In astigmatism, the rays of light are distorted as they enter the eye. Some light rays spin behind the retina and others in front of it. The cause, usually, is a different curvature of the front of the eye, the cornea. The vision is cloudy both from far and near. The correction is made with glasses or contact lenses.
Astigmatism is the most common eye defect and is characterized by blurred vision both from far and near. It is determined by a corneal alteration, so the cornea is not perfectly spherical by traction of the lens or the anatomy of the eye. This will then result in a blurry image because it will not be focused on the retinal center. By using particular lenses, these light rays can be confluent on the retina and the eyes, then, will be able to focus on the image by means of glasses or contact lenses or by laser (excimer, femtosecond) that allows for the correction of the image defect and/or modification of the curvature of the cornea so as to make the vision sharper.
There are astigmatisms that, due to the onset of keratoconus, are absolutely not advisable to use excimer laser with. Astigmatism is very common in children: an early visit will allow for an early diagnosis of the defect and good vision development because other refractive defects (e.g. amblyopia – lazy eye, etc.) can be possibly determined and corrected early.