Normal eyes are free of refractive error, but when refractive error occurs and affects your vision, you will need to seek medical attention to correct it. The number of diopters we usually refer to is the number of refractive errors, which can be determined by an optometric examination. Suffering from myopia, hyperopia, astigmatism and other refractive errors will change the refractive error of the eyes, the degree affects the normal vision, you need to optometry correction, into the annual number of stabilized, but also the option of surgical correction. In general, when there is a decrease in visual acuity, abnormal vision and other manifestations, you need to further consult a doctor for examination. If the decrease in visual acuity is caused by refractive error, you can clarify the nature and specific degree of the refractive error through formal optometry examination.