus. Over time there is a gradual hardening of the material making up the lens; as a result, its ability to focus decreases steadily.
People with presbyopia often believe they have become farsighted; while they can read street signs and watch movies comfortably, they are unable to bring small print, such as the telephone book, or close work, such as embroidery, into focus. In fact, whereas farsightedness is caused by a misshapen eye, presbyopia is simply the result of the lens becoming less flexible.
People who have presbyopia can have their vision corrected either by glasses, contact lenses or surgery