Cornea is the transparent window of eye located within otherwise opaque sclera. It serves to refract the light rays. Option D is incorrect. The ciliary body is one layer of the middle vascular layers of eye ball and is formed by thickening of choroid. It serves to control the shape of the lens for near and far vision. Option B is incorrect. The vascular iris serves to control the size of pupil, a hole in iris, through which light enters the eyeball. Option C is correct. The lens capsule is attached to the ciliary body by a ligament and serves to refract and focus light rays on retina. Option A is incorrect. Correct answer is C.