## **Core Concept**
The question tests the knowledge of strategies to prevent corneal endothelial damage during intraocular lens (IOL) implantation. Corneal endothelial damage can lead to corneal edema and potentially permanent vision loss. The prevention of such damage is crucial during cataract surgery and IOL implantation.

## **Why the Correct Answer is Right**
The correct answer involves the use of a specific type of substance or technique that protects the corneal endothelium during IOL implantation. **Viscoelastic substances** (also known as ophthalmic viscosurgical devices or OVDs) are commonly used for this purpose. They create a protective barrier between the IOL and the corneal endothelium, reducing mechanical trauma and preventing direct contact that could cause endothelial damage. These substances also help in maintaining the anterior chamber depth during surgery.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Without the specific details of option A, it's challenging to provide a direct explanation. However, if option A does not relate to the use of protective substances or techniques during IOL implantation, it would be incorrect because it does not directly address the prevention of corneal endothelial damage.
- **Option B:** Similarly, if option B does not involve a method or substance known to protect the corneal endothelium, it would be incorrect for the same reason.
- **Option C:** If option C suggests a method that might not be directly related to endothelial protection during IOL implantation, it would be incorrect.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **viscoelastic substances** are crucial in protecting the corneal endothelium during cataract surgery and IOL implantation. These substances can significantly reduce the risk of postoperative corneal endothelial damage and subsequent corneal edema.

## **Correct Answer:** . Viscoelastic substances.