**Core Concept**
Postcataract infection is a significant concern in ophthalmology, particularly in developing countries where access to sterile equipment and proper surgical techniques may be limited. The most common cause of postcataract infection is endophthalmitis, an inflammation of the interior of the eye usually caused by a bacterial or fungal infection.

**Why the Correct Answer is Right**
The use of povidone-iodine (PVI) is a critical step in preventing postcataract infection. PVI is a broad-spectrum antimicrobial agent that effectively reduces the bacterial load on the ocular surface. When applied topically, PVI kills or inhibits the growth of a wide range of microorganisms, including bacteria, viruses, and fungi. This reduces the risk of postoperative endophthalmitis and other complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** While antibiotic prophylaxis is sometimes used in cataract surgery, it is not the most effective method for preventing postcataract infection. Antibiotics may not reach the interior of the eye in sufficient concentrations to prevent infection.
* **Option C:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
Povidone-iodine is a critical component of preoperative and postoperative care in cataract surgery. It should be used at a concentration of 5% and applied to the ocular surface for at least 30 seconds to ensure effective antimicrobial activity.

**Correct Answer:** A. Povidone-iodine.