Dr. William A. Boothe Endothelial Cells the cells that line the inner surface of the cornea in a single layer (endothelium). They are responsible for pumping fluid out of the cornea to keep it clear. These cells gradually decrease in number over a lifetime. They can die off faster than normal from damage during surgery or after surgery. If the number of endothelial cells becomes too low, your cornea becomes cloudy, you lose vision and may require a corneal transplant.( DR WILLIAM A. BOOTHE - LA