Achromatic vision is defined as:

Achromatic vision refers to a condition where an individual has an inability to distinguish colors and perceives only shades of gray, white, and black. This condition can stem from various factors, including certain types of color blindness or other vision disorders.

In essence, those with achromatic vision do not experience the full spectrum of color, which is primarily attributed to issues with the photoreceptor cells in the retina that are responsible for color detection.

Understanding how this differs from other conditions also helps clarify why this definition is specific. For instance, seeing all colors clearly corresponds to normal color vision, while reduced sensitivity to lights relates to conditions affecting brightness perception but not necessarily color distinction. Complete absence of vision indicates total blindness, which is a different condition altogether. Thus, the definition captured in the correct response accurately reflects the characteristics of achromatic vision.