Eye Measurements

Each eye sees its own image. Since the eyes are separated by a certain distance, the two eyes see the same object from slightly different angles. By uniting the two visual impressions from the eyes in the brain, it can be easier to assess the distance to objects. Look through the hole with just one eye. Then turn the handle until you see the two rods as standing opposite to each other. Now look through the hole normally, and check your result. Just as you can be right-handed or left-handed, you usually have one eye that dominates over the other. When you aim to throw a ball at a target, you may do this with both eyes open. Only one eye is being used to aim at the target, but the other is useful when judging distance.