Abnormal Vision

Near-sightedness (Myopia)

As the term already implies, images close-up are focused, those far-away are not. A near-sighted eye bundles the light in front of the retina instead of on it, either because the refractive characteristics of the eye are too strong or because the eye is too long. As a result the images from objects further away aren't focused. One sees distant objects blurred. Objects closer, on the other hand, are seen focused.

Near-sightedness can be corrected, for instance, with the help of glasses, contact lenses or an operative procedure.

Far-sightedness (Hyperopia)


The far-sighted eye either does not refract light enough or is generally too short in length. Because of this, the light from distant objects (and from nearby) is bundled behind the retina instead of on it. In this case too, the result is an unfocused image. However, up to a certain age, far-sightedness can correct itself because of the natural aging process, where the form of the lens changes, altering the refractive qualities of the eye. This process is called accommodation. This ongoing process, however, can often lead to eye fatigue, eye pain or headaches.

 

Astigmatism

An astigmatism is the result of a deviation of the cornea's curvature. The cornea is formed essentially elliptical rather than globe-shaped. Because of this, images that are dot-like are projected as small lines. They are distorted. The more deviation of the cornea, the more distortion. In order to correct astigmatisms, special cylindrical glasses or contact lenses can be prepared. Additionally, operative procedures can be successful.

 

Presbyopia

At the age of approximately 45, it often becomes necessary, for instance, while reading the newspaper, to hold it further away. At this age reading is perceived as more laborious. Thus, one who previously needed no vision aids, now needs reading glasses. The cause for presbyopia is natural aging and slow loss of flexibility of the eye lens. The lens loses its ability to alter its form and thus to change its refractive characteristic. This loss of accomodation is a completely normal part of aging. It is not a disease.

Reading glasses for close-up vision are used in correcting for presbyopia.