**Question:** Layers of cornea are all EXCEPT

A. Bowman's layer
B. Descemet's membrane
C. Epithelium
D. Stroma

**Core Concept:**
The cornea is a transparent, avascular, outermost layer of the eye, composed of multiple layers that function to protect and maintain the ocular surface. The cornea is divided into four main layers: epithelium, Bowman's layer, Descemet's membrane, and stroma.

**Why the Correct Answer is Right:**
The correct answer, D. Stroma, is right because it is one of the main layers of the cornea, along with Bowman's layer, Descemet's membrane, and epithelium. Stroma is responsible for transmitting light and maintaining corneal transparency.

**Why Each Wrong Option is Incorrect:**
A. Bowman's layer (Correct) - Bowman's layer is a thin, avascular basement membrane that lies between the corneal epithelium and the stroma. It is essential for corneal transparency and integrity.
B. Descemet's membrane (Correct) - Descemet's membrane is a thin, collagenous layer that lies between the corneal endothelium and Descemet's membrane. It plays a crucial role in maintaining corneal transparency and fluid balance.
C. Epithelium (Correct) - Corneal epithelium is a stratified squamous non-keratinized epithelium that covers the cornea, providing a protective barrier and maintaining corneal transparency.

**Clinical Pearl:**
Understanding the composition and functions of the corneal layers is essential for understanding ocular health and disease. Corneal stroma is not mentioned as an exception because it is a vital component of the cornea, but the focus here is on distinguishing between the correct answer (stroma) and the incorrect options (Bowman's layer, Descemet's membrane, and epithelium). This helps students differentiate between the different corneal layers and their unique roles in maintaining corneal transparency and health.