Which structure forms the white, protective outer layer of the eye?

• A. Sclera
• B. Retina
• C. Iris
• D. Pupil

Answer: (A)

The outer protective layer of the eye is the sclera. This is the tough, opaque fibrous coat that forms the white part of the eye and encloses most of the eyeball, giving it shape and shielding the delicate inner structures from injury. It blends with the clear cornea at the front and with the optic nerve at the back, providing a strong, protective barrier while still allowing the eye to maintain its overall form. The sclera is rich in collagen, making it durable, and it also serves as the attachment point for the extraocular muscles that move the eye.

For context, the retina is the light-sensitive inner layer at the back of the eye, the iris is the colored ring around the pupil that regulates light entry, and the pupil is the opening in the iris.