The Importance of Visual Acquity and Contrast Sensitivity Visual acuity measures our ability to see small detailed black objects on a white background, such as printed text. Contrast sensitivity measures our ability to see an object and separate it from the background under many lighting conditions. This is known as functional vision, or how well we see to perform "real world" activities like driving, cooking, gardening, playing sports and working on computers. These little circles may save your life, or someoneelses!