Astigmatism – it is a refraction anomaly. In normal conditions the cornea is spherical, i.e., its refractive power in the vertical and horizontal plane are similar. In astigmatism the refractive power in these planes are difference, e.g., in the vertical plane the cornea is bending more than in the horizontal.

 Astigmatism is divided in myopic, hypermetropic and mixed. There are three stages of astigmatism:
 

·mild - until 2 dioptres;

·medium – until 3 dioptres;

·severe – 4 and more dioptres.

Treatment of astigmatism is performed by glasses, contact or surgical correction. 
There are several kinds of surgical astigmatism correction. There are the following among them:

 ·Astigmatic Keratotomy – several penetrating micro incisions in cornea in the corresponding meridians, the corneal curvature is selectively decreased in the external plane in the result. This operation is performed in myopic or mixed astigmatism. See www.lasersite.com

www.rothchildeyeinstitute.com

·Thermokeratocoagulation – coagulation if performed in the peripheral corneal zone in corresponding meridians by a heated metallic needle, the corneal curvature and its refractive power is increased in the external plane. The operation is performed for hypermetropic astigmatism correction.

 ·Laser coagulation – is different from the previous methodology by the fact that a beam of laser is used instead of a metallic needle.

 ·Use of an excimer laser was started recently for astigmatism correction. Refractive effect is achieved by heating the corneal surface in a certain depth by an excimer laser. Operations where the laser acts in the centre of the optical zone are photo refractive keratotomy (FRK) and laser keratomilesis in situ (LASIK), used in myopic astigmatism. Operation called hypermetropic LASIK is performed in hypermetropic astigmatism correction, when laser is acting in the periphery of the central optical corneal part. See www.WaveLight.com