Technique used to determine the number, as well as, the health of the endothelial cells.This layer of cells is important in regulating the water contact of the cornea and is therefore important in helping to keep the cornea transparent. We know how many cells per square millimeter a healthy cornea should have. Corneas with a low cell count are often less healthy and may have a more difficult time in maintaining transparency after an eye operation. Any damage to this cell layer could lead to corneal swelling.