As the American Academy of Ophthalmology reports, this is the most effective way to detect the nearsightedness as well as its level and intensity. After that, the healthcare provider uses various test instruments to define the causes of the decreased eye vision. One of such tools is a retinoscope, which helps to analyze how the light refracts off the retina. It is critical to evaluate the number of refractive mistake in place. To do so, doctors use a phoropter. It assists in understanding what should be fixed.