Okay, let's tackle this question about the most common complication of extracapsular cataract surgery. First, I need to recall what extracapsular cataract surgery (ECCE) entails. ECCE involves removing the cataractous lens while leaving the posterior capsule intact. The core concept here is understanding the intraoperative and postoperative complications associated with this procedure.

The most common complications of ECCE are posterior capsule rupture and vitreous loss. I remember that during ECCE, the surgeon removes the lens nucleus through a large incision, which can sometimes lead to accidental rupture of the posterior capsule. This is a significant issue because it can lead to vitreous loss, which complicates the surgery and may require additional interventions like posterior chamber intraocular lens (IOL) implantation or even vitrectomy.

Now, looking at the options, the correct answer should be posterior capsule rupture. The other options might include things like retinal detachment, endophthalmitis, or corneal edema. Let me verify each. Retinal detachment is a late complication, not the most common. Endophthalmitis is rare but serious. Corneal edema can occur due to surgical trauma but is less frequent than posterior capsule issues.

Clinical pearl: Remember that ECCE is more invasive than phacoemulsification, so complications like posterior capsule rupture are more likely. This is a key differentiator from phacoemulsification, which uses smaller incisions and less manipulation.

**Core Concept**
Extracapsular cataract surgery (ECCE) involves removing the cataractous lens while preserving the posterior capsule. The most common intraoperative complication is posterior capsule rupture, often due to surgical trauma during lens removal.

**Why the Correct Answer is Right**
Posterior capsule rupture occurs in 2–5% of ECCE cases. It results from direct trauma by surgical instruments (e.g., nucleus extraction) or from excessive intraocular pressure during irrigation. This complication risks vitreous loss, retinal detachment, and endophthalmitis, requiring urgent vitrectomy or IOL repositioning. The posterior capsule’s thinness and anatomical fragility make it particularly vulnerable during ECCE.

**Why Each Wrong Option is Incorrect**
**Option A:** Retinal detachment is a *late* complication, not the most common intraoperative issue.
**Option B:** Endophthalmitis is rare (0.04–0.1%) and typically postoperative, not the most frequent complication.
**Option C:** Corneal edema may occur but is less common than posterior capsule rupture due to ECCE’s large incision and reduced ultrasonic energy use.

**Clinical Pearl**
ECCE’s posterior capsule rupture rate is higher than phacoemulsification. Always suspect this complication if sudden intraocular hemorrhage or vitreous loss occurs during surgery.

**Correct Answer: C. Posterior capsule rupture**

✓ Correct Answer: B. Opacification of posterior capsule