Which structure provides protection and maintains the shape of the eye?

The sclera is the outermost layer of the eye and is often referred to as the "white of the eye." It plays a crucial role in protecting the more delicate internal structures of the eye, such as the retina and the lens. In addition to providing a protective barrier, the sclera contributes to maintaining the eye's shape, which is vital for proper optical function. Its tough, fibrous nature helps withstand external forces, ensuring the eye remains structurally sound. The sclera also serves as an attachment point for the extraocular muscles, allowing for eye movement without compromising its integrity.

Other structures mentioned, such as the ciliary body, cornea, and iris, have specific functions but do not primarily serve the dual purpose of providing structural protection and maintaining the general shape of the eye like the sclera does. The ciliary body is involved in lens accommodation and aqueous humor production, the cornea is critical for light refraction and vision because of its transparent nature, and the iris controls the size of the pupil for regulating light entering the eye.