What is the responsibility of the corneal endothelium?

• A. For regulating fluid and solute transport between the aqueous and corneal stromal compartments
• B. It produces tears
• C. It stores nutrients
• D. It absorbs light

Answer: (A)

Maintaining corneal dehydration through controlled fluid and solute transport is the main job. The endothelium is a single, highly active cell layer with tight junctions that acts as both a barrier and a pump. It uses ion transport mechanisms (like Na+/K+-ATPase and related channels) to move ions from the stroma into the aqueous humor. This ion movement draws water out of the stroma via osmosis, keeping the stroma relatively thin and the cornea transparent. If this pump–leak balance fails, the stroma swells, causing corneal haze and vision loss.

Tears are produced by the lacrimal glands, not the corneal endothelium. The endothelium does not store nutrients—that role isn’t its primary function—and it doesn’t absorb light in a meaningful way; light transmission and absorption are mainly governed by the epithelium and stroma, with the endothelium remaining transparent to support vision.