The eye’s crystalline lens is a biconvex structure (outwardly curved on both sides), and is suspended behind the colored iris. Both are behind the protective clear covering known as the cornea. The cornea is also a lens, meaning that it is clear and refracts (bends) incoming light to focus it on the retina, the eye’s “camera film”.
The lens has two functions in vision:
While the corneal curvature is fixed, the lens can change its curvature. This ability is called accommodation. The lens curvature becomes steeper for near vision and flatter for distance vision, which makes it an adaptable partner for the cornea. In a 20/20 eye, they work together to provide clear vision at all distances.
There are three structural elements that make up the lens:
Around the lens is a multi-function structure called the ciliary body. It contains:
The ciliary body connects to the choroid, the middle layer of the eyeball wall. The choroid is filled with blood vessels that nourish the retina and other parts of the eye, and it contains a lot of melanin (pigment) to absorb excess light.
For more information, please see Eye Anatomy: Overview.
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