Ideally, the surface of the cornea is uniformly rounded, like the smooth, even surface of a ball. Vision becomes distorted when the surface of the cornea has an uneven curvature, rounded more like the back of a spoon than the surface of a ball. This type of irregularity causes blurred vision because light focuses on more than one spot on the back of the eye. Have you ever looked through a pane of glass that has an irregular, somewhat wavy surface? That uneven surface allows only one part of the view to be in good focus—the rest is blurred and wavy-looking.