What are the two major factors responsible for water transport across the cornea that maintains corneal dehydration?

The maintenance of corneal dehydration is primarily due to the active transport mechanisms involving sodium (Na+) and chloride (Cl-) ions. The correct answer identifies the crucial roles of Na+ absorption and Cl- excretion in this process.

The cornea remains relatively dehydrated to ensure transparency and optimal optical properties, which are essential for proper vision. The corneal endothelium plays a vital role in maintaining this state of dehydration. It actively pumps sodium out of the corneal tissue into the aqueous humor while simultaneously allowing chloride ions to be consciously excreted.

By absorbing Na+, the endothelium creates an osmotic gradient that draws water out of the cornea, thus promoting corneal dehydration. In contrast, the mechanism involving Cl- excretion assists in regulating the fluid balance within the cornea, further supporting the prevention of corneal swelling.

Together, these two actions help maintain the corneal architecture, transparency, and function, which are vital for vision. This is why the correct choice focuses on the interplay of Na+ absorption and Cl- excretion as key factors in this physiological process.