The human eye is a complex organ and visual system, made up of three layers and enclosing various anatomical structures. This section explains how different parts of the eye work together to provide vision.
For nearsighted eyes, objects in the distance appear blurry, but objects up close are sharply focused. This condition can occur if the cornea is too steep and incoming light is not accurately focused onto the back of the eye.
For farsighted eyes, objects up close appear blurry, but objects in the distance are sharply focused. This condition can occur if the cornea is too flat for the length of the eye.
Astigmatism is caused by an unevenly shaped cornea or natural lens. Vision is blurred or distorted to some degree at all distances.
Presbyopia is the age-related, natural regression of vision. It occurs when the natural lens loses its ability to focus on near objects.