The astigmatism is a refractive defect, caused by an alteration of the curvature of the cornea, which is no longer similar to that of a football, but is rather similar to that of a rugby ball and, therefore, is not the same on the different meridians. From this the incapacity of the eye derives to focus on the image of an object or a person.

Before reaching the retina, the luminous rays coming from the external world must cross the cornea and the lens and it is, therefore, necessary that these natural lenses possess a correct focusing power. In particular, the total astigmatism of the ocular diopter is the result of the various combinations of astigmatisms of the cornea and of the lens.

Astigmatism can have origin, in fact, both from the cornea and from the lens: Therefore, visual alterations will occur both if the cornea presents an irregular sphericity and if the surface of the lens is not perfectly spherical or its optic axis does not correspond to the visual axis.




Astigmatism can be corrected by the use of glasses with cylindrical or toric lenses, which can have a negative or positive dioptric power in case of the simultaneous presence of shortsightedness and hypemethropy or, in alternative, rigid or toric contact lenses can be used.  


If the astigmatism is of corneal origin, then it is possible today to use the refractive surgery and permanently correct the curvature of the cornea, in such a way as to restore its spherical symmetry and compensate in this way the refractive defect avoiding the use of glasses or contact lenses.

Among the surgical methods more frequently used we point out: PRK, i-LASIK and SMILE.

The refractive surgery is executed under local anesthesia, without pain both during and after surgery, it lasts only a few minutes and consists in modifying the curvature of the corneal surface.  The “excimer laser” enables to have a disintegration or “vaporization” of the more superficial corneal structure, i.e. the corneal epithelium, the Bowman membrane and a part of the stroma. Thanks to this surgery, the eye can focus again the images on the retinal plan and, in particular in the macular area and the patient can see again distinctly in a very short time without the need of glasses or contact lenses.

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