A refraction test is typically given as a part of a routine eye examination. it's going to even be called a vision test. This test tells your ophthalmologist exactly what prescription you would like in your glasses or contact lenses. Normally, a worth of 20/20 is taken into account to be optimum, or perfect vision. Individuals who have 20/20 vision are ready to read letters that are 3/8 of an inch tall from 20 feet away. If you don’t have 20/20 vision, you've got what's called a refractive error. A refractive error means the light isn't bending properly when it passes through the lens of your eye. The refraction test will tell your doctor what prescription lens you ought to use so as to possess 20/20 vision.