While corneal endothelial damage in its most advanced stage results in bullous keratopathy where corneal transplantation is needed, there is no severity grading for corneal endothelial damage. The Japanese Corneal Society formed a working group to establish a severity grading for corneal endothelial damage. The following are the proposed severity grading criteria. Normal: Corneal endothelial cell (CEC) density is 2000 cells/mm2 or more. Grade 1: CEC density between 1000 and 2000 cells/ mm2. The corneal endothelium is below the normal physiological condition. Grade 2: CEC density between 500 and 1000 cells/ mm2. The transparency of the corneal endothelium is endangered. Even slight damage can induce bullous keratopathy. Grade 3: CEC density below 500 cells/mm2 but no corneal edema is observed. Grade 4: Bullous keratopathy. The cornea is opaque with edema.