== cm Measurement ==
A simple test for your level of myopia is to hold a ruler up to your eye, and measure how far away you can still read text without [[blur]]. If you measure this distance in centimetres, this is your "cm measurement". The ideal precise measurement is from the surface of your eyeball, but this is obviously not safe, so measure from some facial structure near your eye. Consistency is more important than accuracy, you want to be able to track your small changes over the course of a day, and larger changes over time. [[Diopters]] = -100cm/cm measurement. This test is fairly accurate up to about -10 Diopters. This is not corrected for [[vertex distance]] , but below - 4D vertex distance has no significant effect, and your [[normalized]] lenses should be a little low anyway.
== Trial Refraction ==