Eye position, the position of the eye during an eye exam, is used to diagnose the presence and degree of strabismus. There are first eye position, second eye position and third eye position. First eye position: When both eyes are gazing at a target at infinite distance (more than 6m) in the true horizontal plane, the two eyes are parallel to each other in the same line of gaze to the front, which is the first eye position. The second eye position: If the two eyes in the line of gaze up and down the left and right rotation, its position is called the second eye position. There are four second eye positions: upward, downward, outward and inward. Third eye position: If the two eyes are turned in the direction of upward or downward, the position is called the third eye position. There are four third eye positions: superior temporal, inferior temporal, superior nasal, and inferior nasal.