What is the primary function of the endothelial cell layer?

The correct choice highlights the primary role of the endothelial cell layer in regulating the water content of the cornea's stroma, which is crucial for maintaining its transparency and overall health. The endothelium is the innermost layer of the cornea and plays a vital role in pumping excess water out of the stroma. This function ensures that the stroma remains at the correct hydration level, which is typically around 78%. When the endothelial cells struggle to perform this function, it can lead to corneal swelling and opacity, impacting vision.

In contrast, the production of tears is primarily the function of the lacrimal glands, which are not related to the endothelial cell layer. While the endothelial layer does provide some degree of protection to the cornea, its primary function is not to protect but to regulate hydration. Nutrient exchange with the anterior chamber primarily involves the corneal epithelium and the aqueous humor, rather than the endothelial cells, further illustrating the specific nature of endothelial function.