What is the primary function of the retinal pigment epithelium?

The primary function of the retinal pigment epithelium is to nourish retinal visual cells. This layer of cells plays a crucial role in supporting and maintaining the health of photoreceptors (rods and cones) in the retina. It is essential for the phototransduction process, where light is converted into electrical signals, and it helps in the recycling of visual pigments needed for this process.

Additionally, the retinal pigment epithelium facilitates the absorption of excess light, preventing scattering and enhancing visual clarity. It also plays a protective role by phagocytosing the outer segment discs shed by photoreceptors, which helps maintain the overall function of the retina.

While options discussing the production of aqueous humor, filtering UV light, and controlling pupil size are important functions in other areas of the eye, they do not pertain directly to the primary role of the retinal pigment epithelium. Therefore, the correct choice highlights the essential supportive relationship between the retinal pigment epithelium and the photoreceptors it nourishes.