[Essential features of astigmatism and its correction with excimer laser].

The correction of astigmatism is an essential element for the refractive surgery because the majority of patients have important preoperative cylinder An uncorrected astigmatism decreases visual acuity and can also cause glare, asthenopia, headaches, monocular diplopia. It is important to remark that a complete elimination of astigmatism for the eye is very rarely achieved.