Did you know?  The human eye has the sharpest vision when light rays passing through the various structures of the eye meet at a sharp focal point on the foveal area of the retina.  Although the cornea and lens of the eye may be perfectly round, if light rays are focused before they reach the retina (a condition known as Myopia or Nearsightedness), distance vision will not be clear.   If light rays are focused behind the plane of the retina (a condition known as Hyperopia or Farsightedness) vision may or may not be clear depending on the amount of hyperopia and the amount of someone’s focusing ability.  Although a hyperopic person may see clearly both at distance and near, if too much focusing effort is needed, discomfort, headaches, etc. may occur.  If not enough focusing ability is available, vision will not be clear up close or at both up close and distance. 

Distortion of vision can also occur when the curvature of the cornea is football-shaped (a condition known as Astigmatism) rather than uniformly round as light rays will not be focused at a sharp focal point.