What is the main histology of the sclera?

• A. Dense regular connective tissue with elastin fibers.
• B. Loose connective tissue with adipose cells.
• C. Dense irregular connective tissue with predominantly type II collagen.
• D. Dense irregular connective tissue with predominantly type I collagen.

Answer: (D)

The sclera is built for strength and shape, and that comes from dense irregular connective tissue in which collagen fibers are interwoven in multiple directions. The key fiber is collagen type I, which provides high tensile strength and rigidity to resist forces from inside the eye as intraocular pressure changes. Elastic fibers are present but not the primary component, and the tissue is relatively low in cells, mainly fibroblasts, with very little adipose tissue or cartilage-like organization. This is why the description that fits best is dense irregular connective tissue with predominantly type I collagen.