What is the primary collagen type in the sclera?

• A. Type II
• B. Type III
• C. Type IV
• D. Type I

Answer: (D)

The sclera relies on a strong, robust network of collagen to resist tearing and maintain shape under intraocular pressure, and this strength comes from type I collagen. Type I forms thick, parallel lamellae that provide high tensile strength, which is essential for the opaque, protective outer layer of the eye.

Other collagen types have different roles: type II is the main collagen in cartilage; type III is a reticular collagen found in more pliable, mesh-like networks such as certain vessels and early wound healing; type IV builds basement membranes. Because the sclera needs to be firm and resilient rather than flexible or basement-membrane rich, type I collagen is the primary type present.