Normal Vision
Occurs when light rays focus exactly on the retina, creating a clear image.

Myopia (Nearsightedness)
Occurs when light focuses before it reaches the retina due to an eyeball which is too long or a cornea with excessive curvature. This causes images which are far away to be blurred while images that are close are seen clearly.

Astigmatism
Occurs when light focuses in more than one location within the eye, due to a football-shaped or slightly oval shaped eye. This causes images to be blurred and distorted.

Hyperopia (Farsightedness)
Occurs when light focuses behind the retina, due to an eyeball which is too short or a cornea with too little curvature.