||HOW THE NORMAL EYE WORKS|
HOW THE EYE WORKS
How clearly you see depends in large part on the shape of your cornea. This structure is the clear covering of the eye, which you look through. In the normal eye, your cornea helps to focus light rays directly on the retina (which acts like the film in a camera). If the eye is not shaped correctly, the image will fall in front of or behind the retina, causing images to be blurry.
In myopia (nearsightedness), the distance from the cornea to the retina is too long. This causes the image to fall short of the retina, making images blurry.
With astigmatism, the cornea is oval shaped instead of round. This makes both distance and near objects look distorted.
In hyperopia (farsightedness), the distance between the cornea and the retina is too short. This causes the image to fall behind the retina, making images blurry.
How refractive surgery changes vision
Glasses and contact lenses work by bending light rays before they hit the cornea. The light rays are then focused directly on the retina , resulting in clear images. Refractive surgery changes the shape of the cornea itself, so it can bend the light rays to focus more directly on the retina without the use of contacts or glasses. These procedures can, therefore, reduce your dependence on your contacts or glasses and may help you get rid of them completely for most daily activities. They will not, however, stop you from needing reading glasses if you are over 40, even if you did not need them prior to surgery.