Which part of the eye is primarily responsible for low-light vision?

The correct choice highlights the function of rods in the eye, which are specialized photoreceptor cells that play a crucial role in low-light (scotopic) vision. Rods are highly sensitive to light and allow us to detect images in dim environments. They are predominantly located in the peripheral regions of the retina, where they can respond to lower levels of illumination effectively, enabling better night vision or vision in dark conditions.

Cones, on the other hand, are photoreceptors that are responsible for color vision and function best in bright light. The optic disk is the point in the retina where the optic nerve exits the eye, and it does not contain photoreceptors, making it insensitive to light. The iris is the colored part of the eye that controls the size of the pupil and regulates the amount of light that enters the eye but does not play a direct role in the actual detection of light or vision in low-light conditions.