The Eye

The human eye has a clear lens (the cornea) on the outside, then the colored iris, and a crystalline biconvex lens (both sides of the lens are convex) behind the cornea that focuses images upside down on the retina at the back of the eye. The brain converts images to right side up. This human lens can change/accommodate seeing objects at greater distances by pulling by the eye’s ciliary muscles (e.g., when the muscles tense they pull the lens flatter/thinner to see distant objects). If a person’s eye lens can not be pulled thick or thin enough to focus a person is said to be near- or far-sighted; their focusing can be corrected with glasses or contact lenses.






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