What term describes the extent to which a person can see?

The term that best describes the extent to which a person can see is visual acuity. Visual acuity specifically refers to the clarity or sharpness of vision, commonly measured using a standardized eye chart. It indicates how well a person can distinguish shapes and details at a given distance, reflecting the overall effectiveness of the visual system. High visual acuity signifies clear vision, while low visual acuity means that the individual may have difficulty seeing details.

Residual vision refers to any remaining vision that a person retains after a vision impairment, and it does not encompass the full range of clarity and sharpness described by visual acuity. Functional vision refers to the vision required for everyday tasks and activities, which includes the ability to perceive and make use of visual information in practical ways but doesn't specifically measure clarity. Tunnel vision describes a loss of peripheral sight, where a person can only see directly in front of them, which does not accurately describe overall visual extent. Thus, visual acuity is the most precise term for the clarity and sharpness of a person's vision.