Refraction is to check the concentration of light after entering the eyeball. It uses the state of emmetropia as the standard to measure the degree of difference in vergence and dispersion between the inspected eye and the emmetropia. Since many people will almost become attached to glasses in their lifetimes, optometry is currently one of the most basic, most commonly used but important jobs for optometrists. Therefore, as far as the term optometry is concerned, in social life, Both ophthalmologists and ordinary people are very familiar with it.