The Whole Truth About Long-Sightedness and Short-Sightedness

When light reaches the eye it travels on through the cornea. There the light rays are refracted. The rays then pass into the pupil and the light is refracted once again by the lens. Normally the cornea and the lens focus the light so that a sharp image is formed on the retina. That is how we are able to see things. If for some reason the eye cannot focus the light exactly on the retina, we see poorly. So, what happens inside the eye?

What Is Short-Sightedness?

Sometimes the eyeball grows too long or the cornea is too strongly curved, so the light rays are focused before they reach the retina. As a result, objects that are far away look blurred, while nearby objects are seen clearly. This phenomenon is called myopia, or short-sightedness. As a rule, most of us are born slightly long-sighted. We see things that are further away better than those that are close to us. This happens because newborns are born with eyes that have not yet fully grown and have not reached their true length. Later, when the eyes are fully grown (this happens at around the eighth year of life), vision normalises. This is called emmetropia. In some cases, however, the eyeball does not stop growing and becomes too long. That is how short-sightedness begins. The first symptoms of this refractive error usually appear at the onset of puberty and gradually become stronger until the person (and their eye) is fully grown. Short-sightedness can range from mild cases, where treatment is not necessary, to severe ones, where a person's vision suffers greatly.

And What Is Long-Sightedness?

Long-sightedness, otherwise known as hypermetropia, is the name given to the refractive error in which the eyeball is slightly too short or the cornea is too flat. The consequence of this disorder is that images are focused behind the retina, at the back of the eye. In that case objects that are close look blurred and hazy. With long-sightedness, reading or working at the computer can sometimes even cause headaches and nausea. On the other hand, hypermetropia has its own advantages — long-sighted people see distant objects well and often notice them long before others can make them out. Long-sightedness, like most other refractive errors, is usually inherited. It may be stable or progressive. Like short-sightedness, long-sightedness can be mild or far advanced. Long-sightedness also develops in old age, when the lens, because of age, is no longer able to curve enough for the image to be focused on the retina.

How Are These Disorders Measured?

The ability of the eyes to refract light rays is measured in dioptres. A dioptre is the unit that describes the optical power of a lens. For example, a refractive error assessed at −3.00 dioptres and less is considered a mild case of short-sightedness; between −3.00 and −6.00 dioptres — moderate short-sightedness. Short-sightedness greater than −6.00 dioptres is considered a severe case. There is no reason to be discouraged, however — today people with refractive errors (even in severe cases) do not have to suffer.

How Is It Treated?

Both short-sightedness and long-sightedness can easily be kept in check by wearing corrective glasses or contact lenses, or can be treated with laser vision correction. Once the correct diagnosis has been made and the appropriate treatment applied, most short-sighted and long-sighted people can regain flawless vision. Book a consultation with the VisioBlu team — our specialists will measure your eyes and help you weigh up the options that suit you.