There is a significant difference in refractive status between the two eyes, which is called anisometropia. Clinically, it is divided into physiological and pathological according to whether it causes binocular monovision. At present, there is no uniform standard for the definition of physiological anisometropia. The standard of the Chinese children’s amblyopia and strabismus prevention group is that the diopter difference of the two eyes is ≥1.50D with spherical lens and ≥1.00D, which is pathological anisometropia. Otherwise, it is physiological anisometropia. Visual Physiology Psychology believes that the maximum difference in visual fusion between the two eyes is 5%. This physiological value corresponds to a corrected diopter difference of ±2.50DS. The problems related to anisometropia include: the prism effect caused by the unequal corrective lenses for the eyes; the adjustment required for the eyes is unequal; the relative magnification of the eyes is unequal. Mild anisometropia can still be fused to produce stereopsis. At this time, patients mostly rely on adjustment to maintain it, but since the adjustment effect of both eyes is simultaneous and equal, in order to make the image of one eye clear, it will affect the other The sharpness of one eye is contradictory, which causes visual fatigue; if anisometropia occurs in childhood and the amount of jitter is high, one eye will be suppressed, resulting in anisometropic amblyopia, and secondary exotropia. Monocular vision. There are also patients with a high degree of variability and difficulty in fusion. They have developed the habit of seeing near and far in both eyes, which is called alternate fixation. It is more likely to occur in mixed anisometropia and simple anisometropia.  .