## **Core Concept**
The sclera is the white, fibrous, connective tissue that provides protection and structure to the eye. It is composed mainly of collagen and is thinnest at specific points, which are clinically significant.

## **Why the Correct Answer is Right**
The thinnest part of the sclera is typically located just posterior to the rectus muscles' insertions, specifically under the superior rectus muscle. This area is clinically significant because it is a common site for the surgical complications during ocular surgeries. The thinnest portion of the sclera is usually considered to be about 0.3 mm thick.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not accurately represent the thinnest part of the sclera.
- **Option B:** This option is incorrect because, although close, it does not specify the correct location or is not considered the thinnest.
- **Option D:** This option is incorrect because it does not accurately represent the thinnest part of the sclera.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the thinnest part of the sclera is usually under the superior rectus muscle, approximately 3 mm from the limbus. This knowledge is crucial for ophthalmologists to avoid complications during surgeries.

## **Correct Answer:** C. Under superior rectus.