## **Core Concept**
Posterior subcapsular cataract (PSC) is a type of cataract that affects the posterior lens capsule. It is often associated with specific risk factors, including certain medications, medical conditions, and radiation exposure. This type of cataract can cause significant visual disturbances, particularly in bright light conditions.

## **Why the Correct Answer is Right**
The correct answer, **C. Steroid use**, is right because long-term use of corticosteroids is a well-established risk factor for the development of posterior subcapsular cataracts. Corticosteroids can cause changes in the lens of the eye, leading to the formation of PSC. This is due to the effects of steroids on the lens epithelium and the accumulation of extracellular matrix.

## **Why Each Wrong Option is Incorrect**
* **Option A:** While trauma can cause various types of cataracts, it is not as specifically associated with posterior subcapsular cataracts as steroid use.
* **Option B:** Diabetes mellitus is associated with an increased risk of cataracts, particularly cortical cataracts, but it is not as strongly linked to posterior subcapsular cataracts as steroid use.
* **Option D:** While radiation exposure can increase the risk of cataract development, it is less specifically associated with posterior subcapsular cataracts compared to steroid use.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that posterior subcapsular cataracts are often associated with steroid use, and this association is a critical consideration in patients on long-term corticosteroid therapy. Clinicians should be aware of this risk and monitor patients accordingly.

## **Correct Answer:** . Steroid use