Final answer:
The opaque middle layer of the eyeball is described by the term choroid. It is a vascularized layer that provides a blood supply to the eyeball and is positioned between the outer sclera and the inner retina. c. choroid
Step-by-step explanation:
The term that describes the opaque middle layer of the eyeball is the choroid. This layer, which is part of the vascular tunic of the eye, is composed of highly vascularized connective tissue and provides a blood supply to the eyeball. Its main function is to nourish the outer layers of the retina. The choroid is situated between the sclera, which is the protective outer layer of the eye that includes the white sclera and the transparent cornea, and the retina, the innermost layer responsible for photoreception.
The cornea, on the other hand, is the clear, protective outer layer at the front of the eye that allows light to enter and is not the opaque middle layer. The sclera forms the majority of the fibrous tunic but also does not correspond to the middle layer. The conjunctiva is a thin layer that covers the sclera and lines the inside of the eyelids, not the middle layer of the eyeball.