**Question:** Commonest type of concussion cataract is:

A. Progressive nuclear cataract
B. Posterior subcapsular cataract
C. Cortical cataract
D. Lens luxation

**Core Concept:** Cataract is a condition where the transparency of the lens in the eye is impaired, leading to vision loss. Concussion cataract is a type of acquired cataract that develops due to traumatic injury to the eye.

**Why the Correct Answer is Right:** The correct answer is **Posterior subcapsular cataract**. This type of cataract occurs when the lens gets damaged at the posterior pole of the lens, specifically in the subcapsular region. This damage disrupts the lens's transparency, causing visual impairment.

**Why Each Wrong Option is Incorrect:**

A. Progressive nuclear cataract (Option A) refers to a type of cataract that develops over time due to aging or other factors, not specifically related to traumatic injury.
B. Posterior subcapsular cataract (Option B) is the correct answer, as explained above.
C. Cortical cataract (Option C) is a type of cataract that develops when the lens fibers become disorganized, also not related to traumatic injury.
D. Lens luxation (Option D) is a condition where the lens is displaced from its normal position, but it is not a type of cataract.

**Clinical Pearl:** Posterior subcapsular cataract is the commonest type of concussion cataract. It is essential for medical students, residents, and practitioners to be familiar with this type of cataract as it is frequently encountered in clinical practice.

**Correct Answer:** Posterior subcapsular cataract (Option B) is the correct answer as it is the most common type of concussion cataract. Understanding the different types of cataracts helps in diagnosing, managing, and treating patients with visual disturbances due to traumatic eye injuries.