Final answer:
Vasodilation of blood vessels in the conjunctiva leads to hyperemia, causing increased blood flow and redness. Inflammatory mediators like histamine can cause vasodilation in the conjunctiva.
Step-by-step explanation:
Hyperemia in the conjunctiva is caused by vasodilation in the blood vessels of the conjunctiva. Vasodilation refers to the widening of blood vessels, increasing their diameter and allowing more blood flow. Inflammatory mediators such as histamine can cause vasodilation, resulting in increased blood flow, heat, and redness in inflamed tissue, including the conjunctiva.