Which type of vision is characterized as rod-only vision with lower acuity?

Scotopic vision refers to the ability of the eye to see in low light conditions, primarily utilizing rod cells in the retina. Rods are highly sensitive to light, allowing for vision in dim environments, but they do not provide the color perception or fine detail that cone cells, used in brighter conditions, can offer. This results in lower acuity, meaning that while scotopic vision is effective in very low light, it lacks the sharpness and detail that is present in vision with cone cells active.

In contrast, photopic vision occurs when there is sufficient light, primarily involving cone cells that allow for high acuity and color perception. Mesopic vision is a combination of both rod and cone activity, which takes place in intermediate lighting conditions, such as during twilight. Dusk vision is a more informal term and isn't widely used in technical discussions of visual physiology.

Thus, scotopic vision is specifically defined by its reliance on rod cells, which leads to its characteristic lower acuity in low-light situations, making it the correct answer in the context of the question.