Many parents take their children to the ophthalmology department of the hospital to see their vision, the doctor will sometimes diagnose: refractive error, many parents do not understand, refractive error is what is it? As opposed to refractive error, there is the concept of orthophoria. Orthokeratology is the concept that light from 5 meters away can clearly form an inverted image on the macula of the retina, and our brain can integrate it into an upright image. Refractive errors include three common classifications: myopia, hyperopia and astigmatism. It is a misconception that people usually think it is myopia when they can’t see near; farsightedness when they can’t see far; and astigmatism when they can’t see light, which is a misconception. In fact, myopia is 5 meters away from the light focused on the front of the retina, see near than see far clear; farsightedness is 5 meters away from the light focused on the back of the retina, sometimes appear to see far than see near clear or see near and see far are not clear; astigmatism is the light from all directions on the retina imaging inconsistent, not to form a focal point but focal plane, so see near and see far have very hard, and very easy to fatigue. If the refractive error is beyond the normal range of the child’s age, there will be vision loss, skewed vision, and even strabismus and amblyopia, so timely correction is needed.