Corneal curvature is too steep or eye ball too long: Incoming light comes to  a focus in front of the retina Distant objects out of focus Close-up objects are clear

Corneal curvature is too flat or eyeball is too short:                  Focal point is behind the retina Distant objects are clear Close-up objects out of focus

Cornea has an oblong or even more irregular shape:               Light rays focus on two or more points Partially blurry vision

With age, lens loses flexibility and some ability to refract light: Close-up objects out of focus