Final answer:
Visual acuity is the eyes' ability to distinguish objects or images clearly. It can be tested using tools like the Snellen chart.
Step-by-step explanation:
Visual acuity refers to the eyes' ability to distinguish objects or images clearly. It is a property of vision related to the sharpness of focus, which varies depending on the position of the retina. Visual acuity can be tested using tools like the Snellen chart, which presents letters of varying sizes to determine the clarity of vision.