Which type of adaptation refers to the eye adjusting to darkness?

Dark adaptation refers to the physiological process by which the eye becomes more sensitive to low levels of light after being exposed to brightness. When entering a dimly lit environment, the rods, which are photoreceptors in the retina responsible for vision in low light, become increasingly active. This adaptation can take several minutes, during which the sensitivity of the rods enhances the ability to perceive outlines and movements in darkness.

In the context of the other terms, light adaptation pertains to how the eye adjusts to bright light conditions, reducing sensitivity to prevent overwhelming glare. Photosensitivity describes the responsiveness of photoreceptors to light stimuli, and contrast sensitivity relates to the ability to distinguish between differences in light and dark, rather than strictly the eye's adjustment to darkness. Thus, dark adaptation is specifically about the eye's ability to adjust to low-light conditions, making it the correct and precise choice.