**Core Concept**
Descemet's stripping automated endothelial keratoplasty (DSAEK) is a type of corneal transplantation surgery used to treat corneal diseases such as Fuchs' endothelial dystrophy. The procedure involves stripping the diseased endothelial layer from the host cornea and replacing it with a donor endothelial layer. A significant concern in DSAEK is the loss of endothelial cells during the procedure, which can affect the long-term success of the transplant.

**Why the Correct Answer is Right**
During DSAEK, the endothelial cells of the host cornea are subjected to mechanical stress, leading to cell loss. Studies have shown that the percentage of endothelial cell loss during DSAEK can range from 30% to 40%. This cell loss is due to the mechanical disruption of the endothelial layer during the stripping process. The remaining endothelial cells can adapt to the new environment, but a significant loss of cells can affect the cornea's ability to maintain its transparency and function.

**Why Each Wrong Option is Incorrect**
**Option A:** 0 – 5% cell loss is too low to be realistic, as the mechanical stress during DSAEK would inevitably lead to some degree of cell loss.

**Option B:** 10 – 20% cell loss is still relatively low and may not accurately reflect the extent of cell loss that can occur during DSAEK.

**Option D:** 50 – 60% cell loss is excessively high and would likely lead to significant complications and failure of the transplant.

**Clinical Pearl / High-Yield Fact**
It's essential for surgeons to carefully balance the need to remove diseased endothelial tissue with the risk of cell loss during DSAEK. Aiming for a gentle stripping technique and minimizing the duration of the procedure can help reduce endothelial cell loss and improve the long-term success of the transplant.

**✓ Correct Answer: C. 30 – 40%**