If you are an optometry or opthalmology student, this is the perfect how-to video for you. Watch these these seven videos and learn how to test a patients vision with a refracting machine. It's a little difficult to describe the controls used for refracting because every instrument is set up differently. If possible, refer to a manual for the specific refracting instrument that you'll be using. This vision tutorial will walk you through all the parts of a optical refracting instrument, sphere establishment, cylinder axis refinement, cylinder power refinement, sphere power refinement and cylinder power search.