Provided is a drug or method for treating or preventing a condition, disorder, or disease of the corneal endothelium caused by transforming growth factor-β (TGF-β) signals and/or mitochondrial abnormalities in corneal endothelial cells. The present invention provides a drug which includes caspase inhibitors, and which is for treating or preventing a condition, disorder, or disease of the corneal endothelium caused by TGF-β signals and/or mitochondrial abnormalities in corneal endothelial cells. In the preferred embodiment, the condition, disorder, or disease of the corneal endothelium is Fuchs' corneal endothelial dystrophy.
