Refractive errors include myopia, hyperopia, astigmatism, and anisometropia. The correction of myopia can be achieved using appropriate concave lenses, while hyperopia requires suitable convex lenses for correction. The correction of astigmatism depends on the degree and axis differences, so it is necessary to use lenses with the appropriate degree and axis for correction. Anisometropia, due to the significant difference in the degree between the two eyes, requires consideration of the sufficient degree and the correction of the magnification rate of the retinal image during correction.