Why is the sclera white and tough?

The sclera is white and tough primarily because of the abundance of collagen fibers present within its structure. These collagen fibers are arranged in a dense, fibrous network, providing strength and stability to the eye. This tough outer layer helps to maintain the shape of the eyeball and protects the inner components from damage. The white appearance of the sclera is due to the lack of pigmentation, which is in contrast to other structures in the eye that may contain melanin or other pigments. This collagenous composition is critical for the overall function of the eye, supporting the attachment of the muscles that move the eye and providing a protective barrier.