german example normal vision vs astigmatism

astigmatism eyesight eyes astigmatismus mit ohne german germany blurred blurry vision distorted stabsichtigkeit brechungsfehler augenheilkunde focus irregular curvature cornea refractive error visual problem focusing disorder optical aberration anomaly rotational asymmetry cause pterygium ophthalmology surgery contact lenses glasses eyeglasses health care medicine sign text background concept hornhautverkrümmung