Astigmatism

The astigmatism is a defect of the optical systems which do not give a point a specific image, but a spot.

In physiology of the eye, normally, the surface of the cornea has the curve of a soccer ball. At the astigmates, it is deformed and its curve is connected more with that of a rugby ball. The image received by the retina is thus different according to the axes from this balloon . Result: the image misses clearness. The luminous rays are focused then in different points behind and in front of the retina what causes a deformation of the image. One speaks about internal astigmatism for the deformation of the internal optical elements to the eye like the Cristallin and the inner face of the cornea.

Vision of the astigmatism

The astigmatism involves a vision scrambled, deformation, vague at all the distances with lengthening of the vertical or horizontal or oblique lines and the confusion of close letters like H the M and the NR the E and B or the 8 and the 0.

Measure astigmatism

It can be expressed either by quantifying the correction necessary in Dioptrie or by quantifying the vision in tenth. The astigmatism is weak between 0 and 1 dioptres, means from 1 to 2 dioptres, extremely with the top of 2 dioptres. The astigmatism can be direct generally (the main roads are horizontal), opposite (vertical main roads) or oblique (axis obliques).

Symptoms of the astigmatism

the astigmatism can not involve any symptom. The people reached of a weak astigmatism have a good sight, but it often sometimes happens to them to fold the eyes, to present headaches or symptoms of ocular tiredness or to note that their vision is fuzzy on certain occasions.
the astigmatism can frequently accompany the Myopie or the Hypermétropie. It then increases the eye trouble of these two anomalies.
the astigmatism can sometimes be the symptom of a Kératocône against indication with the surgery of the cornea by lasik. It is thus fundamental to detect it before any operation of refractive surgery.
It is important to detect in the young child a strong astigmatism of only one eye, in order to correct it precociously to avoid a Amblyopie.

Correction of the astigmatism

The astigmatism is usually congenital and does not evolve/move or very little during the life. When the astigmatism is weak, physiological, it does not require correction. If it is more important, and that it involves eye trouble he must be corrected.

the astigmatism can be corrected by glasses from which glass cylindrical, toric, not having the same power for the various meridian lines makes it possible the image to refer on the retina.
It can be corrected by flexible contact lenses for astigmate known as toric or by spherical rigid lenses (if the astigmatism is mainly of corneal origin) or by toric rigid lenses (if the astigmatism interns appears quite higher than the corneal astigmatism and involves a residual astigmatism in spherical rigid lenses.)
It can be corrected by an operation of astigmatism to the Laser excimer which rounds the shape of the cornea by digging more one meridian line that the other or by incisions arciformes of the cornea incising the most convex zones.

Internal bonds

Optician

External bonds

Astigmatism, vision and correction

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