If vision is normal, seeing is so effortless that we do not notice the different visual functions. The different components of visual function are day vision , night vision , perception of motion , color vision etc.
Vision is measured with many different tests.
Visual acuity Visual acuity is measured with visual acuity charts at distance and at near. The test measures what is the smallest letter, number or picture size that the patient still sees correctly. In the middle of the retina there is a small pit, the fovea , with which we see sharply. When a person with normal vision looks straight forward without moving the eyes, he sees also on both sides. The area visible at once, without moving the eyes, is called visual field .