The eye lens of humans is transparent and crystalline. It is biconvex and responsible for focussing light on the retina. It is present behind the cornea and attached to the ciliary body by ligaments. The biconvex lens is the simple lenses that comprise two convex surfaces in spherical form, generally having the same kind of radius of curvature. Hence, these are also called the convex-convex lens.
The ability of the eye lens to adjust its focal length, to clearly focus rays coming from distant as well a near object on the retina, is called the power of accommodation of the eye.
Relationship between focal length and power
As the focal length decreases, the amount the light bends increases. Therefore, we can conclude that the power of a lens is inversely proportional to the focal length of the lens. Therefore, a short focal length basically contributes to high optical power.