Question

define ciliary muscles , crystalline lens and optic nerve in eye .

Answer 1

Lens is A transparent, biconvex, flexible disc behind the iris. 
ciliary muscles Contraction and relaxation of the ciliary muscle

Answer 2

Ciliary muscles: The part of the eye that connects the iris to the choroid. It consists of the ciliary muscle (which alters the curvature of the lens), a series of radial ciliary process (from which the lens is suspended by ligaments), and the ciliary ring (which adjoins the choroid).

Crystalline lens : The transparent elastic structure behind the iris by which light is focused on to the retina of the eye.

Optic nerve : Each of the second pair of cranial nerves, transmitting impulses to the brain from the retina at the back of the eye.

Hope it will help you