This is the convergence function at work. Convergence is an anisotropic movement that is indispensable for binocular vision. It is the turning of the eyes to the center, commonly known as “cross-eyed”. It includes autonomous and involuntary assembly. 1, autonomous set: is the only visual reflex movement that can be controlled by the will, by the frontal lobe of the cerebral cortex; 2, involuntary set: is a visual mental reflex, is through the brain occipital cortex of the perceptual center to establish the conditioned reflex. It contains the following four components: Tension set: when looking at infinite distance, the set component is maintained by the muscle tension of the extraocular muscles (mainly the internal rectus muscle) alone to maintain the eye position. Fusional assembly: The assembly component that adjusts the position of the two eyes and the angle of the visual axis so that the object image is maintained in the corresponding area of the retina of both eyes (the central macular recess) is fusional assembly. It is used when looking at objects at any distance. Modulated pooling: The pooling component that accompanies the used modulation when looking at a target at a limited distance is the modulated pooling. Mostly used when looking at objects at a distance of less than 5 meters. Near-sensory set: also known as the proximity set or mental set. In addition to the regulation-induced set, there is a small part of the set component caused by the psychological factor of feeling the proximity of the target when gazing at a close object.