Which layer is NOT part of the cornea?

The choroid is not a layer of the cornea; rather, it is part of the uveal tract, which also includes the iris and the ciliary body. The choroid lies underneath the retina and is primarily responsible for providing blood supply to the outer layers of the retina.

In contrast, Bowman's layer, stroma, and endothelium are all integral components of the cornea. Bowman's layer is located just beneath the epithelium and provides a barrier against infections. The stroma is the thickest layer of the cornea, providing structural integrity and transparency due to its unique arrangement of collagen fibers. The endothelium is the innermost layer that regulates the cornea's hydration and maintains its clarity. Thus, recognizing the structure and function of these layers helps to understand the composition of the cornea and the role of each layer in maintaining eye health and vision.