We will comprehensively discuss how to form stereoptic images in normal human eyes. Then we will compare the main differences in images between normal stereoptic and 3D monitors in easy to understand words.In the latter half of this paper, we will focus on how the eye tension will form after short term or long time in 3D monitors usage. We will stress on the symptoms of eye tension and the diseases that could possibly develop will also be discussed.The main goal of this paper is to give the researchers, especially the non-medical teams some useful concepts how the eyes will form 3D images and 3D movies and monitors will affect the eyes and body in order that they could have proper thinking references of human factors engineering in developing 3D monitors in the future.