REFRACTION DEFECTS

The eye is an optical system much like a camera. Light and images from the outside reach the macula part of the retina by being refracted in the cornea

REFRACTION DEFECTS

17-09-2015
The eye is an optical system much like a camera. Light and images from the outside reach the macula part of the retina by being refracted in the cornea (the eye's outermost transparent layer) and the lens. In a normal eye the light coming in from the outside is refracted in the cornea and the lens forming clear images in the macula. However, in some instances the images may not form clearly on the retina due to problems with the cornea, the lens or the makeup of the eye.

MYOPIA/SHORTSIGHTEDNESS
This happens when the light coming in from the outside gets into focus before reaching the macula. It occurs if the axis between the front and the back of the eye is too long or if the refractivity of the cornea or the lens has changed. As the ability to adapt is weak in myopic eyes the person has to wear glasses in order to see at a distance.

MYOPIA/SHORTSIGHTEDNESS
This happens when the light coming in from the outside gets into focus before reaching the macula. It occurs if the axis between the front and the back of the eye is too long or if the refractivity of the cornea or the lens has changed. As the ability to adapt is weak in myopic eyes the person has to wear glasses in order to see at a distance.

 HYPERMETROPIA/FARSIGHTEDNESS
This happens as a result of the outside light coming into focus behind the macula. It occurs if the axis between the front and the back of the eye is too short or if the refractivity of the cornea or the lens has changed. Hypermetropic eyes are able to adapt easily. People with low degrees of hypermetropia are able to see normally by adapting but their eyes tire easily. Severe hypermetropia affects both near and far sight.

PRESBIYOPIA (AGE-RELATED MYOPIA)
The lens loses its elasticity in old age resulting in poor near sight. It begins at around 35-40 years of age and continues to worsen until around 60.

KERATOCONUS
This is where part of the cornea thins and begins to bulge outwards. These people cannot see clearly without glasses. Specially produced contact lenses may be worn depending on the severity of the disease. In very advanced cases a cornea transplant operation called keratoplasti may be necessary.

DO NOT FORGET!
Myopia, hypermetropia, astigmatism and presbyiopia are usually refraction defects. Just as these refraction defects can occur one at a time in the eye, multiple defects can occur at the same time. Refraction defects can occur in one or both eyes. Apart from this, other kinds of refraction defects related to disorders of the cornea or lens are also possible. An eye can have disorders in the cornea, the lens, the retina or the optic nerves in addition to refraction defects. Therefore, people with refraction defects need to have regular eye and ophthalmic examinations ever year. If there is any suspicion of strabismus or sight disorder in children they need to have their eyes checked as soon as possible. Even if there are no problems children aged around the age of 4 need to have their eyes checked.

There are various alternatives for people with refraction defects to see clearly again.
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