Which of the following is NOT a part of the middle tunic of the eye?

The middle tunic of the eye, also known as the uvea, consists of three main components: the choroid, the ciliary body, and the iris. These structures play vital roles in the eye's function, such as providing nourishment to the outer layers, facilitating lens shape changes for focusing, and controlling the size of the pupil, respectively.

In contrast, the cornea is part of the outer layer of the eye, often referred to as the fibrous tunic. The cornea is a transparent structure that covers the front of the eye and is responsible for most of the eye's light refraction. Since the cornea does not belong to the middle tunic, it is the correct answer to identify which structure is NOT a part of that specific layer. Understanding the distinct layers of the eye and their functions is key in recognizing their relevance in ocular anatomy.