Which part of the eye provides nourishment to the outer layers of the retina?

The choroid is the correct answer because it is the vascular layer of the eye situated between the retina and the sclera. The primary function of the choroid is to supply blood to the outer layers of the retina, providing essential nutrients and oxygen required for retinal health and function. This layer contains a rich network of blood vessels that facilitate the metabolic needs of the retina, supporting its role in light perception and image processing.

In contrast, the sclera is the tough, protective outer covering of the eyeball that does not participate in the nourishment of the retina. The iris is the colored part of the eye responsible for controlling the diameter of the pupil and regulates the amount of light that enters the eye but does not play a role in nourishing the retina. The cornea is the transparent front part of the eye that covers the iris and pupil, allowing light to enter the eye; while it is crucial for focusing vision, it does not provide nourishment to the retina. Thus, the choroid uniquely fulfills the important role of nourishing the outer layers of the retina.