**Core Concept**
The prevention of endophthalmitis in cataract surgery involves various factors, but the most crucial aspect is maintaining asepsis and preventing bacterial contamination. This is achieved by using sterile techniques, equipment, and intraocular lens (IOL) insertion.

**Why the Correct Answer is Right**
Proper use of **sterile gloves**, **sterile drapes**, and **sterile instruments** is essential in preventing endophthalmitis. The **entry site** of the needle for the paracentesis should be **sterile**, and the **bottle of irrigation** should be **changed** after every case to prevent bacterial contamination. Additionally, the **intraocular lens** should be **sterilized** before insertion. The surgeon should also use **antibiotic prophylaxis** in the form of intracameral antibiotics during the surgery.

**Why Each Wrong Option is Incorrect**
* **Option A:** While **antibiotic eye drops** are used post-operatively to reduce the risk of endophthalmitis, they are not the most important factor in preventing endophthalmitis.
* **Option B:** **Proper patient selection** is crucial in reducing the risk of complications, but it is not the most important factor in preventing endophthalmitis.
* **Option D:** **IOL material** is not a significant factor in preventing endophthalmitis.

**Clinical Pearl / High-Yield Fact**
The risk of endophthalmitis can be reduced by using an **intracameral antibiotic** during cataract surgery. This is a high-yield fact that examiners often test.

**Correct Answer:** C.