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The 3 main visual disorders

 

The term ametropia refers to a condition when the image does not form correctly on the retina. There are three kinds of ametropia: myopia, hyperopia and astigmatism.

 

Myopia

 

Difficult far vision

A person suffering from myopia sees better close up than at a distance. This type of ametropia occurs because the distance between the cornea and the retina is too great. In such cases, the image does not focus on the retina but just in front of it.

 

Different levels of myopia

There are three levels of myopia, characterized by different diopters:

• mild myopia, from 0 to -2 diopters

• moderate myopia, from -2 to -6 diopters

• high myopia, from -6 to -20 diopters

 

How can myopia be corrected?

Myopia can be corrected by means of a divergent lens, i.e. a lens that is thinner in the center and thicker at the edges. This lens, also called a negative or concave lens, is designed to refocus the image on the retina and restore good eyesight ad infinitum. The higher the myopia the heavier and thicker at the edge the lens will be (which is both unattractive and uncomfortable).

 

Are you myopic? You may be myopic if, for example you: crease up your eyes to see distant objects better you write with your nose practically touching the page

 

Hyperopia

 

Exhausting near vision

Hyperopia is the opposite of myopia; it occurs because the distance between the cornea and the retina is not long enough. The eye is said to be too short and is therefore not powerful enough. The image forms behind the retina. Distant objects can be seen clearly but focusing on near objects, though possible, is tiring. Those suffering from hyperopia thus have better far vision than near vision.

 

Different levels of hyperopia

There are three levels of hyperopia:

• mild from 0 to 2 diopters

• moderate between 2 and 4 diopters

• high between 4 and about 10 diopters

 

How can hyperopia be corrected?

Hyperopia is corrected by using a convergent lens (thin at the edge and thicker at the center) to refocus the image on the retina.

The higher the hyperopia the heavier and thicker at the center the lens will be.

 

Are you hyperopic? You may be hyperopic if, for example: you suffer from headaches or a sensation of eye fatigue, especially in the evening during your childhood, you suffered from strabismus (need for immediate correction)

 

Astigmatism

 

Difficulty distinguishing contrast

Astigmatism is generally caused by a defect in the curvature of the cornea. The cornea is a slightly oval shape, where it should be round.

Astigmatic subjects have imprecise near and far vision and cannot see contrasts clearly between horizontal, vertical or oblique lines.

 

How can astigmatism be corrected?

 

Astigmatism is corrected by means of a toric lens whose curvature is designed to compensate the defect of the cornea. The corrective power of the lens will differ according to the axis of the astigmatism; the lens is therefore of variable thickness at the edge.

 

Are you astigmatic? you may be astigmatic if, for example: you confuse similar signs such as m and n, or 8 and 0 you suffer from eye fatigue or headaches after prolonged reading

 

 

Essilor: state-of-the-art comfort Whatever your visual disorder, Essilor seeks to use innovative materials to offer lenses that are ever more efficient, thinner, lighter and adaptable to all frame types.

 

 

Did you know? Presbyopia is not considered an ametropia. Presbyopia is an age-related visual disorder. To find out more, go to the section "Presbyopia and available solutions".