What are the two primary mechanisms that lead to corneal edema?

The two primary mechanisms that lead to corneal edema are epithelial barrier disruption and endothelial pump disruption.

The cornea is a critical structure of the eye responsible for focusing light and maintaining transparency. It relies heavily on the clear balance of hydration within its layers. The epithelium provides a barrier to prevent excessive fluid from entering the cornea from the tear film or ocular surface. Disruption of this epithelial barrier allows fluid to penetrate into the corneal stroma, leading to swelling and vision compromise.

The endothelium, located on the innermost layer of the cornea, plays a critical role in regulating corneal hydration through its active transport mechanisms. This "pump" function helps to draw excess fluid out of the stroma to maintain clarity. When endothelial function is compromised—whether due to disease, surgery, or degeneration—fluid accumulates in the stromal layer, resulting in edema.

This dual mechanism emphasizes the importance of both the integrity of the epithelial barrier and the functionality of the endothelial pump in maintaining corneal health and transparency.