What does it mean when we have 20-20 vision?
The first number in your visual acuity grade is always 20. That's because the 20 is a reference to the distance, in feet, you are standing or sitting from the eye chart. The distance is not a coincidence. Rays of light are just about parallel 20 feet (about 6 m) from the eye chart, so that the muscle controlling the shape of the lens in a normal eye is in state of relative rest when viewing the chart. Ideally, your eyes should be operating under optimal conditions during the eye test.
The first number in your visual acuity grade is always 20. That's because the 20 is a reference to the distance, in feet, you are standing or sitting from the eye chart. The distance is not a coincidence. Rays of light are just about parallel 20 feet (about 6 m) from the eye chart, so that the muscle controlling the shape of the lens in a normal eye is in state of relative rest when viewing the chart. Ideally, your eyes should be operating under optimal conditions during the eye test.
