Which of the following is part of the ocular adnexa?

The ocular adnexa refers to the structures that support and protect the eye. These include the eyelids, conjunctiva, lacrimal glands, and extraocular muscles. The eyelids play a crucial role in protecting the anterior surface of the eye, aiding in tear distribution, and regulating light exposure.

In this context, the eyelid is clearly a part of the ocular adnexa, as it directly contributes to the overall function and health of the eye by providing protection and maintaining the moisture of the ocular surface.

The other options listed pertain to different parts of the eye itself rather than to the supporting structures. The iris is the colored part of the eye that regulates the amount of light entering through the pupil. The vitreous body is a gel-like substance that fills the space between the lens and the retina, providing structural support. The ciliary body is involved in the production of aqueous humor and changes the shape of the lens for accommodation.

Therefore, the eyelid stands out as the correct answer, as it specifically fits the definition of ocular adnexa.