Translations:Adventist Youth Honors Answer Book/Health and Science/Brain and Behavior/24/en
From Pathfinder Wiki
Instructions: Place a very small black dot on the center of a white piece of paper. Close one eye and stare directly ahead. Hold the paper at arms length in front of you and move the paper until the spot "disappears" (usually this is occurs when the dot is just a bit below eye level - it is important).