**Core Concept**
The posterior chamber is a small, narrow space in the eye that plays a crucial role in the optics and the aqueous humor circulation. It is situated between the iris and the vitreous body, and is an essential part of the anterior segment of the eye.

**Why the Correct Answer is Right**
The posterior chamber is filled with aqueous humor, a clear fluid produced by the ciliary body, which flows through the pupil into the anterior chamber. This circulation is essential for maintaining the intraocular pressure and providing nutrients to the cornea and lens. The aqueous humor in the posterior chamber helps to maintain the shape of the vitreous body and prevents it from collapsing.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the posterior chamber is not filled with vitreous humor, which is a gel-like substance found in the vitreous body, located behind the lens.
**Option B:** This option is incorrect because the posterior chamber is not an extension of the anterior chamber, but rather a separate compartment that communicates with the anterior chamber through the pupil.
**Option C:** This option is incorrect because the posterior chamber is not a part of the retina, but rather a space between the iris and the vitreous body.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the posterior chamber is a narrow space that can be easily damaged during eye surgery, leading to complications such as posterior chamber hemorrhage or endophthalmitis.

**Correct Answer: C. The posterior chamber is a small, narrow space in the eye that contains aqueous humor and is situated between the iris and the vitreous body.**